An informal group of lower plants unites the subkingdoms of purple algae, or red algae, and true algae. Both of them are predominantly marine, which, first of all, differs from terrestrial higher plants distributed over the surface of the land. Previously, lower plants called all organisms that were not animals or ordinary land plants: that is, not only algae, but bacteria, lichens.
Today, the lower plants are much more precise: these are those plants that do not have a differentiated structure of their body, that is, they are not divided into several parts. This is their second main difference from the higher sub-kingdom. All are homogeneous: their leaves, shoots, roots, and flowers do not stand out. They consist of the same in all parts of the body.
Lower plants are unicellular and multicellular, and their sizes can vary from invisible to the naked eye to gigantic ones, several tens of meters in length. Lower plants are more ancient than their more advanced relatives: the oldest remains of these organisms are about three billion years old.
Higher plants
Higher plants They grow mainly on land, although there are a few exceptions. They have a complex tissue structure that allows them to lead a richer life: they have developed mechanical, integumentary, and conductive tissues. This is explained by the fact that plants live on land: air, unlike water, is less comfortable - you need to protect yourself from drying out, ensure heat exchange, and firmly gain a foothold in one place.
Parts of the body of these organisms perform different functions and have different structures: the root is fixed in and provides water and mineral nutrition, the stems transport substances obtained in the soil throughout the plant’s body, and the leaves engage in photosynthesis, converting inorganic compounds into organic ones. Thin integumentary tissue protects the body, due to which higher plants are considered more resistant to conditions environment. This property is also ensured by thick cell walls with lignin - they protect the stems from mechanical damage.
Higher plants, unlike lower ones, have multicellular reproductive organs, which are also better protected by dense walls. This subkingdom includes bryophytes (all types of mosses) and vascular plants, which are divided into spore and seed plants.
In appearance, structure and biological characteristics, higher plants are very diverse. Higher plants living today are mosses, mosses, horsetails, ferns, gymnosperms and angiosperms (flowering) plants. The total number of their species exceeds 285 thousand.
Unlike “lower plants,” higher ones are characterized by a number of features of a higher organization. Their body is divided into organs: shoot and root (with the exception of bryophytes). These organs contain many different tissues.
Higher plants have a well-developed conducting system, represented by xylem (tracheids or vessels) and phloem (sieve tubes with accompanying cells). Along with the conducting system, there is a complex system of integumentary tissues, a complex stomatal apparatus; Mechanical ones have received strong development.
A characteristic feature of higher plants is the correct change of generations (gametophyte and sporophyte) in their development cycle. The gametophyte - the sexual generation on which antheridia and archegonia are formed - is replaced by the asexual generation of the sporophyte, on which sporangia with spores are formed. The gametophyte is always a haploid plant, the sporophyte is a diploid plant.
In bryophytes, the gametophyte dominates the life cycle, and the sporophyte occupies a subordinate position and lives on the gametophyte. Mosses, horsetails and ferns are characterized by the biological independence of both the sporophyte and the gametophyte, but the sporophyte predominates in the life cycle, and the gametophyte is reduced to varying degrees. In the most highly organized higher plants (gymnosperms, angiosperms) the greatest reduction of the gametophyte is observed.
Divisions of higher plants
Higher plants are usually divided into 9 divisions, two of which combine only extinct forms - rhinophytes, zosterophyllophytes; seven divisions are represented by living plants - bryophytes, lycophytes, psilotoides, horsetails, pteridophytes, gymnosperms, etc.
Department of Rhyniophyta
Rhiniophytes (psilophytes) became extinct in the Middle Devonian. These first higher plants had a very simple structure. They reproduced by spores and had dichotomously branching bodies with apical sporangia. There was no differentiation into roots, stems and leaves.
It is believed that rhiniophytes are the original ancestral group from which the bryophytes, lycophytes, horsetails and pteridophytes descended.
Division Zosterophyllophyta
This department includes a small group of plants that existed in the Early and Middle Devonian. They had much in common with rhyniophytes. Perhaps the plants of this group lived in water. Like rhiniophytes, they had no leaves; their aboveground shoots branched dichotomously. Sporangia of zosterophyllophytes, which had a spherical or bean-shaped shape, were located laterally on short stalks, this is their difference from rhinophytes.
Division Bryophyta
Bryophytes are evergreen, autotrophic, mostly perennial plants. They number about 25,000 species and have been known since the Carboniferous. This group of higher plants apparently descends from ancient green algae.
The body of bryophytes is either a thallus (thallus) pressed to the substrate, or a stalk with leaves; there are no roots, there are only rhizoids. These are small plants, their sizes range from 1 mm to several tens of centimeters. Bryophytes have a relatively simple internal organization. Their body contains assimilation tissue, but conductive, mechanical, storage and integumentary tissues are weakly expressed in comparison with other higher plants.
Unlike all other divisions of higher plants, the vegetative body of bryophytes is represented by the gametophyte, which dominates in their life cycle, while the sporophyte occupies a subordinate position, developing on the gametophyte.
On the gametophyte of bryophytes, reproductive organs develop - male (antheridia) and female (archegonia). A large number of biflagellate spermatozoa are formed in the antheridia. Each archegonia produces one egg. In wet conditions (during rain), sperm, moving into, penetrate the egg located inside the archegonium. One of them merges with her, producing fertilization. From a fertilized egg (zygote) a sporophyte grows, that is, an asexual generation represented by a capsule sitting on a stalk. Spores form in the box.
When a spore germinates, a protonema appears - a thin branched thread (less often a plate). Numerous buds are formed on the protonema, giving rise to gametophytes - leafy shoots or thalli in the form of a plate.
Gametophytes of bryophytes are capable of vegetative reproduction, and their development cycle can occur for a long time without the formation of a sporophyte.
Bryophytes combine 3 classes: Anthocerotaceae, Liverworts And Leaf mosses.
IN class Anthocerotidae(Antocerotae) there are about 300 species. They are distributed mainly in tropical and temperate warm areas globe. In our country, only the genus Antoceros is found, represented by 3-4 species.
The gametophyte of anthocerotes is a thallus (thallus). In species of the genus Anthoceros, the thallus is rosette-shaped, 1-3 cm in diameter, less often leaf-shaped, dark green, tightly adjacent to the soil. The capsules (sporogony) are numerous, slightly curved, bristle-like. They give anthocerote mosses a distinctive appearance.
IN class Liverworts(Heraticae) there are over 6 thousand species. Liverworts are widespread. Unlike other bryophytes, in most liverworts the protonema is poorly developed and short-lived. The gametophyte has a thalliform or leaf-stem form. The structure of the gametophyte in hepatic mosses is very diverse, but the sporophyte is of the same type.
As an example, we can consider a representative of the Marchantiidae subclass - Marchantia polymorpha. This is one of the most common liverworts in our flora (in swamps and forests at fire sites). The body of Marchantia is represented by a thallus in the form of a dark green plate.
Marchantia is a dioecious plant. On some specimens archegonia are formed, on others - antheridia. Archegonia develop on a special stand, the top of which resembles a multi-rayed star. The male stand with antheridia looks like a flat disk.
The subclass Jungermanniidae contains both thallus and leafy plants. Most Jungermanniaceae have recumbent dorsoventral shoots. The shape and their attachment to the stem are varied, the shape of the box is from spherical to cylindrical, it usually opens with 4 doors.
TO class Leafy mosses(Musci) include 3 subclasses: Sphagnum, andreic and brie mosses; Of these, we will consider two subclasses: Sphagnum and Briaceae.
The subclass Sphagnidae is represented by one family, Sphagnaceae, with a single genus, Sphagnum. There are 42 species found in our country. Sphagnum mosses are widespread in temperate and cold regions of the Northern Hemisphere, forming a continuous cover in swamps and humid forests.
The stems of sphagnum mosses are erect, with fascicle-shaped leafy branches. At the top, the branches are shortened and gathered into a rather dense head.
The leaves are single-layered and have two types of cells - chlorophyll-bearing and aquiferous (hyaline). Chlorophyll-bearing cells are narrow, worm-shaped, and contain chloroplasts. They are located between wide, colorless aquifer cells, devoid of cellular contents. Thanks to its many water-bearing cells, sphagnum can quickly absorb large amounts of water (almost 40 times its dry weight).
Antheridia and archegonia are formed in the upper part of the stems. After fertilization of the egg, a capsule grows from the archegonium.
The Bryidae subclass is represented in your country by approximately 2 thousand species. Green mosses are most often perennial plants with a height of 1 mm to 50 cm. Their color is usually green. They are widespread and form a continuous cover in swamps, coniferous forests, meadows, mountains and tundras.
Green mosses are characterized by a well-developed, often filamentous, branching protonema. By structure vegetative organs green mosses are very diverse.
As an example reflecting the most important characteristics of plants of this subclass, consider the cuckoo flax moss (Polytrichum commune), widespread in damp coniferous forests and along the edges of swamps. The stem of this moss is erect, unbranched, reaches a height of 30-40 cm. It is densely covered with linear-lanceolate leaves.
Kukushkin flax is a dioecious plant. Archegonia are formed at the top of the stems of some plants, and antheridia on others. After fertilization, a capsule develops from the zygote, sitting on a stalk. Spores ripen in the box. The spore, once on moist soil, germinates, giving rise to a filamentous protonema. Buds form on the protonema, from which they grow into leaves.
The importance of mosses in nature is great. Representatives of bryophytes grow almost everywhere. The exception is saline habitats with moving substrate; marine bryophytes are unknown. Mosses are abundant in swamps and forests. They often dominate the ground cover of coniferous forests (spruce forests, pine forests, etc.). Mosses are abundant in the tundra, high in the mountains. The tundra zone and humid highlands are rightly called the kingdom of mosses and lichens.
The ability of bryophytes to quickly absorb water and firmly retain it causes the moss turf to become peaty from below and weakly decompose. Moss cover can contribute to waterlogging of areas. Sphagnum mosses have antibiotic properties and are used in medicine. Participating in the formation of moss cover in raised bogs, they are peat formers. Sphagnum peat is widely used as fuel and in agriculture.
Many green mosses form a continuous carpet in lowland bogs, where they form deposits of lowland peat rich in nutrients. Lowland peat is widely used in agriculture as a fertilizer. Mosses also have a negative meaning. Growing in a continuous dense carpet, they impede soil aeration, causing it to sour. This adversely affects the life of many plants. The role of liverworts in the vegetation cover is generally much less than the role of sphagnum and green mosses.
Division Lycopodiophyta
Lycopods are one of the most ancient groups of plants. The first lycophytes were herbaceous plants. In the Carboniferous period appeared tree species, but they died out, and their remains formed coal deposits. Most of the lycophytes are now extinct. Only a few species of club mosses and selaginella have survived.
All modern representatives of lycophytes are perennial herbaceous, usually evergreen plants. Some of them resemble green mosses in appearance. The leaves of lycophytes are relatively small, this is typical for this group of plants. Dichotomous (forked) branching is also characteristic of lycopods. At the top of the stems of many lycophytes, spikelets (strobilae) are formed, in which spores ripen.
Among the lycophytes there are homosporous and heterosporous plants. In homosporous species, the spores do not differ morphologically; during their germination, bisexual gametophytes are formed; In heterosporous species, small spores give rise to male gametophytes bearing antheridia, and large spores give rise to female gametophytes bearing archegonia. Bi- or multiflagellate spermatozoa are formed in antheridia, and eggs are formed in archegonia. After fertilization, a new generation grows from the resulting zygote - the sporophyte.
The section Mossaceae includes two classes: Mossaceae and Polusniformes. From the class Plaunovs we will consider the order Plaunovs and from the class Polushnikovs - the order Selaginella, representatives of which live at the present time.
Order Lycophytes(Lycopodiales) is characterized by homosporousness. It is represented by one family - Lycopodiaceae. This family includes the genus Lycopodium, which has about 400 species. There are 14 species of mosses found in our country.
Many club mosses are small herbaceous plants. Their leaves are relatively small. A midrib consisting of tracheids and parenchyma cells runs along the leaf.
Let's consider one of the types of club moss - club moss (Lycopodium clavatum). This species has a wide distribution and is found in coniferous (usually pine) forests on poor soils. Moss moss is an evergreen perennial herbaceous plant with a creeping stem up to 1-3 m long. On this stem, rising above-ground shoots up to 20 cm high are formed, ending in spore-bearing spikelets. All shoots are densely covered with small subulate-shaped leaves. The spikelets contain kidney-shaped sporangia, in which a large number of identical small yellow spores are formed.
The spores fall to the ground after ripening. When they germinate, an outgrowth (gametophyte) is formed. The moss growth is perennial and looks like a small nodule (2-5 mm in diameter) with rhizoids. It is colorless, lacks chlorophyll and cannot feed on its own. Its development begins only after the fungal hyphae (endotrophic mycorrhiza) penetrate the body.
On the upper surface of the prothallus, in the depths of its tissue, antheridia and archegonia are formed. Fertilization occurs in the presence of water. From the fertilized egg, an embryo develops and grows into a perennial evergreen plant - sporophyte.
In lycophytes there is a clearly expressed change of generations. The development cycle is dominated by the sporophyte. Reduction division occurs in the sporangium during the formation of spores.
The stems and leaves of club mosses contain alkaloids that are used in medicine. The spores are used as a powder for powders, as well as for sprinkling pills. To protect the reserves of club mosses, when collecting spores, it is necessary to carefully cut off only the spore-bearing spikelets.
Order Selaginellaceae(Selaginellales), belonging to the class Polushnikovye, is characterized by heterosporousness. It is represented by one family, Selaginellaceae. There are almost 700 species in the genus Selaginella, mostly native to tropical and subtropical regions. There are 8 species of this genus found in our country. Selaginella are very diverse in appearance. Most of them are small, usually creeping herbaceous plants. The leaves are simple, entire, small, up to 5 mm long. Asexual reproduction via spores is the main method of reproduction of Selaginella.
Let's take a closer look Selaginella selaginoides(Selaginella selaginoides). This plant has short creeping stems covered with elongated ovate leaves. Spore-bearing spikelets are formed at the top of the shoot. The main difference between Selaginella and club mosses is that the same spikelet contains two types of sporangia. Some of them are larger (megasporangia) and contain 4 large spores (megaspores). Other sporangia are smaller (microsporangia) and contain numerous microspores.
During germination, the microspore forms a highly reduced male prothallus, on which one antheridium develops. A female prothallus grows from the megaspore, on which a few archegonia develop. The movement of sperm occurs in water after rain or dew. Over time, an adult plant grows from a fertilized egg.
Thus, in Selaginella two types of spores are formed - microspores and megaspores - and unisexual prothlae develop. Thickles, especially male ones, are greatly reduced, which is the main direction of the evolution of higher plants. This can be clearly seen in other departments of higher plants. Selaginella are little used by humans.
Division Psilotophyta
The Psilotidae department includes 12 species. It includes two genera: Psilotum and Tmesipteris. Representatives of these genera are distributed outside our country in the tropics and subtropics. They are simply arranged and resemble rhyniophytes. Their structure retains extremely primitive features, which indicate their very ancient origin.
The sporophyte psilota has no roots or leaves. It consists of a dichotomously branching aerial part with small scale-like outgrowths and a branched system of rhizomes with numerous rhizoids.
Psilot is a homosporous plant. Spores are formed in sporangia located at the ends of short lateral branches. An underground gametophyte grows from the spore, on the surface of which are located antheridia and archegonia. Sperm are multiflagellate and require water to reach the egg.
Tmesipteris is similar to psilot, differing from it in larger leaf-like appendages.
Division Equisetophyta
Equisetaceae are characterized by division into clearly defined internodes and nodes with whorled leaves.
Currently, horsetails are represented on Earth by one class Equisetopsida, which includes one order Equisetales and one family Equisetales. There is only one genus in this family - Horsetail (Equisetum), which includes about 30 species, 17 of which are found in our flora (in swamps, forests, meadows, arable lands, etc.).
Horsetails reached their greatest development in the Carboniferous period. Then many of them were represented by large trees. Later the tree-like forms became extinct. Their dead remains gave rise to coal deposits. Many herbaceous forms also became extinct.
Modern horsetails are perennial rhizomatous herbs with a stem up to several tens of centimeters high. At the nodes of the stem there are whorls of branches. Small scale-like leaves grow together with sheaths into a tube; the function of photosynthesis is performed by green shoots. Some shoots end in a spore-bearing spikelet (strobilus), consisting of sporangia. Modern horsetails are homosporous plants.
The sexual generation (gametophyte) in modern horsetails is represented by unisexual or bisexual short-lived, very small, green shoots several millimeters in size. Antheridia and archegonia are formed on them. Multiflagellate sperm develop in antheridia, and eggs develop in archegonia. Fertilization occurs in the presence of droplet-liquid water, and a new asexual generation grows from the zygote - the sporophyte.
The structure of horsetails and their life cycle can be considered using the example of horsetail (Equisetum arvense). This is a perennial rhizomatous plant that grows in fields, meadows, and fallow lands. From rhizome early spring pinkish-brown, short, straight shoots appear, at the top of which a spore-bearing spikelet forms. On the axis of the spikelet there are sporophylls that look like hexagonal scutes. The sporophylls contain sporangia, which contain spores.
Outwardly, all disputes are the same. Each has two appendages in the form of narrow ribbons called elater. The spores are morphologically identical, but physiologically different. Some of them, when germinating, produce male shoots, others - female shoots.
The male prothallus is a small green plate, divided into lobes and attached to the soil by rhizoids. Antheridia containing polyflagellate spermatozoa develop at the ends of the lobes. The female prothallus is larger and bears archegonia. Fertilization occurs in the presence of moisture. A perennial sporophyte develops from the zygote. Green vegetative shoots, devoid of spikelets, develop from the rhizomes of horsetail.
Other types of horsetail have only one type of shoot. It is both spore-bearing and assimilative. Practical significance there are few horsetails.
Division Fern-like (Polypodiophyta)
Ferns are ancient plants. A significant part of them have now become extinct. Today, the pteridophytes far outnumber all other groups of modern spore-bearing vascular plants in number of species; More than 12 thousand species are known. There are about 100 species from this group in our flora.
Representatives of this department are very diverse in appearance, life forms, living conditions. Many of them are herbaceous perennial plants, there are also trees. Tropical tree ferns are up to 25 m tall, and the trunk diameter reaches 50 cm. Among the herbaceous species there are very small plants several millimeters in size.
Unlike lycophytes and horsetails, pteridophytes are characterized by “large leaves”. The “leaves” of ferns are of stem origin and are called “fronds”. Their origin is confirmed by apical growth.
The sizes of fronds of ferns range from a few millimeters to 30 cm. Their shape and structure are varied. The fronds of many ferns combine the functions of photosynthesis and sporulation. Some species (for example, ostrich) have two types of fronds - photosynthetic and spore-bearing. The leaves of the fronds are quite often feathery, often dissected many times.
Most forest ferns of temperate regions have fleshy rhizomes that form new rosettes of fronds every year, which usually prevail in weight and size over the stem in ferns.
Almost all ferns, with the exception of aquatic ones, are homosporous plants. Their sporangia are often located on the lower surface of the fronds and are collected in groups - sori. Fern spores give rise to free-living bisexual growths (gametophytes) bearing antheridia and archegonia. For fertilization, the presence of droplet-liquid water is necessary, in which multiflagellate sperm can move.
A sporophyte develops from a fertilized egg. As the sporophyte grows, it becomes independent and the gametophyte dies.
The Fern division is divided into 7 classes. Of these, 4 classes are represented exclusively by fossil forms, which differed in appearance from typical ferns.
Let's take a closer look at the male shield fern (Dryopteris filix-mas), which overall plan structure and development cycle is typical for ferns. It forms a thick creeping rhizome, at the end of which a rosette of large, double-pinnately dissected “leaves” appears annually. Young leaves are snail-shaped at the end and grow from the top (like a stem). Adventitious roots extend from the rhizomes.
Round sori are formed on the lower surface of the fronds in summer. Identical spores are formed inside the sporangium. Male shield fern is a typically homosporous fern. Once on, the spore germinates and a shoot is formed. It is a heart-shaped green plate about 1 cm in size. Archegonia and antheridia are formed on the lower surface of the prothallus. Helically twisted multiflagellate spermatozoa develop in the antheridia. Fertilization occurs in the presence of water. A perennial large sporophyte gradually grows from a fertilized egg.
Aquatic ferns are heterosporous plants. This is a small group. An example is the floating salvinia (Salvinia natans), which belongs to the order Salviniales. This is a small plant that floats on water.
Male and female gametophytes develop from micro- and megaspores, which are formed in micro- and megasporangia. The male gametophyte, developing from a microspore, is greatly reduced.
The female gametophyte develops inside a megaspore and is multicellular. After fertilization, a perennial sporophyte develops. The process of spore germination, fertilization and sporophyte development occur in water.
The practical importance of ferns is small. The young leaves of some herbaceous plants, as well as the core of tree ferns, are eaten. Some ferns are medicinal plants.
In ferns, horsetails and mosses, sexual reproduction can occur only if water is available at the time of fertilization.
The further evolution of higher plants followed the path of ensuring the independence of sexual reproduction from the availability of water.
This possibility was realized in seed plants. Continues here general direction evolutionary development of the sporophytic line - progressive development of the sporophyte and further reduction of the gametophyte. The sporophyte reaches its most complex structure in angiosperms.
Among higher plants, only two divisions are characterized by the presence of a seed: gymnosperms and angiosperms. The seed determined the dominance of seed plants in modern vegetation, since it already contains a sporophyte embryo and contains a significant supply of nutrients.
Seed plants are heterosporous. They produce microspores, which give rise to the male gametophyte, and megaspores, which give rise to the female gametophyte.
Megaspores of seed plants develop in special formations - ovules (ovules), which are modified megasporangia. The megaspore remains permanently enclosed within the megasporangium. In the megasporangium, the development of the female gametophyte, the process of fertilization and embryo development occur. All this ensures the independence of fertilization from drop-liquid water.
During development, the ovule turns into a seed. The seed contains an embryo - a young, embryonic, very small sporophyte. It has a root, a bud and embryonic leaves (cotyledons). A sufficient supply of nutrients in the seed ensures the first stages of embryo development. Thus, seeds provide more reliable plant dispersal than spores.
Division Gymnosperms (Pinophyta, or Gymnospermae)
Gymnosperms are evergreen, less often deciduous trees or shrubs, and rarely lianas. The leaves of gymnosperms vary greatly in shape, size, morphological and anatomical features. Thus, the shape of the leaves can be scale-like, needle-like, pinnate, double-pinnate, etc.
Gymnosperms belong to heterosporous plants. Microspores are formed in microsporangia located on microsporophylls, and megaspores are formed in megasporangia formed on megasporophylls. Micro- and megasporophylls attached to the axis are a shortened spore-bearing shoot (strobilus, or cone). The structure of strobili in gymnosperms is varied.
The Gymnosperm department includes 6 classes, and the classes Seed ferns (Pteridospermae) and Bennettite ferns (Bennettitopsida) are completely extinct. Today's living gymnosperms, numbering about 700 species, belong to the classes Cycadopsida, Gnetopsida, Ginkgopsida and Pinoposida.
Class Seed ferns reached its greatest development during the Carboniferous period. These plants became completely extinct in the Triassic period. They were represented by trees and vines. Their tree-like forms resembled modern tree ferns. Unlike modern ferns, they reproduced through seeds.
Seed ferns had large, mostly feathery leaves. Assimilating leaves differed sharply from spore-bearing leaves (sporophylls). The latter were of two types: microsporophylls and megasporophylls.
From seed ferns evolved primitive groups of gymnosperms, which are characterized by true strobili, or cones (Bennettiaceae, Cycadaceae).
Bennettite class- completely extinct plants. They were mainly represented by tree-like forms. Many of them had slender, tall trunks topped with large feathery leaves at the top.
Many Bennettites had bisexual strobili, reminiscent in structure of the flower of modern angiosperms. Microsporophylls in large quantities were located along the periphery of the strobilus, and reduced megasporophylls were located in the center of the strobilus. Each megasporophyll had one ovule. Bennettite seeds contained an embryo that filled the entire seed.
Bennettites are similar in appearance to cycads, and the two classes are thought to be descended from seed ferns.
Class Cycadaceae- a once widespread group of plants. Currently, this class includes about 120 species from 10 genera, found in tropical and subtropical regions of the globe. Cycads are tree plants, similar to palm trees. Their leaves are large, hard, evergreen. In most cycads, sporophylls are collected in strobili (cones), which are formed at the end of the trunk among the leaves. Cycads are dioecious plants. Male and female strobili are formed on different individuals.
One of the typical representatives of the class is the drooping cycad (Cycas revoluta), widespread in East Asia. This is a tree with a columnar trunk up to 3 m high. At the top of the trunk there is a crown of feathery leaves up to 2 m long. In male specimens, male strobili 50-70 cm long are formed.
Microspores spill out from microsporangia and are transferred a meter to the ovule, where further development male outgrowth.
Megasporophylls in all species of the cycad genus are located in small numbers at the apex of the stem, alternating with vegetative leaves. Megasporophylls are feathery, different from vegetative leaves smaller in size, yellow or reddish in color. In the lower part of the megasporophyll, on its branches, megasporangia (ovules) are located. They are large, up to 5-6 cm long.
In the center of the ovule there is multicellular tissue - endosperm (a modified female prothallus), in the upper part of which two archegonia with large eggs are formed. Fertilization is carried out by motile spermatozoa with numerous flagella. An embryo develops from a fertilized egg. It has all the parts inherent in an adult plant: the first leaves (cotyledons) and the rudimentary stem (subcotyledon), which turns into the root.
Thus, in cycads the sexual generation is greatly reduced. The male gametophyte is reduced to three cells, two of which are antheridium. The female gametophyte is a small formation located inside the macrosporangium on the sporophyte. The female gametophyte has lost the ability to exist independently.
TO Gnetovye class include representatives of three genera: Ephedra, Welwitschia and Gnetum.
The class is characterized by the following general characters: the presence of perianth-like integuments around microsporophylls and megasporophylls; dichasial branching of strobili assemblies; dicotyledonous embryos; the presence of vessels in the secondary xylem; absence of resin passages.
There are 40 species in the genus Ephedra, native to arid and desert regions of the globe. Most species are represented by low, highly branched shrubs, reminiscent of horsetails.
Ephedras are dioecious plants, less often monoecious. On male specimens microstrobiles are formed, on female specimens - megastrobiles. At the top of the megastrobilus there is an ovule, or ovule (megasporangium). An embryo develops from a fertilized egg, and a seed develops from an ovule, surrounded by a juicy, red-colored outer covering.
There is only one species in the genus Welwitschia - the amazing Welwitschia (Welwitschia mirabilis), which lives in the deserts of southwestern Africa. It has a rather long root and a short and thick stem. In the upper part, two opposite ribbon-like leaves extend from the stem, up to 2-3 m long, lying on the ground and growing throughout life. Velvichia is a dioecious plant. Micro- and megastrobiles, forming complex branched assemblies, appear directly above the bases of the leaves, as if in their axil. The mature embryo is surrounded by endosperm and has two cotyledons, a subcotyledon, a primary root and a stalk.
The genus Gnetum has about 30 species. They grow in tropical rainforests. These are small trees, shrubs and vines. They have wide, leathery leaves arranged oppositely. Plants are dioecious. Microstrobili are catkin-shaped and complex. On the axis of the megastrobilus, which looks like an elongated earring, there are ovules (megasporangium). After fertilization, an embryo develops with two cotyledons. The ovules turn into bright pink seeds.
The only modern representative class Ginkgoidae is An ancient relict plant - ginkgo biloba (Ginrgo biloba). It is a deciduous tree, reaching a height of more than 30 m and having a trunk diameter of more than 3 m. Ginkgo leaves are petiolate, the blade is fan-shaped, usually bilobed at the apex. Ginkgo is a dioecious plant. Microstrobiles are catkin-shaped. Ovules (usually two in number) develop on megastrobiles. Two archegonia are formed inside each ovule. Spermatozoa are motile. One of them fertilizes the egg. A seed is formed from the ovule, which in its structure resembles a plum fruit. The outer layer of the shell covering the seed is juicy, underneath there is a hard stony shell and an inner thin layer. The embryo consists of a root, a stalk and two cotyledons.
Class Coniferous includes two subclasses: Cordaitales and Conifers (Pinidae). Cordaites are long extinct plants. They reached their greatest development during the Carboniferous period. Cordaites were large trees with a monopodially branching stem and a high crown. Between the leaves on the branches there were reproductive organs - complex catkin-shaped collections of strobili.
Conifers are the most extensive and richest subclass among all gymnosperms. In terms of its importance in nature and in human life, this group ranks second after flowering plants. Currently, conifers number about 610 species belonging to 56 genera and 7 families. They form forests over vast areas of Northern Eurasia and North America, and are found in temperate regions of the Southern Hemisphere. In terms of their antiquity, conifers are superior to all living groups of seed plants; they have been known since the Carboniferous.
The anatomical structure of coniferous stems is quite uniform. Wood consists of 90-95% tracheids. The bark and wood of many coniferous species contain many horizontal and vertical resin ducts.
The strobili of conifers are exclusively dioecious. Plants are monoecious, less often dioecious. The strobili vary greatly in shape and size.
The main features of the life cycle of conifers can be considered using the example of Scots pine (Pinus sylvestris). This is a slender tree, reaching a height of 40 m. At the ends of the pine branches there are buds that give rise to new shoots every year.
In spring, collections of greenish-yellow male cones - strobili - form at the base of some young shoots. On the axis of the male cone there are microsporophylls, on the lower surface of each there are two microsporangia (pollen sacs). Microspores are formed inside the microsporangia after reduction division. The microspore begins to germinate inside the microsporangium and ultimately turns into a pollen grain that has two cells: vegetative and generative (from the latter, two male gametes - sperm) develop. The pollen grain (pollen) leaves the microsporangium (anther). Mature pine pollen has two shells: the outer one is exine, the inner one is intina. The exine forms two air sacs that facilitate the transfer of pollen by the wind.
Megastrobiles are called female cones. They are collected in groups of 1-3 at the ends of young shoots. Each cone represents an axis from which scales of two types extend in all directions: sterile (covering) and seed-bearing. On each seed scale with inside two ovules are formed. In the center of the ovule, the endosperm or prothallus develops (female gametophyte). It is formed from a megaspore, and its cells have a haploid set of chromosomes. In the upper part of the endosperm, two archegonia with large eggs are laid.
After the pollination process, the fertilization process begins. The period between pollination and fertilization lasts about a year. A long pollen tube grows from the pollen grain and moves towards the archegonium. Two sperm move along the pollen tube to the egg. The tip of the pollen tube, which reaches the egg, ruptures and releases sperm. One of the sperm fuses with the egg, and the other dies. As a result of fertilization, a diploid zygote is formed, and from it an embryo arises.
The mature embryo consists of a pendulum, a primary root, a stalk and cotyledons. Suspension formation is one of the distinctive features of all conifers. In parallel with the development of the embryo, the integument of the ovule is transformed into the seed coat. The entire ovule turns into a seed. After the seeds ripen, the scales of the cones separate and the seeds spill out. A mature seed has a transparent wing.
The subclass Conifers includes seven orders, two of them are extinct. Currently, there are the following: Araucariaceae, Nogocarpaceae, Pine, Cypress and Yew. The last three orders are the most common.
Order Pine(Pinales) is represented by one family - Pine (Pinaceae). There are 11 genera and about 260 species in this family. The largest genera are Pine (Pinus), Spruce (Picea), Fir (Abies) and Larch (Larix).
The largest in this family is the genus Pine, which includes about 100 species. Scots pine, whose needles are collected in pairs, is widespread in our country. In the Asian part of the country, Siberian pine (the so-called “ Siberian cedar"), in which the needles are collected in bunches of five. Siberian pine produces valuable wood and edible seeds - pine nuts.
The genus Spruce includes about 50 species living in the Northern Hemisphere. These are tall slender trees. Characteristic of spruces pyramidal shape crowns The needles are tetrahedral, pointed at the end. In our country, the two most common species are: Norway spruce (Picea abies) and Siberian spruce (Picea obovata).
The Fir genus includes 40 species living in the Northern Hemisphere. These are the big ones tall trees. They are similar in appearance to spruce, but their needles are flat, soft, with two stripes of stomata on the underside. Siberian fir (Abies sibirica) is widespread in Russia. It grows mainly in southern regions Western Siberia and the northeast of the European part of the country.
The Larch genus is represented by 15 species that live in the Northern Hemisphere. These are large, straight-trunked trees that shed their needles in the winter. Larch needles are soft and flat. They are located in bunches on short shoots and singly on elongated shoots. In our country, the most common species are Siberian larch (Larix sibirica) and Dahurian larch (Larix dahurica).
Order Cypress(Cupressales) is represented by two families. The Taxodiaceae family currently includes 10 genera and 14 species. Modern taxodiaceae are large trees, less often shrubs. Among them, we should mention the sequojadendron giganteum, or “mammoth tree” - one of the largest and longest-living plants in the world. Taxodium distichum is also interesting. It grows along river banks and swamps in southeastern North America. In this tree, horizontal roots form vertical outgrowths of a conical or bottle-shaped form - respiratory roots up to 0.5 m high.
The Cypress family (Cupressaceae) includes 19 genera and about 130 species, widely distributed in the Southern and Northern Hemispheres. Cypress - evergreen shrubs and trees. Their leaves are scale-like or needle-shaped, small, arranged oppositely or in whorls of three, rarely four.
The genera Cypress and Juniper contain quite a few species (20 and 55 species, respectively). Types of cypress are monoecious evergreen trees with a pyramidal or spreading crown, less often shrubs. In culture, the most famous is the evergreen pyramidal cypress. The Juniper genus is represented by small evergreen trees or shrubs, sometimes creeping. Leaves are needle-shaped or scale-shaped. In junipers, after fertilization, the scales of megasporophylls become fleshy and grow together, forming the so-called “coneberry.” Junipers are widespread. They are light-loving, drought-resistant, frost-resistant and undemanding to soil conditions.
Order Yew(Taxales) includes evergreen trees and shrubs from two families, 6 genera and 26 species. The most famous genus is Tiss; it is represented by 8 species. In our country, the most common yew, or common yew (Taxus baccata), has flat needles. This tree has hard and heavy wood that is almost resistant to rotting. The seeds are surrounded by a bright red fleshy covering, which makes them look like berries. Yew berry - the most shade tree of all conifers.
The higher ones include all terrestrial leafy plants that reproduce by spores or seeds. The modern vegetation cover of the Earth consists of higher plants, the common biological feature of which is autotrophic nutrition. In the process of long-term adaptive evolution of autotrophic plants in the air-ground habitat, the general structure of higher plants was developed, expressed in their morphological division into leaf-stem shoots and root systems and in the complex anatomical structure of their organs. In higher plants, adapted to life on land, special organs arise for the absorption of mineral solutions from the substrate - rhizoids (in the gametophyte) or root hairs (in the sporophyte). Assimilation carbon dioxide from the air is carried out by leaves, consisting mainly of chlorophyll-bearing cells. Made of conductive tissue that connects the two most important end apparatuses - the root hair and the green leaf cell, and The protostele of the primary stem and root was formed from the supporting tissue that ensures the plant’s stable position in the soil and in the air. The stem, with its branching and leaf arrangement, ensures the best placement of leaves in space, which achieves the most complete use of light energy, and the branching of the root - the effect of placing a huge suction surface of root hairs in a relatively small volume of soil. Primary higher plants inherited from their algae ancestors the highest form of the sexual process - oogamy and a two-phase development cycle, characterized by the alternation of two interdependent generations: the gametophyte, bearing the reproductive organs with gametes, and the sporophyte, bearing sporangia with spores. Only the sporophyte develops from the zygote, and the gametophyte from the spore. At the early stages, two directions in the evolution of higher plants appeared: 1) the gametophyte plays a predominant role in the life of the organism, 2) the predominant “adult” plant is the sporophyte. Modern higher plants are divided into the following types: 1) Bryophytes, 2) Ferns, 3) Gymnosperms, 4) Angiosperms, or Flowering plants.
The most important differences between higher and lower plants
The most common theory of the origin of higher plants associates them with green algae. This is explained by the fact that both algae and higher plants are characterized by the following characteristics: the main photosynthetic pigment is chlorophyll a; the main storage carbohydrate is starch, which is deposited in chloroplasts, and not in the cytoplasm, as in other photosynthetic eukaryotes; cellulose is an essential component of the cell wall; the presence of pyrenoids in the chloroplast matrix (not in all higher plants); formation of phragmoplast and cell wall during cell division (not in all higher plants). Both the majority of algae and higher plants are characterized by an alternation of generations: a diploid sporophyte and a haploid gametophyte.
The main differences between higher and lower plants:
Habitat: the lower ones have water, the higher ones have mostly dry land.
Development of various tissues in higher plants - conductive, mechanical, integumentary.
The presence of vegetative organs in higher plants - roots, leaves and stems - division of functions between different areas bodies: root - fixation and water-mineral nutrition, leaf - photosynthesis, stem - transport of substances (ascending and descending currents).
Higher plants have integumentary tissue—the epidermis—that performs protective functions.
Enhanced mechanical stability of the stem of higher plants due to a thick cell wall impregnated with lignin (provides rigidity to the cellulose skeleton of the cell).
Reproductive organs: in most lower plants they are unicellular, in higher plants they are multicellular. The cell walls of higher plants more reliably protect developing gametes and spores from drying out.
Higher plants appeared on land in the Silurian period in the form of rhyniophytes, primitive in structure. Finding themselves in a new air environment, rhinophytes gradually adapted to the unusual environment and over the course of many millions of years gave rise to a huge variety of terrestrial plants of various sizes and structural complexity.
One of the key events in the early stage of plant emergence on land was the appearance of spores with durable shells that made it possible to tolerate arid conditions. Spores of higher plants can be spread by the wind.
Higher plants have various tissues (conductive, mechanical, integumentary) and vegetative organs (stem, root, leaf). The conductive system ensures the movement of water and organic matter in land conditions. The conducting system of higher plants consists of xylem and phloem. Higher plants have protection from drying out in the form of a covering tissue - the epidermis and a water-insoluble cuticle or a plug formed during secondary thickening. Thickening the cell wall and impregnating it with lignin (giving rigidity to the cellulose skeleton of the cell wall) gave higher plants mechanical stability.
Higher plants (almost all) have multicellular organs of sexual reproduction. The reproductive organs of higher plants are formed in different generations: on the gametophyte (antheridia and archegonia) and on the sporophyte (sporangia).
Alternation of generations is characteristic of all higher land plants. During the life cycle (that is, the cycle from the zygote of one generation to the zygote of the next generation), one type of organism is replaced by another.
The haploid generation is called a gametophyte because it is capable of sexual reproduction and forms gametes in multicellular organs of sexual reproduction - antheridia (male motile gametes - sperm are formed) and archegonia (female immobile gametes - egg are formed). When the cell matures, the archegonium opens at the apex and fertilization occurs (fusion of one sperm with an egg). As a result, a diploid zygote is formed, from which a generation of diploid sporophyte grows. The sporophyte is capable of asexual reproduction with the formation of haploid spores. The successors give rise to a new gametophytic generation.
One of these two generations always predominates over the other and accounts for most of the life cycle. In the life cycle of mosses, the gametophyte predominates; in the cycle of holo- and angiosperms, the sporophyte predominates.
3. Evolution of gametangia and life cycles of higher plants. Works by V. Hoffmeister. Biological and evolutionary significance of heterospory
Higher plants probably inherited their life cycle - the alternation of sporophyte and gametophyte - from their algal ancestors. As is known, algae exhibit very different relationships between the diploid and haploid phases of the life cycle. But in the algal ancestor of higher plants, the diploid phase was probably more developed than the haploid phase. In this regard, it is of great interest that of the oldest and most primitive higher plants of the extinct group of rhiniophytes, only sporophytes have been reliably preserved in the fossil state. Most likely, this can be explained by the fact that their gametophytes were more tender and less developed. This is also characteristic of the vast majority of living plants. The only exceptions are bryophytes, in which the gametophyte predominates over the sporophyte.
The evolution of the life cycle of higher plants went in two opposite directions. In bryophytes, it was directed towards increasing the independence of the gametophyte and its gradual morphological division, the loss of independence of the sporophyte and its morphological simplification. The gametophyte became an independent, completely autotrophic phase of the life cycle of bryophytes, and the sporophyte was reduced to the level of a gametophyte organ. In all other higher plants, the sporophyte became an independent phase of the life cycle, and the gametophyte gradually became smaller and simpler during evolution. The maximum reduction of the gametophyte is associated with the separation of the sexes. Miniaturization and simplification of unisexual gametophytes occurred at a very accelerated pace. Gametophytes very quickly lost chlorophyll, and development was increasingly carried out at the expense of nutrients accumulated by the sporophyte.
The greatest reduction of the gametophyte is observed in seed plants. It is striking that among both lower and higher plants, all large and complex organisms are sporophytes (kelp, fucus, lepidodendron, sigillaria, calamites, tree ferns, gymnosperms and arboreal angiosperms).
Thus, everywhere around us, be it in the field or in the garden, in the forest, in the steppe or in the meadow, we see exclusively or almost exclusively only sporophytes. And only with difficulty and usually after a long search we find tiny gametophytes of ferns, mosses and horsetails on moist soil. Moreover, the gametophytes of many club mosses are underground and therefore extremely difficult to detect. And only liverworts and mosses are noticeable for their gametophytes, on which much weaker, simplified sporophytes develop, usually ending in one apical sporangium. And the gametophyte of any of the numerous flowering plants, like the gametophytes of conifers or other gymnosperms, can only be examined under a microscope.
Works by V. Hoffmeister.
Hofmeister obtained the most significant results in the field of comparative plant morphology. Described the development of the ovule and embryo sac (1849), the processes of fertilization and embryo development in many angiosperms. His work was published in 1851 Comparative studies growth, development and fruiting in higher secretagogue plants and seed formation in coniferous trees, the result of Hofmeister's research on the comparative embryology of archegonial plants (from bryophytes to pteridophytes and conifers). In it, he reported on his discovery - the presence of alternation of generations in these plants, asexual and sexual, and established family ties between spore and seed plants. These works, carried out 10 years before the emergence of the teachings of Charles Darwin, had great value for the development of Darwinism. Hoffmeister is the author of a number of works on plant physiology, mainly devoted to the study of the processes of water and nutrients entering through the roots.
Biological and evolutionary significance of heterospory
Heterospory is heterosporous, the formation of spores of various sizes in some higher plants (for example, aquatic ferns, Selaginella, etc.). Large spores - megaspores, or macrospores - give rise to female plants (throutlets) during germination, while small ones - microspores - produce male plants. In angiosperms, a microspore (a speck of dust), germinating, gives rise to a male prothallus - a pollen tube with a vegetative nucleus and two spermatozoa; The megaspore formed in the ovule grows into the female prothallus - the embryo sac.
Biological meaning:
—The desire for separation of the sexes, i.e. dioecy:
- division in time: protandry (moss mosses) - first developing on the gametophyte. male and then female. floor. gametes.
—protogyny
—physiological diversity.
The evolutionary significance of heterospory led to the emergence of the seed, and this allowed the seed. rast. completely lose dependence on external influences. environment and domination. on the globe.
Read also:
Difference between higher plants and algae.
Higher plants are inhabitants of the terrestrial-air environment, which is fundamentally different from the aquatic environment.
The land-air environment differs sharply from the water environment in gas composition. These environments also differ in humidity, temperature conditions, density, specific gravity, and the ability to change the strength and spectral composition of sunlight. The ecological conditions of the ground-air environment caused changes in the morphological and anatomical structure of the vegetative and reproductive organs of higher plants during the long process of evolution. This led to the development of adaptations to a terrestrial lifestyle in higher plants.
Higher plants, embryonic plants (Embryobionta, Embryophyta, from the Greek. Embryon - embryo and phyton - plant), coppice, leafy plants (Сormophyta, from the Greek Kormos - stem, phyton - plant), thalom plants (Telomophyta, Telomobionta, thalom - aboveground the axial cylindrical organ of ancient higher plants and phyta - plant) differ from lower plants (Thallophyta, from the Greek thallos - thallus, thalus and phyton - plant). Higher plants are complex differentiated multicellular organisms adapted to life in a terrestrial environment (with the exception of a few clearly secondary forms) with the correct alternation of two generations - sexual (gametophyte) and asexual (sporophyte). The organs of higher plants have a complex anatomical structure. The conducting system of the first land plants is represented by special tracheid cells, phloem elements, and in later groups - vessels and sieve-like tubes. Conducting elements are grouped into regular combinations - vascular-fibrous bundles. In higher plants, a central cylinder-stele appears. At first, the central cylinder is simple - pratastela (from the Greek Protos - simple, stela - column, column). Then more complex stelae appear: actynastela (from the Greek Actis - ray), plektastela (from the Greek Plectos - woven, twisted), siphonastela (from the Greek Siphon - tube), artrastela (from the Latin Arthrus - joints), dyktyyastela ( from the Greek diktyon - network), eustela (from the Greek eu - real), ataxtela (from the Greek atactos - chaotic) - the elements of the central cylinder of the meristel on the cross section of the stem are evenly located in its main parenchyma. A diagram of the evolution of stelae is shown in Figure 1.
Higher plants have a complex vocal apparatus. Under the conditions of terrestrial life, highly developed mechanical tissues arise in higher plants. The reproductive organs of higher plants are gametangia and sparangia. Multicellular (or gametangia are reduced). In perfect higher plants they were called anterydyav (male) and archigoniav (female). The zygote of higher plants turns into a typical cellular embryo. The reproductive organs of higher plants probably originated from multilocular gametangia, a type of modern chaetaphoraphyte green algae. Characteristic feature of higher plants is the alternation of generations in the development cycle - gametaphyte (sexual) and sparaphyte (asexual) and the corresponding change in nuclear phases (haploid and diploid). The transition from the haploid nuclear phase to the diploid phase occurs when an egg is fertilized by sperm or sperm. The transition from the diploid nuclear phase to the haploid phase occurs during the formation of spores from aspartic tissue - archespores through meiosis from a reduction in the number of chromosomes. A diagram of the general life cycle of a spore-bearing vascular plant is shown in Figure 2.
Origin of higher plants. The ancestors of higher plants were probably some kind of seaweed, in which, in connection with the transition to land, they developed special devices for water supply, to protect gametangia from drying out and to ensure the sexual process. An opinion has also been expressed about the emergence of higher plants from green shmatcellular algae with heteratrichal thalami such as modern chaetaphorans with multilocular gametangia. Such algae had an isomorphic alternation of generations in the development cycle. The origin of higher plants is also associated with the group of streptaphyta algae, close to the Kaleachaetes or Choraceae. Precise fossil remains of higher plants (rhinite, harnea, harneyaphyton, sporaganites, psilaphyte, etc.) are known from the Silurian (435-400 million years ago). From the moment they reached land, higher plants developed in two main directions and formed two large evolutionary branches - haploid and diploid. The haploid branch of the evolution of higher plants is represented by the department of bryophytes (Bryophyta). In the development cycle of mosses, the gametaphyte, the sexual generation (the plant itself), predominates, and the sparaphyte is reduced and presented to the sparagons in the form of a box on a stalk. The development of bryophytes proceeded from thalomic forms to phyllophytic forms. The second evolutionary branch of higher plants with a predominance of sparaphyte in the development cycle is represented by the remaining divisions of higher plants. Sparaphyte in terrestrial conditions turned out to be more adaptable and lively. This group of higher plants with a predominance of sparaphytes in their development cycle achieved the greatest success in conquering land. Sparaphyte reaches large sizes and has a complex internal and external structure; the gametaphyte of this group of higher plants, on the contrary, has suffered a reduction.
In more primitive higher plants - horsetail, moha, paparacepodaceae and others, some phases of development depend on water, without which active movement of spermatozoa is impossible. Significant moisture of the substrate and atmosphere is necessary for the existence of gametaphytes. In seed plants, as the most highly organized plants, adaptation to a terrestrial lifestyle is expressed in the independence of the sexual reproduction process from the droplet-liquid environment. The scheme of evolutionary changes in plants in the direction of increasing the size of asexual (2n) and reducing sexual (n) generations is shown in Figure 3.
Gradually, higher plants were improved and adapted to the diverse environmental conditions of life on Earth. Currently, there are over 300 thousand species of higher plants. They dominate the Earth, living from the Arctic regions to the equator, from the humid tropics to dry deserts. Higher plants form various types vegetation - forests, meadows, swamps, fill reservoirs. Many of them reach gigantic sizes (sequoias - up to 110 m or more); others are small, a few millimeters in size (duckweeds, some mosses, mosses). With all the great variety appearance higher plants retain a certain unity in structure. Higher plants are divided into 9 divisions: ryniaphytes, zosteraphylaphytes, bryophytes, derawesternaceae, psilotapadoba, horsetail-like, paparacepaphytes, gymnosperms and angiosperms (flowering). They are relatively easily linked to each other, which indicates the unity of their origin.
Description of higher plants. Their origin and characteristics
Place of higher plants in the organic world
Modern science about the organic world divides living organisms into two superkingdoms: prenuclear organisms (Procariota) and nuclear organisms (Eucariota). The superkingdom of prenuclear organisms is represented by one kingdom - shotguns (Mychota) with two subkingdoms: bacteria (Bacteriobionta) And cyanothea, or blue-green algae (Cyanobionta).
The superkingdom of nuclear organisms includes three kingdoms: animals (Animalia), mushrooms (Mycetalia, Fungi, or Mycota) and plants ( Vegetabilia, or plantae).
The animal kingdom is divided into two subkingdoms: protozoa and multicellular animals (Metazoa).
The mushroom kingdom is divided into two subkingdoms: lower fungi (Myxobionta) And higher fungi (Mycobionta).
The plant kingdom includes three subkingdoms: purple algae (Rhodobionta), true algae (Phycobionta) And higher plants (Embryobionta).
Thus, the subject of taxonomy of higher plants are higher plants, which are part of the subkingdom of higher plants, the kingdom of plants, and the superkingdom of nuclear organisms.
General characteristics of higher plants and their difference from algae
Higher plants are inhabitants of the terrestrial-air environment, which is fundamentally different from the aquatic environment.
Cells of higher plants:
a, b - meristematic cells; c - starch-bearing cell from storage parenchyma; g - epidermal cell; e - binuclear cell of the secretory layer of the pollen nest; e - cell of assimilative leaf tissue with chloroplasts; g - a segment of a sieve tube with a companion cell; h - stony cell; and - vessel segment.
Higher plants are leafy plants, many have roots. Based on these characteristics, in Latin they are called Cormophyta(from the Greek kormos - trunk, stem, phyton - plant) in contrast to algae - Thallophyta(from the Greek thallos - thallus, thallus, phyton - plant).
The organs of higher plants have complex structure. Their conducting system is represented by special cells - tracheids, as well as vessels and sieve tubes. Conducting elements are grouped into regular combinations - vascular-fibrous bundles. In higher plants, a central cylinder appears - a stele.
First, the central cylinder is simple - protostele (from the Greek protos - simple, stela - column, pillar). Then more complex steles appear: actinostele (from the Greek actis - ray), plectostele (from the Greek plectos - to twist, twist), siphonostele (from the Greek siphon - tube), arthrostele (from the Greek arthrus - jointed), dictyostele ( from Greek diktyon - network), eustela (from Greek eu - real), ataxostele (from Greek ataktos - disorderly).
Higher plants have a complex system of integumentary tissues (epiderm, periderm, crust), and a complex stomatal apparatus appears. Under the conditions of terrestrial and aerial life, powerfully developed mechanical tissues appear in higher plants.
The reproductive organs of higher plants - multicellular antheridia (male) and archegonia (female) - probably originated from multicellular gametangia in algae such as dictyota and ectocorpus (from brown algae).
A characteristic feature of higher plants is the alternation of generations in the development cycle - gametophyte (sexual) and sporophyte (asexual) and the corresponding change of nuclear favas (haploid and diploid). The transition from the haploid nuclear phase to the diploid phase occurs when an egg is fertilized by a spermatoid or sperm. Conversely, the transition from the diploid nuclear phase to the haploid phase occurs during the formation of spores from sporogenic tissue - archespory through meiosis with a reduction in the number of chromosomes.
Origin of higher plants
The haploid branch of the evolution of higher plants is represented by the bryophyte department ( Bryophyta)
In simpler forms (spore-bearing plants), the gametophyte still has an independent existence and is represented by an autotrophic or symbiotrophic growth ( Lycopodiophyta, equisetophyta, Polypodiophyta), and in heterosporous representatives of these departments it is significantly simplified and reduced. In more organized plants - seed plants - the gametophyte has lost independent method life and develops on the sporophyte, and in angiosperms (flowering plants) it is reduced to several cells.
Higher plants probably evolved from some kind of algae. This is evidenced by the fact that in the geological history of the plant world, higher plants were preceded by algae. The following facts also support this assumption: the similarity of the most ancient extinct group of higher plants - rhiniophytes - with algae, the very similar nature of their branching; similarity in the alternation of generations of higher plants and many algae; the presence of flagella and the ability for independent swimming in male germ cells of many higher plants; similarities in the structure and function of chloroplasts.
It is assumed that higher plants most likely originated from green algae, fresh or brackish water. They had multicellular gametangia, an isomorphic alternation of generations in the development cycle.
The first land plants found in fossil form were rhiniophytes (rhinia, hornea, horneophyton, sporogonytes, psilophyte, etc.).
After reaching land, higher plants developed in two main directions and formed two large evolutionary branches - haploid and diploid.
The haploid branch of the evolution of higher plants is represented by the bryophyte department (Bryophyta). In the development cycle of mosses, the gametophyte, the sexual generation (the plant itself), predominates, and the sporophyte, the asexual generation, is reduced and is represented by a sporogon in the form of a box on a stalk. The development of bryophytes went towards increasing independence of the gametophyte and its gradual morphological division, loss of independence of the sporophyte and its morphological taming. The gametophyte became an independent, completely autotrophic phase of the life cycle of bryophytes, and the sporophyte was reduced to the level of a gametophyte organ.
Mosses, as representatives of the haploid branch of the evolution of higher plants, turned out to be less viable and adapted to living conditions on Earth. Their distribution is associated with the presence of free drop-liquid water, necessary not only for growth processes, but also for the sexual process. This explains their ecological confinement to places where there is constant or periodic moisture.
The second evolutionary branch of higher plants is represented by all other higher plants.
The sporophyte in terrestrial conditions turned out to be more viable and adapted to a variety of environmental conditions. This group of plants conquered land more successfully. Their sporophyte is often large in size, complex internal and external structure. The gametophyte, on the contrary, has undergone simplification and reduction.
In simpler forms (spore-bearing plants), the gametophyte still has an independent existence and is represented by an autotrophic or symbiotrophic prothallus (Lycopodiophyta, Equisetophyta, Polypodiophyta), and in heterosporous representatives of these departments it is significantly simplified and reduced.
In more organized - seed plants - the gametophyte has lost its independent way of life and develops on the sporophyte, and in angiosperms (flowering plants) it is reduced to several cells.
Under the new conditions, there was a gradual increase in complexity of terrestrial plants with the predominance of the sporophyte in the development cycle. They gave rise to a number of independent groups (divisions) of plants adapted to various living conditions on land.
Currently, higher plants number over 300,000 species. They dominate the Earth, inhabiting it from the Arctic territories to the equator, from the humid tropics to dry deserts. They form various types of vegetation - forests, meadows, swamps, and fill water bodies. Many of them reach gigantic sizes (sequoiadendron - 132 m with a girth of 35 m, giant eucalyptus - 152 m (Flindt, 1992), rootless wolfia - 0.1-0.15 cm (Identifier of plants of Belarus, 1999).
With all the huge variety of appearance and internal structure all higher plants retain a certain unity in structure. Higher plants are divided into 9 divisions. However, they are relatively easily linked with each other, which indicates the unity of origin of higher plants.
Date of publication: 2015-02-17; Read: 2096 | Page copyright infringement
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General characteristics of the subkingdom of higher plants. Indicate the main departments in Russian. and lat. language. Describe the origin and main progressive features.
Includes the following existing divisions: bryophytes ( Bryophyta), lycophytes ( Lycopodiophyta), psilotoides ( Psilotophyta), horsetail ( equisetophyta), pteridophytes ( Polypodiophyta).
Spore-bearing plants appeared at the end of the Silurian period, more than 400 million years ago. The first representatives of the spores were Not large sizes and had a simple structure, but already in primitive plants differentiation into elementary organs was observed. The improvement of organs corresponded to the complication of internal structure and ontogenesis. In the life cycle there is an alternation of sexual and asexual ways reproduction and the associated alternation of generations. Asexual generation presented diploid sporophyte, sexual – haploid gametophyte.
On sporophyte are formed sporangia, within which haploid spores are formed as a result of meiotic division. These are small, single-celled formations lacking flagella. Plants that have all the same spores are called homosporous. More highly organized groups have two types of disputes: microspores(formed in microsporangia), megaspores (formed in megasporangia). These are heterosporous plants. During germination, spores are formed gametophyte.
The complete life cycle (from zygote to zygote) consists of gametophyte(period from spore to zygote) and sporophyte(the period from zygote to spore formation). In mosses, horsetails and ferns these phases are, as it were, separate physiologically independent organisms. At the mosses the gametophyte is an independent phase of the life cycle, and the sporophyte is reduced to its peculiar organ - sporogon(sporophyte lives on the gametophyte).
On gametophyte reproductive organs develop: archegonia And antheridia. IN archegonia, similar to a flask, eggs are formed, and in sac-like antheridia- spermatozoa. In homosporous plants the gametophytes are bisexual, while in heterosporous plants they are unisexual. Fertilization occurs only in the presence of water. When gametes merge, a new cell is formed - a zygote with a double set of chromosomes (2n).
Mosses. Give a general description (classification in Russian and Latin, the predominant generation, structural features of the gametophyte and sporophyte, habitat, role in the formation of vegetation).
Indicate representatives (in Russian and Latin), meaning.
The life cycle is dominated by the gametophyte. The sporophyte does not exist independently; it develops and is always located on the gametophyte. The sporophyte is a box where the sporangium develops, on a stalk connecting it with the gametophyte. Mosses reproduce by spores, and can also reproduce vegetatively - in separate parts of the body. The department is divided into three class: Anthocerotic, Liver and Leaf mosses. Gametophyte has dark green thallus, dichotomously branched. The top and bottom of the thallus are covered with epidermis, with numerous stomata. The thallus is attached to the substrate rhizoids. The thalli are dioecious, the organs of sexual reproduction develop on special vertical branches-supports. Male gametophytes have eight-lobed supports, on the upper side of which there are antheridia. On female gametophytes there are supports with star-shaped disks, on the underside of the rays the stars are located (neck down) archegonia. In the presence of water, sperm move, enter the archegonium and fuse with the egg. After fertilization, the zygote develops sporogon. Inside the capsule, as a result of meiosis, spores are formed. Under favorable conditions, the spores germinate and protonema develops from them in the form of a small filament, from the apical cell of which the Marchantia thallus develops.
Moss mosses. Give a general description (classification in Russian and Latin, the predominant generation, structural features of the gametophyte and sporophyte, habitat, role in the formation of vegetation). Indicate representatives (in Russian and Latin), meaning.
Creeping shoots of club moss reach up to 25 cm in height and more than 3 m in length. The stems are covered with spirally arranged lanceolate-linear small leaves. At the end of summer, two spore-bearing spikelets usually form on the side shoots. Each spikelet consists of an axis and small thin sporophylls– modified leaves, at the base of which are kidney-shaped sporangia. In sporangia after reduction cell division sporogenous tissue are formed of the same size, covered with a thick yellow shell, haploid disputes. They germinate after a dormant period in 3-8 years into bisexual shoots, which represent the sexual generation and live saprotrophic in the soil, in the form of a nodule. Rhizoids extend from the lower surface. Through them, the hyphae of the fungus grow into the growth, forming mycorrhiza. In symbiosis with the fungus, which provides nutrition, the shoot lives, devoid of chlorophyll and incapable of photosynthesis. The shoots are perennial, develop very slowly, and only after 6-15 years do archegonia and antheridia form on them. Fertilization occurs in the presence of water. After fertilization of the egg by a biflagellate sperm, a zygote is formed, which, without a resting period, grows into an embryo that develops into an adult plant. In official medicine, moss spores were used as baby powder and as a coating for pills. Shoots of the common ram are used to treat patients suffering from chronic alcoholism.
Horsetails. Give a general description (classification in Russian and Latin, the predominant generation, structural features of the gametophyte and sporophyte, habitat, role in the formation of vegetation). Indicate representatives (in Russian and Latin), meaning.
In all types of horsetail, the stems have a segmented structure with a pronounced alternation of nodes and internodes. The leaves are reduced to scales and arranged in whorls at the nodes. U horsetail(Equisetum arvense) The lateral branches of the rhizome serve as a place for the deposition of reserve substances, as well as organs of vegetative propagation. In spring, on ordinary or special spore-bearing stems, spikelets are formed, consisting of an axis that carries special structures that look like hexagonal scutes ( sporangiophores). The latter bear 6-8 sporangia. Spores are formed inside the sporangia, covered with a thick shell, equipped with hygroscopic ribbon-like outgrowths - elaters. Thanks to elaters spores stick together into clumps or flakes.
The shoots have the appearance of a small long-lobed green plate with rhizoids on the lower surface. Male prothellae are smaller than female ones and carry antheridia with multiflagellate spermatozoa along the edges of the lobes. Archegonia develop on the female shoots in the middle part. Fertilization occurs in the presence of water. From the zygote, the embryo of a new plant develops - a sporophyte.
Vegetative shoots of horsetail (E. arvense) in official medicine it is used: as a diuretic for edema due to heart failure; for diseases bladder and urinary tract; as a hemostatic agent for uterine bleeding; in some forms of tuberculosis.
Ferns. Give a general description (classification in Russian and Latin, the predominant generation, structural features of the gametophyte and sporophyte, habitat, role in the formation of vegetation). Indicate representatives (in Russian and Latin), meaning.
Adventitious roots and large leaves extend from the rhizome ( fronds), having a stem origin and growing at the top for a long time. Among the currently existing ferns there are: homosporous, so and heterosporous. In mid-summer, groups of sporangia appear on the underside of green leaves in the form of brown warts ( sori). The sori of many ferns are covered on top with a kind of blanket - indusium. Sporangia are formed on a special outgrowth of the leaf ( placenta). Spores. When ripe, they are carried by a current of air and, under favorable conditions, germinate, forming a heart-shaped green multicellular plate ( outgrowth), attached to the soil by rhizoids. The prothallus is the sexual generation of ferns (gametophyte). Antheridia (with sperm) and archegonia (with eggs) are formed on the underside of the prothallus. In the presence of water, sperm penetrate into the archegonia and fertilize the eggs. From the zygote, an embryo develops that has all the main organs (root, stem, leaf and a special organ - a stalk that attaches it to the shoot) From rhizomes male fern(Dryopteris filix-mas), a thick extract is obtained, which is an effective anthelmintic (tapeworms).
Give a general description of seed plants (classification in Russian and Latin, the main differences from higher spore plants). Describe the structure of the ovule and seed. Indicate the differences between a seed and a spore, and the evolutionary significance of the seed.
Does everyone know which plants are called higher? This type has its own characteristics. Today, higher plants include:
- Moss mosses.
- Ferns.
- Horsetails.
- Gymnosperms.
- Angiosperms.
There are more than 285 species of such plants. They are distinguished by a much higher organization. Their bodies contain shoot and root (except mosses).
Characteristics
Higher plants live on earth. This habitat is different from the aquatic environment.
Characteristics of higher plants:
- The body consists of tissues and organs.
- With the help of vegetative organs, nutrition and metabolic functions are carried out.
- Gymnosperms and angiosperms reproduce using seeds.
Most of the higher plants have roots, stems and leaves. Their organs are complexly built. This species has cells (tracheids), vessels, and their integumentary tissues form a complex system.
The main feature of higher plants is that they pass from the haploid phase to the diploid phase, and vice versa.
Origin of higher plants
All the signs of higher plants indicate that they may have evolved from algae. Extinct representatives belonging to the highest group are very similar to algae. They have a similar alternation of generations and many other characteristics.
There is a theory that higher plants appeared from or freshwater. Rhinophytes appeared first. When the plants moved to land, they began to develop rapidly. Mosses were not found to be as viable as they require water in the form of droplets to survive. Because of this, they appear in places where there is high humidity.
Today, plants have spread throughout the planet. They can be seen in the desert, tropics and cold areas. They form forests, swamps, meadows.
Despite the fact that when thinking about which plants are called higher, one can name thousands of options, they can still be combined into some groups.
Mosses
When figuring out which plants are called higher, we must not forget about mosses. There are about 10,000 species of them in nature. Outwardly it is small plant, its length does not exceed 5 cm.
Mosses do not bloom, they do not have a root or a conducting system. Reproduction occurs using spores. The haploid gametophyte predominates in the life cycle of mosses. This is a plant that lives for several years and may have outgrowths similar to roots. But the sporophyte of mosses does not live long, it dries out, has only a stalk, a capsule where spores mature. The structure of these representatives of wildlife is simple; they do not know how to take root.
Mosses play the following role in nature:
- They create a special biocenosis.
- The cover of moss absorbs radioactive substances and retains them.
- They regulate the water balance of landscapes by absorbing water.
- They protect the soil from erosion, which allows for even transfer of water flow.
- Some types of mosses are used for medicinal preparations.
- With the help of peat is formed.
Moss-shaped plants
In addition to mosses, there are other higher plants. The examples may be different, but they are all somewhat similar to each other. For example, mosses resemble mosses, but their evolution is more advanced, since these are vascular species. They consist of stems that are covered with small leaves. They have roots and vascular tissue through which nutrition occurs. In the presence of these components, mosses are very similar to ferns.
In the tropics, epiphytic mosses are distinguished. They hang from trees, creating a fringed appearance. Such plants have the same spores.
Some clubmoss plants are listed in the Red Book.
Psilote plants
This type of plant lives for more than one year. This includes 2 genera of representatives of the tropics. They have erect stems similar to rhizomes. But they have no real roots. The conducting system is located in the stem and consists of phloem and xylem. But water does not enter the leaf-shaped appendages of plants.
Photosynthesis occurs in the stems, and spores form on the branches, turning them into cylindrical branches.
Ferns
What plants are also called higher? These include ferns included in the vascular department. They are herbaceous and woody.
The body of the fern includes:
- Petiole.
- Leaf plates.
- Roots and shoots.
The fern leaves were called fronds. The stem is usually short, and fronds grow from the buds of the rhizome. They grow to large sizes and perform sporulation and photosynthesis.
The life cycle alternates between sporophyte and gametophyte. There are some theories that suggest that ferns evolved from mosses. Although there are scientists who believe that many higher plants originated from psilophytes.
Many types of ferns are food for animals, and some are poisonous. Despite this, such plants are used in medicine.
Equisetaceae
Higher plants also include horsetails. They consist of segments and nodes, which distinguishes them from other plants of a higher species. Horsetail representatives resemble some conifers and algae.
This is a kind of representative of living nature. They have vegetative characteristics similar to cereals. The length of the stems can be several centimeters, and sometimes grows up to several meters.
Gymnosperms
Gymnosperms are also distinguished from higher plants. Today there are few types of them. Despite this, various scientists have argued that angiosperms evolved from gymnosperms. This is evidenced by various plant remains found. DNA studies were carried out, after which some scientists came up with theories that this species belongs to a monophyletic group. They are also divided into many classes and departments.
Angiosperms
These plants are also called flowering plants. They are classified as the highest kind. They differ from other representatives by the presence of a flower, which serves for reproduction. They have a feature - double fertilization.
The flower attracts pollination agents. The walls of the ovary grow, change, and turn into a fruit. This occurs if fertilization has occurred.
So, there are different higher plants. Examples of them can be listed for a long time, but they were all disbanded into certain groups.
The appearance of higher plants marked a new era of life on the planet. Their occurrence is associated with geological changes in the structure of continents and the need to adapt to the characteristics of life outside of water.
The diversity of living conditions on Earth contributes to the formation of many forms of existence of living organisms.
Higher plants - definition, structure, characteristics and characteristics
Multicellular terrestrial plants that are capable of using light in the process of life, possessing developed organs and tissues, and characterized by alternating types of reproduction are called higher.
Development took place in an effort to adapt to terrestrial existence.
The result was transformations in the structure:
- roots that absorb water and minerals, and also strengthen the plant in the soil;
- leaves capable of synthesizing organic substances from inorganic ones;
- stems - conduct organic matter and water.
Land plants are characterized by alternation of generations and autotrophic nutrition.
Origin of higher spore plants
The theory states that the ancestors of land plants - streptophyta, were forced due to geological changes to adapt to other living conditions. What was important was that only the fittest algae survived.
Transitional forms developed a protective film, cutin, which was deposited on the surface. The formation of a film in large quantities interfered with gas exchange, causing the plant to die. In organisms whose cutin was formed moderately, an epidermis with stomata was formed - a complex tissue that protects against drying out and also does not interfere with gas exchange.
The appearance of the epidermis prevented the absorption of water throughout the body, thereby promoting the formation of single-cell filaments - rhizoids. The result of the development process was the formation of a more complex system - roots.
Lighting on land significantly exceeds the same indicator in water, due to this the number and size of photosynthetic organs - leaves - have increased significantly. The distribution of substances formed during photosynthesis and water absorbed by the roots is carried out by the conducting organ - the stem.
The rapid increase in species and the spread of higher organisms is explained by the development of vegetative organs and changes reproductive system, which, under terrestrial conditions, must have reliable protection.
The reproductive multicellular organs of land plants - gametangia and sporangia - have a shell of living cells that protects the spores from drying out.
How do higher plants differ from lower ones?
Let's list the main ones:
- The tissues and organs that make up plants have a complex multicellular structure.
- The habitat is mostly dry land.
- During development, there is an alternation of generations - gametophyte and sporophyte.
- The spore is protected by a hard multicellular membrane.
Divisions of higher plants
According to the classification, the subkingdom of higher plants includes 9 divisions.
Representatives of the first three divisions completely died out. The remaining six make up living organisms.
Rhiniophytes
The first higher plants that gave rise to other divisions are Rhiniophytes or Rhiniaceae. They are characterized by a primitive herbaceous appearance, reaching a height of 60 cm. They had the simplest structure. There were no real leaves and roots; instead of roots there was a rivomoid organ, from which rivoids extended downwards, and stems extended upwards.
Photosynthesis was carried out by a stem that branched mainly into two shoots. Sporangia attached to the axes, and spores developed within them.
The presence of integumentary tissues, as well as stomata, indicates that representatives of the department grew on land. The most ancient representative of the department is considered to be Cooksonia.
Zosterophyllophytes
They have much in common with rhinophytes. Some scientists believe that Zosterophyllophytes gave rise to the Lycophytes. They differ in that they had an erect stem covered with a thick layer of cuticle.
Sporangia, collected in spike-shaped formations, have a short stalk, as well as identical spores. A representative is Goslinglia, it has no roots, and the stems have branches with twisted tops.
Bryophytes
A peculiarity is the predominance of the haploid phase (sexual generation); the diploid phase is poorly developed. For the sexual process of mosses, a moist environment is required, so they must grow in low-lying, swampy places, which is facilitated by their small size.
The main differences between bryophytes and other divisions:
- low lighting is sufficient for the formation of organic matter;
- water is absorbed by the entire body;
- the ability to grow on nutrient-poor soils and assume a state of suspended animation for a long period. All this ensures competitiveness in comparison with other representatives of departments.
Bryophytes are divided into three classes:
- Hepatic class. Gametophytes are characterized by a dorsinventral structure. The leaves are always single-layered, the rhizoids are unicellular. They grow in the tropics, entangling the soil, trunks, and leaves of trees in a continuous carpet. These include small Blassia (Blassia pusilla).
- Class Antocerotaceae. At the edges of the rosette-shaped lamellar thalli there are meristematic cells that form lobes that overlap each other and give the thallus a curly appearance. The most common is the genus Antoceros.
- Moss class. They are characterized by the presence of leafy shoots of radial symmetry. Rhizoids are located on leaves and stems - always multicellular. Most mosses grow in northern and temperate latitudes. A bright representative are sphagnum, their types differ not only in structure, but also in their association with natural conditions.
Moss-moss
Herbaceous forms of lycophytes can still be found today. They have shoots with small leaves and roots.
The leaves represent a whole leaf blade with an expanded pad-shaped base. They are divided into two classes - Moss-moss and Half-moss.
Psilotoides
Psilotophyta are represented by only one family - Psilotaceae. There are no roots, so they often grow on other trees. They can be found both on soils rich in organic matter and on the rocks of tropical forests. Water must be involved in the fertilization process.
One of the representatives is Psilot naked - a decorative fern. It got its name due to the lack of leaves. Grows at the base of palm trunks or humus soils. Reproduces by spores.
Horsetails
The department is divided into two classes - Sphenophyllaceae and Equisetaceae.
A prominent representative is horsetail, a perennial herbaceous plant with roots. Serves as an indicator of acidic soils.
The stems are divided into internodes, from which poorly developed, dark, clove-like leaves emerge. The spores are located in the spore-bearing spikelet. Reproduction occurs when high humidity: rain or heavy dew.
Ferns
Perennial herbaceous, less often tree-like plants. They are characterized by macrophyllia - powerfully developed leaves of relatively short length. Their large leaves (fronds) are whole or strongly dissected, twisted like a snail in the bud.
In most ferns, leaves perform two functions - photosynthesis and sporulation. They are distributed throughout the globe, but the maximum diversity of species is found in the tropics.
The department has five classes: Cladoxyleaaceae, Zygopteriaceae, Uzhovniaceae, Marattiaceae, and Polypodiaceae.
Gymnosperms
Modern biology includes four classes: Cycadaceae, Ginkgoaceae, Conifers and Gnetaceae. In ancient times, they included two more, already extinct, classes: Seed ferns and Bennettitaceae.
Reproduction of gymnosperms is carried out by seeds - multicellular organs containing the embryo rudiment, endosperm and multilayered skin. They are the most highly organized department in their morphological characteristics, approaching the angiosperm department.
Kokha Pine (Crimea)
Typical representatives of our country are spruce and pine.
Conclusion
The subkingdom of higher plants has come a long way in the process of its evolution. In the most developed representatives you can see a flower, a seed, a fruit. All changes in the body occurred in order to gain a foothold on land: the appearance of roots, leaves, and the improvement of the method of reproduction.
Only higher plants are capable of producing organic matter from inorganic matter.