Among the diaspores adapted to be transported by the wind, mention should be made of those equipped with flylets made of hairs.
The number of species having such seeds or fruits is extremely large, but the forms of the flights are not as diverse as the forms of devices for air transportation, which we have already considered. The main thing in the structure of flies is possible higher magnification surface, allowing to reduce the speed of falling fruits or seeds in the air. The center of gravity of the fruit or seed is always at the bottom, so the flight is the same as flying with a parachute.
The fly formed by a tassel-like tuft of hairs is called a “crest.” Such volatiles are present in the fruits of many cereals, for example, common reed (Phragmites communis), as well as representatives of the sedge family, for example, cotton grass (Eriophorum), but above all, most plants from the family Asteraceae (Compositae, = Aste-raceae). Let us name only the species-rich genera: hawkweed (Cr?pis), ragwort (Cirsium) and thistle (Carduus). The seeds of many plants, such as willows (Salix), poplars ( Populus) and fireweed (Epilobium). The seeds of many representatives of the families of swallowtails (Asclepiadaceae), bromeliads (Bromeliaceae) and some others are also equipped with tufts.
In their structure, umbrella-shaped flaps differ relatively little from crests; the fly itself looks like an umbrella with a saucer-shaped dome and a relatively long rod. The fruits of many Asteraceae have such volatiles, in particular the already mentioned dandelion (Taraxacum officinale), species of goat grass (Scorzonera) and salsify (Tragopogon). Many members of the teasel (Dipsacaceae) and valerian (Valerianaceae) families also have fruits with umbrella-shaped flaps, and seeds with the same type of flight adaptations are found among species of the genus Strophanthus, important medicinal plants. Tufts and umbrella-shaped flaps provide highest degree effective distribution of fruits or seeds through the air; such fruits and seeds are even called “parachute landings” land plants" Let us mention once again the territory near Berlin from which the turf was removed, which made it possible to trace the settlement of plants again. Here, among the species discovered in the first years, at least 86^0 were anemochores. And among the latter there were approximately equal numbers of species that reproduce by tiny, wind-borne seeds, and species that have fruits or seeds with tufts or umbrella-shaped flaps. During the colonization of plants on the island of Krakatoa, the vegetation cover of which was completely destroyed as a result of the volcanic eruption in 1883, a similar picture was observed: all the plants that grew there in the first years after the eruption were anemochores, and most of them reproduced by tiny seeds. In second place were plants that produce fruits and seeds with flakes. Consequently, the diasporas had to travel a distance of at least 40 km.
Wind, wind! You are powerful
You are chasing flocks of clouds.
You disturb the blue sea
Everywhere you breathe in the open air...
A. S. Pushkin
You scatter pollen on trees and grasses, you scatter their seeds throughout the world.
In fact, what would happen if there was no wind? What would happen if all the seeds ripened on the plant fell right there, near the mother? It's not hard to imagine. They would smother each other upon germination. There wouldn't be enough room for all of them. Therefore, mature seeds scatter as far as possible from the mother plant and from each other.
This is where the wind comes to the rescue. He is always and everywhere ready to serve. The direction and speed of the wind are constantly changing. It blows now to the right, now to the left, sometimes soars up or spreads along the ground itself. Air masses never remain motionless. Even if it seems to us that the day is completely windless, at this time air currents are blowing around us in various directions, sometimes stronger, sometimes weaker.
The seeds and fruits of many plants have many adaptations in order to fly away “on the wings of the wind.”
The simplest of devices is the lightness of the seed. In orchids, heather, and gentian, the seeds are so small and extremely light that they float freely in the air and are transported over long distances even by a weak, barely perceptible breeze. The fruit capsule of some orchids has an interesting structure: inside it there are the finest hairs. For the time being, they are modestly pressed against the wall of the fetus. But one day, in dry weather, the capsule opens, the dried hairs straighten and throw weightless dust-like seeds into the air. There are even microscopic bubbles on the surface of some of these seeds that help them rise higher.
However, not all plants have small and light seeds. After all, the seed contains the embryo - the future new plant. The larger the seed, the more nutrients it contains for the growing embryo and small seedling, the faster the young individual will grow. So nature has made all sorts of flying machines for seeds. Yes, so witty that man could not come up with anything better, but only copied them from nature. Who made the first parachute? Who invented the propeller? Who designed the glider and the helicopter? Nature, nature and more nature!
Anyone who doesn't believe it should check it out. You don't have to go far. Just look closely at the fluffy ball of a dandelion. This is truly a geometrically regular ball, consisting of many small oblong fruits - achenes, each of which is crowned with a hairy tuft on a long stalk. By the way, what do these balls look like when it rains or late in the evening? Did not notice? Yes, there are none at all! In inclement weather, the achenes with parachutes are securely packed in a basket wrapper and lie there quietly until the new sun shines. Dandelion baskets open only in dry weather. The hairs straighten out in the warm air, the former home for the achenes with tufts becomes cramped, and they again form a transparent ball, ready to disintegrate at the slightest breath. So the parachute with the fruit came off the balloon, rose above the meadow and stopped, swaying slightly, as if waiting for a fair wind.
And the breeze came, flattened the hairs, turning the parachute into a sail, and carried the fruit into the distance. But how long can you fly? And where? The native meadow was left behind. The crest of a parachute absorbs moisture very well. And no matter how dry the air is, there is always the smallest amount of water droplets in it. Along the way, these invisible droplets settle on the hairs of the tuft, the hairs stick together and... the parachute ceases to be a parachute. The fruit slowly dives down.
The flying adaptations of many other herbs are arranged in approximately the same way - thistle, thistle, fireweed.
In places where poplars grow, blizzards rage every summer on windy days: light white flakes fly in the air, land on the shoulders of passers-by, and smoothly fall to the ground. Not far from the treetops, a continuous cover lies a huge amount of soft fluff, similar to loose lumps of cotton wool. These are poplar seeds huddled together in heaps, entangled in thin hairs. Gusts of wind drive the seeds along the surface of the soil, lift them into the air and carry them away from the parental shelter.
If you are observant, you will have noticed that the fruits or seeds of tree species are most often equipped not with parachutes, but with wings of various shapes and sizes. Why? Because if they had hairs, they would get tangled in the dense crowns of trees. And any wing as a flying device will be most effective precisely when the seed falls from a great height. For the movement of seeds in the air, both the size of the wing and its massiveness, design, and outline are important. Their entire fate will depend on what wing nature has bestowed on the seeds of a tree. Some seeds have a soaring flight, others have a gliding flight, and others have a screw flight. The duration and range of flight of a fruit or seed are determined solely by the structure of its aircraft - it is either an airplane or a helicopter. For example, maple lionfish, falling even from a small height, always rotate very quickly. It turns out air propeller, carrying away the fruit with a fair wind. The rotational movement of the fetus increases the duration of the flight and its range.
Sometimes in winter, on the shiny clean snow around the trees, you can see many black dots. These are fruits and seeds prepared for a long journey. Maybe alder fruits, maybe pine or spruce seeds. Each seed has its own sail - a small wing. The drifting snow will blow and the seeds, dispersing each other, will roll along the smooth crust. One seed will glide ten meters, another a hundred, some can roll ten kilometers or even further.
Some small bubbles glide along the smooth surface of sand in the deserts of Central Asia like toy balloons. These are air-inflated sacs, each of which contains a swollen sedge seed. Such a bubble can roll far! The desert is smooth as a table. True, the ridges of loose sand, rolled by the wind, strive to fill the bubble. But the stronger the wind blows, the faster the aerostat flies across the sand, outpacing the heavy sand waves.
But there was some large, shaggy, spherical object rolling along the sand, like a coil of barbed wire. This can be a dried katran inflorescence, or a stem of a bug or solyanka. So semi-desert and desert plants During fruiting, they dry out, come off the soil and roll over the earth's surface with the wind, gradually dispersing the seeds. They are called tumbleweeds.
The dispersal of the seeds of the queen of our ponds - the white water lily - is helped together by wind and water. Each seed of this plant is surrounded by a sac filled with air. Driven by the wind, the seed floats in a bag, like in a rubber inflatable boat. But the boat is defective: somewhere in it there is an invisible hole that gradually releases all the air. The heavy seed falls to the bottom.
The heavy seeds of the yellow egg capsule growing in the same pond are immersed in abundant mucus containing microscopic air bubbles. A lump of mucus with seeds floats in the water for quite a long time, gradually becoming soggy. After this, the seeds are immersed in muddy soil.
Seeds and especially fruits different plants vary enormously in shape, size and scope of travel. If a strawberry fruit (“seed” stuck into the sweet pulp of the berry) is no larger than a grain of sand, then a half-meter nut of the Seychelles palm tree, growing on some islands of the Indian Ocean, would be difficult for even a strong person to lift. If the seeds of water lilies and egg capsules float only on the surface of a pond or shallow lake, then the ocean serves as a pool for the coconut.
The coconut palm is one of the most popular trees in the tropics. Slender and graceful, light and proud, she, slightly tilting her straight trunk towards the ocean, throws a fountain of huge feathery leaves high into the sky. Coconut tree blossoms all year round. And throughout the year, massive, round or oval smooth fruits gradually ripen. They are called "coconuts" (although from a botanical point of view they should be called drupes). The coconut hangs on the tree for a whole year until it ripens. Despite its large size and apparent massiveness, the fruit of a coconut palm will not drown - it is light, like a cork. Judge for yourself: in the center of the fruit there is liquid. It is surrounded by a fatty, loose mass. Fat, you know, is lighter than water. Then comes the woody shell, which is also light. Behind it is a fibrous case filled with air. This one is actually like a life belt. The case is protected by a dense green peel. And all the shells taken together are so strong, dense and durable that no matter how long the nut wanders across the sea, no matter how much the salty wave corrodes it, no matter how much it is thrown against the coastal stones, the nut will not get wet, will not rot, will not crack. Even after floating for many months, the coconut palm fruit is able to germinate on the sandy soil of the coast. And the fresh liquid contained inside the fruit is needed for the first time by the young sprout.
In the Crimea and the Caucasus there is a large, rigidly pubescent grass with large heart-shaped leaves. For its fruits that look like small cucumbers, this plant is called “ squirting cucumber" It’s not for nothing that it has such a sonorous name. Those with weak nerves should not approach this green creature. You can be scared. Even a light touch of a ripe fruit causes an amazing effect! In an instant, the cucumber is torn off the stalk, and a strong stream of mucus is ejected from the hole formed at the base of the fruit, carrying the seeds with it. A cucumber may “spit” in the face or on clothes. With such an artillery salvo, the seeds are thrown out quite far by the mother plant, sometimes at a distance of up to six meters.
No less expressive is impatience, which grows everywhere near human dwellings or along forest ravines, in damp, shady places. When yellow tubular flowers hang on the juicy, tender stems of impatiens, you can walk nearby without paying attention to it. But when long green pod-like fruits appear instead of flowers, you cannot pass by without noticing them. The slightest touch of these small pistols causes a real shot! The fact is that all five valves of the fetus, like springs, are drawn to the central column by thin threads. At the slightest shock, the delicate threads break and the valves forcefully twist inward. If the thickets of this plant are touched by the wind or disturbed by a passing person (or maybe a cat), the pods instantly explode, scattering seeds far around.
In approximately the same spirit, the opening of the elongated, pencil case-like fruits of the meadow geranium flower occurs. In the center of such a fruit there is a pentagonal column, along which five flaps are stretched. When the seeds ripen, the valves dry out, but unevenly. One day on a hot day, the lower edge of the sash, unable to withstand the tension, comes off and quickly curls into a spiral. In this case, the seed, having described a sharp arc, is thrown far to the side.
"Gunners" are not rare among our plants. During the ripening of pods, beans, and boxes, great tension arises in their walls surrounding the seeds. The flaps, bursting with a slight crack, act like springs, scattering seeds far around. Yellow acacia and gorse beans, violet and sour pods, and the fruits of many other plants are arranged in a similar way.
A ripe poppy box looks like a pepper shaker: it’s round, pot-bellied and with holes at the top. The poppy stem sways in the wind and sows poppy seeds from the box in all directions.
The tulip, bell and carnation boxes are arranged very similarly. They all prefer to act independently, without relying on the mercy of external forces.
The “independence” of the action of other fruits causes amazement. For example, a small and inconspicuous wild oat grain is capable of moving independently. At one end of it sticks out a long, bent, spiny spine. The lower knee of this spine has the ability to curl when the air is humidified. When twisted, the spine deviates to the side and rests its sharp end on the ground. When dry, the awn unwinds, lifts the grain and pushes it forward. Since the air humidity changes during the day, the spine gradually curls and unwinds. So, waddling from side to side, bouncing, the amazing grain slowly but stubbornly moves through the meadow or field until it hits some obstacle.
Endless feather grass steppe. Under the steppe wind, the silken strands of feather grass sway in waves, losing ripe grains one after another. Equipped with a long feathery awn, which serves as a glider for them, the grains are picked up by air currents and spread throughout the area. Peaceful, idyllic picture...
However, during the fruiting period of this cereal, cattle breeders try not to let their herds get close to it: having made their way through the wool, for example, of a sheep, the fruitlets can pierce the skin and penetrate its body, which will cause illness or even death of the animal.
The design of feather grass grain is amazingly perfect. The lower end of the fruit is turned into an awl. When the fruit dives down, its feathery spine, curled into a corkscrew and bent almost at a right angle, prevents it from falling on its side. The grain pierces the soil with its sharp end as it flies away. The awn is tightened with a screw only in dry weather. After dew or rain, getting wet and swollen, it begins to unwind. In this case, the upper end of the spine, bent at a right angle, clings to the grass and remains motionless. This means that the grain has to spin. It spins, gradually screwing into the soil. But then the weather changed. The sun dried up the moisture. The dried awn curls again. She could pull the grain back, but she fails: the entire surface of the fruit is covered with tiny hairs directed obliquely upward. These hairs hold the grain firmly in the soil.
He who cannot take with skill takes with numbers. How many seeds do you think ripen during the summer on one individual? One hundred? Five hundred? Thousand? Someone like. For example, on one copy weed Quinoa produces one hundred thousand seeds. But this is not a record yet. It is estimated that acorn grass, a quinoa-like garbage grass, produces five hundred thousand seeds, and mustard's relative garden weed reveler - seven hundred thirty thousand. Of course, almost all of these seeds, if they do not find suitable conditions, die (otherwise, any of these plants would not leave a place on Earth for anyone else). But one or two seeds germinate near the mother plant, and three or four will be accidentally carried away by a passer-by somewhere else and dropped there.
Man, without noticing it, spreads weeds all over the world to his detriment. Either he sows weed seeds together with the seeds of cultivated plants, or he transfers weed seeds from area to area on shoes or clothes.
Some weeds have additional accessories for distribution. For example, the seeds of the nondescript rye bromegrass, which is a weed in rye, have a deep groove running along the seed. It is very difficult to completely separate these seeds from the rye seeds - some percentage of them will certainly be sown in the field along with the rye. A. in the groove of the seed, the width of which is only two millimeters, hidden tiny seeds of other field weeds- sorrel, toritsy, daisies, which in shape and size exactly correspond to the size of the groove, as if specially adjusted to this size.
Thus, when sowing rye contaminated with fire, up to one and a half million seeds of various field weeds are introduced into the field per hectare of crop. It turns out that these weeds were also sown, albeit unwittingly, creating the same good conditions, as for rye.
Weeds have access to all types of transportation. They ride in cars, cross oceans and seas on ships, fly from country to country on airplanes. Sometimes green aliens spread so widely across territory that is foreign to them that they become, as it were, local plants. Can you really think that the fragrant chamomile that grows everywhere along our roads, in crops and in garbage places is a foreigner? And yet this is so. Some hundred and fifty years ago it was completely absent in Europe. And it would still not exist if someone had not accidentally brought it by ship from North America. Maybe they were carrying poorly winnowed flax seeds, or maybe wheat. It is impossible to establish this now. One way or another, at present, fragrant chamomile has spread not only throughout Europe, but has occupied Siberia and even penetrated into the Far East.
But what an anecdotal incident happened with the Canadian small petal. This plant, similar to a wild-growing small aster, has fruits equipped with fluffy flakes. Until 1655, it grew only in Canada. Some eccentric Canadian stuffed a stuffed bird with the fruits of the canadian petal and brought it to Paris as a gift for someone. In Paris, where the traveler arrived, the scarecrow was placed on the windowsill. The cat attacked the scarecrow, ripped it open, and the small petal seeds scattered in the wind. And what? Now this plant can be found in any European country.
Many similar examples could be given. So, our usual plantain, well known to us, our thistle, wild oats, tribulus and some other weeds were brought by Europeans to America and feel great there.
You see how weeds take advantage of human insufficient vigilance to spread. It is not for nothing that quarantine inspections have now been established in all countries, whose employees carefully ensure that neither diseased plants nor weed seeds are transported from country to country.
But the border is not a decree for a bear. And the border is not a hindrance for the squirrel. And the fox is not afraid of the border. In autumn, the unkempt fur of shaggy defectors is full of not only fleas, but also fruits and seeds with all sorts of hooks, hitches, hooks, spines, and bristles, thanks to which the fruits firmly cling to the animal’s fur. Remember the sticky fruit heads of burdock. The ones you love to throw around. If such a basket gets into your hair, it can be very difficult to unhook it. At least take scissors and cut it off along with your hair.
Our plants have relatively small spines and hooks on their fruits. And, for example, in South Africa, thorns the size of crow’s claws grow on the fruits of a plant called Harpagophyton. If an animal accidentally steps on such a fruit (and this often happens), then the sharp thorns will grip the hoof with a death grip, piercing into the meat. An unfortunate sheep or goat, losing its mind from pain, rushes headlong, not knowing where. It’s good if, during a frantic race, you manage to crush the fruit capsule in an hour or two. Sometimes several days pass before the box cracks and the seeds contained in it spill out onto the ground.
In the bushes, in the meadows in the thick grass, along the edges of the forests here and there throughout the summer, red strawberries glow with lights. At the beginning of autumn, among the yellow-green lacy leaves, orange bunches of rowan blaze, under the weight of which the branches bend. The berries of elderberry and viburnum, hawthorn and rose hips burn with a bright flame. Prickly raspberry trees attract with their crimson color. Large blue blueberries were on display. Feathered, four-legged, and even legless inhabitants of forests and meadows hunt for tasty, nutritious, juicy gifts of the earth. Trees, shrubs and herbs generously give them their harvest. The seeds inside any such juicy fruit, no matter what plant it belongs to, are always covered with durable and strong armor. The embryo inside the seed that has passed through the digestive tract of a bird or animal remains intact.
In our country, wild magnolia grows only in one of the regions of the Kuril Islands in mixed and deciduous forests. By autumn, ten-centimeter fruits develop on this large tree, resembling a cone with red scales. At the moment of ripening, bright raspberry seeds are exposed, covered with a fleshy case. This part of the seed coat serves as food for birds - nuthatches, woodpeckers, nutcrackers, jays - and is completely digested in their stomachs. On the contrary, the black seeds - magnolia seeds - are thrown out along with excrement. Such seeds are protected by a stony shell, and therefore their embryo remains intact. Their color blends in with the soil and does not attract anyone's attention. Birds do not touch fruits with unripe seeds and do not peck seeds from them.
Moreover, there are plants (for example, those belonging to the Araliaceae family and living in the Far East), whose seeds must certainly ripen in the stomach of some bird, otherwise they will not be able to germinate. The embryo of such seeds is very tiny and underdeveloped. He needs a heating pad to fully develop. And the bird’s stomach has a temperature of forty degrees. Only once in such an “oven” will the embryo develop fully, and a plant can subsequently grow from it.
For birds, two to four hours pass between eating food and throwing out its remains. During this time, the bird can fly far enough and deposit (along with droppings) these seeds somewhere in a secluded place.
By eating berries, achenes and nuts, the bear and wild boar, squirrel and hare, chipmunk and vole help spread the seeds. Even predators love to eat berries. For dessert. After a hearty meat dish. While chasing prey, they carry the seeds of the fruits they swallow far. Snails, too, to the best of their ability, contribute to this useful cause. Having treated themselves to strawberries or blueberries, which are great hunters, they carry the seeds of these berries in their stomachs for several tens of meters.
But not only juicy berries attract forest dwellers with their gastronomic qualities. Most dry seeds coniferous trees for a long time harsh winter feed many birds and small animals. All seeds are good - spruce, pine, and fir. However, none of them can compare in taste and nutritional value with large, sweet, fatty pine nuts. Siberian cedar(Siberian pine) is the main forest-forming species of the dark coniferous Siberian taiga. The kernel of pine nuts consists half of fatty oil. Nature deprived this tree of only one thing - it did not give its seeds the ability to fly. A pine nut cannot fly away from its mother tree even a meter on its own. The cones fall under the tree, the “nuts” scatter from them, and lie like brown beads under the shade of the cedar, waiting in the wings. As a rule, they don’t have to wait long - nutcrackers, squirrels, chipmunks, voles and other small rodents take fatty, sweet food into their pantries and hide it further and deeper. Many seeds will be eaten. But some of them will still survive. Either a squirrel will forget one of his pantries, or a chipmunk will drop a “nut” along the way.
Some of the seeds will remain under the cedar and will germinate in the spring. However, under the thick canopy of an old tree, not receiving enough light, young trees often dry out. Only in open places - in clearings, edges, clearings, strong cedar undergrowth appears from seeds lost by rodents.
But not all plants can boast delicious seeds or fruits. Some plants have fruits so small and hard that they have to adapt somehow to attract bird-spreaders. For example, in an American cereal with the affectionate name “cosmatic”, the spikelets containing inconspicuous grains imitate berries: their large rounded spikelet scales are painted black. The fatty pulp of these scales is very popular with fruit-eating birds.
In hot countries, in addition to birds, bats, monkeys and elephants distribute the seeds of sweet fruits. Monkeys are especially partial to the fruits of a tree called Brazil nut or “monkey pot.” The nuts on this tree are packaged in an original hard box the size of a football. At the lower end of the box there is a rounded door, which the monkeys deftly open to collect unripe nuts. When the fruit ripens, the door opens by itself and the nuts spill out onto the ground.
The fruits of the Nigerian button tree, similar to a huge button, grow along the entire trunk, tightly pressed to the bark. Their slimy, musty pulp is eaten with pleasure by elephants, carrying numerous small seeds throughout the jungle in their stomachs. And the ricinodendron tree, which grows in Southern Rhodesia, cannot exist without elephants at all, because its seeds germinate only after they have been in the stomach of an elephant.
Even turtles and snakes are absolutely necessary for the dispersal and germination of certain seeds. For example, a large herb grows on the Galapagos Islands - the perennial tomato. Tomato seeds germinate only if they pass through the digestive tract of a giant turtle, which loves to feast on tomatoes and takes these seeds all over the island.
In Africa, in the eastern regions of Uganda, a small viper lives. Curled into a ring, this snake lies motionless under a pisonia bush, similar to our honeysuckle. He lies there as if waiting for something. It stays for a day, it stays for two. Finally, a small bird fluttered onto the bush. Easily jumping from branch to branch, the bird suddenly fluttered desperately, shaking itself. It was the disturbed bush that showered her with a fountain of small sticky fruits that covered her wings and tail. Exhausted, tied “hands and feet,” the bird fell onto the grass and instantly became a victim of the viper. The snake had waited its time. That's why she lay here for so long. The fruits of the pisonia, having got into the stomach of the viper along with the unfortunate bird, will spread throughout the forest. It’s good for the pisonia and it’s good for the viper. Only the bird feels bad.
There are a huge number of ants living in the world. Many of them feed on plant seeds, carrying them over long distances. We'll talk about this in the next chapter.
Distribution of fruits and seeds (according to V. N. Korsunskaya)
At the end of April - beginning of May, walking along the bank of a river overgrown with willow trees, it is not difficult to get into a real “blizzard”. White flakes, like snow, fly from trees and bushes. Under trees, between bushes, they can be raked into piles with your feet. Small bodies of water are covered with a thick fluffy carpet so that the surface of the water is not visible. But is it snow?
Let's take a piece of fluff stuck to the sleeve of a dress and examine it through a magnifying glass. It is clearly visible that this is a seed surrounded by a tuft of long white hairs. The bundle plays the role of a parachute, with the help of which the seed is carried by the wind over long distances. The willow fruit is a capsule. When the willow capsules ripen, they burst and the seeds are sown from them. The parachutes of the seeds unfold and the seeds fly. This device increases the area of air resistance when falling. Therefore, seeds can float in the air for a long time and fly far from the mother plant. Poplar and aspen also have parachutes, tufts of hairs around the seeds. It also “snows” in the poplar alley, when the fruits open slightly with the first heat and seeds are sown from them.
The seeds and fruits of many weeds are equipped with tufts and tufts of hairs. Their flying devices are very diverse in their design.
In many plants, the achenes are placed in baskets, heads, and boxes. They are closed in wet weather. Bundles of hairs are compressed. As soon as the weather becomes drier, the baskets or heads with achenes open.
Hairs, crests - parachutes of achenes - quickly straighten and spread out. Thanks to this, the achenes end up at the edges of the baskets. The wind picks them up and the journey begins.
Hairs and fluff are by no means the only flying devices in plants. It is worth going to the forest at the height of leaf fall to observe the various ways in which fruits and seeds adapt to flight.
Usually late autumn You can see how, whirling, the seeds and fruits of most of the trees that form the upper canopy of the broad-leaved forest scatter in the wind. Sometimes the tree crowns are completely bare, and the fruits of linden, ash, and American maple still hang on bare branches. The exceptions are elm and aspen. Already at the very beginning of summer, the soil under the elms is completely strewn with the flat greenish winged achenes of these plants.
Most trees in the upper canopy of a broadleaf forest distribute their fruits by wind. The fruits of these trees have a small mass. For example, 50,000 aspen fruits weigh only 4 g. And there are plants whose fruits are many times lighter.
The winged fruits of birch can fly 1.6 km from the mother plant. Its seeds, which spill out of the cones in winter, can move significantly further away from the spruce tree. Their wings are like a sail. And the seeds slide along the crust. Like a boat under a sail, they rush with a fair wind far, far from their native forest. And maple lionfish travel over relatively short distances - only 0.09 km. Ash lionfish also fly away not far from their native tree - only 0.02 km.
Some plants' parachutes are composed of branched hairs that resemble a bird's feather - this further increases the sail surface of the parachute. In this regard, the fruits weed purple thistle may perhaps be in first place. One sow thistle plant produces up to 35,000 fruits. Each fruit has a dense white tuft of feathery hairs. Such fruits can fly with the wind over great distances.
Many of us have noticed that thistles and thistles often grow under the fence and along the hedge walls. The fence stopped the progress of the fruits of these plants. Many weeds grow along boundaries, ditches and ravines, where fruits also linger.
Of course, a great many fruits and seeds die in nature, but some of them can settle on the eaves of a balcony, the roof of a stone house, and an even smaller part will produce young seedlings. It may happen that a poplar tree will grow on the roof, or even groups of trees or thickets of fireweed will grow there.
In a number of plants, flying devices help not only to move seeds, but also to bury them in the ground, like a gimlet.
In the steppes, the wind picks up whole plants, breaking them at the root, and carries them, rolling them from place to place. Tumbleweeds - this is what people called the jumping dry plants driven by the wind. Rolling across the expanses of the steppe, jumping up, hitting the ground, bumping into ditches, hillocks and other obstacles, tumbleweeds scatter seeds over long distances.
Ants play a significant role in the distribution of fruits and seeds. Anyone who has been in the forest knows these forest inhabitants and their amazing structures well; I have, of course, seen more than once how ants drag seeds of various plants to their anthill, for example, celandine, corydalis, thyme, and fragrant violet.
Probably many people have encountered abundant thickets of celandine near anthills. The leaves of this plant are light green, delicate, deeply pinnate. Towards the top of the stem the leaves are smaller than the lower ones. The stem is covered with sparse protruding hairs and has golden-colored juice, which folk medicine remove warts. For this reason, celandine is also called warthog or jaundice. But there are ants in this medicinal plant What attracts people is not the tenderness of the foliage, not the golden flowers, not the fruits in the form of long pods, but the seeds with an appendage.
Celandine has black seeds with a large, fleshy white appendage. Ants readily eat these appendages. Because of them, ants drag celandine seeds, which are quite heavy for them, to their anthill. Very often, ant roads are strewn with celandine seeds with bitten off appendages. Ants will drag celandine seeds into the anthill, but do not eat them themselves. The appendages are separated from the seed by a dense skin. Under it, the seeds remain intact. The next year, the seeds germinate in the anthill, through its walls, and along the road to it.
In summer it is interesting to watch ants stealing seeds and fruits. Ants use their sensitive organs of smell and touch, located on their antennae, to search for seeds. In addition to the plants already mentioned, it can be hoofweed, willow-herb, coppice, goose onion. But almost always these are the seeds of early flowering plants, the fruits of which ripen no later than mid-summer. As autumn approaches, ants stop collecting seeds.
In nature, almost all animals can be direct or indirect distributors of seeds over long distances from the mother plant.
IT IS KNOWN
That the appearance of cherries in Europe is associated with the famous Roman commander Luculus. This happened in 64 BC. e. After Luculus's victories in Asia, his solemn entry into Rome took place. The commander's chariot was decorated with branches containing cherry fruits, which had long before been cultivated as a cultivated plant in Iran and Asia Minor.
In the age of technological progress, the seeds of many plants can “roam” on car tires and aircraft chassis, cross rivers and seas on barges and ships, and then germinate in a new place.
Hair-like appendages on fruits and seeds are the most widespread anemochoric adaptation.
It is characteristic of representatives of a wide variety of families. All kinds of tufts or “parachutes” of hairs are more often found on fruits than on seeds, but they are not uncommon for seeds either.
Hairs on seeds, as a rule, are single-celled formations, while on fruits they consist of many cells arranged in 2-3 rows.
A common property of all hair-like appendages is their hygroscopicity. Only in dry air do they straighten out and can serve as an aircraft; when moistened, the hairs fall off and immediately lose their parachute properties. This hygroscopicity of the hairs is of great importance not only during the flight of the primordia, but also during their release from boxes and baskets. Bolls and baskets containing seeds and fruits with hairs open only in dry weather. The hairs straighten out in the dry air, the former containers become cramped for the buds, which now form a loose mass rising above the edges of the boxes or baskets. In this position, the rudiments can be caught by gusts of wind.
The distribution of hairs on the surface of the rudiment, the size of the hairs, and their origin are extremely diverse.
By origin, several categories of hair-like formations can be distinguished: a) Outgrowths of seed coats (seeds of cotton and some types of kenaf), b) Outgrowths of exocarp (fruits of anemones), c) Outgrowths of anemones (seeds of willows and poplars), d) Outgrowths of flower scales (pearls) ). e) Outgrowths of the spikelet axis (reeds, reeds), f) Modified perianth (cattails), g) Modified calyx (valerians and, possibly, Asteraceae). We cannot reliably attribute all the numerous fruits with hair-like parachutes from the Asteraceae family to any of the listed categories, since the question of the nature of the tuft of the Asteraceae is still debatable. It is quite widely believed that the pappus of Asteraceae is a modified calyx (Cassini, Hoffmeister, Lund, etc.). Other authors believe that the calyx has grown to the ovary, so that the pappus is only the free edge of the calyx (Auguste de Candolle, Endlicher). Finally, others put forward the assumption that the crest is a trichome formation (Warming, Buchenau, Kozo-Polyansky). The discussion of this issue is presented in great detail in Small’s monograph, in which a special chapter is devoted to the crest. We will not go into a discussion of various hypotheses about the nature of the tuft of Asteraceae, since the origin of the hairs does not determine the flight properties of the rudiment, and therefore from an ecological point of view it is not so significant.
The aerodynamic properties of the rudiment depend on the distribution of hairs on its surface, the position of the pappus relative to the center of gravity of the fruit or seed, the structure of the hairs and their size relative to the size of the rudiment.
Based on the position of the hairs on the rudiment, we will distinguish three categories.
Hairs cover evenly the entire surface of the seed or fruit
The rudiments of this category are relatively rare. The most typical example is the cotton seed (Gossypium), which has long, dense hairs. In passing, we note that the length of cotton hairs has increased significantly under the influence of culture. The seeds of a number of species of kenaf (Hibiscus) are also equipped with a continuous hair coat.
Of the fruits that are evenly covered with hairs, we can name the nuts of the anemone and some other types of anemone.
In a number of pearl barley species, the flower scales are often equipped with long hairs. Particularly notable is the pearl barley, which inhabits the dry rocky slopes of the mountains of Southern Transcaucasia and Central Asia. The grains of this species are densely covered with flower scales, evenly covered with long hairs. The hairs are several times larger than the width of the grain and almost equal to its length.
The hairs sit in a bunch at the base of the bud
This category of rudiments is even less common than the previous one. The hairs here can be of very different origins, but they are always much larger than the size of the fruit or seed. The rudiments of this type themselves are very small.
Let's name the well-known seeds of willows (Satix) and poplars (Populus), the fruits of cattails (Turka) and reed grass (Calamagrostis), and the fruits of plane trees (Platanus orientalis).
Apparently, the fruits of cotton grass (Eriophorum) can be attributed to the same category of rudiments. The hairs develop here at the base of the fruit, but they do not sit in a bunch, but are arranged in two longitudinal rows, exceeding the length of the fruit several times.
In willows, hairs develop on the achene stalk at the very base of the seed. In aspen (Poputus tremula), for example, they are three times larger than the seed. As noted above, in cattails the perianth is transformed into hairs, which grow strongly by the time of fruiting. The mature fruit of the broadleaf cattail has a long spout at the top, three times the length of the fruit. A very long stalk develops at the base of the fruit, from which numerous hairs extend. The length of the hairs reaches 10 mm, while the length of the fruit is only 2-3 mm. The hairs of reed grass are outgrowths of the spikelet axis and are 1.5-2 times larger than the grain.
The elongated sycamore nuts bear at the base a thick tuft of hairs, which are almost equal in length to the fruit (without a style). Unlike other rudiments of this category, the sycamore nuts are too large and massive in comparison with the tuft; Obviously, they should be classified as hemianemochorous rudiments.
Hairs form a tuft at the top of the fruit or seed
The vast majority of rudiments with hair-like appendages fall into this category. Tufts develop both on seeds and, especially, on the top of fruits. Among the seeds with well-developed tufts are the seeds of fireweed (Epilobium), cottonweed (Aselepias), swallowweed (Antitoxicum) and others.
Tufts on fruits are characteristic of many Asteraceae and representatives of some other families.
The size of the crests varies greatly. Based on the nature of the hairs, a distinction is made between simple tufts and feathery ones. Feathery crests represent a more advanced aircraft, as they provide stronger resistance to air flow. The rudiments, equipped at the top with large feathery crests, are well adapted for soaring flight, since the center of gravity of the rudiment lies below the parachute. Pinnate tufts are found in valerian and such genera of Asteraceae as elecampane (Inula), grouse (Achyrophorus), thistle (Cirsium), kulbaba (Leontodon), bitterling (Picris), salsify (Tragopogon) and many others.
Particularly stable balance in the air is maintained by those rudiments in which the parachute is strongly elevated above the center of gravity. This is achieved by the presence of long outgrowths at the top of the fruit, the so-called “spouts”. The pappus, thus, is attached not to the very top of the fruit, but to the spout, which sometimes even exceeds the length of the achene. Achenes with spouts are quite common among Asteraceae; Here you can name pasnik, salsify, dandelions, lettuces and others.
The size of the hairs that form the pappus or evenly cover the rudiments varies greatly both in absolute values and relative to the size of the rudiment.
Tufts of simple hairs (cat's foot - Antennaria; thistle - Carduus; hawkweed - Hieracium, groundsel, swallowtail) significantly exceed the length of the achene, while pinnate tufts are almost equal to the length of the achene (grassroot, kulbaba, salsify).
In terms of the aerodynamic properties of the flying device, fruits or seeds with tufts at the top are more similar than other anemochoric rudiments to a real parachute.
Gliding, i.e. smooth lowering without rotation, is achieved by the fact that the center of gravity and the center of pressure are on the same vertical. The hairs on the fruits of salsify, dandelion and many other species form cones with the apex at the bottom, i.e. an inverted parachute. As Mordukhai-Boltovskoy points out, the crests of such rudiments can be called a Cocking parachute, with the only difference being that they are not of a rigid type, so they easily change their shape. The variability of the shape of the tufts in anemochoric primordia is important. adaptive value. With horizontal gusts of wind, the crests are flattened and turn into a sail, due to which the rudiments are carried away into the distance. When the wind dies down, the shape of the parachute is quickly restored, thanks to a special kind of adhesion of the hairs; Thus, in calm air the fall of the rudiments slows down and they glide again until new gusts of wind.
As for the outgrowth (“spout”), thanks to which the pappus rises above the rudiment, then, apparently, it (the outgrowth) not only creates a more stable equilibrium of the rudiment in the air, but also contributes to a more energetic separation of the fruit from the receptacle. The fruit is torn from the receptacle by the force of the wind acting from the side on the pappus. In this case, the place of attachment of the fetus can be likened to the point of rotation of the body. It is known from mechanics that the rotating effect of a force depends not only on the magnitude of the force, but also on the distance between the force and the point around which the body rotates, i.e., on the magnitude of the force arm. The spouts, which lift the pappus above the point of attachment of the rudiment, thus increase the shoulder, and, consequently, the moment of force that separates the rudiment from the receptacle.
However, the most detailed morphological and aerodynamic studies and descriptions of the aircraft of fruits and seeds still say nothing about the feasibility of all these devices. To solve this basic biological question, it is necessary to study the effectiveness of certain devices in action and their actual significance in the dispersal of species.
The effectiveness of devices and methods of spreading germs should be assessed in two ways: from the point of view of range and mass dispersal. We will return to the question of the effectiveness of dissemination; here we will only note that the mass dispersal of rudiments in one way or another is usually not taken into account, although it is of paramount importance in the dispersal of species.
So, let’s move on to assessing the effectiveness of hair parachutes, primarily from the point of view of the dispersion range of the rudiments equipped with them. In the literature one can very often find statements that in open spaces easily accessible to the wind (steppe, desert, etc.), there are a lot of anemochores, that they occupy the upper tiers of the grass stand and their primordia, equipped with various volatiles, are carried away in masses wind over very long distances. However, following these statements, as a rule, no factual data is provided. Our observations of the dispersal of anemochorous primordia, carried out in the Streletskaya steppe in the summer of 1948 and 1949, force us to take a critical view of conventional ideas.
First of all, it is not true that anemochores always occupy the upper tiers of the grass stand. Among the most characteristic species of the Streletskaya steppe plateau, there are 40 anemochores (including hemianemochores). They are distributed among tiers as follows: first tier - 1; second - 12; third - 12; fourth - 15.
The height of the stems of anemochorous species, as a rule, does not exceed the height of the main mass of the grass stand (40-50 cm).
In terms of stem height, anemochoras are inferior to ballistae. Thus, for eight species of ballistas for which the stems were measured, the following figures were established: the smallest height of the stems (in cm) - 23.12; the highest - 114.72 and the average - 64.96. Corresponding figures for 8 species of anemochores: 29.64; 83.83 and 47.08 cm. If we take into account that the force of the wind fades from top to bottom, especially in dense grass, it becomes clear that the insignificant height of the stems of anemochorous species greatly reduces the effectiveness of the wind in dispersing their primordia.
The dispersal of the primordia by the wind occurs quite gradually. Even quite mature achenes with well-developed tufts are not immediately carried away from the open baskets by the first gust of wind. So, for example, with very strong wind it was impossible to notice the rapid seeding of open bitterling baskets with fully mature achenes. One might think that the shape of the infructescence and the degree of its streamlining play a big role. This conclusion suggests itself from observations of the infestation of eastern salsify. Its completely open basket (like other species of this genus) with mature achenes represents a geometrically regular ball. For half an hour, such a spherical basket was blown by fairly strong gusts of wind, but the achenes did not fly around. As soon as one of the achenes rose above the level of the others, it was blown away by the wind, followed by all the others within one minute.
We observed a gradual dispersion of fruits in the rough-leaved kulbaba. 10 fully opened baskets with mature achenes were noted. Their seeding lasted 5 days (from 9 to 14.VII), and from some baskets the achenes gradually flew off, and every day a decrease in the number of achenes in the basket could be noted. In other cases, the baskets lost all the achenes within one day - last day observations. There was no lull during the observation period; the wind reached strength from 2 to 9 m/sec. There was almost no precipitation. The wind strength here, as in the future, is given according to the weather station of the reserve where the observations were made. In grassy areas, the wind force is, of course, much weaker.
The distances to which anemochoric primordia are carried are largely determined by the height of the fruiting stems. If the height of the plant is lower than the level of the main mass of the herbage, then the primordia, even with very well developed shoots, are carried away over insignificant distances. You can verify this by observing the infestation of forest anemone. In the Streletskaya steppe, this species grows in clumps reaching 1-2 m in diameter. Its small nuts are densely covered with long, thin, twisted hairs and fall from the receptacle not individually, but in large “flakes.” These flakes, resembling loose lumps of cotton wool, remain hanging either on the stem and leaves of the mother plant, or very close to neighboring plants. Even single fruits in large quantities lie on the leaves of nearby plants. 5.VII mature nuts on 3 anemone specimens were colored various colors (alcohol solution eosin, methylene blue and gentian violet). The beginning of seeding of colored specimens was noted after 2 days. Colored fruitlets, both single and in small lumps, were found around the mother plants on different distances from 1 to 15 cm; the most distant nut is at a distance of 30 cm. After another 2 days, i.e. 9.VII at 15 o’clock, despite the fact that a strong wind was blowing all the time in the morning, the colonization of colored specimens remained unchanged.
The seeds of the medicinal swallowtail also fly over short distances, although they are equipped with well-developed tufts, 5 times longer than the light flat seeds. The stems of the swallowtail are weak, somewhat lodging. The fruits are located over a considerable distance and the lower ones are at a height of 13 and even 10 cm above the soil level, and the uppermost ones are at a height of 52-61 cm. The number of seeds in a leaflet varies from 7 to 38, more often from 14 to 21 and on average (out of 100 counts) - 18.7.
Seeds are carried away by the wind only when they lie very loosely in the open fruits or even hang along the edge of the leaflet, caught by their tufts. But even in this case, the wind does not carry away the seed immediately, but fiddles with it for a long time (an hour or two or more). Flying out of the leaflet, the seeds often cling with their tufts to the mother or neighboring plants and, despite the strong wind that continuously shakes them, remain for a long time in their original places. Let us present some digital data characterizing the infestation of the swallowtail.
19.VII (1948) - a fruiting plant with one open leaflet (at a height of 25 cm), from which 6 seeds flew out. Of these, 3 seeds hung with tufts on the mother plant, and 3 others - on neighboring ones at a distance of 15-17 cm and at a height of 16-17 cm, i.e. below the level of the fruit. After 4 days on the same plant, one leaflet was completely seeded, the other just began to seed. At a distance of 50 cm from the plant in the grass stand, 29 seeds were found. (There were no other specimens of this species nearby.)
26.VII - 4 specimens with seeding fruits. On the plants themselves and next to them there are many seeds with fluffy tufts, and sometimes only tufts torn from the seeds; the distance from the departure of seeds or tufts is 10-30 cm. A day later, one of the observed plants, despite the strong wind, retained all the seeds in the same position as the day before. A group of seeds was found at a distance of 50 cm and single ones at a distance of 1-2 m.
8.VIII - 2 seeded specimens. On them, 1 leaflet is empty, the other 2 contain 18 seeds. 48 seeds were found at a distance of 30-40 cm from the plants; 90-100 cm - 3 seeds. The wind force on August 7th reached 20 m/sec, and on August 8th - 9 m/sec.
Our further observations of the swallowtail gave the same results. They allow us to conclude that the bulk of its seeds remain close to the mother plants. The farthest drift of single seeds reached 7.5 and 9 m. Of course, some seeds fly to longer distances, but it must be taken into account that puny or underdeveloped seeds, which are least likely to ensure the spread of the species, are carried farthest.
In anemochoric plants with taller stems, the primordia disperse over long distances. Thus, in Jacob's godson (height 65 cm), single achenes fly up to a distance of 3 m even in a weak wind; in the eastern salsify with a stem height of 54 cm, some achenes are carried away 1-1.8 m.
As is known, in some Asteraceae the tufts fall off very easily, so that a flying achene, encountering some obstacle, almost always falls off, and the tuft either remains hanging, caught on something, or is carried away by the wind. In the vast majority of cases, the tufts that float high in the air and disappear from view do not carry achenes with them.
Observing the seeding of thistles, you can notice that sometimes even only tufts without achenes fly out of the basket. Near one fruiting plant, we found on the soil surface 14 achenes with tufts and 88 tufts alone, devoid of achenes.
The distances to which thistle achenes are carried are measured in a few meters. At least, this conclusion can be drawn based on our few observations. With fairly strong gusts of wind, the achenes flew out of the basket (at a height of 70 cm) and after some time settled in the grass at a distance of 0.8; 0.9; 2.3 and 4.1 m from the mother plant. In another case, from a basket at a height of 90 cm, the achenes flew 4.5 or (single) 9.4 m. Apparently, the achenes of Carduus are so heavy that despite the relatively huge crest, even in a strong wind they fly low above the ground, well below the height of the plant, gradually decreasing. When there was a very noticeable wind, a free tuft and an achene with a tuft were launched simultaneously from the height of the basket. The tuft very quickly overtakes the achene, rises up and disappears from view, and the tuft with the achene, having flown 1-2 m, begins to descend and settles at a distance of 5-6 m from the mother plant.
Some interesting digital data characterizing the distribution of thistle fruits are given by Leshchenko (1926). Two boards with an area of 7 square meters. m each were smeared with glue and placed on the ground at a distance of 85 and 850 m from the sow thistle foci. The achenes caught by the boards were counted 3 times a day for 6 days. During this period (from 14 to 20.VII) the wind reached strength from 1 to 6 points.
At a distance of 85 m, a total of 400 achenes were found on the board. At a distance of 850 m from the source, not a single rudiment was found on the board in the first 4 days, and only in the last two days 17 achenes arrived.
Leshchenko's observations showed that at night, as well as during the day, with winds of no more than one point, sow thistle rudiments do not occur.
In tree species, seeds equipped with tufts are capable of being carried over longer distances than the rudiments of herbaceous species, which is associated with the height of the rudiments on the mother plant. According to Brun's observations (1939), single aspen seedlings grew at a distance of 60 and even 450 m from the seed plants.
Nesterov (1950) points out that aspen seeds fly abundantly into cutting areas even at a distance of 1-2 km. Let us recall, however, the picture that is well known to everyone, when a huge number of poplar seeds lie in a continuous cover on the soil surface not far from the tree crowns. In urban conditions, where the soil is usually devoid of grass, one can often observe how gusts of wind drive seeds across the surface of the soil or lift them into the air and carry them over distances of several meters or tens of meters. It must be assumed that the transfer of seeds that have fallen to soil with more or less dense grass cover is much less effective. Seeds of willows growing along the banks of reservoirs sometimes fall into the water and in these cases can be carried by the wind along the surface of the water, but such a phenomenon should be considered as anemohydrochory.
When assessing the effectiveness of wind in dispersing primordia with tufts, it is necessary to take into account the high hygroscopicity of tufts. Being in the air for some time, they condense moisture on themselves, stick together and lose their properties as parachutes. This applies primarily to the tufts of Asteraceae.
Seeds with hairy pods are rare in tree species. In our nature, they are characteristic only of willows. Apparently, for trees that form more or less dense stands, pubescent buds are of little use, since they will be retained en masse by the crowns themselves. At a level of several meters, and even more so tens of meters above the ground, wing-shaped flying devices are more effective. And, indeed, the vast majority of anemochorous primordia of tree species belong to this category.
On the green roadside - a dandelion - a glorious warrior,
he captured everything around: the garden and grove, field, meadow...
While it’s quiet, he’s silent, but only the wind blows,
sends its parachute landing force into the ocean of air.
Daredevil skydivers climb into the grass, water, leaves,
and yesterday I saved two strays from the group from the soup.
Cheerful quatrains attribute rather warlike intentions to the most harmless dandelion. Here it is - a typically human approach to natural phenomena! However, the poems also contain some truth. Firstly, the dandelion actually sends its “parachutists” only after waiting for a good wind. Secondly, Dandelion paratroopers who stray from the group are more the rule than the exception. Both are done quite deliberately, because the plant strives to populate as many new lands as possible. Its tiny flying parachute fruits are unusually light and adapted to be carried by the wind.
However, having matured, they do not immediately take flight with the first whiff of the breeze. They, like many other balloonists from the plant world, patiently wait for the moment when a good wind blows. And only when it is dry enough, when it becomes moderately warm and when, finally, the air around begins to move and it will not be an instant light breeze, but an evenly and energetically blowing wind, only then will the parachuting fruits risk leaving their father’s house and going on a long air journey - website. In order not to miss this favorable moment, the plant itself regularly “assesses” the weather conditions: relative humidity air, temperature and wind strength. Likewise, many trees that resort to the services air flow as a vehicle, they release pollen or seeds mainly in the first, usually windy, afternoon hours. In these cases, the flight range is greatest.
The fact that dandelion fruits look so amazingly like miniature parachutes is by no means an accidental fact. On the one hand, the wind can carry such lightweight creatures far away. On the other hand, the design with the fruit hanging under a parachute ensures a landing in which the fruit falls vertically down, that is, being in the most favorable position for germination. The elongated shape and the hook-like hook at its upper end allow the fruit to maintain this vertical position after it lands in some crevice in the soil or in low and dense grass cover.
Many plants, including those belonging to different families, have, like dandelion, their own “paratroopers”. Regardless of your systematic position different plants solve the same transport problem in the same way.
But, as you know, parachute flights do not exhaust all the possibilities of air navigation. They also allow you to take to the air Balloons and winged aircraft that use the lift of a wing or propeller. Man has mastered all these types of movement in the air. Perhaps he was ahead of plants in this area? Not at all, because plants have long been familiar with the methods listed above. In addition, plants are successfully used by some other, very unusual ways flights that have not yet been mastered by man.
In the tropics, high in the crowns of a support tree, one of the species of vines, Zanonia macrocarpa, lives. Its beautiful bright green garlands hanging freely from its branches always attract the attention of travelers. Winged vine seeds give us one of most interesting examples plant aeronautics.
“Between the branches, high above, brown fruits hang like giant lampshades. You need to wait a little until a gust of wind sways them, and then suddenly a myriad of large “butterflies” shimmering with satin flash before your eyes. A large, pumpkin-like fruit with a diameter of 20-24 centimeters suddenly bursts, and at the outer end a large triangular hole is formed with carpels unfolding along its edges. Having opened, the fruit becomes like a bell, inside which many winged seeds are arranged in dense parallel rows. The flat, yellow-brown seed closely resembles a large one. pumpkin seed. The width of each of both wings curved in profile is 5 centimeters, and the length is 7-8 centimeters, which allows this aircraft to have a wingspan of 14-16 centimeters. The fabric of the wings is translucent like a veil, shiny like raw silk or satin, and elastic like mica leaves. And, although the fragile wings are easily torn at the edges, their size and the insignificant weight of the seed itself, barely reaching one third of a gram, enable the impeller to maintain excellent flight qualities even in a damaged state. Swaying slightly, describing large circles in the air, the seed slowly, as if against its will, falls to the ground. But the very next breath of wind, like a smart, light-winged butterfly, it again continues its leisurely flight.”
The botanist Haberlandt so poetically describes his meeting with flying seeds zanonia. However, the gliding flight of the seeds of this plant made a strong impression not only on botanists.
In 1898, that is, five years after the publication of Haberlandt's book, aeronautics pioneers Ignaz and Igo Etrich purchased two aircraft: a glider and an ornithopter. Their former owner, Otto Lilienthal, was the first to regularly perform gliding flights with a range of several hundred meters on devices of his own design, starting in 1891. In 1896, at the age of 48, he died during another flight. His tragic death could not help but cast a shadow on the successes he had achieved. Two years later, the father and son of Etrich, manufacturers from Bohemia, decided to continue the work begun by Otto Lilienthal. First of all, it was necessary to look for ways to ensure maximum reliability of aircraft. And yet their first glider (1899) could not survive its first short flight. The failure did not discourage the designers.
It became clear that it was necessary to search, find and carefully study existing examples of reliability. There were no such examples in technology. For a number of years, Etrich studied the anatomy and laws of movement of flying animals. For a long time he considered an acceptable role model bats, since from the technical side it seemed easy to create something similar to their flying membranes. However, the inability to achieve wing geometry mobility as high as that of bats led to the collapse of bright hopes. This forced Etrich to create a model of the glider look for a pattern in nature, which would have a rigid, immovable structure.
And then chance came to his aid. A certain Ahlborn, a teacher from Hamburg, has just discovered the exceptional flight properties of the seeds of Zanonia macrocarpa. In the article “Stability of Aircraft,” he pointed out the enormous significance that the flight characteristics of Zanonia seeds could have for the development of aeronautics. The article fell into the hands of Etrich. Without delaying matters, he and his collaborator Wels went to Hamburg, where they received from the author of the article a model of the seed and a detailed description of its properties.
The tropical vine seed aircraft is a flying wing glider, that is, a glider without a tail. In subsequent years (1904-1909), Etrich built only this type of gliders, which exactly copied his original. The very first of them had a wingspan of 6 meters and could carry 25 kilograms of payload. The second glider had a wingspan of 10 meters, but, like the first, it was an unmanned aerial vehicle that lifted 70 kilograms of payload into the air. Its flight range reached 300 meters. In 1906, Igo Etrich built a similar model, which was used by a man to fly. In 1909, the glider was equipped with a 40 power engine. Horse power. Difficulties in flying a vehicle with an engine and a person on board were created by the inaccuracy of its alignment, on which the stability of the vehicle in flight depended.
As for the vine seed, no such problems arise here, since the center of gravity of the seed does not move. Any change in a person’s posture entails a movement of the center of gravity. For this reason, the next model of Etrich's glider was equipped with a stabilizer, the shape of which was borrowed from the dove. In May 1910, the new aircraft successfully took off. Its prototype was the flying seed of a tropical liana.
The encyclopedic dictionary gives following definition the term "aeronautics":
Aeronautics is movement in the airspace using aircraft. In accordance with international air law, the latter include:
1) aircraft, the lifting force of which is created by gas enclosed in the shell, for example, balloons, airships;
2) aircraft, the lifting force of which is created by air flows flowing around the wings, for example airplanes (including gliders, helicopters and rocket planes), as well as parachutes and kites.
We have already become acquainted with parachutes in the plant world. We also know a glider that is most interesting in its design (in nature there are a number of significantly different variants of aircraft of this type). We encountered the principle of jet propulsion, similar to that which is used in rocket technology, when we were talking about the methods of dispersing fruits and seeds. In botany it plays a minor role: for plants, its use on a large scale would be uneconomical. Plants prefer to use the power of the wind, and here they are masters of their craft.
In order to most effectively connect to such an ancient source of energy as wind, it is necessary to create the largest load-bearing surface. The thought of the human designer worked in this direction (gliders, spherical and kite balloons, airships). Plants followed a similar path in this area. For example, in the perennial herbaceous plant physalis (Physalis alkekengi - website), after flowering, swollen, very large coral-red cups with a fruit inside them are formed. Covered with the thinnest skin-film, they become playthings of the wind as soon as they tear away from the mother plant. But not all aeronauts from the plant kingdom grow to such large sizes. The poppy seed has many tiny voids that make it smaller specific gravity; overall it weighs just one thousandth of a gram and has a diameter of 0.7 millimeters. Due to the cellular structure, the area of the external surface accessible to the wind significantly increases.
For larger bodies, for which the use of the balloon principle would mean too high a rate of descent, nature invented something different. In the interests of reducing the weight of those traveling at the behest of the winds, nature is forced to save construction materials. Just by using the thinnest shells that cover all the smallest and smallest stiffening ribs, a very noticeable effect is achieved, which can be further enhanced with the help of a very skillful technique. Plant aircraft built like a “main rotor” are capable of simulating the presence of an additional surface.
In particular, the fruit of the Norway maple ( Acer platanoides). Its surface area is 2 square centimeters. When dry, its weight barely reaches one-eighth of a gram. Having come off the tree, the fruit, falling, begins to spin quickly due to air resistance and due to its own eccentric design. The lionfish rotates around its center of gravity, which is located at one end of the wing, where the seed is located. Just like the wind turns its wings windmill, and the oncoming air flow forces the fruit to describe circular movements. The effect is the same as that of a helicopter descending with the engine turned off: the rotor blades rotating under the influence of the oncoming air flow allow it to successfully glide. The rotation of the lionfish around the center of gravity creates the appearance of a closed circular surface, which can be affected by the wind and whose area for the fruit is about 20 square centimeters.
Thus, the plant achieves an almost tenfold imaginary increase in area in the simplest way. As a result, the rate of descent of the lionfish decreases by eight or more times. A light gust of wind, barely swaying the branches of a tree (wind force 4), is quite enough to carry a maple lionfish falling from a height of 10 meters to a distance of up to 100 meters. Note that this calculation does not take into account the influence of air turbulence or rising air currents, which increase the flight range many times over.
Without such a truly ingenious device, the fruits would fall from the tree more or less vertically. As a result, they would germinate in the shade of the crown of the mother tree, and the young shoots would be forced to compete with each other for light and living space.
From a design point of view, rotary plant aircraft using the "main rotor" principle have an ideal shape. However, one cannot expect anything else from an object of long-term evolutionary development. The rate of descent of such a device is hardly higher than that of an optimally designed “carrying wing”, and only one and a half times greater than that of a hemispherical parachute with a total surface of over 40 square centimeters.
Why, then, do not our engineers take advantage of these advantages of plant flight technology? Of course, they can do this, but only by sacrificing the necessary structural stability, which is so important in aviation and which the plant does not require.
We will simply mention two more types of aircraft without going into details. These are, firstly, disc planes, a kind of “flying saucers” in the plant world. They are extremely light and fragile formations, shaped like disks, in the center of which are seeds or fruits. Secondly, “shuttlecocks”, so named for their external resemblance to a badminton ball (note that the latter are not such good flyers). The shuttlecock in this case plays rather the role of a parachute, the task of which is to reduce the rate of descent of the seed and prevent it from being damaged when it hits the ground. In short, There is not a single principle of aerial flight worthy of attention that has not been observed in the plant world.
If you start to talk about the possibilities of using wind power for the purposes of movement, then, against your will, first of all remember about balloons, airplanes, parachutes, in other words, about various types of aircraft. But the wind helps not only those who are in the air. It also helps to achieve high speeds, for example, on ice boats mounted on wheels. Where there are extensive sandy beaches on the sea coast and where favorable winds blow, iceboat racing becomes one of the sports. Plants living in similar conditions resort to the same method of movement. But for them, driven by the wind along the sand dunes, this is no longer entertainment, but a way and path to exploring new spaces.
In India, with the onset of a dry and long period of monsoon winds, the dune vegetation of the sea coasts begins to wither. Plants wither, dry out and finally shed their leaves completely. And that’s when the bluish-green hard-leaved grass Spinifex squarrosus sends its “descendants” in search of new lands. They are a light, feather-like structure of a regular spherical shape, in the center of which there are many spikelets tightly pressed to each other. The monsoon sweeping over the coast easily breaks off this ball and drives it along the ground at high speed. Children willingly play with this elastic “ball” that bounces well when hit. “Sailing races” provide the plant with ideal conditions for dispersal: rolling along the ground, it sows its seeds over a large area. A similar method of movement is observed in herbaceous plants steppe regions, where they are called “tumbleweeds”.