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05.12.2016
Among the numerous physical, chemical and biological factors affecting growth and development flora, one of the main ones is lighting. Light rays can speed up or slow down chemical processes in plant cells, stimulate metabolic processes and regulate growth processes. Thus, light energy promotes the passage of chemical reactions synthesis of organic substances from carbon dioxide (photosynthesis). The length of light waves (spectral composition) and their intensity influence the size and shape (morphology) of flora representatives ( photomorphogenesis). No less important for the development of plants is their biological response to the duration of light exposure - photoperiodism. The lighting needs of plants can vary greatly. Depending on the geographical features of their origin, they are distinguished: long-day plants, plants short day and neutral.
Characteristic difference long day plants is the beginning of the flowering phase, subject to increasing duration daylight hours up to 13 or more hours a day. If the daylight hours are shorter and there is insufficient lighting, they will continue to grow, intensively forming green mass, but without entering the flowering phase. As a rule, this group includes plants of temperate and northern latitudes.
Of the garden crops known to us, long-day plants include: carrots, celery, beets, onions, radishes, cabbage, potatoes, lettuce, spinach, radish, parsley, dill, turnips, parsnips, rutabaga, etc.; from cereals: wheat, rye, barley, oats. At short period When exposed to light, long-day plants will not be able to produce fruits, or the harvest will be negligible. This feature of long-day plants determines correct timing their sowing. Thus, in the case of late sowing, they give a smaller harvest and of worse quality than with early spring sowing. It is interesting that after the fruiting of the plants is completed, their further development practically independent of the duration of daylight.
Short day plants- These are, as a rule, inhabitants of southern latitudes. Most frequently cultivated garden crops included in this group: beans, peppers, eggplants, tomatoes, cucumbers, pumpkin, melon, corn, zucchini, sunflowers, basil; from grains: millet, cotton, Sudanese grass, mogara, sesame, soybeans, etc.. For their flowering and fruiting a necessary condition is the duration of darkness of more than 12 hours.
Third group - neutral crops(buckwheat, cyclamen, watermelon, asparagus, as well as most varieties and hybrids of crops grown and adapted for mid-latitudes). They develop, bloom and bear fruit without a pronounced dependence on the length of day and night.
Sensitivity of racesshadows to the relationship between day and night may not how much to vary depending on the ambient temperature, humidity, intensity and quality of lighting, as well as mineral nutrition plants. It can react to the duration of illumination as follows: mature plant, and its seeds.
Germination of some crops is possible only in the dark, others require alternating light and darkness, or only light.Knowing this feature of plants, you can easily regulate the fruiting of long-day or short-day crops and collect several harvests in one year. summer period. It is enough just to create the necessary conditions for them - shading or additional lighting.
Plant lighting can be either natural (sunlight or moonlight) or artificial (electric lamps and various emitters). It is also impossible to ignore the different effects of the spectrum of light rays depending on their wavelength. The most important are the red and blue-violet zones of the spectrum. They influence the metabolism and growth process of plants. Short-day plants perceive blue light as darkness and are more likely to flower. Long-day plants also react to light in the red spectrum. But blue-violet provokes a slowdown in their growth and inhibition of fruit formation functions.
The most neutral is light in the green spectrum. It does not cause noticeable changes in plant growth and development. Infrared radiation promotes rapid harvesting. And when it decreases, the growing season is prolonged, but the yield increases.
To successfully grow vegetable and grain crops, it is necessary to take into account the influence of both the duration of lighting and the quality of light on them. By controlling these factors, growth processes and yield levels can be adjusted to improve crop productivity.
Many novice vegetable growers are surprised by the fact that such a simple crop as dill fails during summer sowing. Such failures are largely due to long duration June and July days. And since the length of daylight hours seriously affects the development of vegetable and green crops and the formation of their yield, it is customary for agricultural science to highlight short and long day plants.
Plants growing in certain geographic zones adapt over time to cyclical (diurnal and seasonal) changes in the length of day and night. In this way, the so-called photoperiodism is formed, that is, the dependence of development different cultures on the duration of dark and light hours of the day.
In long-day plants under 24-hour lighting conditions, accelerated growth and they quickly move on to the flowering and fruiting phase. But with short daylight hours, on the contrary, their development is sharply inhibited to such an extent that they may not even bloom. For short-day crops, the opposite is true: under shortened day conditions (12-14 hours), they vegetate intensively, bloom quickly and bear fruit more abundantly than under long days.
There are also varieties and species of plants that practically do not respond to fluctuations in day length. As a rule, they grow in the equator region, where the length of day and night is almost identical.
Photoperiod has a certain effect not only on flowering and fruiting of plants, but also on some others important processes their life activities. For example, the formation of bulbs in onions and garlic, as well as the formation of root crops and tubers in root and tuber crops, depends on this parameter.
Most crops cultivated in mid-latitudes are better adapted to the length of the summer day (15-17 hours or more). But in tropical countries cultivated plants grown in winter period when the day is only 10-12 hours long. Therefore, rice, corn, millet, peppers, tomatoes, beans, and many other southern natives tend to be short-day plants.
For full development, these plants at a certain stage require shortened daylight hours. Therefore, sowing tomato and pepper seedlings at a time when the day length is still limited leads to a decrease general period vegetation and stimulates fruit formation.
By the way, long-day plants, in which the harvest is formed in the form of vegetation organs (various green crops), root and tuber crops, also need a reduction in photoperiod at the initial phase of their development. This can be achieved by creating daily shading of plants or (which is much simpler) shifting the planting/sowing dates to early spring or autumn period when the daylight hours are still short.
For example, all types of lettuce are long-day plants. Thus, as the day length increases, plants sown in mid-summer quickly begin to form seeds, become very elongated and produce few leaves. As a result, the exit commercial products turns out to be minimal - neither generous watering nor regular loosening of row spacing can save the situation. Thus, in order for green crops to form a lush rosette of leaves, a necessary condition is a short day, that is, they should be sown in early spring or in the fall. Otherwise, the plants quickly begin to bloom to the detriment of productivity.
Plants need light as a source of energy for photosynthesis and the accumulation of organic matter. Green plants, containing chlorophyll, are capable of synthesizing and accumulating organic substances with the help of radiant energy and forming fruits. The formation of chlorophyll, vitamins, enzymes and other substances that play an important role in plant life depends on the intensity of lighting and its spectral composition.
The visible region of the solar radiation spectrum, which is called photosynthetically active radiation, is especially important for plants. In its composition, red, orange, blue and violet rays have the greatest influence on plants.
It is the intensity of active radiation that determines the yield of vegetable crops.
Sunlight consists of visible and invisible rays. Especially great importance have visible rays, which take part in photosynthesis, photoperiodic reactions, and the movement of substances during plant growth and development. Most of the energy required for photosynthesis is provided by red and orange rays. Blue and violet are involved in photosynthesis, but they stimulate the transition of short-day plants to flowering and slow down the development of long-day plants. Yellow and green rays have less physiological activity. Short infrared rays increase the energy of photosynthesis, and also affect growth, development and other physiological processes occurring in plants. Long ultraviolet rays have a formative effect, delay plant branching, increase the content of synthesized compounds in vegetable products
substances, especially ascorbic acid, help increase the cold resistance of plants.
Vegetable plants respond differently to light intensity, its spectral composition, and the duration of daylight. With increasing light intensity photosynthesis and accumulation are enhanced organic matter, plant development is accelerated; in cloudy weather On the contrary, sugars and dry substances accumulate poorly. For most plants, the optimal illumination is about 20-30 thousand lux.
IN open ground
plants use for their growth and development only solar energy
.
In protected ground Plants are sometimes grown with additional lighting or completely under artificial lighting.
Most demanding on light intensity fruit crops families Pumpkin, Solanaceae, Legumes; less demanding- Cabbage, root vegetables, onions and green crops.
According to requirements for lighting intensity vegetable plants
are divided into the following three groups:
* highly demanding of light- tomato, pepper, eggplant, cucumber, corn, beans, peas, melon, watermelon, pumpkin;
* moderate light requirements- garlic, onions, cabbage, root vegetables, spinach, perennial crops;
* low light requirements- forcing crops: onions, parsley, celery, sorrel, asparagus, chicory, lettuce, in which leaves are formed even in very low light due to the reserve nutrients, located in the underground part of the plant (bulbs, roots, rhizomes).
Less light-demanding crops may suffer from excessive exposure to heat rays as part of the spectrum, as a result of which assimilation is weakened and product quality deteriorates.
To improve quality sometimes darken individual plant organs: in cauliflower - the head; in asparagus and leeks, the productive organs are spud.
Vegetable plants that form vegetative productive organs in the form of roots, rhizomes, bulbs, and when growing seeds from them, need good lighting, and when forced in winter they can grow with a lack of light, sometimes without it at all.
The ratio of time during which a plant receives solar energy (day) and processes it (night) is called photoperiod.
TO day length vegetable crops are treated differently. For vegetable plants it is of great importance lighting duration.
According to their response to day length, vegetable plants are divided into three groups:
1. Long-day plants (long-day plants)- cabbage (species), parsnip, rutabaga, radish, radish, carrots, parsley, onion, lettuce, sorrel, spinach, dill, vegetable peas, beets, turnips - varieties of northern origin.
In conditions of long daylight hours, they quickly move on to the formation of generative organs and begin to bloom and bear fruit earlier.
2. Short-day plants (short-day plants)- pumpkin, cucumber, pepper, eggplant, tomato varieties, corn, zucchini, squash, beans.
The darkness factor is essential early in their life(vegetation), and in the future they can successfully develop and bear fruit in long-day conditions.
3. Day-neutral plants- watermelon, asparagus, some varieties of tomato, cucumber, peas, beans, bred in temperate and northern latitudes of the country.
These crops do not respond to changes in day length, that is, the period during which the plant receives solar energy.
By adjusting the length of daylight hours, you can have the necessary impact on crops. By lengthening or shortening daylight hours, you can change the flowering time of vegetable crops and obtain higher yields.
So, to prevent bolting and flowering, for radishes, lettuce, spinach, and onions grown for greens in open ground, a shorter day is artificially created. To do this, light frames made of wire or thin wires are installed on the ridges. wooden slats and at certain hours they attach a material that does not allow light to pass through, thus creating a kind of screen.
To shorten the daylight hours, plants in the beds are usually closed from 8 pm to 8 am the next day. In the morning, the material is removed from the frame and the plant goes from shading to full sunlight.
For late summer sowing, when the length of the day decreases, lettuce, radishes, onions green leaf do not bloom and produce good harvests.
Light is the most difficult to regulate factor in the complex of main conditions for plant growth.
Light regime on site can be adjusted compliance with sowing deadlines, its optimal density, timely weeding And thinning plants, because unfavourable conditions lighting can be created when plants are very dense and when they are shaded by weeds.
The higher the air temperature, thefasterplants react to lack of light.
To maximize the use of solar energy when growing vegetables, the beds should, if possible, be placed in the most illuminated southern and southwestern parts of the site.
In protected ground It is quite possible to adjust the light mode. If there is a lack of lighting, supplementary illumination is used with the help of various light sources, or to create a shortened day, plants are shaded at certain times of the day. In addition, it is possible to grow plants entirely under artificial light.
You need to pay particular attention to the lighting conditions when growing seedlings in closed ground . Low illumination at high air temperatures has a negative effect on plants: the degree of assimilation decreases, the consumption of plastic substances for respiration increases, as a result, the quality of seedlings, especially in light-loving plants, decreases, they become pale and elongated.
Excessive crop density reduces their illumination, which has a detrimental effect on the development of plants, and then on the yield of vegetables and on the speed of production.
Period after emergence- the most crucial moment when growing seedlings in protected soil. It is at this time that, due to the consumption of seed nutrients, plants develop greatest need for light. Insufficient lighting also affects the root system: in shaded plants it develops worse than in plants that receive enough light.
To make the most of solar energy when growing vegetables in protected soil, greenhouses are placed on a lighted slope of the site.
It turns out that daylength matters a lot for some plants. Some plants produce buds when the daylight hours increase, while others, on the contrary, bloom only when the daylight hours decrease.
Long day plants They bloom when daylight hours become more than 12 hours. Long-day plants include bougainvillea, pelargonium, saintpaulia, gloxinia, calceolaria, primrose, hibiscus, viola, delphinium, and cornflowers.
Short day plants do not bloom until daylight hours are shorter than 12 hours. These plants include natives of the tropics and subtropics. In these latitudes it is light and dark time days are about the same. Once in temperate latitudes where the length of daylight in summer is more than 15-17 hours, plants change their biorhythm and begin to grow very rapidly to the detriment of flowering.
Unless, when keeping short-day plants, the daylight hours are reduced to 8-10 hours, such plants are unlikely to bloom. Short-day plants include begonias, azaleas, poinsettias, kalanchoes, asters, chrysanthemums and other plants that bloom in late summer or fall.
There is also a group of plants that do not respond to day length. They can be called neutral. These include most indoor plants.How to make short-day plants bloom?
Amateur flower growers have a lot of trouble with short-day plants. In order for them to begin to bloom, it is necessary to artificially create a “night” lasting more than 14 hours a day. Azalea and poinsettia will bloom only if this regime is followed. Sometimes artificial lighting in the room does not allow these plants to bloom. To make it bloom houseplants"short" day, you need to take the plants into a dark pantry or cover them with a box or dark bag on top for three months. During this period, plants can be hampered not only by the light in the room, but also by street lighting.
In the same way, shortening daylight hours affects the flowering of autumn-flowering plants. garden plants. It is unlikely that anyone expects to see late-blooming varieties of dahlias, asters, and especially chrysanthemums blooming in the summer.
However, there is nothing surprising in this; it is enough to reduce the daylight hours to seven hours for these plants to transfer their flowering from autumn to summer.
Most annuals that bloom in the second half of summer respond not to a decrease in temperature, but to a reduction in daylight hours. Many of them, in the natural light of long summer days, can reach gigantic sizes before they bloom.
Exactly because of this reason early sowing can lead to excessive development of shoots and leaves and weak flowering. Late sowing of such plants, on the contrary, with abundant flowering may have dwarf forms.
Knowing the reaction of “short” day plants to the reduction in daylight hours, it is possible to cause flowering in some in July, and, on the contrary, delay others until October. Even chrysanthemums can be easily made to bloom in July by simply shortening the daylight hours. So the onset of autumn coolness does not count important factor affecting plant flowering.
Short-day plants are representatives of the flora that bloom during the period when daylight hours last no more than 12 hours. These are plants native to the tropics and subtropics. These include Kalanchoe, chrysanthemums, zygocactus, cornflower, gladiolus, pansies etc.
Plants that come from the tropics and subtropics to mid-latitudes are accustomed to daylight hours that are equal to night. When they are moved to mid-latitudes, where daylight is often much longer than night, they begin to behave completely differently. For example, these representatives of the flora bloom only during short daylight hours.
Characteristics of short-day plants:
- Such plants bloom mainly in autumn or winter, when the night is longer than the day and artificial lighting is used indoors.
- The development cycle of these representatives of the fauna occurs on a short daylight hours.
- Most often such plants bloom in autumn.
- In order for them to begin to bloom in the summer, daylight hours must be significantly reduced.
- Most plants in this category, which bloom in the second half of summer, respond to the length of daylight hours.
- A decrease in temperature has absolutely no effect on their flowering.
If these representatives of the fauna are exposed to long daylight hours, they can achieve sufficient large sizes before flowering. If such plants are planted very early, they can not only reach large sizes, but also bloom very weakly, which will not make them attractive.
Transplantation of short-day plants should be done during early spring when daylight hours are still short. Thanks to this, the plant will take root most successfully.
Plants with short daylight hours can be propagated by seeds, cuttings from leaves or roots.
These representatives of the fauna have green foliage. Despite the fact that they mainly stay in the dark, the process of photosynthesis in them occurs several times faster than in plants with long daylight hours. They may have which are characterized big amount color shades.
Plants with short daylight hours are very demanding to care for. In order for them to fully grow and develop, they need to create conditions in which the night will last 14-16 hours. Performing this action is almost easy, but troublesome. To do this, you need to place the plants in the middle of the room and prolong the night by closing the curtains. But this may not be absolutely enough to stop the flowers from blooming.
Features of plant care:
- In order for flowering to begin, it is necessary to perform certain actions for three months. After this, the flower pots can be placed on permanent place, but during the flowering period these actions must be strictly followed. To do this, you need to take the plant out into a dark pantry every day in the early evening before sunset. Plants must be brought back early in the morning.
- If you don’t have a pantry, you can put an opaque bag on the potty in the evening or cardboard box. The box or bag must be removed early in the morning. In this case, the plant must be protected from the effects of natural light.
- It is best to use lighting for these representatives of the fauna. fluorescent lamps, but at the same time, the duration of daylight hours should not exceed 9-10 hours.
If there is no frost outside, you can put such plants on the balcony or take them outside until the first buds appear. As soon as buds appear on it, it must be brought indoors. During this period, it is necessary to not only protect the fauna from daylight, but also completely protect it from the effects of even artificial light.
In order for short-day plants to bloom fully and continuously, they need to be provided with:
- Optimal daylight hours.
- The right temperature.
Plants with short daylight hours need to provide not only short daylight hours, but also proper watering, as well as at the optimal temperature.
These plants do not like cool weather, so they need to provide a warm indoor climate. Under no circumstances should you take them outside if there is a threat of frost. These representatives of the fauna may not tolerate frost and die.
This type of plant does not like waterlogged soil, which requires rational watering.
They need to be watered as needed when the soil is completely dry. If the soil is often excessively waterlogged, this can lead to their death. When providing optimal conditions For the development of these plants, you can achieve high-quality and beautiful flowering.
More information can be found in the video.