The period of a plant's life when growth slows down sharply. Why does tomato seedlings grow poorly, and what to do in this case? Features of the growth of plant organs

If tomato seedlings grow poorly, what to do in this case? Many people who grow vegetables on their own have this question.

Everyone who has at least a small part of free land usually tries to adapt it to create a vegetable garden. This solution makes it possible to independently grow various vegetable or fruit crops, which are a receptacle of vitamins and minerals. One of these crops that our gardeners love is tomatoes. Most modern winter preservation recipes are based on the use of tomatoes or their juice. At the same time, the cultivation of this vegetable itself has some features, if not observed, it is extremely difficult to get a full-fledged strong and healthy plant.

The use of a garden gives a person a lot of advantages, among which a special place is occupied by saving material resources and obtaining a natural crop containing only useful substances. Tomatoes are rightfully one of the most beloved garden crops of our people.

At the same time, many people, trying to grow them at home, are faced with a problem when tomato seedlings do not grow. This state of affairs can become a serious problem and significantly reduce the yield of this vegetable, or even completely destroy it.

Why are tomato seedlings not growing? To date, several reasons have been identified for which a plant can slow down its growth or even dry out completely. It should be taken into account that all of them can be eliminated on their own, which will make it possible not only to save the plant and ensure its normal growth, but also to get a full harvest in the future.

Improper watering is the cause of slow growth

These criteria, which contribute to the seedlings growing slowly, look like this:

• malnutrition;
• improper watering;
• lack of ultraviolet;
• pick violation;
• diseases and pests.

The above factors cover almost all the reasons why tomato seedlings can slow down their growth or die altogether. At the same time, the slightest signs of disturbances in the development of plants should be the cause of an immediate response, since untimely assistance can adversely affect the overall health of the crop and the further formation of fruits.

Nutrients and seedlings of tomatoes

The first and one of the most common reasons why tomato seedlings do not grow is a banal lack of nutrients in the soil. In most cases, this factor is the main reason for the slowdown in plant growth and violation of their integrity.

Diagnosing such problems is quite simple, since the lack of nutrition has its own visual features that are easy to notice even with the naked eye.

The main nutrients for this kind of vegetable crops are the following:

• nitrogen;
• phosphorus;
• potassium;
• magnesium;
• iron.

What to do to make tomatoes grow in full force? The presence of the above elements in the soil guarantees the full development of plants and their health.

In turn, limiting the intake of any substance negatively affects the overall development of tomatoes:

1. Nitrogen deficiency causes the shoot to develop poorly enough, and its stem remains too thin for a long time, giving the whole plant a stunted appearance.
2. Phosphorus deficiency is also quite easy to spot, as it is expressed in a change in the color of the leaves, which acquire a red-violet hue.
3. Insufficient intake of potassium contributes to the drying of the lower tier of leaves, and a deficiency of magnesium makes them unnecessarily hard and dull.
4. Restriction of iron intake contributes to the development of a disease such as chlorosis.

If tomato seedlings do not grow well and there are these signs, it is necessary to add the missing nutrients, and the plant will return to normal.

Reasons for poor seedling growth (video)

Solving other problems

What to do if the tomatoes do not grow? Other factors do not often lead to the fact that tomato seedlings do not want to grow, but still the reason for this phenomenon may lie precisely in them. The first of these is the incorrect organization of irrigation, which can be expressed in two main conditions: lack of moisture or its excess. In the first case, the plant begins to dry out, and in the second - to rot. As a rule, normalization of soil moisture eliminates this problem once and for all.

Small seedlings can be the result of a lack of sunlight, since they need a large amount of ultraviolet to grow properly.

In turn, its restriction helps to slow down the growth of shoots and their stunting. In order for the seedlings to be strong, it needs to be provided with access to sunlight.
Violation of picking can also cause stunted plants, since in the process of it sometimes the root system of the plant is damaged or voids form in it.

Coping with such a problem is not so simple, since it is almost impossible to restore the integrity of the rhizome, but it is quite possible to eliminate voids. To do this, compact the earth a little, ensuring its tight fit to the roots and full access to all the necessary nutrients.

Tomato seedlings (video)

Estimate

Plant growth is due to division and sprains cells various organs. Growth processes are localized in meristems. Distinguish apical, intercalary and lateral meristems.

Apical , or apical, meristems are located at the ends growing shoots and tips roots all orders ( apexes, or points of growth). Taper escape apex called growth cone. Due to these meristems, the growth of axial organs is carried out. in length, education rudiment of an organ and its initial division into fabrics. By activating or suppressing the activity of the apical meristem, it is possible to influence the productivity and resistance of plants. According to V.V. Polevoy (1989), the apical meristems of the shoot and root are the main coordinating (dominant) centers plants that determine its morphogenesis.

Due intercalary (intercalary) meristem located at the base of young internodes grows stem and leaves of monocots plants.

Lateral (lateral) meristems provide thickening stem and root: primary - procambium and pericycle and secondary - cambium and phellogen. The constant growth of a plant at all stages of ontogenesis allows it to meet the needs for energy, water and mineral nutrients.

The activity of meristems depends on the influence of external conditions, complex relationships within the plant organism (polarity, correlation, symmetry, etc.). In the village - x. practice through watering, top dressing, thinning and other measures can influence the number of metameric organs laid in the growth cones, on their subsequent growth, reduction and, as a result, on plant productivity.

1. Features of the growth of plant organs

stem growth. The stem apex measures 0.1-0.2mm in dimeter and protected by leaves. Stem elongation occurs due to the growth of internodes. First, the upper internodes grow. The next internode passes to intensive growth with a decrease in its rate at the previous one. Each individual internode is characterized slow initial growth(cell division), subsequent rapid growth (stretching cells) and finally growth retardation in a mature internode.

At growing internodes outdoor fabrics are tested tension(stretch) and domestic- compression ( compression), which, along with the turgor pressure of the cells, provides strength stems of herbaceous plants.

AT favorable conditions the longest internodes are formed in middle part escape.

Lateral branching comes from the growth axillary or sprouting adnexal(adventive) kidneys.

Thickening - result of activity lateral meristem - cambium. At annual plant division cambium ends in bloom. At woody cambium forms from autumn to spring ( winter) is in the state rest(determines the presence growth rings).

The rate of elongation of the stem of the shoots is regulated by incoming auxins and gibberellins. Intensively growing internodes are characterized by increased content of gibberellins and auxins.

plant height determined by their genome, and to a large extent - by growing conditions.

Bookmark generative organs connected with photoperiodic sensitivity vernalization and other factors. At cereals ear differentiation begins in the tillering phase.

leaf growth. Several leaf buds are present in the germinal bud, but most of them are formed after germination. Rudimentary leaves appear on the growth cone of the shoot (from ridges or tubercles - primordia). The interval between the initiation of two leaf primordia in different plants ranges from several hours to several days and is called plastochrone . For the formation of primordia and leaf tissues, cytokinin and auxin. Auxin affects the formation of vascular bundles, and gibberellin - the elongation of the leaf blade.

At dicots leaf blade is enlarged by uniform cell growth(mostly by stretching) throughout the area sheet. Availability several points of growth defines education teeth, blades, leaves.

At monocots the sheet is lengthened by basal and intercalary growth.

Thickening leaf is carried out due to the division and stretching of the cells of the palisade parenchyma and mesophyll cells.

Leaf growth is strongly influenced by intensity and quality of light. In the dark leaf growth is retarded. Light stimulates fission, but inhibits stretching cells. In shade, the leaves are larger and thinner. . intense light causes thickening leaf blades due to the formation additional layers of columnar parenchyma.

At lack of water small leaves with a xeromorphic structure are formed, which is associated with an increase in ABA and ethylene.

At nitrogen deficiency the number of cell divisions decreases during the period of leaf growth, its surface is reduced.

Low temperature slows down leaf growth in length and stimulates thickening. Wherein in frost-resistant varieties In winter wheat, the duration of the cell elongation phase is reduced to a greater extent than in unstable wheat.

Growth sheet stops when the intense export photosynthesis products.

root growth. The rate of cell division and growth in the roots is much higher than in other organs of the plant. Primary the root is formed in embryo seed, and its growth before leaving the seed occurs by sprains basal cells of the meristem of the germinal root. At dicots plant germinal root becomes main(pivotal), forms lateral roots. At monocots plants, the primary root is supplemented by adventitious roots formed at the base of the shoot, is formed fibrous root system.

When germinating seed appears embryonic root, which fast growing, then its growth rate are declining while accelerating the growth of above-ground organs. In the future, the growth of the root again resumes. These features ensure rooting at the first stage and the harmonious development of the heterotrophic and autotrophic parts of the plant in the subsequent period.

Apical meristem root forms root cap , which performs very important functions (protects the meristem when the root moves in the soil; secrete polysaccharide mucus and constantly peel off from its surface; mucus protects against pathogens and drying out; is sensory area, perceiving the action of gravity, light, soil pressure, chemicals and determines the direction and speed of root growth; it synthesizes ABA).

On the border with the cap in the meristem are resting center cells , which includes initial cells of different tissues 500-1000 cells). resting center restores the number of meristem cells due to natural wear or damage.

At the roots of all types, 4 zones : division , sprains , root hairs and holding (branching).

At the roots corn, peas, oats, wheat and others growing part is short - less than 1 cm. The thinner the root, the shorter its meristem. Fundamentally short stretch zone, which is important to overcome soil resistance (develop pressure before 8-16 atm by 1 cm). Branching and a high rate of root growth ensure a constant uptake of water and ions.

For stretch zones roots are characteristic increased ID, row activation enzymes(auxin oxidase, polyphenol oxidase, cytochrome oxidase, etc.). As a result of growth by extension, the initial volume of the meristematic cell increases by 10-30 times due to the formation and increase of vacuoles, in which the content of osmotically active substances - ions, OK, sugars, etc. increases.

Some epidermal cells of the root form root hairs long 0.15-8mm. The number of root hairs in corn reaches 420 by 1 cm 2 root surface. They operate on average. 2-3 days and die. In the absence of calcium in the nutrient solution, aeration root hairs are not formed.

Lateral roots laid in pericycle maternal root in the zone takeovers or higher. Its meristematic cells secrete hydrolytic enzymes that dissolve the membranes of the cells of the cortex and rhizoderm, ensuring its release to the outside.

adventitious roots are laid in meristematic or potentially meristematic tissues (cambium, phellogen, medullary rays) of various plant organs (old parts of the root, stems, leaves, etc.).

Root growth depends on the age and type of plant, environmental conditions. Environmental conditions favorable for photosynthesis promote root growth, and vice versa. Shading plants or mowing the aerial part inhibits growth and reduces root mass. Optimal temperature a few for root growth lower than for escape. The ratio of roots to temperature changes in ontogeny. So, the roots of young plants tomatoes grow best at 30°C than at 20 °C, and adults vice versa. At soil drying up before wilting moisture root growth stops. With moderate irrigation, wheat roots are located in the upper layers of the soil, and without watering they penetrate deeper. Optimal soil density for growing roots of corn and other crops 1.1...1.3 g/cm 3 . AT dense soil, the length of cells and the size of the elongation zone decrease due to the formation ethylene, the cost of breathing increases. critical content O 2 in the soil air - about 3-5 % volume. The need for roots in oxygen is greater, the higher the soil temperature. Minimum different oxygen requirements rice and buckwheat, a maximum - tomato, pea, corn. Roots rice have aerenchyma. In plants of winter rye and wheat on crops flooded with melt water in spring, the leaves, while in the air, can also supply oxygen to the roots for a short time. For the growth of the roots of most plants, the optimal pH 5-6.

Hormonal regulation of root growth . Root growth requires low (10 -11...10 -10 M) auxin concentrations. An increase in the flow of auxin from the shoot inhibits the growth of the root in length, which is also explained by the induction of ethylene synthesis. Gibberellins do not affect root growth, but cytokinins in high concentrations inhibit it. ABK, formed by the root cap, slows down the growth of the root in length, the root tip inhibits the formation of lateral roots, so removing it stimulates their formation. Apparently, this is the result of the action of cytokinins inhibiting rhizogenesis, which are formed in the root apex.

The initiation of lateral roots begins at a distance from the root apex where a certain ratio of cytokinin and auxin (an activator of rhizogenesis) coming from the stem is provided. Ethylene promotes the establishment of lateral roots closer to the root tip, and the treatment of plants with it causes the mass formation of adventitious roots. On dense soils, the mechanical resistance of the environment leads to the synthesis of "stress" ethylene in the roots. In this case, instead of elongation, a thickening occurs in the cell elongation zone, which facilitates the separation of soil particles and the subsequent elongation of the root. A decrease in root increments can also be associated with the accumulation of phenolic inhibitors in cells and further lignification of cell walls.

Sooner or later, any grower is faced with the problem of slow growth of indoor plants. If there is a pause in development during the resting phase or after transplantation, then this is a natural process. But any signs of dwarfing or stunted growth at "normal" times are signs of problems with caring for the plant or its health. Improper watering, lack of nutrients and even individual trace elements can lead to serious growth problems. And the sooner you can diagnose the cause and take appropriate measures, the more likely that your plant will soon return to normal.

Calathea in the room. © Verity Welstead Content:

Causes of stunting and dwarfism

Natural or problematic plant stunting is always conspicuous. It is usually noticeable in spring and summer, when any normal plant produces at least a couple of leaves, or even a dozen, young shoots develop and a visible change in their development occurs. But if natural causes do not require any measures, they just correspond to the stage of development or adaptation, then all other possible causes of an unexpected and atypical stop in growth require much more serious actions.

To understand why indoor crops have a developmental delay, you should first analyze all possible natural causes and factors. They belong to:

1. acclimatization to new conditions;
2. rest period;
3. root growth and development of the substrate (many cultures develop slowly in the first years of life until they grow a sufficient mass of roots);
4. natural features of a species or variety - very slow, almost imperceptible development;
5. the first month after transplantation (in shrubs and trees - up to 3 months);
6. division or other vegetative propagation methods that require very long adaptation.

Only by eliminating all of the possible causes of a natural nature, it is worth starting to worry. In addition to natural factors that lead to growth retardation, dwarfism can also be factors that require you to take active measures. The main problems that cause growth to stop or slow down include:

1. Too tight capacity, complete development of the substrate by the roots.
2. Poor soil nutrition or incorrect, insufficient feeding and resulting nutrient deficiencies (minor or severe).
3. Improper watering with complete drying of the substrate.
4. Lack of calcium in the soil.
5. Salinity of the substrate.
6. Contamination of the substrate with toxins and heavy metals.
7. Leaf spotting.
8. Infectious dwarfism due to infection of the substrate with nematodes.

In houseplants, various problems that manifest themselves in slow growth are most often associated with care. But there are also specific diseases or pests, which are not so easy to deal with than to compensate for the lack of certain substances. Depending on what exactly was the reason for stopping growth, methods of struggle are also applied. If the wrong approach to watering or top dressing, which can be compensated quickly enough, then the fight against serious lesions requires some patience and endurance.

It should always be remembered that improper care increases the likelihood of problems with the growth and development of the plant. Thus, the use of improperly selected fertilizers without a systematic approach threatens leaf spot and dwarfism, and overflows or the use of random earth mixtures - nematodes. If you follow all the requirements of plants and carefully study their characteristics, then the risk that your plant will suffer from growth retardation will be minimal.

Nutritional deficiencies or the need for a transplant

It is usually with insufficient fertilizing or depleted soil, improperly selected fertilizers and cramped containers that the simplest of all symptoms of stunting are associated. Such a slowdown manifests itself, without accompanying signs and problems: there are no leaf lesions, no loss of decorative effect, no drying, but normal growth simply slows down or stops. Solving these problems is very simple:

1. If the roots come out of the drainage holes, this clearly means that the entire substrate has been mastered, and it has not changed for a long time. The plant needs to be transplanted.
2. If there is enough free soil in the containers, you need to fertilize with complex fertilizers, check your fertilizing schedule with the recommendations for this plant, and if necessary, change fertilizers to a more suitable mixture, having carefully studied the description of the plant.

In plants, one can often observe signs of a lack of a certain macro- or microelement. But most of them are manifested in a change in leaf color, and not in stunting. With one exception: a lack of calcium (including) can also manifest itself in dwarfism, stunting, a clear discrepancy between the size of the bushes declared for this type of indoor plants. It is possible to recognize the symptoms of calcium deficiency only by the problems associated with dwarfism - the death of the upper buds on the shoots, thickening, shortening of the roots, the appearance of mucus on them.

Irrigation and water quality problems

If slow growth or stunted growth is due to improper watering, then identifying the problem is also quite simple. In plants that suffer from drying out of the substrate, insufficient, irregular watering and lack of moisture, in addition to growth retardation, the leaves also wilt, they begin to turn yellow, their tips dry, individual leaves wrinkle and dry, most often from the bottom of the crown or the oldest leaves. Flowering also stops, flowers and buds fall off.

With the growth retardation caused by the drying of the soil, it is necessary to fight in a complex way. Before returning the plant to the optimal watering schedule, the soil is saturated with water in several ways:

1. Immerse the container with roots in water for irrigation, saturating the earthen ball with water, and after air bubbles stop appearing, carefully remove it and allow all excess water to drain. This option is not suitable for plants that are sensitive to waterlogging, prone to rot, succulents with succulent stems, tubers and bulbs.
2. Slow bottom feeding of the soil with moisture, when water is poured into the pan in small portions, at intervals, to uniformly and gradually moisten the earthen clod from below.
3. Dividing the usual amount of water for watering into several waterings with an interval of 4-5 hours is a series of light but frequent waterings, which gradually restores comfortable moisture to the plant.

After any moisture-charging irrigation, the substrate is allowed to dry only in the upper layer - 2-3 cm - of the substrate. After that, a new schedule of procedures is selected that will maintain the soil moisture that a particular plant needs.

If you use ordinary tap water for watering plants, do not defend it, or even use settled, but not soft water for those plants that are afraid of alkalization, then salting and a change in the reaction of the soil will occur quite quickly in the substrate, the accumulation of trace elements that will cause problems with development plants. Salinity is determined by white deposits on the walls of the container and the surface of the substrate. In this case, there is only one way to help - transplanting into a fresh substrate and correcting care.

Only if you notice signs of alkalization in the initial stages, you can acidify the water for irrigation and start using soft water in time. But such measures do not save the situation and are temporary, helping to reduce harm before transplanting and changing the soil.

Diseases, pests and substrate poisoning

Leaf spot is a disease that is always associated with stunting or severe stunting. Of course, they define it by completely different signs: spots of brown, gray, black colors that appear on the surface, as well as yellowing and dying of foliage, loss of decorative effect. But stunting is a companion, without which spotting never appears.

To save the plant, you will have to apply fungicides. You can use both copper-containing preparations and systemic pesticides. But if the disease was noticed in the early stages and growth did not slow down critically, then you can try to cope with the problem with infusions of marigolds, ash, horsetail decoction.

Infectious dwarfism in indoor plants is diagnosed only by the exclusion of any other possible causes. Most often, it is associated with contamination of the soil with nematodes, but sometimes it manifests itself. It is impossible to fight it, the plant must be isolated, careful care must be taken, systemic treatments with fungicides and insecticides must be carried out. But the chance of success is low. If dwarfism is the result of the activity of nematodes, then they are fought not only with an emergency transplant, but also with special insecticides from soil pests, lowering the moisture level of the substrate, and correcting care. When transplanting, the roots are additionally disinfected, as well as fresh soil and containers.

Substrate contamination with heavy metals and toxins is not uncommon. If there are no other possible reasons, and the ecological situation is far from optimal, the apartment or house is located near highways and large industrial plants, plants are taken out into the open air for the summer, where toxins can get into the soil, or untreated water with a high content of heavy metals is used, then stunting may well be toxic. Expanded clay and vermiculite drainage usually helps with the inevitable partial accumulation of toxins, but it is better to take measures to protect plants from polluted air and water, including the use of special filters, avoiding fresh air and limiting ventilation.

Growth and development are integral properties of any living organism. These are integral processes. The plant organism absorbs water and nutrients, accumulates energy, countless metabolic reactions take place in it, as a result of which it grows and develops. The processes of growth and development are closely interrelated, since usually the body grows and develops. However, the rate of growth and development may be different, rapid growth may be accompanied by slow development or rapid development by slow growth. So, for example, a chrysanthemum plant at the beginning of summer (long day) grows rapidly, but does not bloom, therefore, it develops slowly. A similar thing happens with winter plants sown in spring: they grow rapidly, but do not go on to reproduction. It can be seen from these examples that the criteria determining the rates of growth and development are different. The criterion for the rate of development is the transition of plants to reproduction, to reproduction. For flowering plants, this is the laying of flower buds, flowering. Criteria for growth rates are usually determined by the rate of increase in the mass, volume, and size of the plant. The foregoing emphasizes the non-identity of these concepts and allows us to consider the processes of growth and development consistently.

The plant grows both in length and in thickness. Growth in length usually occurs in the tips of shoots and roots where the cells of the educational tissue are located. They form the so-called growth cones. Young cells of the educational tissue are constantly dividing, their number and size increase, as a result of which the root or shoot grows in length. In cereals, the educational tissue is located at the base of the internode, and the stem grows in this place. The growth zone at the root does not exceed 1 cm, at the shoot it reaches 10 cm or more.

The growth rate of shoots and roots varies from plant to plant. The record holder for the growth rate of shoots is bamboo, in which a shoot can grow up to 80 cm per day.

The growth rate of the root depends on humidity, temperature, oxygen content in the soil. Tomatoes, peas, corn have a large need for oxygen, less - in rice, buckwheat. Roots grow best in loose, moist soil.
Root growth depends on the intensity of photosynthesis. Conditions favorable for photosynthesis also have a positive effect on root growth. Mowing the aboveground parts of plants thermos the growth of roots, leads to a decrease in their mass. A bountiful fruit harvest also retards the growth of the tree's roots, and the removal of inflorescences promotes root growth.

Photo: Mark Koeber

The growth of plants in thickness occurs due to cell division of the educational tissue - the cambium, located between the bast and the wood. In annual plants, cambium cells stop dividing by the time of flowering, while in trees and shrubs they stop dividing from mid-autumn until spring, when the plant enters the dormant stage. The periodicity of cambial cell division leads to the formation of growth rings in the tree trunk. The annual ring is the growth of wood in a year. By the number of annual rings on the stump, the age of the sawn tree is determined, as well as the climatic conditions in which it grew. Wide annual rings indicate favorable climatic conditions for plant growth, and narrow annual rings indicate less favorable conditions.

Plant growth occurs at a certain temperature, humidity, light. During the growth period, organic substances and the energy contained in them are intensively consumed. Organic substances enter the growing organs from photosynthetic and storage tissues. Water and minerals are also necessary for growth.
However, water and nutrients alone are not enough for growth. We need special substances - hormones - internal growth factors. They are needed by the plant in small quantities. An increase in the dose of the hormone causes the opposite effect - inhibition of growth.
The growth hormone heteroauxin is widely distributed in the plant world. If you cut off the top of the stem, then its growth slows down, and then stops. This indicates that heteroauxin is formed in the growing zones of the stem, from where it enters the elongation zone and affects the cytoplasm of cells, increases the plasticity and extensibility of their membranes.
The hormone gibberellin also stimulates plant growth. This hormone is produced by a special type of lower fungi. In small doses, it causes elongation of the stem, pedicel, acceleration of flowering plants. Dwarf forms of peas and corn after treatment with gibberellin achieve normal growth. Growth hormones bring seeds and buds, tubers and bulbs out of dormancy.

In many plants, special substances have been found - inhibitors that inhibit growth. They are found in the pulp of apple, pear, tomato, honeysuckle, in the shells of chestnut seeds, wheat, in sunflower germs, onion and garlic bulbs, in the roots of carrots, radishes.
The content of inhibitors increases by autumn, due to which fruits, seeds, root crops, bulbs, tubers are well stored and do not germinate in autumn and early winter. However, closer to spring, under favorable conditions, they begin to germinate, since the inhibitors are destroyed during the winter.

Plant growth is a fickle process: the period of active growth in spring and summer is replaced by the attenuation of growth processes in autumn. In winter, trees, shrubs and grasses are dormant.
During the dormant period, growth stops, vital processes in plants slow down greatly. For example, in winter their breathing is 100-400 times weaker than in summer. However, one should not think that plants in a state of rest completely stop vital activity. In resting organs (in the buds of trees and shrubs, in tubers, bulbs and rhizomes of perennial grasses), the most important processes of vital activity continue, but growth completely stops, even if there are all conditions for this. During a period of deep dormancy, it is difficult for plants to "awaken". For example, potato tubers just harvested from the field will not germinate even in warm and moist sand. But after a few months, the tubers will sprout and this process will be difficult to delay.

Rest is the body's response to changing environmental conditions.
Changing environmental conditions can lengthen or shorten the dormant period. So, if you artificially lengthen the day, you can delay the transition of plants to a state of rest.
Thus, the dormancy of plants is an important adaptation to the experience of adverse conditions that arose in the course of evolution.
Growth processes underlie the movement of plants. Plant movements are different. Tropisms are widespread in nature - bending of plant organs under the influence of a factor acting in one direction. For example, when lighting a plant from one side, it bends towards the light. This is phototropism. The plant bends because its organs on the illuminated side grow more slowly than on the unlit side, since light slows down cell division.
The response of plants to the action of gravity is called geotropism. The stem and root react differently to gravity. The stem grows upwards, in the opposite direction to the action of gravity (negative geotropism), and the root grows downwards, in the direction of this force (positive geotropism). Turn the germinating seed upside down and the stem down. After a while, you will see that the root will bend down, and the stem up, i.e. they will take their usual position.

Plants also react with movement to the presence of chemicals in the environment. This reaction is called chemotropism. It plays an important role in mineral nutrition, as well as in the fertilization of plants. So, in the soil, the roots grow towards the nutrients. But they bend in the opposite direction from pesticides, herbicides.
The pollen grain germinates, as a rule, only on the stigma of the pistil of plants of its own species, and the sperm (male sex cells) move towards the ovule, the ovum and the central nucleus located in it. If the pollen grain falls on the stigma of a flower of another species, then it first germinates, and then bends in the opposite direction from the ovule. This indicates that the pistil releases substances that stimulate the growth of "own" pollen grains, but inhibit the growth of foreign pollen.
Plants also respond with tropisms to the effects of temperature, water, and damage to organs.
Plants are also characterized by another type of movement - nastia. Nastia is also based on plant growth, which is caused by various stimuli acting on the plant as a whole. There are photonasts caused by a change in lighting, thermonasts associated with a change in temperature. Many flowers open in the morning and close in the evening; respond to changes in lighting. For example, in the morning, in bright sunlight, dandelion baskets open, and in the evening, with a decrease in illumination, they close. Fragrant tobacco flowers, on the contrary, open in the evening, with a decrease in illumination.
Nastia, like tropisms, is also based on uneven growth: if the upper side of the petals grows stronger, the flower opens, if the lower side closes. Consequently, the basis of the movement of plant organs is their uneven growth.
Tropisms and nastia play an important role in plant life; this is one of the signs of plant adaptability to the environment, to an active reaction to the impact of its various factors.

Photo: Sharon

Growth processes are an integral part of the individual development of plants, or ontogenesis. The entire individual development of an individual is made up of a whole series of processes, certain periods in the life of an individual, from the moment of its appearance to its death. The number of periods of ontogeny and the complexity of developmental processes depend on the level of plant organization. Thus, the individual development of unicellular organisms begins with the formation of a new, daughter cell (after the division of the mother cell), continues during its growth and ends with its division. Sometimes unicellular organisms have a dormant period - during the formation of a spore; then the spore germinates and development continues until cell division. With vegetative reproduction, individual development begins from the moment of separation of a part of the maternal organism, continues with the formation of a new individual, its life and ends with death. In higher plants during sexual reproduction, ontogenesis begins with the fertilization of the egg and includes periods of development of the zygote and embryo, the formation of a seed (or spore), its germination and the formation of a young plant, its maturity, reproduction, wilting and death.

If in unicellular organisms all the processes of their development and life activity take place in one cell, then in multicellular organisms the processes of ontogenesis are much more complicated and consist of a number of transformations. During the development of a new individual, as a result of cell division, various tissues are formed (integumentary, educational, photosynthetic, conductive, etc.) and organs that perform various functions, the reproductive apparatus is formed, the body enters the time of reproduction, gives offspring (some plants - once in a lifetime , others annually for many years). In the process of individual development, irreversible changes accumulate in the body, it ages and dies.
The duration of ontogeny, i.e. life of an individual also depends on the level of organization of plants. Unicellular organisms live for several days, multicellular organisms - from several days to several hundred years.

The duration of the development of plant organisms also depends on environmental factors: light, temperature, humidity, etc. Scientists have found that at a temperature of 25 ° C and above, the development of flowering plants accelerates, they bloom earlier, form fruits and seeds. Abundant moisture accelerates the growth of plants, but delays their development.
Light has a complex effect on plant development: plants respond to the length of the day. In the process of historical development, some plants develop normally if the daylight hours do not exceed 12 hours. These are short-day plants (soybean, millet, watermelon). Other plants flower and produce seeds when grown under longer day conditions. These are long-day plants (radishes, potatoes, wheat, barley).

Knowledge about the patterns of growth and individual development of plants is used by man in practice when growing them. Thus, the property of plants to form lateral roots when the tip of the main root is removed is used in the cultivation of vegetable and ornamental plants. In seedlings of cabbage, tomatoes, asters and other cultivated plants, when transplanted into open ground, pinch the tip of the root, i.e., carry out a pick. As a result, the growth of the main root in length stops, the growth of lateral roots increases and their spread in the upper, fertile soil layer. As a result, plant nutrition improves and their yield increases. Picking is widely used when planting seedlings of cabbage. The development of a powerful root system is facilitated by hilling - loosening and rolling the soil to the lower parts of the plants. In this way, the intake of air into the soil improves and thus normal conditions are created for respiration and root growth, for the development of the root system. This, in turn, improves leaf growth, resulting in increased photosynthesis and the production of more organic matter.

Pruning the tops of young shoots, such as apple, raspberry, cucumber, leads to the cessation of their growth in length and increased growth of side shoots.
Currently, growth stimulants are used to accelerate the growth and development of plants. They are usually used for cuttings and transplanting plants to accelerate the formation of roots.
For economic purposes, it is sometimes necessary to slow down the growth of plants, for example, the germination of potatoes in winter and especially in spring. The appearance of sprouts is accompanied by a deterioration in the quality of tubers, the loss of valuable substances, a decrease in the starch content, and the accumulation of the toxic substance solanine. Therefore, to delay the germination of tubers before storage, they are treated with inhibitors. As a result, the tubers do not germinate until spring and remain fresh.

The general scheme of development of each organism is programmed in its hereditary basis. Plants vary dramatically in lifespan. Plants are known that complete their ontogeny within 10-14 days (ephemera). At the same time, there are plants whose life expectancy is calculated in millennia (sequoias). Regardless of lifespan, all plants can be divided into two groups: monocarpic, or fruiting once, and polycarpic, or fruiting repeatedly. Monocarpic plants include all annuals, most biennials, and some perennials. Perennial monocarpic plants (for example, bamboo, agave) begin to bear fruit after several years of life and die off after a single fruiting. Most perennial plants are classified as polycarpic.

Growth - is the process of new formation of structural elements

organism, which include organs, tissues, cells, cell organelles. Growth is accompanied by an increase in the mass and size of the plant. Unlike animals, plants grow throughout their lives, forming new cells, tissues and organs.

Development - these are qualitative changes in the structure and functional activity of the plant and its parts in the process of its individual development (ontogenesis). Growth and development are closely related to each other and occur simultaneously. Growth is one of the properties of development, and development cannot proceed without growth; it needs at least a barely begun growth. In the future, the development process is decisive.

The basis of plant growth is the division and growth of meristematic cells. Cell growth occurs in three phases: embryonic, stretching and differentiation.

AT embryonic phase growth is carried out due to the division of the meristematic cell with the formation of daughter cells. Daughter cells increase in size and, reaching the size of the parent, divide again. These processes require large amounts of nutrients and energy.

Stretch phase characterized by a significant increase in cell size. Vacuoles appear in them, which gradually; merge into one big one. The cell wall is stretched, its new dimensions are fixed by the inclusion of cellulose microfibrils.

After the deposition of cellulose molecules inside and especially on the surface of the primary membrane (secondary thickening), the extensibility of the cell membrane decreases, and the turgor increases, which stops the process of absorption of water by the cell.

During this period, the cell gradually loses its ability to further stretch.

AT phase of differentiation the final formation of the cell occurs, its transformation into a specialized one, i.e. performing a certain specific function: water-conducting (xylem vessels and tracheids), conducting organic substances (phloem sieve tubes), storage (pa-

renchyma), mechanical (libriform), etc.

growth regulators.

Growth is due to heredity and is regulated with the help of specific physiologically active substances - phytohormones and inhibitors. The first cause acceleration of growth and development, the second, on the contrary, limit growth. An important role in the regulation of plant growth with the help of phytohormones is played by their concentration. Growth stimulation is observed only at very low concentrations of these substances in plant cells; high concentrations can act as inhibitors.

Phytohormones include auxins (indolylacetic acid IAA), gibberellins, and cytokinins. Natural inhibitors are abscisic acid, phenolic inhibitors, ethylene.

The general properties of phytohormones are as follows: each hormone is involved in the regulation of a number of structural and functional processes, i.e. has polyfunctional properties; the strength and nature of the action of hormones depend on the concentration; In a plant, hormones do not act in isolation, but in close interaction with each other. Hormones are formed in small amounts mainly in meristematic tissues, as well as in leaves and from them move to those parts of the plant where growth or morphogenesis processes occur.

Auxins activate cell division and elongation, participate in growth movements, provide apical dominance - suppression of lateral growth by the apical bud, stimulate root formation.

Gibberellins enhance the growth of the stem in length, accelerate the growth of fruits and seed germination.

Cytokinins accelerate cell division, delay the aging of leaves, callus tissues cause the formation of shoots, interrupt the dormancy of dormant buds, increase plant resistance to adverse effects.

Natural growth inhibitors suppress the action of phytohormones or inhibit their synthesis. They are widely distributed in seeds, dormant buds. They are also associated with lignification of shoots of woody plants, which contributes to their successful overwintering.

Abscisic acid regulates the processes of aging and leaf fall, ripening of fruits, stimulates the transition to rest of the kidneys, seeds, bulbs. Regulates the movement of stomata during drought. This acid is called the stress hormone, as its amount increases under adverse conditions.

Ethylene inhibits cell division, promotes tissue aging, accelerates leaf fall, fruit ripening.

Phenolic compounds regulate the amount of auxins in the cell, and also participate in the regulation of root formation, cell elongation.

Synthetic plant growth regulators are widely used in plant growing practice. They are used in pre-sowing seed treatment, rooting cuttings, transplanting vegetable and flower crops, as well as mature woody plants.

Basic patterns of growth

In nature, plants experience alternation of periods of intensive growth and slowing down or complete cessation of growth. This phenomenon is called periodicity of growth and associated with the change of seasons. In autumn, plants shed their leaves, and sometimes entire shortened shoots, stop growing and fall into a dormant state. Distinguish daily and age growth frequency. The daily frequency of growth depends on temperature. Most of our tree species grow most intensively in height at the age of 20 - 30 years, and the increase in trunk volume usually reaches maximum values ​​​​at 50 - 60 years.

Peace is the state of a plant in which there is no visible growth. It is characterized by a reduced water content in plant tissues, a weakened metabolism and reduced respiration. Not the whole plant often goes into a dormant state, but its individual organs, for example, dormant buds, seeds. There are two types of rest: organic and forced. At organic peace the plant and its organs do not come out of dormancy even under favorable conditions. Deep dormancy is characteristic of the seeds of many tree species. Under forced rest understand such a physiological state of seeds, buds, shoots, in which they cannot bloom due to adverse external conditions (lack of water, low temperature).

All parts of the plant have a mutual influence on each other, they are coordinated with each other. This phenomenon is called cor- relation growth. So, for example, the central shoot is ahead of the lateral ones in the ro-et, but it is worth damaging the apical bud or removing the upper part of the central shoot, as the lower branches begin to grow vertically, taking on the functions of the apical shoot. This technique is widely used in gardens and landscape plantings in the formation of tree crowns. The inhibitory effect of the apical kidney on the lateral is called apical dominance. A similar correlative inhibition is observed at the roots. "Nipping" the main root leads to the formation of numerous lateral roots. Growth correlation is based on hormonal regulation of the redistribution of nutrients and physiologically active substances in the plant.

Polarity plants is a specific orientation of structures and processes in space. It manifests itself in the formation of shoots at the morphologically upper end of the stem cutting, and roots at the morphologically lower end, regardless of whether the cutting is in a straight or inverted position. The phenomenon of polarity is associated with the transport of auxin along the phloem from the morphologically upper end to the lower one. Polarity ensures the organization in space of individual parts of an organism, the division of functions along the axis of the plant.

plant movements

The reason that causes a change in the arrangement of plant organs in space is an external factor. In response to the unilateral action of the factor, bends occur in plants, leading to a change in the orientation of the organ. These movements, caused by a unilaterally acting stimulus, are called tropisms. If the bend is caused by the directional action of light, this is phototropism, gravity - geotropism, uneven distribution of moisture in the soil - hydrotropism, nutrients - chemotropism. Due to positive phototropism, plants form sheet mosaic, those. leaves in space are arranged so as to maximize the use of light. The most striking example of chemotropism is the growth of roots towards higher concentrations of nutrients in the soil.

Nastyami are called growth movements that occur in response to the action of diffuse, i.e. not having a strict direction, factors. Such factors include temperature (termonasty), light (photonasty), etc. Nastia is characteristic of leaves, petals, and sepals. An example is the opening and closing of flowers during the change of day and night. One of the factors resulting in nastia is uneven cell growth by stretching. In most cases, nastic bends are turgor movements. They are carried out due to the increase and decrease in the vacuoles of specialized cells of osmotically active substances, as a result of which the turgor pressure changes. The process of opening and closing of stomata is associated with a change in turgor pressure in guard cells.