Rhythm of growth- alternation of slow and intensive growth of a cell, organ, organism - sometimes daily, seasonal - is the result of the interaction of internal and external factors.

Periodicity of growth typical for perennial, winter and biennial forms, in which the period of active growth is interrupted by a period of rest.

Long period of growth law- The rate of linear growth (mass) in ontogeny of a cell, tissue, any organ, plant as a whole is variable and can be expressed by a sigmoid curve (Sachs curve). The linear growth phase was called by Sachs the big growth period. Allocate 4 sections (phases) of the curve.

1. The initial period of slow growth (lag period).
2. Log period, long growth period according to Sachs)
3. Growth retardation phase.
4. Stationary state (end of growth).

Growth correlations (stimulating, inhibitory, compensatory)- reflect the dependence of the growth and development of some organs or parts of the plant on others, their mutual influence. An example of stimulating correlations is the mutual influence of the shoot and the root. The root provides the above-ground organs with water, nutrients, and organic substances (carbohydrates, auxins) necessary for root growth come from the leaves to the roots.

Inhibitory correlations (inhibitory) - O During days, organs inhibit the growth and development of other organs. An example of these correlations is the phenomenon a peak dominance- inhibition of the growth of lateral buds, shoots by the apical shoot bud. An example is the phenomenon of the “royal” fruit that sets in first. Using in practice the technique of removing apical dominance: crown formation by cutting off the tops of dominant shoots, picking seedlings and seedlings of fruit trees.

TO compensatory correlations reflect the dependence of growth and the competitive relationship of individual organs on the supply of nutrients to them. In the process of growth of the plant organism, there is a natural reduction (abscission, dying off) or part of the developing organs is artificially removed (pinching, thinning of the ovaries), and the rest grow at a higher rate.

Regeneration - restoration of damaged or lost parts.

• Physiological - restoration of the root cap, replacement of the crust at tree trunks, replacement of old xylem elements with new ones;
• Traumatic - healing of wounds of trunks and branches; associated with the formation of callus. Restoration of the lost aboveground organs due to the awakening and regrowth of axillary or lateral buds.

Polarity - specific differentiation of structures and processes in space inherent in plants. It manifests itself in a certain direction of growth of the root and stem, in a certain direction of movement of substances.

60. Phases of growth: embryonic, stretching, differentiation and their physiological characteristics. Differentiation of cells and tissues.

Embryonic phase or mitotic cycle the cell is divided into two periods: the actual cell division (2-3 hours) and the period between divisions - interphase (15-20 hours). Mitosis is a method of cell division in which the number of chromosomes is doubled, so that each daughter cell receives a set of chromosomes equal to the set of chromosomes of the mother cell. Depending on the biochemical characteristics, the following stages of interphase are distinguished: presynthetic - G 1 (from the English gap - interval), synthetic - S and premitotic - G 2. During stage G 1, the nucleotides and enzymes necessary for DNA synthesis are synthesized. RNA synthesis takes place. During the synthetic period, DNA duplication and the formation of histones occur. At the G 2 stage, the synthesis of RNA and proteins continues. Replication of mitochondrial and plastid DNA occurs throughout the entire interphase.

Stretching phase. Cells that have stopped dividing proceed to growth by stretching. Under the action of auxin, the transport of protons into the cell wall is activated, it loosens, its elasticity increases, and it becomes possible for additional water to enter the cell. The growth of the cell wall occurs due to the inclusion of pectin substances and cellulose in its composition. Pectin substances are formed from galacturonic acid in the vesicles of the Golgi apparatus. Vesicles approach the plasmalemma and their membranes merge with it, and the contents are incorporated into the cell wall. Cellulose microfibrils are synthesized on the outer surface of the plasmalemma. An increase in the size of a growing cell occurs due to the formation of a large central vacuole and the formation of cytoplasmic organelles.

At the end of the stretching phase, the lignification of the cell walls increases, which reduces its elasticity and permeability, growth inhibitors accumulate, and the activity of IAA oxidase increases, which reduces the auxin content in the cell.

Cell differentiation phase. Each plant cell contains in its genome complete information about the development of the whole organism and can give rise to the formation of a whole plant (the property of totipotency). However, being a part of an organism, this cell will realize only a part of its genetic information. The signals for the expression of only certain genes are combinations of phytohormones, metabolites, and physicochemical factors (for example, the pressure of neighboring cells).

Maturity phase. The cell performs the functions that are laid down in the course of its differentiation.

Cell aging and death. With aging of cells, the weakening of synthetic and strengthening of hydrolytic processes occurs. In organelles and cytoplasm, autophagic vacuoles are formed, chlorophyll and chloroplasts, endoplasmic reticulum, Golgi apparatus, nucleolus are destroyed, mitochondria swell, the number of cristae decreases, the nucleus vacuolizes. Cell death becomes irreversible after the destruction of cell membranes, including the tonoplast, the release of the contents of the vacuole and lysosomes into the cytoplasm.

Aging and cell death occurs as a result of the accumulation of damage in the genetic apparatus, cell membranes and the inclusion of genetic programmed cell death - PCD (programmed cell death), similar to apoptosis in animal cells.

Characteristics of the factors that determine the patterns of plant growth and development.

All previously studied processes in the aggregate determine, first of all, the implementation of the main function of the plant organism - growth, the formation of offspring, and the preservation of the species. This function is carried out through the processes of growth and development.

The life cycle of any eukaryotic organism, i.e. its development from a fertilized egg to full formation, aging and death as a result of natural death is called ontogenesis.

Growth is a process of irreversible neoplasm of structural elements, accompanied by an increase in the mass and size of the organism, i.e. quantitative change.

Development is a qualitative change in the components of an organism, in which the existing forms or functions are transformed into others.

Both processes are influenced by various factors:

external abiotic environmental factors, such as sunlight,

internal factors of the organism itself (hormones, genetic characteristics).

Due to the genetic totipotency of the organism, determined by the genotype, there is a strictly sequential formation of one or another type of tissue in accordance with the stage of development of the organism. The formation of certain hormones, enzymes, tissue types at a certain stage of plant development is usually determined by the primary activation of the corresponding genes and is called differential gene activation (DAG).

Secondary activation of genes, as well as their repression, can also occur under the influence of some external factors.

Phytohormones are one of the most important intracellular regulators of gene activation and the development of a process associated with growth processes or the transition of a plant to the next phase of development.

The studied phytohormones are divided into two large groups:

growth promoters

growth inhibitors.

In turn, growth stimulants are divided into three classes:

gibberellins,

cytokinins.

Auxins include substances of an indole nature; indole-3-acetic acid (IAA) is a typical representative. They are formed in meristematic cells and move both basipetally and acropetally. Auxins accelerate the mitotic activity of both apical meristems and cambium, delay the fall of leaves and ovaries, and activate root formation.

Gibberellins include substances of a complex nature - derivatives of gibberellic acid. Isolated from ascomycete fungi (genus Gibberella fujikuroi) with a pronounced conidial stage (genus Fusarium). It is in the conidial stage that this fungus causes the disease of "bad shoots" in rice, characterized by the rapid growth of shoots, their elongation, thinning, and, as a result, death. Gibberellins are also transported in the plant acropetally and basipetally both along the xylem and phloem. Gibberellins accelerate the phase of cell elongation, regulate flowering and fruiting processes, and induce new formation of pigments.

Purine derivatives belong to cytokinins, the typical representative of which is kinetin. This group of hormones does not have such a pronounced effect as the previous ones, however, cytokinins affect many links of metabolism, enhance the synthesis of DNA, RNA, and proteins.

Growth inhibitors are represented by two substances:

abscisic acid,

Abscisic acid is a stress hormone, and its amount increases greatly with a lack of water (closing of the stomata) and nutrients. ABA inhibits the biosynthesis of nucleic acids and proteins.

Ethylene is a gaseous phytohormone that inhibits growth and accelerates fruit ripening. This hormone is secreted by the ripening organs of plants and affects both other organs of the same plant and plants nearby. Ethylene accelerates the shedding of leaves, flowers, fruits due to the release of cellulase at the petioles, which accelerates the formation of a separating layer. Ethylene is formed during the decay of etrel, which greatly facilitates it practical use in agriculture.

Plant growth (patterns and types).

The term growth in plants means several processes:

cell growth,

tissue growth,

the growth of the plant organism as a whole.

Cell growth is characterized by the following phases:

Embryonic phase (there are no vacuoles, the rest of the organelles are in small quantities).

The stretching phase (appearance of a vacuole, strengthening of the cell wall, increase in cell size).

The phase of differentiation (the appearance in the cell of organelles specific for a given tissue).

The growth of tissue, depending on its specificity, can take place according to any of the types:

Apical (shoot, root).

Basal (leaf).

Intercalary (stem in cereals).

The growth of a plant organism as a whole is characterized by the presence of the following phases:

Lag phase or induction growth (seed germination).

Log-phase or the phase of logarithmic growth (the formation of the vegetative mass of the plant).

The phase of slow growth (during the fruiting period, when the formation of new vegetative parts of the plant is limited).

The stationary phase (coincides, as a rule, with the aging and dying off of the plant).

The growth rate and the relative growth or gain in plants are determined by measuring the parameters of the plants in a certain time regime.

To determine the growth, a variety of methods are used, in particular:

using a ruler,

using a horizontal microscope,

using labels,

with the help of an auxanograph,

using large-scale photography.

On average, the growth rate of plants is 0.005 mm / min., However, there is fast growing plants and organs: stamens of cereals grow at a speed of 2 mm / min., bamboo - 1 mm / min.

According to the results of modern research (V.S.Shevelukh), the following classification of growth types has been proposed:

sinusoidal type (the curve of the daily variation of the linear growth rate has the form of a sinusoid with a phase of maximum in the daytime and minimum in the early morning hours) (typical for cereals),

impulsive type of growth (the curve of increasing the rate of growth processes and their inhibition occurs abruptly at a right or acute angle for tens of minutes. The maximum growth rate occurs at 20-21 hours and lasts all night, in the daytime growth is inhibited) (typical for root crops and tubers),

two-wave type (during the day, the growth rate has two waves, reaching two maximum and minimum),

leveled type of growth (the growth curve is smooth).

Types of movement in plants.

Despite the fact that plants, as a rule, are permanently fixed in the surrounding space, they are capable of a number of types of movement.

The main types of movement in plants:

tropisms,

Taxis are characteristic only of lower aquatic unattached plants,

the first three species are characteristic of higher plants.

Nutations are made by growing apical shoots, rotating around their axis, and aboveground shoots make them only under the influence of hormones, and the roots - both under the influence of hormones and with the help of special cells (statocytes (with statolith organelles), which are able to use the natural forces of gravity during implementation of this process.

The plant produces nastia under the influence of a uniformly acting abiotic factor (light, water, etc.).

The plant performs tropisms under the influence of an unevenly acting abiotic factor (light, water, gravity, etc.).

Plant development (types of ontogenesis, stages of ontogenesis, features of the evocation period, features of the dormancy phase).

The development of plants or ontogenesis is characterized by the fact that a very large number of factors act on the transition of a plant from one phase of ontogeny to another, and their combined action is often necessary.

The following types of plant ontogenesis are distinguished:

By life expectancy:

annual,

biennial,

perennial;

By the number of fruiting:

monocarpic,

polycarpic.

Any plant goes through the following stages of development in the process of ontogenesis:

the embryonic phase (from fertilization of the ovule to the formation of the seed),

juvenile phase (from seed germination to emergence on the soil surface),

the phase of formation of aboveground vegetative organs,

flowering and fruiting phase,

ripening phase,

the phase of withering away.

The most intense is the juvenile phase of development, which is divided into periods such as:

swelling,

pecking,

heterotrophic seedling growth in the dark,

transition to autotrophic type of nutrition.

Almost every ontogenetic change occurs under the influence of internal and external factors. In this case, sunlight is the most important external factor. The transition to an autotrophic method of nutrition, the transition to the budding and flowering phase, the transition to a dormant state in perennial plants are directly related to the effect of the duration of sunlight and are therefore called photomorphogenesis. Light is a signal not only for a change in the phase of development, but also directly affects growth, transpiration, and other physiological processes in the plant. The direct effect of light is expressed in the ability of cells to form the appropriate hormones, in particular abscisic acid, which allows the plant to slow down its growth rate when switching to autotrophic nutrition. The indirect effect of light in the form of the duration of daylight hours determines the transition to the next phase of development, in particular to flowering.

The plant's perception of exposure to sunlight is due to the presence of special photoreceptors and hormones.

The direct influence of light is perceived by the plant with the help of the "cryptochrome" photoreceptor and the "phytochrome" pigment. Phytochrome is especially important, which is capable of perceiving various components of the spectrum of sunlight and, depending on the absorbed wavelength, transforms either into the FK form, absorbing red light with a wavelength of 600 nm, or into the Fdc form, which absorbs far red light with a wavelength 730 nm. Under normal conditions, this pigment is in both forms in equal proportions, however, when conditions change, for example, to shaded, the formation of more pigment Ф to, and this determines the elongation and etiolation of shoot tissues. Based on the action of these photoreceptors and pigments, the plant undergoes daily changes in a certain rhythm, which is called the circadian, or biological clock of the plant.

The light factor also causes the synthesis of certain hormones, which determine the transition of the plant to the flowering phase or to the evocation phase, i.e. transition from vegetative state to generative development. The main hormone acting at this stage of ontogenesis is the hormone "florigen", which consists of two groups of hormones:

gibberellins, causing the formation and growth of peduncles,

anthesins, causing the formation of flowers.

Understanding this point is very important in practice, especially in fruit growing, where the use of the rootstock and scion in certain phases of ontogenesis will affect the rate at which the grafted plant begins to bear fruit. The flow of hormones, including florigen, goes from the scion to the stock, so it is important to use the stock from a plant in a certain phase of development. Floral morphogenesis is controlled by a complex system of many factors, each of which, in the required concentration and at the right time, starts its own chain of processes leading to the setting of flowers.

Second important factor The temperature factor plays a definite role in the formation of floral morphogenesis. It is especially important for winter and biennial crops, since it is the lowered temperatures that cause in these crops those biochemical transformations that determine the synthesis of florigen and other accompanying hormones that determine the initiation of flowering.

It is on the action of low temperatures that the vernalization technique is based, which is used in various experimental studies, when it is necessary to accelerate the change of generations in winter crops. Treatment of plants with gibberellins leads to the same results, thanks to which it is possible to accelerate the flowering of biennial plants.

In relation to the photoperiod, plants are divided into three groups:

short-day plants (flowering with a day length of less than 12 hours) (chrysanthemum, dahlia, Jerusalem artichoke, millet, sorghum, tobacco),

long-day plants (flowering with a day length of more than 12 hours) (aster, clover, flax, onions, carrots, beets, spinach),

neutral plants (flowering does not depend on the length of the day) (sunflower, buckwheat, beans, rapeseed, tomato).

In the ontogeny of plants, there is necessarily a phase of weakening of vital activity, which is called the state of dormancy. In annual plants, this state occurs only once - during the formation of the seed, in perennial plants - many times during the transition to existence in unfavorable environmental conditions (winter, drought). Rest is a state of a plant that is characterized by the absence of growth phenomena, an extreme degree of respiratory depression and a decrease in the intensity of the transformation of substances.

Distinguish between summer and winter dormancy in perennials, deep and forced dormancy in all plants. Forced rest is possible only with the participation of a person who can provide special conditions for storing resting organs in special storage facilities using special methods. A very important moment in the transition to a state of dormancy is the stage of post-harvest ripening, which allows preventing premature germination of seeds, concentrating the maximum amount of reserve substances.

Krenke's theory of aging and rejuvenation of plants.

In the process of ontogeny, the plant undergoes certain changes that are associated with the phenomenon of age-related variability. A theory explaining the patterns of this variability was proposed in the 40s of the last century by N.P. Krenke. The main postulates of this theory:

Every organism, from its inception, is continuously aging until its natural death.

In the first half of life, aging is interrupted periodically by rejuvenation, i.e. the formation of new shoots, leaves, etc., which slows down the rate of aging.

Plants are characterized by a physiological age, which determines the true age of a plant organ: the leaves of one-year and ten-year-old trees are unequal, and the leaves on the same tree, but on the shoots of a different order, are also unequal. Distinguish between the concept of "age" (calendar age) and "age" (physiological age. Age is determined by the age of the organ and the mother plant. fruit tree leaves on shoots of higher branching orders are physiologically older than leaves of the same age on shoots of lower branching orders. Therefore, in form, anatomical structure According to physiological and biochemical characteristics, the upper leaves, despite their younger age, show signs of greater aging, their lifespan is often shorter than that of middle leaves on the same shoot.

The cyclical nature of ontogenetic development lies in the fact that daughter cells, during their neoplasm, are temporarily rejuvenated in relation to mother cells.

The aging rate and normal average life span are determined by the initial potential for viability and are determined by the genetic characteristics of the species.

P.G. Shitt. In the 60s of the last century, he first established the presence of age-related qualitative changes at the roots. I.V. Michurin also pointed to a close relationship between organ-forming processes in organisms and age-related variability.

The established N.P. Krenke, the patterns of changes in the morphology of leaves and shoots in connection with their age made it possible to develop recommendations for the early diagnosis of early maturation of plants within a species, to reveal correlations between the quality of tubers and root crops and early maturity of the variety. It has been established that early ripening varieties are characterized by a sharp change in the morphological characteristics of leaves (rapid yellowing and leaf death), while in late ripening varieties, changes occur gradually. This regularity is important in the process of breeding varieties for early maturity and quality.

Morphological characters are closely related to genetically inherent early maturity, which makes it possible to use them in the selection of fruit crops, for example:

in annual seedlings of early ripening varieties of apple, internodes are shorter, branching is stronger, leaves are thicker than in varieties that later enter fruiting,

in biennial apple seedlings, the intensity of green leaf color during the transition from the upper tiers to the lower in early ripening forms changes more sharply than in late ripening ones,

the higher the stem fruit plant a stalk or bud is taken (with vegetative propagation), the sooner after rooting or budding the plant is able to bloom.

On the basis of Krenke's theory, the techniques of pruning plants, the technology of selecting shoots and their parts of the required quality during vegetative propagation of plants, providing better rooting of cuttings, the technology of achieving an optimal combination of vegetative and generative development of plants during cuttings and grafting were improved.

Features of the maturation of the productive parts of plants.

The productive parts of plants are referred to as organs generative reproduction(fruits, seeds) and organs of vegetative reproduction (tubers, bulbs). The rest of the productive parts (leaves in green crops, stems, root crops, etc.) do not have the function of reproduction and therefore the patterns of growth and development are not so important.

seed protection,

spreading seeds.

For the implementation of these functions, various fruits have appropriate adaptations (dry and juicy fruits, hooks, lionfish, attractive taste, etc.).

There are four phases in fetal development:

Formation of the ovary before pollination,

Growth through cell division immediately after pollination and fertilization,

Growth by stretching cells

Maturation.

The growth of the ovary is stimulated by germinating pollen even before the formation of the zygote, and the intensity of this growth is directly proportional to the amount of germinating pollen. Even foreign pollen can promote the growth of the ovary, which is explained by the high IAA content in the pollen.

The treatment of flowers with exogenous auxin in many plants with succulent fruits induces the growth of the ovary and the formation of parthenocarpic ones, i.e. seedless fruits. Treatment with gibberellin also causes fruit setting in many plants (grapes, apple trees, tomatoes, etc.). The presence of cytokinin is necessary for the growth of young fruits, but exogenous cytokinins do not cause the formation of parthenocarpic fruits.

At the beginning of the formation of an ovary in a flower, its growth occurs as a result of cell division, which sharply increases after pollination. Then comes a more prolonged phase of cell stretching. The growth pattern is highly dependent on the type of fetus.

The regulation of fruit growth is carried out by phytohormones. IAA in the ovary first comes from the column and from germinating pollen. Then the developing ovule becomes the source of IAA. In this case, the aging hormone (ethylene) also plays a role, which ensures the wilting of the flower after pollination. The resulting seeds supply auxin to the pericarp, which activates growth processes in it. With a lack of auxin (a small number of seeds formed), fruits fall off.

Thus, in wheat caryopses, the maximum amount of cytokinins is observed immediately after flowering during the transition to the formation of endosperm. Then the content of gibberellins begins to increase, and later IAA, the concentration of which reaches its maximum value in the phase of milk ripeness. With the transition to waxy ripeness, the level of gibberellins and auxins rapidly decreases, but the content of ABA increases, which contributes to the deposition of reserve substances in the endosperm. When the increase in dry mass of caryopses stops and the seeds become dehydrated (full ripeness), the ABA content decreases. The decrease in the amount of all phytohormones is explained by their transition to a bound state. This order of change in the ratio of phytohormones in forming wheat caryopses is determined by the sequence of development of the embryo and endosperm. When the caryopsis ripens, carbohydrates and proteins accumulate, changes in nucleic acid metabolism occur, and plastic substances actively move into the caryopsis from the stems and leaves. The stems become lignified (the content of fiber and lignin decreases, which are converted into starch). When the grain ripens, the protein becomes more resistant to the action of proteolytic enzymes, the amount of monosaccharides decreases and the amount of starch increases.

Legumes store significantly less starch and other carbohydrates than cereals.

In the cultivation of grain and leguminous crops, a separate method of harvesting is often used, which makes it possible to better ensure the transfer of plastic substances from stems to seeds after mowing and ripening in swaths. Treatment of crops during the period of waxy ripeness with a solution of ammonium nitrate accelerates the ripening of these crops by 5-7 days.

When oilseeds ripen, fats not only accumulate, but also qualitatively change. Unripe seeds contain more free and saturated fatty acids, while mature seeds increase the content of unsaturated fatty acids.

In juicy fruits, the highest content of gibberellins and auxin in the pericarp is observed at the beginning of its development. Then the level of these phytohormones decreases and increases again in the last phase of growth. The content of cytokinin temporarily increases during the period of the most intense growth of the fetus. Cessation of pericarpal growth coincides with the accumulation of ABA in its tissues.

The period of cell elongation in juicy fruits and especially the end of this period are characterized not only by intensive growth, but also by the accumulation of organic matter. There is an increase in carbohydrate content and organic acids, starch is deposited.

Ripening of some fruits correlates well with an increase in respiration rate. The period of increased production of carbon dioxide by the fetus is called menopause, and during this period the fetus undergoes a change from immature to ripe. Ethylene treatment stimulates this period and the ripening of ripe fruits. Ethylene increases membrane permeability in fetal cells, which enables enzymes previously separated from substrates by membranes to react with these substrates and begin their destruction.

Auxin is also involved in fruit ripening, and during fruit ripening and leaf fall, auxin and ethylene act as antagonists. Which hormone dominates in this case depends on the age of the tissue.

In a number of crops, the predominant method of reproduction has become precisely the method of reproduction using the organs of vegetative reproduction (for example, potatoes). Therefore, the formation of these bodies, as performing and reproductive function, and, at the same time, serving as a source of food for humans, requires separate consideration.

The process of tuberization in physiological terms is best studied in potatoes. With a long day and high temperatures (over 29 degrees), they can turn into vertical leafy shoots, and at normal (lower) temperatures, a tuber forms at the end of the stolon. Tuberization is always associated with inhibition of the growth of both aerial shoots and stolons. A short day promotes the entry of plastic substances into the tubers.

Tuber formation includes three stages;

preparatory - the appearance and growth of stolons,

the laying and growth of the tuber itself,

ripening and dormancy of the tuber.

The formation of stolons from axillary buds is favored by their darkening (which is why hilling is required in the technology of potato cultivation). IAA, together with gibberellins, supplied in sufficient quantities from the aerial parts, switch the genetic program of axillary bud development from the development of a vertical leafy shoot to the formation of a stolon. Gibberellin is also necessary for lengthening the internodes of the stolon.

The laying of tubers at the distal ends of the stolons is associated with a sharp inhibition of their growth in length. Apparently, this suppression is caused by an increase in the concentration of ABA, which is formed in large quantities in leaves on a short day. Under short-day conditions, the synthesis and intake of IAA and gibberellins decrease. At the same time, the ratio of cytokinins to auxins increases.

The dormancy of tubers is associated with a sharp slowdown in respiration, disintegration and synthesis of biopolymers, and cessation of growth processes. In potato tubers, only meristematic tissues, primarily the eyes, are in a state of deep dormancy. The storage tissue is able to quickly activate in response to damage (wound peridermis is formed during mechanical damage).

The state of deep dormancy of the eyes is due to the high content of ABA, caffeic acid and scopoletin.

The release of ocelli from a state of deep dormancy is associated with a drop in the ABA content (by a factor of 10-100) and an increase in the concentration of free gibberellins. Treatment with stimulants based on gibberellic acid ends the dormant state of the tubers and allows for summer potato planting in the south.

Growth processes do not stop in bulbs during the dormant period, although they are very slow. The resting state is maintained by a high concentration of ABA. Before germination, the ABA level decreases, while the content of cytokinins, gibberellin, and auxins increases.

The processes of formation of rhizomes and stolons, as well as the ability of plants to root with the help of layering and cuttings, obey the same patterns in the change in the work of different phytohormones.

The use of growth regulators in agricultural practice.

Growth regulators are widely used in agricultural practice in the following areas:

At the stage of sowing, planting,

At the stage of flowering, setting, crop formation management,

At the stage of cleaning,

At the resting stage.

At the sowing stage, planting is used:

for rooting hard-to-root cuttings, such as grapes,

for better survival of vaccinations,

for better seed germination

At the stage of flowering, setting, crop formation management, the following are used:

to stimulate the beginning of flowering,

to increase the number of fruit set,

to stimulate female flowering in dioecious species.

Gibberellins:

to increase the size of the fruit,

to improve the quality of economically valuable organs (contribute to an increase in sugars in fruits, stems, stems, root crops, etc.),

to stimulate male flowering in dioecious species.

Ethylene and abscisic acid also stimulate female flowering in dioecious species.

At the stage of cleaning use:

Ethylene and abscisic acid and a number of other growth inhibitors (for example: magnesium chlorate, hydrel, etrel):

to accelerate ripening, increase the harmony of the return of the crop,

for defoliation,

for desiccation (pre-harvest drying of stems and leaves),

for senication (acceleration of ripening by 5-7 days in areas with a short warm period)

At rest stage:

To prolong the state of dormancy, ethylene and abscisic acid are used to process ware potatoes, root crops, fruits (either sprayed with a 0.5% solution of Hydrel, or regulate the composition of the atmosphere in the storage),

To disturb the state of rest, use:

etherification: for germination of shoots, rhizomes - treatment with sulfuric ether,

warm baths: for distilling lilacs for the New Year (they lower the shoots of the bush in warm (30-35 o C) water for 9-12 hours),

gibberellins for obtaining a second crop of potatoes from freshly harvested tubers (they are soaked for 30 minutes in a mixture of 0.0005% gibberellin and 2% thiourea).

The mechanism (patterns) of plant growth.

Plant growth begins with germination of the seed, which is rich in nutrients, enzymes and phytohormones. The seed germination process requires water, oxygen and optimum temperature... During germination, the intensity of respiration increases, which leads to the breakdown of storage substances: proteins, fats and polysaccharides.

Starch breaks down into sugars, proteins are broken down to amino acids, and the latter to organic acids and ammonia. Fats are broken down into fatty acids and glycerin.

Thus, during seed germination, soluble compounds are used either as a building material, or their transformation, transport and formation of new substances that are used to build cells and organs. Energy for these processes is supplied by oxidative reactions during respiration.

At the same time, as a result of germination, morphogenetic processes begin; root, stem, kidney. (Figure 20).

The mesocotyl grows. epicotyl or hypocotyl. The coleoptile or composite first leaf plays the role of an organ. perforating the soil: light induces leaf growth; the coleoptile breaks through. the complex first sheet is revealed.

It is known that seed germination occurs at the expense of ready-made organic substances, and as soon as the first green leaves appear, photosynthesis begins and the plant enters the juvenile (young) phase of heterotrophic nutrition.

At the top of the stem and root, growth cones are formed, consisting of a meristem, which are capable of a longer division and are resistant to adverse environmental conditions. In addition, the generative organs of plants are formed from these cells. The plant organ (leaves, stem, roots) consists of many cells, therefore organ formation includes the processes of cell differentiation.

Apical meristems, located at the ends of the stem, growing shoots and roots, provide the apical type of growth. Intercalary meristems located between tissues provide width growth. The basal meristems, located at the base of the organ, support growth from the base (eg leaves). In the cells of the meristem, physiological and biochemical differences accumulate, which are due to interaction with other cells, as well as the genetic program that is embedded in it.

Using the tissue culture method, it has been shown that embryonic structures appear in the meristems, which are similar to an embryonic kidney or root. For their occurrence, phytohormones (auxins, cytokinins) are needed in a certain ratio. Whole plants were obtained on isolated protoplasts by adding hormones in a certain ratio.

Organ formation and growth are two fundamentally different processes. They are under different control. For example, shoot formation is inhibited by gibberillin, and shoot growth is accelerated by this hormone; the formation of roots is associated with high, and their growth with low concentrations of auxin.

An important property the growth process is polarity, this is a specific property of plants to differentiate processes and structures in space. In this case, physiological-biochemical and anatomical-morphological differences change in a certain direction, as a result, one end differs from the other. The phenomenon of polarity is manifested both on one cell and on tissue; they have a top and a bottom. Polarity is manifested in the fact that the top of the shoot is positively charged with respect to the base, and the core with respect to the surface.

The influence of external factors on growth.

Plant growth depends on light, temperature, water, mineral nutrition. Plant growth is usually depicted as an S-shaped curve, which means that the growth rate is low at the beginning, then increases, and then slows down again. The optimum temperature for plant growth depends on the latitude to which the plants are adapted. For each type of plant, three points are distinguished: the minimum temperature at which growth is just beginning, the optimal temperature is the most favorable for growth processes and the maximum temperature at which growth stops. The growth rate of the plant rises sharply with increasing temperature. Changes in the temperature coefficient (Q10) show that the growth rate, for example, for cotton, quadruples when the temperature rises by 10 ° C.

The influence of light is associated with phytochrome - a pigment system that absorbs the red part of the spectrum. Light can only be effective when absorbed by the pigment.

The effect of light on etiolation is complex and includes the effect on growth in the extension phase of cells in leaves and internodes, on the formation of true leaves.

Growth is regulated by the duration of daylight (day length). Starting from a certain “critical day length”, this or that process occurs or does not occur.

Photoperiodic exposure affects the rate of growth in the length of internodes, the activity of the cambium, and the shape of the leaves.

A number of metabolic and growth processes are subject to rhythmic fluctuations, which often do not always follow the change of day and night, and in this case has a 24-hour period. The most famous rhythmic movements are the closing of the flowers at night or the lowering of the leaves and the opening during the day.

At the end of the growth process, the aging of the whole plant is observed, the organs fall off, the fruits ripen, the transition to dormancy of the buds, seeds and fruits is observed.

1. 
   What physiological and biochemical processes occur during seed germination?
2. 
   How does light affect the growth process?
3. 
   How does temperature affect plant growth?

Topic number 21.

Plant movement.

Movement is one of the most noticeable manifestations of life, although in plants it manifests itself rather slowly.

In contrast to animals, in plants there is mainly movement of organs by bending, twisting, etc.

In the process of growth and development, plants change their position in space. The movements carried out in this case are sometimes almost impossible to distinguish from "true movements". For example, the unfolding of a flower bud during the blooming of a flower is considered a growth process, but if the same flower closes in the evening and reopens in the morning, then this is considered a movement, despite the common mechanisms underlying both phenomena. Inductive motion is caused by an external stimulus (light, gravity, temperature, etc.); endogenous movement does not need external stimuli.

Irritation and reaction.

Stimulation is understood as an external chemical or physical effect (light, gravity, temperature, touch, shock, etc.) that causes movement, but does not give the energy necessary for movement.

This effect can provide only that amount of energy on which the triggering mechanism of the reaction of movement (the beginning of movement) depends, while the movement itself occurs due to the cell's own energy resources.

The inductive nature of stimulation is manifested, for example, in the fact that one-sided illumination of a shaded plant for a few fractions of a second causes movement (bends) lasting for many hours.

The ability of protoplasm to actively respond to changes external conditions the response to irritation is considered - i.e. irritability.

Perception of irritation includes arousal, which is a change in the state of the cell; it begins with the emergence of an electrical potential (action potential) and leads to a temporary absence of irritability (absence of excitability, refractory period).

In the absence of irritation, the plant cell has a negative resting potential (from –50 to –200 mV); its protoplasm is negatively charged with respect to the outer surface. As a result, a membrane potential arises, leading to the removal of the action potential and the restoration of the resting potential. The restoration of the original potential is called restitution that follows irritation. Restitution is associated with the expenditure of energy, which is inhibited by drugs, with a lack of O 2 and a decrease in temperature.

There are several types of movement - these are tropisms, nastia and endogenous movement.

Tropisms are bends caused by a unilaterally acting stimulus, on which their direction depends. They have names that are determined by the nature of irritation: phototropism (reaction to light), geotropism (reaction to gravity), tiglotropism (reaction to touch), chemotropism (reaction to exposure to chemicals), etc. With positive tropisms, the movement is directed towards the irritating factor, with negative ones from it. With plagiotropisms, a certain angle is maintained to the direction of the stimulus; for diotropisms 9, bends in the transverse direction), this angle is 90 (Fig. 21).

Nastia are bends caused by diffusely acting stimuli, which differ from tropisms in that their direction depends on the structure of the reacting organ. An example of nastic movements: the raising and lowering of petals caused by a change in temperature (opening and closing of a flower) in saffron.

While tropisms are mainly growth movements, nastia are mostly turgor movements. Like tropisms, nastia gets a name depending on the causing stimulus: thermonastia, tigmonastia, etc.

Seismonastia is a reaction to a concussion.

It can occur when an entire plant is shaken, and can be caused by wind, rain, or touch. The seismic response is an extremely rapid turgor movement. The definition of the cell is compressed with a drop in turgor; since this occurs only on one side of an organ, for example a leaf segment, the movement is based on the hinge principle. An example of seismic movements: movement of mimosa, (Fig. 22, 23) flycatcher, duckweed.

The mechanism of movement in seismic reactions is as follows: the first result of stimulation in motor cells is the emergence of an action potential. At the same time, in the motor cells of mimosa, a high concentration of ATP during movement rapidly decreases, which leads to a loss of turgor.

At the end of the movement, restitution occurs, i.e. reverse movement, restoration of the cell to its original state: in the motor tissues, work is done to absorb substances against the concentration gradient, or the formation of osmotically active substances and their secretion in the vacuole. The cell is restored in volume. Endogenous circular movements are performed by a young antenna. (fig. 24)

This circular nutation represents, like the lianas, growth movements. If during its movement the tendril touches something, then the touch causes a bend. The reaction time ranges from 20 seconds to 18 hours. When the touch is short-lived, the curled tendril straightens again. When twisting the antennae, there is a loss of turgor from the lower side and an increase in the upper side, as well as a change in cell permeability and the participation of ATP in this process.

Questions and tasks for verification:

1. 
   What is the difference between the mechanism of movement and the process of growth and development of plants?
2. 
   How does the plant react to external chemical or physical influences?
3. 
   What is tropism and how does it differ from nastia and endogenous movement?

Topic number 22.

Plant development.

Development is the qualitative changes in plants that the body undergoes from emergence from a fertilized egg to natural death.

Plants are divided into two groups according to their lifespan - monocarpic, or once fruiting throughout life, and polycarpic, or multiply fruiting during life. Monocarpic ones include - annual plants, most biennials; to polycarpic - perennial plants.

Development includes: 1) embryonic - from fertilization of the egg to germination of the embryo. This stage is divided into two periods: a) embryogenesis - the period in which the embryos are in the mother plant; b) dormancy - the period from the end of seed formation to its germination; 2) youth (juvenile) - from germination of the embryo to the laying of flower rudiments (the duration of this stage varies and can last up to 10 years); 3) maturity - the first 3-5 years of flowering; 4) adulthood - subsequent years of fruiting; 5) aging.

During each stage of development, new organs appear. The process of forming these organs is called organogenesis.

F.I. Kuperman identified 12 consecutive stages of organogenesis: 1 and 2 - differentiation of vegetative organs occurs; on 3 and 4 - the differentiation of the rudimentary inflorescence; 5 - 8 - the formation of flowers, 9 - fertilization and the formation of a zygote, 10 - 12 - the growth and formation of seeds.

At each stage, first intracellular physiological - biochemical processes occur, and then morphological. The newly formed structures affect cell metabolism.

The shape of the organ is determined by the formative process and is an integral part of organogenesis. In the determination of organogenesis, genetic information is realized, which determines the external and internal shape of the organ.

An organ consists of many cells, which differentiate many times in contrast to cell differentiation. These processes occur in the conditions of interconnection and interaction of the organs of the entire plant organism.

According to Chailakhyan M.Kh. for the transmission of morphogenetic signals, nonspecific growth substances are used, including auxins, gibberellins, cytokinins, etc.

The theory of cyclical aging and rejuvenation assumes that the body as a whole and its individual parts are continuously subjected to aging processes, but at the same time each newly formed cell or organ is young again - the body is rejuvenated in them.

The age state of each part of the plant, according to Krenke, is determined by its own age and the age of the entire maternal organism. With the age of the plant, the rejuvenation of new parts and organs progressively decreases, i.e. aging is progressively declining rejuvenation.

However, the study of a physiologist - the biochemical mechanism of plant development showed that the period of youth (juvenile), maturity and the beginning of the reproduction period is characterized by a gradual increase in the energy level in young tissues, an increase in organic forms of phosphorus; RNA accumulates in the apical meristematic cells. After flowering, a drop in the content of reducing substances and a decrease in the content of nucleic acids are again observed. Consequently, metabolic changes in plant ontogeny have ascending and descending branches of age.

The influence of external factors on the development of plants.

Light affects not only the growth but also the development of plants. Formative processes depend on the length of daylight hours and the quality of light. This phenomenon is called photoperidism. The flowering process of plants depends on the length of the day. From this point of view, plants are divided into two groups: short-day and long-day.

Short-day plants flower under the influence of a light period of less than 12 hours. Long-day - bloom when the length of the day is more than 12 hours. Such plants grow mainly in northern latitudes. Short-day ones grow in southern latitudes, for example, cotton, tobacco, dzhugara, corn, rice and many others. Neutral plants do not respond to day length.

The development process also depends on the quality of light. A number of plant pigments are activated under the influence of red or of blue color, but their activity sharply decreases under the influence of the red long-wave part of the spectrum.

It has been shown that the effects of day length and the phytochrome system are closely interrelated. Active pigments - anthocyanins, are found in chloroplasts, mitochondria and in the cytosol. Many of them are found in the meristematic tissue of the root tip and stem. These pigments were not found in the nucleus and vacuole.

Temperature can also induce plant development. For each plant species, there is an optimum temperature at which the rate of metabolic processes is best passed. Optimum daytime temperatures should alternate and be variable with a nighttime optimum of 15-20C.

Low temperatures (below + 8C) can disturb seed and bud dormancy and stimulate seed germination and bud opening. Induction of this process is called vernalization. Vernalization plays an important role in the formation of flowers in winter crops; in the absence of low temperatures, such plants remain in a vegetative state for several years. In most rosette plants that need cold (for example, turnips, carrots, cabbage) and seedlings (for example, rape, but not winter cereals), gibberellin treatment replaces vernalization; on a long day (Figure 25).

Questions and tasks for verification:

1. 
   What are the phases of plant development?
2. 
   What is the mechanism of organogenesis?
3. 
   How conditions affect external environment on the development of plants?

Topic number 23

Plant resistance to unfavorable environmental conditions.

Plant resistance is an urgent problem in crop production. The relationship of plants with the environment is in the nature of their response to unfavorable environmental conditions: it is high, low temperature, lack of water, soil salinity, environmental pollution, etc.

Plants are subdivided into drought, frost, heat, and salt tolerant plants.

V Central Asia one of the urgent problems is the salt tolerance of plants. Salinization of the soil creates extremely unfavorable conditions for the growth of plants. The accumulation of even harmless salts increases the osmotic pressure of the soil solution, which complicates the water supply to plants. Some salts act as specific poisons on plants. As a result, it is difficult to distinguish between the osmotic and toxic effects of salts, since it depends on the concentration and physical and chemical properties of salts. At the same time great importance also have biological properties of plants.

Plants are divided into two main groups according to their relation to soil salinity; holophytes and glycophytes. According to the definition of P.A. Genkel “halophytes are plants of saline habitats. easily adapting in the process of their ontogenesis to the high content of salts in the soil, due to the presence of signs and properties that have arisen in the process of evolution under the influence of the conditions of existence. Plants of fresh habitats that have a relatively limited ability to adapt to salinity in the processes of individual development are called glycophytes. since the conditions of their existence in the processes of evolution did not favor the emergence of this property ”.

Halophytes and glycophytes are found both among higher plants and lower ones. However, in nature there are plants with intermediate properties, facultative halophytes, such as cotton. There are many plants with varying degrees of glycophytism or halophyticism. Halophytes of various plant families on saline soils form the so-called saline vegetation with a peculiar morphological and anatomical appearance. A relatively high content of salts in the soil is necessary for their growth and development (with the amount of salts from 0.3 to 20%). Study of the ecology, morphology and physiology of many halophytes.

By virtue of biological features some halophytes absorb relatively small amounts of salts, others absorb significant amounts. accumulating them in tissues and thereby regulating the internal osmotic pressure. They have the ability to regulate their salt regime: with excessive accumulation of salts, they can release them with the help of special glands by dropping leaves overflowing with salts and through root excretions. Salicornia tissues accumulate 10.1% salts (NCl, Na 2 SO 4) based on the water contained in a living plant. The absorption of non-nutritive salts play an essential role in the life of halophytes as regulators of water loss by plant organs. Due to the large accumulation of salts, holophytes have a high osmotic pressure of the cell sap. With a large sucking force of the root system, exceeding the osmotic pressure of the soil solution, halophytes are able to absorb water from saline soil. Due to their peculiarities, halophytes relatively easily overcome the high osmotic pressure of the soil solution. Their peculiarities are that they are able to accumulate organic matter or mineral salts. The metabolism of holophytes differs from glytophytes. Photosynthesis, respiration, water exchange, enzymatic reactions are lower in halophytes than in glycophytes. An increase in the viscosity and a decrease in the elasticity of protoplasm in halophytes in comparison with glycophytes changes their water regime and drought resistance. In the processes of ontogenesis, halophytes are more adapted to grow in conditions of high salt concentration and do not lose their ability to form the process. (fig. 26)

Salinity is mainly due to the increased sodium content in the soil, which prevents the accumulation of other cations such as potassium and calcium.

Salinization is harmful to glycophytes, which include cultivated plants. Under conditions of salinity, water inflow is hindered due to the increased water potential; nitrogen metabolism is disturbed: ammonia and other substances poisonous to plants accumulate. Increased concentration of salts, especially chloride. uncouples oxidative phosphorylation (P / O) and reduces the content of ATP. In plants that are not resistant to salinity, the ultrastructure of the cytoplasm and chloroplasts of cells is disrupted. The negative effect of salts affects, first of all, the root system and at the same time the outer cells of the root, which are in direct contact with the salt solution, suffer. In glycophytes, all cells are affected, including cells of the conducting systems. Analysis of Fig. 27 shows that in control plants and in plants that grew earlier under conditions of salinization with sodium sulfate, the isolation of protoplasm is absent and plasmodesmata are easily detected. In plants that previously grew on a nutrient medium with sodium chloride, there is no isolation of protoplasm at the points of growth,

But in some cells it is still preserved.

Rice. 27. The state of protoplasm at the points of growth and in the leaves of cotton during stratification of the nutrient medium.

Control: a - growth point, b - leaf; after salinization with Na 2 SO 4; c - growth point, g - leaf; after salinization with NaCl: e - point of growth, f - leaf. I took it away. 400

Halophytes, in turn, are divided into three groups:

Group I includes plants whose protoplasm is resistant to accumulation a large number salts. (salineros)

Plants belong to II. which accumulate salts in the roots. but do not accumulate in the cell sap. (bush tamariks. sucker)

Group III includes plants. in which the cytoplasm of cells is poorly permeable to salts, and high pressure cells are provided due to the accumulation of carbohydrates formed during intensive photosynthesis. Salt tolerance of plants is a genetic trait and manifests itself in the process of growth and development.

Drought resistance is determined by a number of physiological and biochemical features and, above all, by the nature of the accumulation of proteins.

Drought-resistant and heat-resistant plants are capable of synthesizing more heat-resistant enzyme proteins. These plants have the ability to increase transpiration, which allows or reduces the temperature.

It was found that the effect of low temperatures changes depending on the hydration of tissues. Dry seeds are able to withstand -196C and not die. The main damage to plants is caused by ice formation in the cells and in the intercellular spaces, while the structure of the cytoplasm is disrupted and the cell dies. The hardening process helps plants to increase their resistance to low temperatures and it is confined only to a certain stage of development. So. woody plants must complete the growth process and there must be an outflow of plastic substances from the aboveground organs into the root system. Therefore, the weight period of plants must have time to end in summer period... Plants that did not have time to complete their growth processes by autumn are not capable of hardening.

Drought changes the growing season of plants and negatively affects the resistance of plants to low temperatures.

Possessing adaptive functions, the plant is able to grow under the most unfavorable conditions. For example. glycophytes growing on salted are characterized, like halophytes, by reduced metabolism.

The toxicity of salts invariably increases with increasing temperature.

Ratio mineral substances Plants also change under the influence of toxic salts and therefore the plant experiences hunger for essential nutrients. Since non-nutritive salts fill the plant cell and are ballast.

The plant is able to get rid of unnecessary salts by gutting, sedimentation, internal deposition. Along with this, cultivated plants are able to increase the internal sucking force in comparison with the osmotic pressure of the external solution. They (wheat, sunflower, etc.) increase their sucking power due to the accumulation of assimilation products in the tissues.

These phenomena indicate. that plants that have adapted to salinity use non-nutritive salts expediently to maintain their living standards; Plants that cannot tolerate salinization prevent the penetration of salts, and the incoming salts are somehow removed from the sphere of influence on the plasma.

Life cycle (ontogeny) of a plant. In ontogenesis, four stages of development are distinguished: embryonic, which takes place on the mother plant from the formation of the zygote to the maturation of the seed and from the inception to the maturation of the organs of vegetative reproduction; juvenile (youth) - from germination of a seed or vegetative bud to the onset of the ability to form reproductive organs; maturity stage (reproductive) - the inception of the rudiments of the reproductive organs, the formation of flowers and gametes, flowering, the formation of seeds and organs of vegetative reproduction; the stage of old age - the period from the cessation of fruiting to death.

The passage of ontogenesis is associated with qualitative age-related changes in metabolic processes, on the basis of which there is a transition to the formation of reproductive organs and morphological structures.

In the practice of vegetable growing, the term "developmental phase" is often used to denote the age state of plants, denoting a certain morphological manifestation of the age state of a plant. Most often, phenological phases are used for this (seed germination, emergence of seedlings, branching, budding, fruit formation, etc.), the establishment of organs in the apical meristem (stages of organogenesis).

Majority vegetable crops forming food organs from vegetative formations (cabbage, kohlrabi, Brussels sprouts, lettuce crops), ends their stay at the vegetable plantation in the juvenile period, without proceeding to the formation of generative organs before harvesting.

Harvesting is associated with growth - an increase in the size of the plant, its organs, an increase in the number and size of cells, the formation of new structures.

The germination period is an important stage in the life of plants - the transition to self-feeding. It includes several phases: water absorption and swelling (ends with pecking of the seed); formation (growth) of primary roots; sprout development; the formation of the seedling and its transition to independent nutrition.

During the period of water absorption and swelling of the seed, and in some crops and at the beginning of the growth of the primary roots, the seeds can dry out and return to a state of dormancy, which is used in some methods of pre-sowing seed preparation. In the later stages of germination, moisture loss leads to the death of the seedling.

The rate of germination and initial growth of the seedling depends to a large extent on the size of the seeds. Relatively large-seed crops and large seeds from one heap provide not only a faster emergence of seedlings, which is associated with a relatively high growth force, but also a stronger initial growth. The strongest initial growth is possessed by lianas (families Pumpkin, Legumes), which have large seeds. Cucumber uses up to 17% of the allotted area a month after the emergence of shoots, and carrots, according to V.I. Edelstein, - about 1%. Weak initial growth of crops from the families Celery and Onions not only does not allow to use solar radiation, but also significantly increases the cost of protecting crops from weeds.

Annual and perennial fruit crops (tomato, pepper, eggplant, cucumber, melons, chayote, etc.) are represented mainly by remontant plants, a characteristic feature of which is extended fruiting. These are multi-harvest crops. The plant can simultaneously have ripe fruits, young ovaries, undeveloped flowers and those in the fruiting phase.

Crops and varieties can differ significantly in the degree of remontance, which determines the growth rhythm and yield of the crop.

From the moment the seed pecks, the formation of roots outstrips the growth of the stem. Complex metabolic processes are associated with the root system. The absorbent surface of the root is far superior to the evaporative surface of the leaves. These differences are not the same for crops and varieties, depending on the age of the plants and growing conditions. The strongest lead in the development of the root system is inherent in perennial crops, and among the later varieties, with the exception of onion crops, as well as perennials, but growing on mountain plateaus, where the layer of fertile soil is small.

The primary root of the embryo forms into the main root giving rise to a highly branched root system. In many cultures, the root system forms the roots of the second, third and subsequent orders.

For example, in the conditions of the Middle Urals, white cabbage of the Slava variety in the technical ripeness phase had a total length of roots of 9185 m, and their number reached 927,000, for tomato - 1893 and 116,000, respectively, for onions - 240 m and 4600. For cabbage and tomato the branching of the roots reached the fifth order, in the onion - the third. In most vegetable crops, the main root dies off relatively early and the root system becomes fibrous. This is facilitated by the transplant (seedling) culture, as well as by limiting the amount of soil nutrition. In many crops (families Solanaceae, Pumpkin, Cabbage, etc.), adventitious roots, formed from the hypocotal knee or other parts of the stem after hilling and picking, play a significant role. The root system of vegetatively propagated tuberous and bulbous crops (potatoes, sweet potatoes, Jerusalem artichoke, onion and multi-tiered, etc.) is represented exclusively by adventitious roots. At seed reproduction onions, the bulk of the roots by the beginning of the formation of the bulb is represented by adventitious.

Growth roots are distinguished, with the help of which the progressive growth of the root system occurs, including its active part - root hairs. The absorbing surface of the roots is much larger than the surface of the assimilating part of the plant. This is especially pronounced in lianas. So, a cucumber, a month after planting seedlings, has an area work surface roots reached 20 ... 25 m 2, exceeding the leaf surface by more than 150 times. Apparently, this feature is related to the fact that vines do not tolerate damage to the root system in seedling culture, which is possible only if potted seedlings are used, which excludes damage to the roots. The nature of the formation of the root system depends not only on the genetic characteristics of the plants, but also on the cultivation method and other growing conditions. Damage to the apex of the main root in seedlings leads to the formation of a fibrous root system. High soil density (1.4 ... 1.5 g / cm 3) slows down the growth of the root system, and in some crops it stops. Plants vary greatly in the response of the root system to soil compaction. Compaction is best tolerated by crops with relatively slow growth rates, such as carrots. In cucumber, high growth rates of the root system are closely related to the need for sufficient aeration - a lack of oxygen in the soil causes rapid death of the roots.

The root system has a tiered structure. The bulk of the roots in most cases is located in the arable horizon, but deep penetration of roots into the soil is also possible (Fig. 3). For broccoli, white cabbage, cauliflower and Peking cabbage, kohlrabi, onion, batun, onions and leeks, parsley, radish, lettuce, celery, garlic and spinach, the depth of root penetration is 40 ... 70 cm; for eggplant, rutabagas, peas, mustard, zucchini, carrots, cucumbers, peppers, turnips, beets, dill, chicory - 70 ... 120; for watermelon, artichoke, melon, potato, parsnip, oat root, rhubarb, asparagus, tomato, pumpkin and horseradish - more than 120cm.

The active surface of the roots usually reaches its maximum size by the beginning of fruiting, and in cabbage - by the beginning of technical ripeness, after which in most crops, especially in cucumber, it gradually decreases as a result of the death of root hairs. During ontogenesis, the ratio of the absorbing and conducting roots also changes.

Root hairs are short-lived, die off very quickly. As the plants grow, the active part of the root system moves to the roots of higher orders. The productivity of the root system depends on the conditions in which the roots are located and the supply of photosynthetic products to them by the aboveground system. The biomass of the roots in relation to the aboveground system is low.

In annual vegetable crops, the roots die off during the season. Often the end of root growth is the reason for the beginning of plant aging. Most perennial vegetable crops have seasonal rhythms in the development of the root system. In the middle and late summer, the roots die off completely or partially. In onions, garlic, potatoes and other crops, the root system dies off completely. In rhubarb, sorrel and artichoke, mainly the active part of the roots dies off, while the main root and part of its branches remain. With the onset of autumn rains, new roots begin to grow from the bottom of the bulbs and the main roots. This happens differently in different cultures. Garlic grows roots and soon a bud awakens, which gives leaves. Onions only grow roots, since the bulb is dormant.

Other perennials (onion, tarragon, sorrel) grow new roots and leaves. Autumn root development is the main condition for successful wintering and rapid growth in spring, which ensures early production.

While the potato tuber is dormant, root formation cannot be caused, since this process is preceded by tuber germination.

Autumn regrowth of roots is also observed in biennials vegetable plants, if they remain in the field, which is what happens in seed production with a direct culture or autumn planting of mother plants.

The growth of the root and aboveground systems is regulated by phytohormones, some of which (gibberellins, cytokinins) are synthesized in the root, and some (indoleacetic and abscisic acids) - in the leaves and tops of the shoots. Following the growth of the embryonic root, elongation of the shoot hypocotyl begins. After it reaches the surface of the earth, growth is suppressed by the influence of light. Epicotyl begins to grow. If there is no light, the hypocotyl continues to grow,

which leads to weakening of the seedlings. To obtain strong, healthy plants, it is important to avoid stretching the hypocotyl. When growing seedlings, it is necessary to provide sufficient illumination, low temperature and relative humidity during the period of emergence.

External conditions in this crucial period of transition to self-feeding largely determine the subsequent growth rates, development and productivity of plants.

Further growth of shoots is associated with the processes of differentiation of apical and lateral meristems, morphogenesis, that is, the inception of organs for the growth and development of cells and tissues (cytogenesis). vegetative and generative organs (organogenesis). Morphogenesis is genetically programmed and changes depending on external conditions that affect phenotypic traits - growth, development and productivity.

The growth of vegetable plants is associated with branching, which in crops belonging to different life forms can be monopodial, when the apical bud during ontogenesis remains growth (Pumpkin), sympodial, when the first-order axis ends in a terminal flower or inflorescence (Solanaceae), and mixed combining both types of branching.

Branching is a very important feature associated with the rate of formation of the crop, its quality and productivity of plants, the possibility of mechanization, with the cost of labor for pinching and pinching.

Crops and varieties differ in the nature of branching. It also depends on the conditions of the external environment. Branching is much stronger under optimal conditions. Cabbage plants, root crops, onions, garlic do not branch in the first year of life when grown from air bulbs. Peas and beans are weakly branching. The varieties of tomato, pepper, cucumber and melons differ significantly in the strength of branching (the number of branches and orders).

The reproductive stage of ontogenesis begins with the inception of the primordial rudiments of the generative organs. In most cultures, it stimulates the active growth of axial organs and the assimilation apparatus. Active growth continues in the initial period of fruit formation, gradually dying out with an increase in the load of fruits. Cucumber, pea and many other crops stop growing during the period of mass fruit formation and seed formation. A high load of fruits contributes to the acceleration of plant aging and can be the cause of premature death. In peas and cucumbers, the collection of unripe ovaries makes it possible to significantly extend the growing season.

Crops and varieties of vegetable plants are characterized by seasonal and daily rhythms of growth and development, determined genetically (endogenous) and environmental conditions (exogenous).

Perennial, biennial and winter crops originating from

zones of temperate and subtropical climate, represented mainly by rosette and semi-rosette plants. In the first year of life, they form a very short thickened stem and a ground rosette of leaves.

In the spring of the second year, a flowering stem is rapidly formed, leafy in semi-rosette life forms (sorrel, rhubarb, horseradish, cabbage, carrots, etc.) and without leaves in rosette (onion). By the end of summer, with the maturation of the seeds, this stem dies off. In biennials (monocarpic plants), the entire plant dies. In perennials (polycarpic plants), part of the stems die off, partially or completely (onion, garlic) leaves and roots. Plants enter a state of physiological and then forced dormancy.

The presence of a rosette, which determines the small size of the stem, ensures overwintering of plants in winter and perennial crops. Emergence flower stem, meaning the transition to generative development, is possible only under the condition of vernalization - exposure to the plant during a certain period of low positive temperatures. In perennial plants, the stem should appear every year. Moreover, lower temperatures (in rhubarb) help to end the dormant period and stimulate the regrowth of leaves, which is used for forcing in greenhouses.

Rosettes are formed differently in cabbage and cauliflower. At the beginning of the seedling and post-seedling periods, the plants of these crops grow as rosetteless, and only after the formation of 10 ... 15 leaves does the formation of an aboveground rosette begin. The stem is longer than that of root crops and is more vulnerable to freezing temperatures. In the first year of life, when grown from seeds, rosette and semi-rosette crops do not branch. Branching is observed only in the second year in biennial crops and starting from the second year in perennial crops.

After overwintering, perennial and biennial crops are characterized by a very strong (explosive) growth, providing in a short time the formation of a rosette of leaves and stems. Plants are highly branched. From active buds, fruiting shoots are formed, from dormant ones that have not undergone vernalization - vegetative ones.

Perennial plants form the assimilation apparatus more quickly in the second and subsequent years, providing more early harvest than when grown from seed in the first year.

A feature of biennial vegetable crops, as well as onions, is the long duration of the juvenile period (60 ... 70%) compared to the reproductive period (30 ... 40%). The main photosynthetic organs in the reproductive period in cabbage, radish, turnips are stems and pods of seed plants, in onions - arrows and fruit integuments.

In annual crops, the reproductive period is twice as long as the juvenile.

Lianas are climbing, creeping, climbing plants that are not able to maintain an upright position, so they use other plants as a support. For climbing and climbing (barbel-bearing) lianas, strong initial growth and a significant size of the growing shoot zone are characteristic, which determines very high growth rates in the future. Young climbing vines (beans) do not have a circular nutation to wrap around the support; she appears later. Their feature is the slow growth of laid leaves on the growing shoot zone.

Antennaeous climbing lianas (vegetable crops from the Pumpkin family and peas), due to the presence of tendrils with high sensitivity to contact with the support (tigmomorphogenesis), have the ability to quickly and thoroughly attach to it. Among the tendril-bearing lianas in the Pumpkin family, a special place is occupied by a group of creeping lianas, which include melons (watermelon, melon and pumpkin) and field European varieties of cucumber. They are characterized by a plagiotropic (creeping) position of the stem, relatively fast lodging of stems after sprouting, strong branching associated with the fastest possible capture of the territory and dominance on it. In conditions of sufficient moisture, some of these lianas (for example, a pumpkin) form adventitious roots in the nodes, which provide additional attachment of the stem to the soil.

The growth of the plant, its individual organs, the formation of the yield largely depend on the distribution between the individual parts of the products of photosynthesis, which is associated with the activity of the attracting (mobilizing, attracting) centers. The direction of activity of these centers of hormonal regulation changes during ontogenesis. Along with genetic conditioning, it is largely determined by the conditions of the external environment. Attracting centers are usually growing parts of plants: growth points and leaves, roots, generative (forming fruits and seeds), as well as storage (roots, bulbs and tubers) organs. Often, there is competition between these organs in the consumption of photosynthetic products.

The intensity of photosynthesis, the rate and ratio of growth of individual plant organs, and, ultimately, the yield, its quality and timing of receipt depend on the activity of the attracting centers.

A particularly strong attracting ability of the generative organs distinguishes varieties of fruit vegetable crops (peas, beans, tomato, cucumber, pepper, etc.) intended for simultaneous machine harvesting. For most of these varieties, fruit formation and ripening of the crop take place in a short time. Relatively early cessation of growth is also characteristic of them.

Many agrotechnical techniques are based on the regulation of the location of the attracting centers and their activity (the period of crop cultivation, management of seedling growth, plant formation, temperature regimes, irrigation, fertilization, the use of growth-regulating substances). The creation of conditions during the storage period of onion sets that exclude the possibility of vernalization will make the onion center of attraction, which will make it possible to obtain good harvest... When storing uterine onions, mother plants of biennial crops, on the contrary, it is important to create conditions for their vernalization.

Yield losses and a decrease in product quality are observed with the flowering of root crops, cabbage, lettuce, spinach and other crops. The center of attraction in these cases shifts from the storage vegetative organs to the generative ones. Radish roots become flabby (cottony), lettuce leaves become rough and tasteless, bulb growth stops.

The topography and activity of the attracting centers, their balance with the photosynthetic activity of the assimilation apparatus determine the economic efficiency of photosynthesis, the timing of harvesting, and the quantitative and qualitative indicators of the harvest. For example, big number fruits per unit area of ​​leaves in some varieties of tomato and melon leads to a decrease in the content of dry substances in fruits and a loss of taste.

Growth points and young leaves consume all products of photosynthesis, as well as a significant portion of mineral compounds from adult and senescent leaves. In addition, old leaves give to the young also some of the previously accumulated plastic substances.

The phenomenal attracting ability of fertilized embryos is manifested in some crops in fruits torn away from the mother plant. Peduncles with blossoming flowers of potatoes, onions, cut after pollination or even pollinated after cutting, placed in water, form seeds from part of the ovules. All this time, flower stalks and fruits assimilate. The weekly greens of cucumber collected from plants, unripe fruits of green-fruited varieties of squash, pumpkin in favorable conditions of lighting, heat and relative humidity do not dry out for one to two months before the seeds ripen and assimilate carbon dioxide (CO2). Part of the ovules, depending on the size and age of the ovary, forms full-fledged viable seeds, which are often much smaller than the seeds formed in the fruits on the mother plant. Fruits that do not have chlorophyll (white) do not have this ability.