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General patterns of growth and development of plants. General ideas about the growth and development of plants. Basic patterns of plant growth

One of important processes carried out in the course of individual development is morphogenesis. Morphogenesis is the formation of a form, the formation of morphological structures and an integral organism in the process of individual development. Plant morphogenesis is determined by the continuous activity of meristems, due to which plant growth continues throughout ontogenesis, albeit with varying intensity.

The process and result of morphogenesis are determined by the genotype of the organism, interaction with individual conditions of development and patterns of development common to all living beings (polarity, symmetry, morphogenetic correlation). Due to polarity, for example, the apical meristem of the root produces only the root, while the apex of the shoot produces the shoot and inflorescences. The shape of various organs, leaf arrangement, actinomorphism or zygomorphism of flowers, etc. are associated with the laws of symmetry. Correlation action, i.e. interconnections different signs in a holistic organism, affects the appearance characteristic of each species. Natural violation of correlations in the course of morphogenesis leads to various deformities in the structure of organisms, and artificial (by pinching, pruning, etc.) leads to the production of a plant with traits useful for humans.

- Latent (hidden) - dormant seeds.

Degenerative, or virginal, from seed germination to first flowering.

Generative - from the first to the last flowering.

- Senile, or senile - from the moment of loss of the ability to bloom until death.

Within these periods, more fractional stages are also distinguished. Thus, in the group of virginal plants, as a rule, seedlings are isolated that have recently emerged from seeds and retain germinal organs - cotyledons and endosperm remnants; juvenile plants still bearing cotyledon leaves, and the juvenile leaves following them are smaller and sometimes not quite similar in shape to the leaves of adults; immature individuals that have already lost their juvenile features, but have not yet fully formed, "semi-adults". In the group of generative plants, according to the abundance of flowering shoots, their size, the ratio of living and dead parts of roots and rhizomes, young, middle-aged, mature and old generative individuals are distinguished.

Each type of plant has its own rate of initiation and development of organs. Thus, in gymnosperms, the formation of reproductive organs, the course of fertilization and development of the embryo takes about one year (in

GROWTH AND DEVELOPMENT OF PLANTS

Plant growth and development processes have a number of distinctive features compared to animal organisms. First, plants are able to reproduce vegetatively. Secondly, the presence of merestematic tissues in plants provides a high rate and ability to regenerate. Third, to ensure nutrients plants maintain growth throughout their lives.

The concept of growth and development. General

growth patterns

Every living organism undergoes constant quantitative and qualitative changes, which stop only under certain conditions with periods of rest.

Growth is a quantitative change in the course of development, which consists in an irreversible increase in the size of a cell, organ or whole organism.

Development is a qualitative change in the components of the body, in which the existing functions are transformed into others. Development is the changes that occur in a plant organism during its life cycle. If this process is considered as the establishment of a form, then it is called morphogenesis.

An example of growth is the growth of branches due to the multiplication and increase of cells.

Examples of development are the formation of seedlings from seeds during germination, the formation of a flower, etc.

The process of development includes a number of complex and highly coordinated chemical transformations.

The curve characteristic of the growth of all organs, plants, populations, etc. (from the community to the molecular level) has an S-shaped, or signoid appearance (Fig. 6.1).

This curve can be divided into a number of sections:

- the initial lag phase, the duration of which depends on internal changes that serve to prepare for growth;

is the logarithmic phase, or the period when the dependence of the logarithm of the growth rate on time is described by a straight line;

– phase of gradual decrease in growth rate;

- the phase during which the body reaches a stationary state.

The length of each of the phases that make up the S-curve and its character depend on a number of internal and external factors.

The duration of the lag phase of seed germination is affected by the absence or excess of hormones, the presence of growth inhibitors, the physiological immaturity of the embryo, the lack of water and oxygen, the absence optimum temperature, light induction, etc.

The length of the logarithmic phase is associated with a number of specific factors and depends on the features of the genetic development program encoded in the nucleus, the gradient of phytohormones, and the intensity of transport nutrients etc.

Growth inhibition may result from changes in environmental factors, as well as be determined by shifts associated with the accumulation of inhibitors and peculiar aging proteins.

Complete inhibition of growth is usually associated with the aging of the organism, that is, with the period when the rate of synthetic processes is decreasing.

During the completion of growth, the process of accumulation of inhibitory substances occurs, plant organs begin to actively age. On the last stage all plants or some of its parts stop growing and can fall into a dormant state. This final stage of the plant and the timing of the arrival of the stationary phase is often determined by heredity, but these characteristics can be changed to some extent under the influence of the environment.

Growth curves indicate the existence different types physiological regulation of growth. During the lag phase, there are mechanisms associated with the formation of DNA and RNA, the synthesis of new enzymes, proteins, and the biosynthesis of hormones. During the logarithmic phase, there is an active stretching of cells, the appearance of new tissues and organs, an increase in their size, i.e., stages of visible growth occur. From the slope of the curve, one can often quite successfully judge the genetic pool, which determines the growth potential of a given plant, and also determines how well the conditions match the needs of the plant.

As growth criteria, an increase in the size, number, volume of cells, wet and dry weight, protein or DNA content is used. But to measure the growth of a whole plant, it is difficult to find a suitable scale. Thus, when measuring length, no attention is paid to branching; it is not possible to accurately measure the volume. When determining the number of cells and DNA, no attention is paid to the size of the cell, the definition of protein includes storage proteins, the definition of mass also includes storage substances, and the definition of wet weight, in addition to everything, includes transpiration losses, etc. Therefore, in each case, the scale that can be used to measure the growth of a whole plant - this is a specific problem.

Shoot growth rate averages 0.01 mm/min (1.5 cm/day), up to 0.07 mm/min (~ 10 cm/day) in the tropics and 0.2 mm/min in bamboo shoots (30 cm/day).

Every living organism undergoes constant quantitative and qualitative changes, which stop only under certain conditions with periods of rest.

Growth is a quantitative change in the course of development, which consists in an irreversible increase in the size of a cell, organ or whole organism.

An example of growth is the growth of branches due to the multiplication and increase of cells.

Examples of development are the formation of seedlings from seeds during germination, the formation of a flower, etc.

The process of development includes a number of complex and highly coordinated chemical transformations.

The curve characteristic of the growth of all organs, plants, populations, etc. (from the community to the molecular level) has an S-shaped, or signoid appearance (Fig. 6.1).

This curve can be divided into a number of sections:

- the initial lag phase, the duration of which depends on internal changes that serve to prepare for growth;

is the logarithmic phase, or the period when the dependence of the logarithm of the growth rate on time is described by a straight line;

– phase of gradual decrease in growth rate;

- the phase during which the body reaches a stationary state.

Fig 6.1. S-shaped growth curve: I – lag phase; II - logarithmic phase; III - decrease in growth rate; IV - stationary state

The length of each of the phases that make up the S-curve and its character depend on a number of internal and external factors.

The length of the logarithmic phase is associated with a number of specific factors and depends on the features of the genetic development program encoded in the nucleus, the phytohormone gradient, the intensity of transport of nutrients, etc.

Growth inhibition may result from changes in environmental factors, as well as be determined by shifts associated with the accumulation of inhibitors and peculiar aging proteins.

Complete inhibition of growth is usually associated with the aging of the organism, that is, with the period when the rate of synthetic processes is decreasing.

During the completion of growth, the process of accumulation of inhibitory substances occurs, plant organs begin to actively age. At the last stage, all plants or some of its parts stop growing and can fall into a dormant state. This final stage of the plant and the timing of the arrival of the stationary phase is often determined by heredity, but these characteristics can be changed to some extent under the influence of the environment.

Growth curves indicate the existence of different types of physiological regulation of growth. During the lag phase, there are mechanisms associated with the formation of DNA and RNA, the synthesis of new enzymes, proteins, and the biosynthesis of hormones. During the logarithmic phase, there is an active stretching of cells, the appearance of new tissues and organs, an increase in their size, i.e., stages of visible growth occur. From the slope of the curve, one can often quite successfully judge the genetic pool, which determines the growth potential of a given plant, and also determines how well the conditions match the needs of the plant.

Shoot growth rate averages 0.01 mm/min (1.5 cm/day), up to 0.07 mm/min (~ 10 cm/day) in the tropics and 0.2 mm/min in bamboo shoots (30 cm/day).

Characterization of the factors that determine the patterns of growth and development of plants.

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 complete formation, aging and death as a result of natural death is called ontogeny.

Growth is an irreversible process 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 the body, 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 traits).

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 in a certain phase 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 particular 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 stimulants

growth inhibitors.

In turn, growth stimulants are divided into three classes:

gibberellins,

cytokinins.

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

Gibberellins are 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, which is 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 in the xylem and in the phloem. Gibberellins accelerate the phase of cell elongation, regulate the processes of flowering and fruiting, and induce new formation of pigments.

Cytokinins are purine derivatives, typified by kinetin. This group of hormones does not have such a pronounced effect as the previous ones, however, cytokinins affect many parts 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, 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 maturing plant organs and affects both other organs of the same plant and nearby plants. Ethylene accelerates the fall of leaves, flowers, fruits due to the release of cellulase from the petioles, which accelerates the formation of a separating layer. Ethylene is formed during the decomposition of etrel, which greatly facilitates its practical use in agriculture.

Plant growth (patterns and types).

The term growth in plants refers to several processes:

cell growth,

tissue growth,

the growth of the plant organism as a whole.

Cell growth is characterized by the presence of the following phases:

Embryonic phase (no vacuoles, other organelles in a small amount).

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

Phase of differentiation (the appearance in the cell of organelles specific to a given tissue).

Tissue growth, depending on its specificity, can proceed according to any of the following 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 phase of logarithmic growth (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 phase of the stationary state (coincides, as a rule, with the aging and death of the plant).

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

To determine the growth, various methods are used, in particular:

with a ruler,

using a horizontal microscope

with labels,

using an auxanograph,

with large scale photography.

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

According to the results of modern research (V.S. Shevelukha), the following classification of growth types was proposed:

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

impulse type of growth (the curve of the increase in the rate of growth processes and their deceleration occurs abruptly under the direct or acute angle within tens of minutes. The maximum growth rate occurs at 20-21 hours and persists all night, growth is inhibited during the day) (typical for root crops and tubers),

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

leveled type of growth (growth curve has a smooth character).

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 non-attached plants,

higher plants are characterized by the first three species.

Nutations make growing apical shoots, rotating around their axis, and above-ground shoots make them only under the influence of hormones, and 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 when implementation of this process.

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

A 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 dormant phase).

Plant development 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 ontogenesis to another, and their combined action is often necessary.

There are the following types of plant ontogeny:

By lifespan:

annual,

biennial,

perennial;

By number of fruits:

monocarpic,

polycarpic.

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

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 above-ground vegetative organs,

flowering and fruiting phase,

ripening phase,

dying phase.

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

swelling,

pecking,

heterotrophic seedling growth in the dark,

transition to autotrophic nutrition.

Almost every ontogenetic change occurs under the influence of internal and external factors. At the same time, sunlight is the most important external factor. The transition to an autotrophic mode of nutrition, the transition to the phase of budding and flowering, the transition to a dormant state in perennial plants are directly related precisely to the effect of the duration of sunlight and therefore are 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 the growth rate during the transition to autotrophic nutrition. The indirect effect of light in the form of day length determines the transition to the next phase of development, in particular to flowering.

The plant perceives the effects of sunlight due to the presence of special photoreceptors and hormones.

The direct impact of light is perceived by the plant with the help of the photoreceptor "cryptochrome" and the pigment "phytochrome". Particularly important is phytochrome, which is able to perceive various components of the sunlight spectrum and, depending on the absorbed wavelength, turns either into the Fk form, which absorbs 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 found in both forms in equal proportions, however, when conditions change, for example, to shaded ones, a larger amount of pigment Fk is formed, and this determines the stretching 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 the biological clock of the plant.

The light factor also causes the synthesis of certain hormones that determine the transition of the plant to the flowering phase or the evocation phase, i.e. transition from a 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, which cause the formation and growth of peduncles,

anthesins that cause flower formation.

Understanding this moment is very important in practice, especially in fruit growing, where the use of rootstock and scion in certain phases of ontogeny will affect the rate of fruiting of the grafted plant. The flow of hormones, including florigen, comes from the scion to the rootstock, so it is important to use the rootstock from a plant that is 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, launches its chain of processes leading to the laying of flowers.

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

It is on the effect of low temperatures that the method of vernalization is based, which is used in various experimental studies when it is necessary to accelerate the change of generations in winter crops. The 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:

plants short day(flowering at day length less than 12 hours) (chrysanthemum, dahlia, Jerusalem artichoke, millet, sorghum, tobacco),

long-day plants (blooming when the day length is more than 12 hours) (aster, clover, flax, onion, carrot, beetroot, spinach),

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

In the ontogenesis of plants, there is necessarily a phase of weakening of vital activity, which is called the dormant state. In annual plants, this state occurs only once - during the formation of a seed, in perennial plants - many times during the transition to existence in adverse environmental conditions (winter, drought). Dormancy is such a state of a plant, which 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.

There are 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 the storage of resting organs in special storage facilities using special methods. Highly important point transition to a dormant state is the stage of post-harvest ripening, which helps to prevent premature germination of seeds, to concentrate the maximum amount of reserve substances.

Kroenke's theory of aging and rejuvenation of plants.

In the process of ontogenesis, the plant undergoes certain changes that are associated with the phenomenon of age-related variability. The 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, starting from its inception, continuously ages until its natural death.

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

Plants have a physiological age, which determines the true age of the plant organ: the leaves of one-year-old and ten-year-old trees are unequal, and the leaves on the same tree are also unequal, but on shoots of a different order. There is a distinction between the concept of "age" (calendar age) and "age" (physiological age. Age is determined by the age of the organ and the mother plant. Within the 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 terms of shape, anatomical structure, physiological and biochemical characteristics, the upper leaves, despite their younger age, show signs of greater aging, their life span is often shorter than that of the middle leaves on the same shoot.

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

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

The problem of aging and rejuvenation of fruit and berry crops was also dealt with by P.G. Schitt. 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.

Installed 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 precocity of plants within a species, to identify correlations between the quality of tubers and root crops and the precocity of a variety. It has been established that early ripening varieties are characterized by a sharp change morphological features leaves (rapid yellowing and death of leaves), and in late-ripening varieties, changes occur gradually. This pattern is important in the process of breeding varieties for early maturity and quality.

Morphological traits are closely related to genetic precocity, which makes it possible to use them in breeding fruit crops, for example:

in annual seedlings of early-ripening varieties of apple trees, the internodes are shorter, the branching is stronger, the leaves are denser than in varieties that bear fruit later,

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

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

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

Features of maturation of productive parts of plants.

The productive parts of plants are called both organs of generative reproduction (fruits, seeds) and organs vegetative propagation(tubers, bulbs). The remaining productive parts (leaves of green crops, stem crops, root crops, etc.) do not carry out the function of reproduction, and therefore the patterns of growth and development are not so important.

seed protection,

seed distribution.

To carry out these functions, various fruits have appropriate adaptations (dry and juicy fruits, hooks, lionfish, attractive taste, etc.).

There are four phases in the development of the fetus:

Formation of the ovary before pollination,

Growth by cell division immediately after pollination and fertilization,

Growth due to cell elongation,

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 contribute to the growth of the ovary, which is explained by the high content of IAA in 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, i.e. seedless fruits. Gibberellin treatment also causes fruit set in many plants (grapes, apple, tomato, etc.). The presence of cytokinin is necessary for the growth of young fetuses, but exogenous cytokinins do not cause the formation of parthenocarpic fetuses.

At the beginning of the formation of the ovary in the flower, its growth occurs as a result of cell division, which increases sharply after pollination. Then comes a longer phase of cell elongation. The nature of growth is strongly dependent on the type of fetus.

Fruit growth is regulated by phytohormones. IAA first enters the ovary from the style and from germinating pollen. The developing ovule then becomes the source of IAA. In this case, the aging hormone (ethylene) also plays a certain role, which ensures the withering of the flower after pollination. The resulting seeds supply auxin to the pericarp, which activates growth processes in it. With a lack of auxin (small number of seeds formed), fruit fall off.

Thus, in wheat grains, the maximum amount of cytokinins is observed immediately after flowering during the transition to the formation of the endosperm. Then the content of gibberellins begins to increase, and later IAA, the concentration of which reaches its maximum value in the phase of milky 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 the dry weight of the grains stops and the seeds become dehydrated (complete ripeness), the ABA content decreases. The decrease in the number of all phytohormones is explained by their transition to a bound state. This order of change in the ratio of phytohormones in emerging wheat grains is determined by the sequence of development of the embryo and endosperm. When the grain ripens, carbohydrates and proteins accumulate, changes occur in the nucleic metabolism, plastic substances actively move into the grains from the stems and leaves. There is a wooding of the stems (the content of fiber, lignin, which are converted into starch, decreases). 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 accumulate significantly less starch and other carbohydrates than cereals.

When cultivating cereals and leguminous crops, a separate harvesting method is often used, which makes it possible to better ensure the transfer of plastic substances from stems to seeds after mowing and ripening in windrows. Treatment of crops in the period of wax 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 change in quality. Unripe seeds contain more free and saturated fatty acids, while mature seeds contain more 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 intensive growth of the fetus. The cessation of pericarp growth coincides with the accumulation of ABA in its tissues.

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

The ripening of some fruits correlates well with an increase in the rate of respiration. The period of increased carbon dioxide production 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 the permeability of membranes in fetal cells, which allows enzymes previously separated from substrates by membranes to react with these substrates and begin their destruction.

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

In a number of cultures, the method of reproduction with the help of vegetative propagation organs (for example, potatoes) has become the predominant method of reproduction. Therefore, the formation of these organs, both performing a reproductive function and, at the same time, serving as a source of nutrition for humans, requires separate consideration.

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

Tuber formation involves three stages;

preparatory - the appearance and growth of stolons,

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 potato cultivation technology). IAA, together with gibberellins, supplied in sufficient quantities from the aerial parts, switch the genetic program for the development of the axillary bud 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, decomposition and synthesis of biopolymers, and a halt in growth processes. In potato tubers, only meristematic tissues, primarily eyes, are in a state of deep dormancy. The storage tissue is able to quickly activate in response to damage (wound periderm is formed in case of mechanical damage).

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

The exit of ocelli from the state of deep dormancy is associated with a decrease in the content of ABA (by 10–100 times) and an increase in the concentration of free gibberellins. Treatment with gibberellic acid-based stimulants breaks dormancy in tubers and allows summer planting of potatoes in the south.

In bulbs during the dormant period, growth processes do not stop, 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 take root with the help of layering and cuttings, are subject to the same patterns in the change in the work of various phytohormones.

Use of growth regulators in practice Agriculture.

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,

At the stage of cleaning

At the dormant stage.

At the stage of sowing, planting use:

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

for better survival of vaccines,

for better seed germination

At the stage of controlling flowering, setting, crop formation, 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 fruit size

to improve the quality of economically valuable organs (contribute to an increase in sugars in fruits, stems, stem crops, 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 friendliness of the return of the crop,

for defoliation,

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

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

At rest:

To prolong dormancy, use ethylene and abscisic acid to treat 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:

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

warm baths: for forcing lilacs for the New Year (dip the shoots of the bush in warm (30-35 ° C) water for 9-12 hours),

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

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Plan

1. The planetary significance of plants
2. Metamorphosis of roots
3. Inflorescence
4. Basic patterns of plant growth
5. The concept of ontogenesis, growth and development of plants
6. Plant communities

1. The planetary significance of plants

The planetary significance of plants is associated with their autotrophic mode of nutrition through photosynthesis. Photosynthesis is the process of forming organic substances (sugar and starch) from minerals (water and carbon dioxide) in the presence of light with the help of chlorophyll. During photosynthesis, plants release oxygen into the atmosphere. It was this feature of photosynthesis that led to the fact that in the early stages of the development of life on Earth, oxygen appeared in its atmosphere. He not only provided anaerobic respiration most organisms, but also contributed to the appearance of an ozone screen that protects the planet from ultraviolet radiation. Nowadays, plants also affect the composition of the air. They moisturize it, absorb carbon dioxide and release oxygen. Therefore, the protection of the green cover of the planet is one of the conditions for preventing a global ecological crisis.

In the process of vital activity of green plants, huge masses of organic matter are created from inorganic substances and water, which are then used as food by the plants themselves, animals and humans.

The organic matter of green plants accumulates solar energy, due to which life develops on Earth. This energy, accumulated by ancient plants, forms the basis of the energy resources used by man in industry: coal, peat.

Plants provide a huge amount of products needed by man as raw materials for various industries. Plants satisfy the basic human needs for food and clothing, medicines.

2. Metamorphosis of roots

plant photosynthesis phytocenosis autotrophic

A feature of root metamorphoses is that many of them reflect not changes in the main functions of the root, but changes in the conditions for their implementation. The most common root metamorphosis should be considered mycorrhiza, a complex of the root and fungal hyphae fused with it, from which the plants receive water with minerals dissolved in it.

The root crop is formed from the main root due to the deposition in it a large number nutrients. Root crops are formed mainly in the conditions of cultural cultivation of plants. They are found in beets, carrots, radishes, etc. In the root crop, there are: a) a head bearing a rosette of leaves; b) the neck - the middle part; c) the root itself, from which lateral roots depart.

Root tubers, or root cones, are fleshy seals of lateral as well as adventitious roots. Sometimes they reach a very large size and are a reservoir of reserve substances, mainly carbohydrates. In the root tubers of chistyak, orchids, starch serves as a reserve substance. Inulin accumulates in the adventitious roots of dahlias, which have turned into root tubers.

Of the cultivated plants, one should name sweet potato, from the bindweed family. Its root tubers usually reach 2 - 3 kg, but can be more. Cultivated in subtropical and tropical regions for starch and sugar production.

Aerial roots form in some tropical plants. They develop as adnexal stems, are brown in color and hang freely in the air. Characterized by the ability to absorb atmospheric moisture. They can be seen in orchids.

Clinging roots, with the help of which weak stems of vines climb up tree trunks, along walls, slopes. Such adventitious roots, growing into cracks, fix the plant well and enable it to rise to great heights. The group of such vines includes ivy, which is widespread in the Crimea and the Caucasus.

Respiratory roots. In marsh plants, to the ordinary roots of which access to air is very difficult, special roots grow upwards from the ground. They are above water and get air from the atmosphere. Respiratory roots are found in swamp cypress. (Caucasus, Florida).

3. Inflorescence

Inflorescence (lat. inflorescentia) - part of the shoot system angiosperm, bearing flowers and, as a result, varied in many ways. The inflorescences are usually more or less clearly demarcated from the vegetative part of the plant.

The biological meaning of the emergence of inflorescences is in the increasing probability of pollination of flowers of both anemophilous (that is, wind-pollinated) and entomophilous (that is, insect-pollinated) plants.

Inflorescences are laid inside flower or mixed buds. Classification and characteristics of inflorescences:

By the presence and nature of the bracts (brracts):

Frondose (Latin frondis - foliage, leaves, greens), or leafy - inflorescences in which bracts have well-developed plates (for example, fuchsia, tricolor violet, loosestrife).

Bracteous - inflorescences in which bracts are represented by scaly leaves of the upper formation - bracts (for example, lily of the valley, lilac, cherry).

Ebracteous, or naked - inflorescences in which the bracts are reduced (for example, wild radish, shepherd's purse and other cabbage (cruciferous).

Branching degree:

Simple - inflorescences in which single flowers are located on the main axis and, thus, branching does not exceed two orders (for example, hyacinth, bird cherry, plantain, etc.).

Complex - inflorescences in which private (partial) inflorescences are located on the main axis, that is, branching reaches three, four or more orders (for example, lilac, privet, viburnum, etc.).

According to the type of growth and direction of opening of flowers:

Racemosous, or Botrician (from Latin raczmus and Greek botryon - brush, bunch) - inflorescences characterized by a monopodial type of growth of axes and acropetal (that is, directed from the base of the axis to its top) opening of flowers (for example, Ivan tea, shepherd's purse and etc.)

Cymose (from Latin cyma - semi-umbrella) - inflorescences characterized by a sympodial type of axes growth and basipetal (that is, directed from the top of the axis to its base) opening of flowers.

By the nature of the behavior of apical meristems:

Closed, or certain - inflorescences in which the apical (apical) meristems of the axes are spent on the formation of an apical flower (all cymose inflorescences, as well as racemose of some plants: corydalis, crassula, bluebells, etc.).

Open or indeterminate - inflorescences in which the apical meristems of the axes remain in vegetative state(lily of the valley, hyacinth, wintergreen, etc.).

4. Basic patterns of plant growth

The main laws of plant growth: the law of a long period of growth; rhythm and periodicity; growth correlations, polarity; regeneration

The rhythm of growth - the alternation of slow and intensive growth of a cell, organ, organism - can be daily, seasonal - is the result of the interaction of internal and external factors.

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

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

The initial period of slow growth (lag period).

Log period, a large period of growth according to Sachs

phase of deceleration.

Stationary state (end of growth).

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

Inhibitory correlations (inhibitory) - some organs inhibit the growth and development of other organs. An example of these correlations is the phenomenon of apical dominance - inhibition of the growth of lateral buds, shoots by the apical bud of the shoot. An example is the phenomenon of the "royal" fruit, which began first. Use in practice of removing apical dominance: crown formation by cutting the tops of dominant shoots, picking seedlings and seedlings of fruit trees.

Compensatory correlations reflect the dependence of the growth and competitive relations of individual organs on the provision of their nutrients. In the process of growth of a plant organism, a natural reduction occurs (falling off, dying off) or part of the developing organs is artificially removed (stepping, thinning of the ovaries), and the rest grow at a faster rate.

Regeneration - the restoration of damaged or lost parts.

Physiological - restoration of the root cap, replacement of the bark of tree trunks, replacement of old xylem elements with new ones;

Traumatic - healing of wounds of trunks and branches; associated with callus formation. Restoration of lost above-ground organs due to the awakening and regrowth of axillary or lateral buds.

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

5. The concept of ontogenesis, growth and development of plants

Ontogeny (life cycle), or individual development, is a complex of successive and irreversible changes in the vital activity and structure of plants from the emergence from a fertilized egg, embryonic or vegetative bud to natural death. Ontogeny is a consistent implementation of the hereditary genetic program for the development of an organism in specific conditions. external environment.

The terms "growth" and "development" are used to characterize plant ontogeny.

Growth is a neoplasm of the cytoplasm and cellular structures, leading to an increase in the number and size of cells, tissues, organs and the whole plant as a whole (according to D.A. Sabinin, 1963). Plant growth cannot be viewed as a purely quantitative process. So, emerging shoots, leaves are qualitatively different from each other. Plants, unlike animal organisms, grow throughout their lives, but usually with some interruptions (rest period). Indicators of growth rates - the rate of increase in the mass, volume, size of the plant.

Development - qualitative changes in living structures, due to the passage of the body's life cycle. Development - qualitative changes in the structure and functions of the plant as a whole and its individual parts - organs, tissues and cells that occur in the process of ontogenesis (according to D.A. Sabinin). The emergence of qualitative differences between cells, tissues and organs is called differentiation.

Form formation (or morphogenesis) in plants includes the processes of initiation, growth and development of cells (cytogenesis), tissues (histogenesis) and organs (organogenesis).

The processes of growth and development are closely interrelated. However, rapid growth can be accompanied by slow development and vice versa. Winter plants, when sown in spring, grow rapidly, but do not proceed to reproduction. In autumn, at low temperatures, winter plants grow slowly, but they undergo development processes. An indicator of the rate of development is the transition of plants to reproduction.

According to the duration of ontogenesis, agricultural plants are divided into annuals, biennials and perennials.

Annual plants are divided into:

ephemera - plants whose ontogeny occurs in 3-6 weeks;

spring - plants (cereals, legumes), the growing season of which begins in spring or summer and ends in the same summer or autumn;

winter - plants whose vegetation begins in the fall and ends in the summer or autumn of the next year.

Biennial plants in the first year of life form vegetative and rudiments of generative organs, in the second year they flower and bear fruit.

Perennial plants (forage grasses, fruit and berry crops) have a duration of ontogenesis from 3...10 to several decades.

Annual and many biennial (carrots, beets, cabbage) plants belong to the group of monocarpic plants or single-bearing plants. After fruiting, they die.

In polycarpic plants, fruiting is repeated for a number of years (perennial grasses, berry bushes, fruit trees). The division of plants into monocarpic and polycarpic is conditional. So, in tropical countries, cotton, castor bean, tomato and others develop as perennial polycarpic forms, and in temperate latitudes - as annuals. Wheat and rye are annual plants, but there are also perennial forms among them.

Periodization of ontogeny. The ontogeny of higher plants is classified in different ways. Usually distinguished:

Vegetative and reproductive periods. During the vegetative period, the vegetative mass intensively accumulates, root system, tillering and branching occur, flower organs are laid. The reproductive period includes flowering and fruiting.

Phenological phases are distinguished by clearly expressed morphological changes in plants. Applied to specific crops phenophases are described in detail in plant growing, vegetable growing, and fruit growing. So, in cereals, the following phases are distinguished: seed germination, seedlings, the appearance of the third leaf, tillering, tube formation, heading, flowering, phases of milk, wax and full ripeness.

Stages of plant organogenesis. 12 stages of organogenesis, reflecting the morphophysiological processes in plant ontogenesis, were identified by F.M. Cooperman (1955) (Fig. 1):

at stages 1-2, differentiation of vegetative organs occurs,

on III-IV - differentiation of the rudimentary inflorescence,

on V-VIII - the formation of flowers,

on IX - fertilization and the formation of a zygote,

on X-XII - growth and formation of seeds.

With a good supply of cereals with water and nitrogen, a large ear with large quantity spikelets. The end of vernalization in winter crops can be judged by the elongation of the cone of growth and the beginning of differentiation of spikelet tubercles (stage III). Photoperiodic induction ends with the appearance of signs of flower differentiation (stage V).

Main age periods. There are 5 age periods:

embryonic - the formation of a zygote;

juvenile - germination of the embryo and the formation of vegetative organs;

maturity - the appearance of the rudiments of flowers, the formation of reproductive organs;

reproduction (fruiting) - single or multiple formation of fruits;

aging - the predominance of the processes of decay and low activity of structures.

The study of the patterns of ontogeny of agricultural plants is one of the main tasks of particular plant physiology and crop production.

6. Plant communities

Plant communities (as well as individual species, intraspecific forms, and terats) that have a sufficiently definite and stable relationship with environmental conditions and are used to recognize these conditions are called indicators. Conditions determined with the help of indicators are called indication objects, or indicators, and the process of determination is called indication. Indicators can be individual organisms or their combinations (cenoses), the presence of which indicates certain properties of the environment. However, there are frequent cases when one or another species or cenosis has a very wide ecological amplitude and therefore is not an indicator, but its individual features change dramatically in different ecological conditions and can be used for indication. In the sands of the Zaunguz Karakum (Turkmenistan), for example, prickly leaves are widespread. (Acanthophyllum brevibracteatum), having usually pink flowers, but in areas with a close occurrence of sulfur accumulations (for example, in the Sulfur Hills region), the color of the flowers changes to white. In the landscapes of the Moscow region, accumulations of perched perches in meadows can be determined not so much by the floristic composition of meadow phytocenoses, but by the duration of individual phenophases, since the areas under which perched trees occur are indicated by long-term flowering of a number of species, which affects the aspect of the meadow. In both cases, not species or cenoses as such are used for indication, but only some of their features.

The connection between an indicator and an indicator is called an indication. Depending on the nature of the indicative connection, indicators are divided into direct and indirect. Direct indicators are directly related to the indicator and usually depend on its presence.

An example of direct indicators of groundwater can serve in arctic regions of the community with the dominance of plants from the group - obligate phreatophytes (i.e., plants constantly associated with groundwater) - chievniki (association. Achnatherum splendens) camel thorn communities (species of the genus Alhagi). These communities cannot exist outside the indicative connection, and if it is broken, then they die. Indirect, or mediated, is an indicative connection carried out through some intermediate link connecting the indicator and indicat. So, sparse thickets of psammophilic Aristida pennata in desert sands they serve as an indirect indicator of local accumulations of subsand perched water. Although there is no direct connection here, the psammophyte pioneers point to the weak fixation of the sand, which leads to good aeration of the sandy stratum and free infiltration of sediments, i.e., those conditions that favor the formation of perched water. Direct indicators are more reliable and reliable than indirect ones.

According to the degree of geographic stability of indication links, indicators can be divided into pan-realistic, regional and local. The connection of pan-realistic indicators with the indicat is uniform throughout the entire range of the indicator. Yes, reed (Phragrnites australis) is a pan-real indicator of increased substrate moisture within the development of its root system. Panareal indicators are not numerous and usually belong to the direct ones. Much more frequent are regional indicators that have a constant relationship with the indicate only within a certain physical-geographical region, and local indicators that remain indicative constancy only on the area of a known physical-geographical region. Both those and others turn out to be mostly indirect.

All of the above subdivisions of indicators in terms of the nature and stability of the relationship with the indicate are significant only in relation to some specific indicative connection with a known indicate in a particular indicator-indicate system. Outside of it, they don't matter. Thus, the same community can be a direct pan-realistic indicator for one indicator and an indirect local indicator for some other. Therefore, it is impossible to talk about the indicator significance of a cenosis or a species in general, without determining exactly which indicator in question. plant photosynthesis phytocenosis autotrophic

Indicators determined using botanical indicators are very diverse. They can be both different types of certain natural objects (soils, rocks, groundwater, etc.), and various properties of these objects (mechanical composition, salinity, fracturing, etc.), and certain processes occurring in the environment (erosion, suffusion, karst, deflation, swamping, salt migration, etc.), and individual properties of the environment (climate). When the object of indication is one or another process, not individual species or cenoses, but interconnected systems of plant communities, their ecological and genetic series, act as indicators. Indicators can be not only natural processes, but also changes created in the environment by man, occurring in it during land reclamation, the impact of industrial enterprises on it, mining, and construction.

The main directions of indicator geobotany are distinguished by indicators, for the determination of which indicator-geobotanical observations are used. The following areas are currently the most important:

1) pedo-indication, 2) litho-indication, 3) hydro-indication, 4) indication of permafrost conditions, 5) indication of minerals, 6) indication of natural processes, 7) indication of anthropogenic processes.

Pedoindication and lithoindication are often combined into geoindication. Pedoindication, or soil indication, is one of the most important areas, since the connections between soil and vegetation cover are the most indisputable and well known. This direction has two branches: the indication of various taxa (i.e., types, subtypes, genera, and types of soils) and the indication of certain soil properties (mechanical composition, salinity, etc.). The first, which is of exceptionally great importance, turns out to be rather complicated, since in the typology and classification of soils (especially in the lowest taxonomic units) there is not always complete uniformity, so that the scope of the indicat sometimes turns out to be somewhat indefinite. The second branch has now been developed much more fully, since soil properties in most cases can be characterized by quantitative indicators (according to the results of analyzes), and therefore it is possible to establish with great accuracy the relationship of certain plant communities with a certain amplitude of these indicators.

Lithoindication is called geobotanical indication of rocks. Lithoindication is closely related to pedoindication, but covers deeper layers of the earth. The connection of vegetation with these horizons can be either direct (due to plants with the most powerful root system) or indirect (through the rock-soil-vegetation system). Many plant communities are indicators of the weathering of rocks at early stages of soil formation on them (for example, communities of lithophilic lichens and algae). Vegetation indicators can indicate the fracturing of rocks (due to the predominant development of vegetation in cracks), certain chemical features of rocks (gypsum content, iron content, carbonate content, etc.), their granulometric composition (denoting clays, sands, sandy loams, loams, pebbles).

Hydro indication, or indication ground water, is based on the ability of many plants to develop only when their root system is connected to water-saturated horizons. Here, as in the field of lithoindication, plant communities with a predominance of deep-rooted plants are used. With geobotanical indication, it is also possible to assess the mineralization of groundwater. At the same time, indicators of highly mineralized groundwater are often (but not always) the same communities that indicate salt-bearing rocks. Indication of permafrost conditions is very complex. It is based on the idea that the vegetation cover of the permafrost zone depends on the thermal properties of the substrate and seasonal processes of thawing and freezing. However, these properties of permafrost soils depend both on their granulometric composition and on geomorphological, hydrological, and hydrogeological conditions. Therefore, the indication of permafrost conditions is, as it were, the result of the integration of pedo-indication, litho-indication, and hydro-indication studies. All considered directions - pedoindication, lithoindication, hydroindication and indication of permafrost conditions - have

similarity in that the main indicators are plant communities.

The indication of mineral resources differs in many respects from other areas of indication geobotany. Here, not plant communities are usually used as direct indicators, but individual species, small intraspecific forms of plants, and also terats. In this case, the indication is based on the facts established by observations about the strong shaping role of many compounds, as well as their pathological effect on the appearance of the plant - its color, morphology of its organs and their typical proportions. Indirect indication can also be made by communities if they designate lithological differences of rocks with which the distribution of certain minerals is associated. But such indirect indicators are usually local in nature, and therefore their practical value is limited.

The indication of processes, both natural and anthropogenic, is made not by individual plant communities, but by their ecological and genetic series. These are spatial series of communities, the sections of which are located one after another in the order in which they succeed each other in time. In other words, it is a successional series deployed in space. Each community participating in such a series reflects a certain stage of the process that created this series. Under field conditions, such series are found in the form of various complexes and combinations. Ecological and genetic series indicating natural processes reflect both endodynamic successions (resulting from the development of the phytocenosis itself, which changes the environment) and exodynamic successions (arising under the influence of external causes).

Indicators of anthropogenic processes are usually exodynamic series.

In addition to the main directions listed above, there are some types of indication that have not yet received such wide development and application, but nevertheless are quite important. These include: indication of climatic conditions, indication of the tectonic structure of the territory and, in particular, the location of various types of tectonic faults. Some cases of application of indication to these objects will be considered in the chapters devoted to those zones and subzones where these types of indication are most clearly expressed.

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