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

60. Growth phases: embryonic, stretching, differentiation and their physiological features. 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 stage G 2, the synthesis of RNA and proteins continues. Replication of mitochondrial and plastid DNA occurs throughout the entire interphase.

Stretch phase. Cells that have stopped dividing go on to growth by extension. Under the action of auxin, proton transport to the cell wall is activated, it loosens, its elasticity increases, and additional water inflow into the cell becomes possible. There is a growth of the cell wall due to the inclusion of pectin substances and cellulose in its composition. Pectins are formed from galacturonic acid in the vesicles of the Golgi apparatus. The vesicles approach the plasmalemma and their membranes fuse 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, cell wall lignification intensifies, which reduces its elasticity and permeability, growth inhibitors accumulate, and IAA oxidase activity increases, which reduces the auxin content in the cell.

phase of cell differentiation. Each cell of a plant 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. 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.

Aging and cell death. With cell aging, there is a weakening of synthetic and an increase in hydrolytic processes. In the organelles and cytoplasm, autophagic vacuoles are formed, chlorophyll and chloroplasts, the endoplasmic reticulum, the Golgi apparatus, the nucleolus are destroyed, mitochondria swell, the number of cristae decreases in them, and 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 occur as a result of 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.

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

Growth frequency characteristic of perennial, winter and biennial forms, in which the period of active growth is interrupted by a dormant period.

The law of the 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 not constant 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, 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 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) - about 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 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.

To compensatory correlations reflect the dependence of growth and competitive relations of individual organs on the provision of their nutrients with you. 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 - 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 - peculiar to plants specific differentiation of structures and processes in space. It manifests itself in a certain direction of growth of the root and stem, in a certain direction of movement of substances.

Life cycle (ontogenesis) of a plant. In ontogenesis, four stages of development are distinguished: embryonic, passing on the mother plant from the formation of a zygote to the maturation of the seed and from the inception to the maturation of the organs of vegetative propagation; juvenile (youth) - from the germination of a seed or vegetative bud to the onset of the ability to form reproductive organs; stage of maturity (reproductive) - the laying of the rudiments of reproductive organs, the formation of flowers and gametes, flowering, the formation of seeds and organs of vegetative propagation; the stage of old age is the period from the cessation of fruiting to the 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, to designate the age state of plants, the term “development phase” is more often used, denoting a certain morphological manifestation of the age state of the plant. Most often, phenological phases are used for this (seed germination, germination, branching, budding, fruit formation, etc.), the initiation of organs in the apical meristem (stages of organogenesis).

Most vegetable crops that form food organs from vegetative formations (headed cabbage, kohlrabi, Brussels sprouts, lettuce crops) end their stay on a vegetable plantation with a juvenile period, without proceeding to the formation of generative organs before harvesting.

Harvest 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 independent nutrition. 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 primary roots, the seeds can dry out and return to a dormant state, which is used in some methods of pre-sowing seed preparation. At later stages of germination, moisture loss leads to the death of the seedling.

The rate of germination and initial growth of the seedling largely depends on the size of the seeds. Relatively large-seeded crops and large seeds from one heap provide not only faster germination, which is associated with a relatively high growth force, but also a stronger initial growth. The strongest initial growth is possessed by creepers (Pumpkin, Legume families), which have large seeds. Cucumber, a month after germination, uses up to 17% of the area allotted to it, and carrots, according to V.I. Edelstein, use about 1%. The weak initial growth of crops from the Celery and Onion families not only does not allow full use of solar radiation in the early stages, but also significantly increases the cost of protecting crops from weeds.

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

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

From the moment the seed is pecked, the formation of roots outstrips the growth of the stem. Complex metabolic processes are associated with the root system. The absorbing surface of the root considerably exceeds the evaporating 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 varieties, later ones, 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 develops into the main root, giving rise to a highly branched root system. In many cultures, the root system forms 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 phase of technical ripeness had a total root length of 9185 m, and their number reached 927,000, in a tomato - 1893 and 116,000, respectively, in onions - 240 m and 4600. In cabbage and tomato branching of the roots reached the fifth order, in the onion - the third. In most vegetable crops, the main root dies relatively early and the root system becomes fibrous. This is facilitated by transplant (seedling) culture, as well as limiting the amount of soil nutrition. In many cultures (families Nightshade, Pumpkin, Cabbage, etc.), adventitious roots play a significant role, which are formed from the hypocotyl knee or other sections of the stem after hilling and picking. The root system of vegetatively propagated tuber and bulbous crops (potato, sweet potato, Jerusalem artichoke, onion and multi-tiered, etc.) is represented exclusively by adventitious roots. During seed propagation of onion, the bulk of the roots by the beginning of the formation of the bulb is represented by adventitious ones.

Growth roots are isolated, 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 considerably exceeds the surface of the assimilating part of the plant. This is especially pronounced in lianas. So, in a cucumber a month after planting the seedlings, the area of the working surface of the roots reached 20 ... 25 m 2, exceeding the surface of the leaves by more than 150 times. Apparently, this feature is connected with the fact that creepers do not tolerate damage to the root system in seedlings, 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 plants, but also on the method of cultivation and other growing conditions. Damage to the top of the main root in the seedling culture 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 considerably in how their root system responds to soil compaction. Crops with relatively slow growth rates, such as carrots, tolerate compaction best. In cucumber, the high growth rate of the root system is closely related to the need for sufficient aeration - a lack of oxygen in the soil causes the roots to die off quickly.

The root system has a tiered structure. The bulk of the roots in most cases is located in the plow horizon, however, deep penetration of the roots into the soil is also possible (Fig. 3). For broccoli, white, cauliflower and Beijing cabbage, kohlrabi, batun, onion and leek, parsley, radish, lettuce, celery, garlic and spinach, the root penetration depth is 40...70 cm; for eggplant, rutabaga, 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 120 cm.

The active surface of the roots usually reaches its maximum size by the beginning of fruit formation, 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 suction and conduction roots also changes.

Root hairs are short-lived, die off very quickly. As 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 photosynthesis products to their above-ground system. The biomass of roots in relation to the above-ground system is low.

In annual vegetable crops, the roots die off during the season. Often the end of root growth causes the plant to begin to age. Most perennial vegetable crops have seasonal rhythms in the development of the root system. In the middle and end of summer, the roots completely or partially die off. In onions, garlic, potatoes and other crops, the root system dies off completely. In rhubarb, sorrel and artichoke, it is mainly the active part of the roots that 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. Roots grow in garlic and soon a bud awakens, which gives leaves. In onions, only roots grow, as the bulb is at rest.

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

While the potato tuber is at rest, the formation of roots cannot be caused, since this process is preceded by the germination of the tuber.

Autumn regrowth of roots is also observed in biennial vegetable plants if they remain in the field, which occurs in seed production with a direct crop or autumn planting of queen cells.

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 shoot tips. Following the growth of the germinal root, elongation of the hypocotyl of the shoot begins. After its release to the surface of the earth, growth is suppressed under the influence of light. The 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 prevent the hypocotyl from stretching. When growing seedlings, it is necessary to provide sufficient illumination, low temperature and relative humidity during the emergence of seedlings.

External conditions during this crucial period of transition to independent nutrition largely determine the subsequent growth, 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 formation of organs for the growth and development of cells and tissues (cytogenesis). vegetative and generative organs (organogenesis). Morphogenesis is genetically programmed and varies 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 various life forms can be monopodial, when the apical bud remains growth during ontogenesis (Pumpkin), sympodial, when the first-order axis ends with a terminal flower or inflorescence (Solanaceae), and mixed combining both types of branching.

Branching is a very important trait associated with the rate of crop formation, its quality and plant productivity, the possibility of mechanization, and the labor costs for pinching and pinching.

Cultures and varieties differ in the nature of branching. It also depends on the environmental conditions. Under optimal conditions, branching is much stronger. Cabbage plants, root crops, onions, garlic do not branch in the first year of life when grown from air bulbs. Weakly branched peas and beans. Varieties of tomato, pepper, cucumber and gourds differ significantly in branching strength (number of branches and orders).

The reproductive stage of ontogeny begins with the initiation 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 fading with an increase in fruit load. In cucumber, peas and many other crops, growth stops during the period of mass fruit formation and seed formation. A high load of fruits contributes to the acceleration of plant aging and may be the cause of premature death. In peas, cucumbers, the collection of unripe ovaries makes it possible to significantly extend the growing season.

Cultures 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

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

In the spring of the second year, a flowering stem quickly forms, leafy in semi-rosette life forms (sorrel, rhubarb, horseradish, cabbage, carrots, etc.) and has no leaves in rosette (onion) life forms. By the end of summer, with the ripening of 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 (onions, 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 the overwintering of plants in winter and perennial crops. The appearance of a flower-bearing stem, which means the transition to generative development, is possible only under the condition of vernalization - exposure of the plant during a certain period of low positive temperatures. For perennial plants, the stem should appear every year. Moreover, lower temperatures contribute (in rhubarb) to the termination of the dormant period and stimulate the growth of leaves, which is used when forcing in protected ground.

In cabbage and cauliflower, rosettes are formed differently. 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 above-ground 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 cultures do not branch. Branching is observed only in the second year in biennial crops and from the second year in perennials.

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

Perennial plants form the assimilation apparatus more quickly in the second and subsequent years, providing an earlier harvest than when grown from seeds 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 during the reproductive period in cabbage, radish, turnips are the stems and pods of seed plants, in onions - arrows and integuments of fruits.

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

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

Climbing climbing vines (vegetable crops from the Pumpkin and pea families), due to the presence of antennae with high sensitivity to contact with the support (thigmomorphogenesis), have the ability to quickly and thoroughly attach to it. Among the cirriform vines in the Cucurbitaceae family, a special place is occupied by a group of creeping vines, which include gourds (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 the stems after emergence, strong branching associated with the fastest possible capture of the territory and dominance on it. Under conditions of sufficient moisture, some of these vines (for example, pumpkins) form adventitious roots at the nodes, providing additional fastening of the stem to the soil.

The growth of a plant, its individual organs, and the formation of a crop largely depend on the distribution between the individual parts of the products of photosynthesis, which is associated with the activity of attracting (mobilizing, attracting) centers. The direction of activity of these centers of hormonal regulation changes during ontogeny. 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 (root crops, bulbs and tubers) organs. Often between these organs there is competition in the consumption of photosynthesis 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 attracting centers.

A particularly strong attracting ability of generative organs distinguishes varieties of fruit and vegetable crops (peas, beans, tomatoes, cucumbers, peppers, etc.) intended for simultaneous machine harvesting. In most of these varieties, fruit formation and crop ripening take place in a short time. They are also characterized by a relatively early cessation of growth.

Many agricultural techniques are based on the regulation of the location of attracting centers and their activity (the period of cultivation of a crop, seedling growth management, plant formation, temperature regimes, irrigation, fertilizers, the use of growth-regulating substances). The creation of conditions during the storage period of onion sets that exclude the possibility of its vernalization will make the bulb the center of attraction, which will allow you to get a good harvest. When storing onions, queen cells 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 attraction center in these cases moves from the storage vegetative organs to the generative ones. Radish roots become flabby (cotton), lettuce leaves become rough and tasteless, bulb growth stops.

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

Growth points and young leaves consume all the products of photosynthesis, as well as a significant part of the mineral compounds from adult and aging leaves. Old leaves, in addition, give the young and part of the previously accumulated plastic substances.

The phenomenal attraction ability of fertilized embryos is manifested in some cultures in fruits torn from the mother plant. Peduncles with blooming 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. Collected from plants, weekly cucumber greens, unripe fruits of green-fruited varieties of zucchini, pumpkin, under 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 germinating 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.

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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. It not only provided anaerobic respiration for 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 metamorphosis of the root should be considered mycorrhiza, a complex of the root and hyphae of fungi 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 of a large amount of nutrients in it. 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) - a part of the shoot system of an angiosperm plant that bears flowers and, therefore, is variously modified. The inflorescences are usually more or less clearly demarcated from the vegetative part of the plant.

The biological meaning of the appearance 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, monetized loosestrife).

Bractose - 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 the 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 a 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 environmental conditions.

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, the root system grows intensively, 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. With regard to specific crops, the 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 a large number of spikelets is formed at stages II and III. 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 under 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 perches 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 indication relationship, 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 strata 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 connection 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 speak about the indicator significance of the cenosis or the species in general, without determining exactly which indicator is being discussed. 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 this or that process is the object of indication, 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, being of exceptionally great importance, turns out to be rather complicated, since there is not always complete uniformity in the typology and classification of soils (especially in the lowest taxonomic units), 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). Vegetative indicators can indicate the fracturing of rocks (due to the predominant development of vegetation in cracks), certain chemical features of rocks (gypsum content, ferruginous content, carbonate content, etc.), their granulometric composition (denoting clays, sands, sandy loams, loams, pebbles).

Hydroindication, or groundwater indication, 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 formative 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 (occurring as a result of 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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Characteristics 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 a process of irreversible new formation 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 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 primary activation of the corresponding genes and called differential gene activation (DAG).

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

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 are phytohormones.

The studied phytohormones are divided into two large groups:

growth stimulants

growth inhibitors.

In turn, growth stimulants are divided into three classes:

gibberellins,

cytokinins.

To auxinam 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 fall leaves and ovaries, activate root formation.

To 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, 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.

To cytokinins include purine derivatives, a 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 parts of metabolism, enhance the synthesis of DNA, RNA, and proteins.

growth inhibitors represented by two substances:

abscisic acid,

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

Ethylene - it is a gaseous phytohormone that inhibits growth and accelerates the ripening of fruits. 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.