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Physiology of plants

Plants will continuously transform a sunlight to energy and, thereby, are the important link in the vital chain covering all planet.

Plants are live "§шьшёхёъшх чртюф№" where continuously there are difficult reactions. Gas exchange accompanying these reactions does our planet suitable for a life. The majority of plants - from remains-snowdrop to a tree-giant - are rather similar on an internal structure, despite striking external distinctions. The spending system on which nutrients and substances-intermediaries circulate, represents the network of spending bunches covering roots, stalks and leaves.

Cages of plants

In spending bunches there are two basic types of cages. On cages ksilemy as on channels, upwards from roots water and mineral salts rises. And cages floemy serve for transportation of products of photosynthesis in places where in them there is a requirement. These two types of spending channels are divided by the most thin layer of cages kambija which one party develops the first type of cages, and another - the second. At a wood plant all growth at thickness occurs for the account kambija which makes at once three different types of cages - new cages ksilemy from the inside, cages floemy - with external and cages most kambija, providing increase in this layer together with tree growth. In plants there are three major processes - photosynthesis, breath and transpiratsija, or evaporation.


Though a plant and a beret from soil nutrients, however in itself they no more than bricks for which packing in new molecules photosynthesis process is necessary.

The Chlorophyll is the molecule performing all work on splitting of carbonic gas and water on oxygen and sugar (carbohydrates). It "Ёрсюёшщ чх§" - hloroplasta, in considerable quantities being in special cages of leaves. They paint the majority of plants in green colour familiar to us. Even brown, red or grayish leaves contain a chlorophyll, is simple except it here there are also other pigments. Only plants-parasites, like a dodder or mushrooms, do not contain a chlorophyll and are compelled to exist at the expense of the energy developed by other plants.

Physiology of plants the Chemical equation of transformation of water (from soil) and carbonic gas (from air) in oxygen and sugar simply enough; and all laborious work on splitting and synthesis of new molecules is carried out by a chlorophyll. The sugar developed thus is, as a matter of fact, the form of potential chemical energy.

The Sunlight - a stimulator of chemical reaction in chlorophyll molecules, therefore without a sufficient water-supply, carbonic gas and illumination plant growth is slowed down.


If photosynthesis is in the dark impossible, process of breath and splitting of sugar in the presence of the oxygen, accompanied by energy liberation, occurs at any time. Thus the plant allocates carbonic gas and evaporates a moisture. When with arrival of darkness photosynthesis stops, the volume of carbonic gas allocated with a plant exceeds volume of the consumed oxygen.

However in global scales this process plays the major role in formation of a chemical compound of atmosphere, and with arrival of new day air again is exposed to processing by photosynthesis.


Transpiratsija - process at which the moisture evaporates from a surface of leaves through minute pores, or ustitsa. Together with root pressure it supports vsasyvanie waters from soil and its lifting to leaves.

At high humidity of air evaporation is slowed down, and the requirement of a plant for water decreases. But in hot windy weather the plant evaporates more moisture and, not to wither, requires in additional polive. The plants adapted for a life in hot droughty countries, or at all have no (as the majority of cactuses), or in their modified leaves it is less than foliage ustits, capable besides densely to be closed, to keep a precious moisture.

a sheet Structure

At the majority of plants the sheet surface is great enough effectively to use a sunlight, and they are placed on a stalk or in pairs the friend opposite to the friend, or mutovkami (surround a stalk around) so that each leaf is minimum shaded the bottom neighbours. The plants, got used to live in a shade, differ disproportionately wide leaves, capable to catch a sunlight maximum. Besides, plants are able to turn foliage and even to direct growth to the sun. Such change of growth under the influence of a sunlight is called as phototropism.


Far not at all plants leaves are adapted for fast absorption of gases and gas exchange. In foliage of many shade-loving kinds diffusion process proceeds in a slowed-up way. However, it at all does not harm to plants, for their growth depends not so much on a sunlight, how many from carbonic gas. They usually reduce evaporation of a moisture and, accordingly, require photosynthesis less. Leaves are protected from superfluous evaporation epidermisom, allocating voskopodobnoe substance - kutin. On a surface epidermisa a numerous small time ustits thanks to which the plant regulates process of absorption of gases and moisture evaporation is scattered.

Photosynthesis occurs mainly in palisadnyh cages. They are located directly under epidermisom and filled hloroplastami. The median layer of a sheet plate is spongy mezofill, in which as in a time warehouse, photosynthesis products before sending in other parts of a plant are stored.

a Food

Water is soaked up by roots in the course of osmotic diffusion. It extends on a plant partly by osmotic processes, and partly on capillaries, getting into all sections up to the top of a high tree.

Besides carbon received from air and hydrogen arriving with water and oxygen, many other chemical elements - nitrogen, phosphorus, magnesium, iron, calcium and kaly, and also the long list of other elements in microscopic doses are necessary to plants for growth. Plants show certain selectivity, absorbing from soil something more, and it is less than something as required even if all nutrients are in soil much.

the Building material

Sugar (carbohydrates) Developed in the course of photosynthesis, having passed a chain of chemical reactions, it will be transformed to all other substances necessary for a plant. Their further way lies through floemu spending bunches in all fabrics and plant bodies.

Energy is often stored in a kind of kernels of starch (if to drip iodine on the slice of a crude potato containing in it starch, will turn black - means, at this plant energy stocks collect in tubers).

Unlike animals, plants do not have difficult nervous system, therefore their reactions are stimulated with hormones, i.e. Substances which are developed in one part of a plant, and operate - in another. One - for example, gibberelliny - promote their growth, others, like abstsizovoj acids, suppress it. This acid stimulates formation otdelitelnogo a layer thin-walled, ryhlo the located cages in shanks of leaves and ripe fruits, and those under the influence of a wind and a gravity fall to the ground.


Gibberellovaja acid is the hormone, capable to change character of growth. For example, it is possible to force to grow up a dwarfish plant in height, influencing it gibberellinom. Other substances, on the contrary, create effect karlikovosti at usually high kinds. These hormones are quite often used for reception of high or undersized and compact plants.

Phototropism is a natural aspiration of a plant upwards, to a sunlight. geotropizm - reaction of a plant to terrestrial gravitation, i.e. Growth of roots downwards. Hemotropizmom name reaction to chemical stimulus, for example, auksin. The hormone auksin plays the important role in regulation of rates of increase of various bodies of a plant. Depending on plant position, starch is postponed in its this or that part, forcing auksin to collect in roots or runaways.

Concentration auksina decreases from a top to a root and though, as a whole, it stimulates growth, however the requirement of different bodies in auksine far is not identical. At surplus auksina in this or that body its growth even will be slowed down. If to place a plant it is horizontal, auksin will accumulate below. Thanks to it growth of a top of runaway will be accelerated - i.e. Places, where auksina most of all (and the plant will be curved upwards). But at the very bottom, at a root, growth will be slowed down, and the stalk again will hang.


Under condition of uniform distribution auksina on all fabrics, runaway will grow vertically upwards, but thus the hormone will start to accumulate on the shaded party. Thanks to it growth of cages here will be accelerated, and runaway will turn to light. In the given phenomenon of phototropism (aspiration to light) it is possible to make out action of the hormone wisely operating movement of a plant after the sun.

The Same auksin promotes disclosing of buds under the influence of light or temperature. Heat accelerates growth of each petal on the one hand and as a result the flower is dismissed. At some plants under the influence of a cold the same process occurs upside-down.

Ability of many plants to be twisted or cling to support too depends on distribution of hormones. Hardly the sweet pea short moustache concerns support, hormones immediately move on a plant opposite side, stimulating its growth, and the short moustache is twisted in the meantime round a support.

Substances-intermediaries regulate also the form and kustistost plants. Developed by growing tops auksin it is carried by juice in all other bodies of a plant where can oppress growth of lateral runaways. The further from a top, the action auksina is weaker, and each body manages optimum quantity for growth. As at high concentration this hormone can oppress development of the runaways located behind the main point of growth, they will not compete to the basic stalk. But if this stalk breaks or will be damaged (or the gardener prishchepit it for stimulation of growth of lateral branches), level auksina will decrease and will cease to oppress development of the kidneys located below an old point of growth. After that new runaways will start to develop more auksina and, in turn, will establish the control, oppressing development located behind runaways. This phenomenon name apikalnym (top) domination.

Force of light

Physiology of plants Light not only plays a key role in the course of photosynthesis, but also operates flowering. Day length and makes nights also certain impact on growth. One garden and window plants have come to us from the hot equatorial countries (where day is equal to night), others - from high widths with long summer days and winter nights. The plants of the high widths which have got used by long light day, name plants of long day.

If them to move in moderate widths it will by all means affect flowering. For example, delfinium - a plant of long day and consequently blossoms in the beginning of summer (when duration of light day increases) that seeds had time to ripen before colds. But the guest from hot Mexico of a dahlia - a plant of short day which starts to blossom with approach of autumn.