The importance of water for plant life. The role of water in plant life
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The importance of water in plant life
Water is necessary for the life of any plant. It makes up 70-95% of the plant's wet body weight. In plants, all life processes occur using water
Functions of water in a cell Water is the internal environment in which metabolism occurs. It connects organs and coordinates their activities in the whole plant. Water is part of membranes and cell walls, making up the main part of the cytoplasm. Water ensures the transport of substances throughout the plant and the circulation of solutions. Water protects plant tissues from sudden temperature fluctuations. Provides the elastic state of plants, which is associated with maintaining the shape of herbaceous plants and the orientation of organs in space.
water exchange - the flow of water into the plant and its release by the plant, necessary for its life activity
water exchange consists of three stages: 1) absorption of water by the roots, 2) movement of it through the vessels of the wood, 3) evaporation of water by the leaves. Usually, with normal water exchange, as much water enters the plant as it evaporates.
Transport of water through vessels
Transpiration The process of water evaporating through leaves
The water current in the plant goes in an upward direction from bottom to top. It depends on the strength of water absorption by the cells of the root hairs below and on the intensity of evaporation above. A constant flow of water from the root system to the above-ground parts of the plant serves as a means of transporting and accumulating minerals and various chemical compounds coming from the roots in the body organs. It unites all the organs of the plant into a single whole. In addition, the upward flow of water in the plant is necessary for normal water supply to all cells. It is especially important for the process of photosynthesis in leaves.
Of the entire huge amount of water passing through the plant, only a very small part of it is used by it to synthesize the substances of its body. The plant absorbs only 0.2% of all water passed through. The remaining 99.8% of absorbed water is spent on evaporation. But this “waste” is very important for the plant.
01/21/2013 Municipal educational institution "Secondary school No. 2" city Chernushka, Perm region Maybe the roots can do without water? Is it enough to simply spray the stem and leaves of the plant with water?
Ecological groups are groups of plants in relation to any one environmental factor that determines the adaptive properties of organisms
Ecological groups in relation to water Hydatophytes (from the Greek hydatos - “water”, phyton - “plant”) - aquatic herbs (elodea, lotus, water lilies). Hydatophytes are completely submerged in water. The stems have almost no mechanical tissue and are supported by water. Plant tissues contain many large intercellular spaces filled with air. Water lily
Elodea canadensis
Water lily
Hydrophytes (from the Greek hydros - “aquatic”) plants partially submerged in water (arrowleaf, reeds, cattails, reeds, calamus). They usually live along the banks of water bodies in damp meadows. Rogoz
Arrowhead
Calamus marsh
Hygrophytes Sedge (from the Greek hygra - “moisture”) plants of humid places with high air humidity: marigold, sedge, cyperus, rush.
Mesophytes (from the Greek mesos - “middle”) are plants that live in conditions of moderate moisture and good mineral nutrition: colza, lily of the valley, strawberry, apple tree, spruce, oak. They grow in forests, meadows, and fields. Most agricultural plants are mesophytes. They develop better with additional watering
Mesophytes
Xerophytes (from the Greek xeros - “dry”) plants of dry habitats, where there is little water in the soil and the air is dry aloe, cacti, saxaul.
Succulents Succulent xerophytes with fleshy leaves (aloe, crassula) or fleshy stems (cacti - prickly pear, mammillaria, cereus)
Opuntia Crassula
sclerophytes Dry xerophytes - (from the Greek scleros - “hard”) are adapted to strictly conserve water and reduce evaporation (feather grass, saxaul, kermek, camel thorn). feverweed
Feather grass Saxaul Sclerophytes Camel thorn
Subject: “THE IMPORTANCE OF WATER IN PLANT LIFE”
Goals and objectives: form concepts about ecological groups of plants; show the importance of water for plant life; reveal the essence of the process of water metabolism in plants; develop students’ knowledge about the life processes of plants; to cultivate interest in cognitive and creative activities, the desire for knowledge, interest in the subject, and respect for nature.
Equipment: textbook, tables: NH-1 “Classification of fertilizers”, NB-11 “Natural community”, “Internal structure of a leaf”, presentation for the lesson.
During the classes:
1. Organizing time (students have the necessary supplies for the lesson, greeting).
2. Survey d/z (orally according to §29).
- Motivation.
- What is the role of water in plant life?
- Think about whether different types of plants use the same amount of water?
- Does the amount of water used depend on where the plant grows?
4. Studying a new topic. Teacher's story.
Listen to what the plants talked about in Vsevolod Garshin’s story “Attalea princeps”:
“- Please tell me, will we be watered soon? - asked the sago palm, which loved dampness very much. - I really think I’m going to dry out today.
“Your words surprise me, neighbor,” said the pot-bellied cactus. - Is the huge amount of water that is poured on you every day not enough for you? Look at me: they give me very little moisture, but I am still fresh and juicy.
“We are not used to being too thrifty,” answered the sago palm. - We cannot grow on such dry and crappy soil as some cacti. We are not used to living somehow.
Having said this, the sago palm became offended and fell silent.”
The writer correctly noted how different plants need water - for some it can be 80-90 times more than for others. And if plants could really discuss their problems, one of the most important for them would be the issue of water. Any plant is at least half, and sometimes even 98%, water. In just one summer day, a sunflower “drinks” 1-2 liters of water, and a century-old oak tree drinks more than 600 liters.
A person evaporates sweat primarily to cool down. The plant also needs cooling. But a significant part of the evaporated moisture is spent for another purpose. Only through a moistened surface can a plant absorb carbon dioxide from the air in order to grow. Involuntarily, he has to constantly evaporate water. This is why plants in dry places, where there is little water, grow so slowly.
By the way, such plants have learned to limit their water intake in different ways. Some, in the course of evolution, acquired juicy, fleshy stems or leaves (cacti, aloe) filled with moisture, and evaporate it very sparingly. They are called succulents. The exact opposite of them are sclerophytes, hard, dry plants (for example, camel thorn). They tolerate drought in a semi-dried form.
Water is an essential factor determining the life of plants. K. A. Timiryazev divided the water entering the plant organism into organized (which is bound by the body) and waste (evaporated by the leaf surface). Of 1000 g of water absorbed by a plant, about 990 g evaporates, and 10 g is retained in the plant. The body of plants is 50-98% water. All physiological processes occur with the participation of water, therefore it is one of the most significant environmental factors influencing the growth and development of the plant organism and the distribution of plants on earth.
Plants obtain water from the soil and air. But the amount of water in different areas of land is not the same (swamps and deserts). In this regard, various adaptations can be seen in plants.
Land plants in most cases obtain water from the soil. This is facilitated by a well-developed root system. Going deep into the soil to the aquifer, the roots can reach a considerable length. In sandy deserts, water falling in the form of dew is of great importance, and plants can be observed developing fine roots in the surface layer of sand.
Some plants in very dry places have adapted to retain moisture in their bodies in succulent stems (cacti, some euphorbias) or leaves (aloe, agaves, sedums, juveniles, etc.). The appearance of these plants is very unique.
Atmospheric precipitation can play both a positive and negative role. Snow cover protects wintering plants from freezing. In high mountain regions and the Far North, where snow lies most of the year, plants have adapted to a short growing season.
Snow and hail have a mechanical impact on plants, sometimes causing significant damage to plants.
The distribution of precipitation during the growing season is of great importance for plants. In areas with dry summers and wet springs, plants have developed that manage to complete their development cycle before the onset of the dry period. During the dry season, they hide underground in the form of bulbs or rhizomes (ephemera) or are stored as seeds (ephemera).
May and June rains are of great importance for obtaining a good harvest for cereals.
Water supply conditions affect the appearance and internal structure of plants. By appearance it is not difficult to determine in what moisture conditions the plant grew.
In relation to moisture, there are three main ecological groups of plants: hygrophytes, mesophytes and xerophytes.
Hygrophytes are plants in abundantly moist habitats with high atmospheric humidity. These plants have a thin cuticle, highly developed internal cavities in the leaves and stems, thin leaf blades, and the leaves have special glands - hydathodes (water stomata), through which water is released. These plants are: impatiens, marsh bedstraw, circe.
Mesophytes are plants in habitats with average moisture. These are the majority of meadow and forest plants.
Xerophytes are plants in habitats with insufficient moisture. These plants have a variety of adaptations that increase their drought resistance. They are capable of sharply reducing transpiration during the dry period, have devices that enhance the extraction of water when there is a lack of water in the soil, as well as devices that allow creating water reserves during a long interruption in water supply. Reducing transpiration is achieved in different ways: reducing the surface of the leaves, developing a layer of cuticle or waxy coating, dense pubescence of the leaves, deepening the stomata into the mesophyll, tightly connecting the cells of the parenchyma tissue of the leaf. The extraction of water from the soil is associated with the powerful development of the root system in depth (in camel thorn, the root reaches 18-20 m in depth) and horizontally to the surface. The water supply is contained in the water-storing tissue of the leaf (in aloe, sedum, agaves) or stem (in cacti). According to different methods of plant adaptation to lack of moisture, sclerophytes and succulents are distinguished. Sclerophytes have hard leaves and stems, and often the entire plant is heavily pubescent or covered with a thick layer of cuticle. Succulents are succulent, fleshy plants.
Another group of xerophytes has become widespread in the arid regions of our planet. These are ephemera and ephemeroids.
A plant may experience a lack of moisture not only in cases where there is little moisture in the soil. Severe soil acidity and high concentrations of readily soluble salts in the soil can limit the absorptive power of roots when water content is sufficient. This state of the soil, in contrast to physical dryness, is called physiological dryness.
A special ecological group is formed by aquatic plants - hydrophytes. Among them, a distinction is made between plants that are not completely immersed in water (by half or one third) - reeds, reeds, arrowheads, some sedges, etc., and plants that are completely immersed in water (only their inflorescences rise above the water or their leaves are on the surface of the water ) - pondweed, water lily, egg capsule, cabomba. Among this group of plants one can find striking examples of the influence of the aquatic lifestyle on their appearance. Thus, in arrowhead and cabomba, leaves immersed in water differ sharply from leaves floating above the water (Fig. 1). Plants immersed in water have characteristic features: very thin leaf blades, consisting of only 2-3 layers of cells, sometimes heavily dissected; the stem is herbaceous with air-bearing cavities, the conducting vessels occupy a central position in the stem; There are no mechanical tissues. This allows the plant to bend freely in the water column. Cells have low osmotic pressure. Plants that live on swampy soils or along river banks have different adaptations to living conditions: the leaves are large, tender, but thicker and stomata are located on both sides of the leaf; the root system penetrates shallowly into the soil; stems with large air cavities, conducting vessels and poorly developed mechanical tissue.
5. Physical exercise.
6.
Consolidation. View and discuss the presentation for the lesson. Independent reading of the material§30, answers to questions
7 .Summarizing the lesson, reflection, assessment of students' knowledge.
8 .Homework: §30, repeat §25 – 29.
Water in plant life plays a huge role, it is an integral part of every plant, every organ. Percentage of water in the plant body:- protoplasm contains about 80% water,
- in cell sap - 96-98% water,
- in the membranes of plant cells up to 50% water.
- in the leaves the water content reaches 80-90%.
- c - up to 98%,
- in - 94%,
- in - 92%,
- c - 77%.
Water is the main solvent
High water content in plant tissues is necessary for active synthetic activity. Water is the main solvent, and with its participation, nutrients dissolved in water enter the plant through the roots and move them from one cell to another.Water in the interaction of plants with the environment
Thanks to water is where the plant interacts with the environment. IN process of photosynthesis water is directly involved in education carbohydrates. Of 1000 parts of water passing through a plant, only 2-3 parts are used in the process of photosynthesis to form carbohydrates, and 997-998 parts of water pass through the plant to maintain its tissues in a state of saturation and to compensate for evaporating water. The large leaf surface of plants leads to the waste of a huge amount of water: in one hour, plants consume up to 80-90% of the water they contain. The degree of their opening depends on the amount of water in the guard cells of the stomata; when its content is high, the stomata are open, and carbon dioxide enters the plant through them.Plant water consumption
Various plants contain unequal amounts water, it changes both during the day and during the growing season. Towards the end of the growing season, the water content decreases.
Water consumption by plants. Of the higher plants, very few representatives of the desert flora can withstand dehydration, (more details:) while dry seeds and some lichens can remain viable even with low water content. In different growing conditions, the plant's need for water is not the same. In dry and hot climates, plants spend 2-3 times more water during the growing season than in temperate climates. State of water in plants
Water in plants happens in two states- V free and bound. Bound by water consider water, which is retained by hydrophilic colloids of protoplasm and active substances. Bound water loses its solvent properties and does not take an active part in the transformation and movement of substances throughout the plant. The role of bound water is that it prevents micelles from sticking together and imparts structural stability to hydrophilic colloids of protoplasm. The amount of bound water in a plant is not constant; young plants have more bound water than old ones. Free water in a plant - the environment in which all the processes of its life take place. A large amount of free water is evaporated by the plant. This division of water into free and bound is conditional, since all the water present in the cells is associated with substances that make up the protoplasm, cell sap and membrane. These forms of water differ only in the nature and strength of the bonds. Biologists have conducted a number of experiments with heavy water containing O 18. In young bean plants immersed by their roots in heavy water, there was a rapid replacement of part of the tissue water with water containing O18.
Bush bean plant in bloom. In the tissues of leaves and roots, which have a rapid metabolism, equilibrium with the external solution occurred within 15-20 minutes, with slightly more than half of the water being exchanged. The water in the stem was replaced by 90%. When leaves withered, the cell sap lost water most quickly, the water of the cytoplasm was retained much more strongly, and the least amount of water was lost, which is part of the organelles. Based on these experiments, it was concluded that the plant contains hard and easy to exchange water.
Of course, the supply of water is one of the main processes in plant life.
After all, plants (like all living organisms) mainly consist of water. Its leaves usually contain about 85% of the total mass, and its roots - 99%.
However, there are also exception plants (for example, mosses), which can easily lose it under conditions of severe water shortage, while maintaining viability. Dried plants contain only tightly bound water, usually only 5-10%. Such water is retained due to electrostatic interactions with biological macromolecules and is necessary to maintain the intact structure of these molecules. When normal water supply is restored, the plants return to active life.
Dehydration is one of the necessary stages in the maturation of seeds of most plants. After the seed is formed, water flows out of it through vascular bundles into other plant tissues. Biochemical processes in the seed almost completely stop, and after leaving the mother plant, it can lie in the soil all winter. In the spring, the seed will germinate, having absorbed the required amount of water from the soil, and over the summer it will form a full-fledged organism capable of preparing for the next winter - if the plant is perennial. From the seeds of annuals, plants develop in the spring, which must have time to bloom and produce new seeds in the summer in order to continue life in subsequent generations.
But although plants can adapt to water deficiency (for example, as mosses do) or even dehydrate their seeds themselves (protecting them from death in winter), high water content of all organisms is a general law.
There is a concept of homeostatic water necessary for homeostasis - the internal balance of the body (homeostasis is translated as balance). This is the minimum level of water content below which life cannot be sustained.
Plants in different habitats have different water content minimums. For plants in near-water areas (cattail, arrowhead, chastuha, core) and tropical rainforests, a decrease in tissue water content below 65-70% means death. Plants in moderately humid areas (deciduous trees, most forest and meadow grasses, field weeds, agricultural crops) can reversibly reduce their water content by up to 45-60%. And for plants in deserts and other dry habitats, the minimum level of water in tissues is 25-27%.
It is curious that only 1% of the water in the plant is involved in chemical transformations! The rest of the water moves all the time, is absorbed by the roots and evaporates by the leaves. Water is the mobile internal environment of the body. Even in aquatic plants, water in the tissues is renewed and circulates through the vascular bundles. Thanks to the directed flow of water, the “building blocks” necessary for the synthesis of biological macromolecules are delivered to different parts of the plant.
The entry of water occurs at the root. Water enters the root hair cells through osmosis. Cells actively absorb potassium salts from the soil, but sodium salts do not pass through (the concentration of potassium ions inside becomes much higher than outside). This process is ensured by special “pumps” in the outer membrane. Water freely penetrates into the cells to “equalize” (dilute) the concentration of potassium ions. Cells control their water balance by regulating the internal salt concentration, and water moves under the influence of osmosis. If water in the soil is fresh (contains very little salt), then the absorption of potassium ions by the roots provides a higher concentration of salt inside the cells than outside. As a result, water moves inside the cells, maintaining the plant elastic (in a state of turgor). The walls protect the cells from rupture. If the outside is high concentration of salts (especially sodium salts that are not absorbed by cells), then water is drawn from the cells, causing wilting and death of the plant.
To evaporate water (transpiration), plant leaves have special structures called stomata.
The stomata is a collection of two guard cells. They have the shape of bean seeds and face each other with concave sides, between which there is an intercellular space - the stomatal fissure. The guard cells have a thickened middle part of the wall facing the stomatal fissure. Usually the stomata is surrounded by parastomatal (side) cells.
So, the root sucks up water from the soil, and the water evaporates through the stomata of the leaves.
Inside plants, water moves through special vessels.
Neighboring cells of different plant tissues are connected by plasmodesmata. Through these channels, water can move from one cell to another.
Various substances are transported with the flow of water.
All organelles (an organelle is a small organ) - the nucleus, mitochondria, chloroplasts, vacuole - also move inside the cell. Cytoplasm, the liquid basis of any cell, is always in constant circular motion, involving organelles in it.
There is still no answer to the question. "What are the reasons for this movement?" It is only known that inside the cells there are special “rails”, the structure of which is reminiscent of our muscles. These “rails” form an internal framework in cells called the cytoskeleton. It is believed that it is this that sets the cytoplasm in motion.
Van Helmont's experiments prompted other researchers to study the role of water in plant life. But even now in this area of science there remain many mysteries that are waiting to be solved.
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AGRICULTURE. (no 14,16)
Laws of agriculture and their use in modern agricultural production
The law of irreplaceability and equivalence of plant life factors. None of the plant life factors can be replaced by another. This is the first law of agriculture - the law of the indispensability of plant life factors. As a logical consequence of this law, the conclusion follows about the physiological equivalence of plant life factors. In agricultural practice, the law of the indispensability of life factors always manifests itself when they try to compensate for the lack of one of them with another, for example, water with fertilizer or vice versa. Attempts to replace one plant nutrition element with another were not successful either. The law of equivalence is expressed in the fact that the insignificant need of a plant for any element, if it is not satisfied, leads to disruption of the normal functioning of plants, as well as the lack of an element consumed in immeasurable quantities. larger quantities. The law of minimum, optimum and maximum. Despite the fact that the yield of any agricultural crop depends on the supply of plants with all life factors, it is limited, first of all, by the factor that is at a minimum. As the plant's need for the missing factor is satisfied, the yield increases until it is limited by some other factor that is at a minimum. Liebig formulated the law of the minimum as follows: “The productivity of a field is directly dependent on the necessary component of plant food, contained in the very minimum amount.” This is easy to see if we look at the effect of heat on plants. Any life process begins at some minimum temperature, proceeds best at the optimal temperature, slows down, and then completely stops as it further increases. The law of the cumulative action of life factors does not eliminate the law of the minimum, since the factor at the minimum has the leading meaning in the totality and it is necessary, first of all, to direct the efforts of the farmer. This will make it possible to increase the productivity of agricultural crops with the least amount of labor and money. The law of return was first formulated by Liebig. As an application of the law of conservation of matter to agriculture, it obliges, in order to preserve the fertility of the soil, to return all substances that are taken from the soil by harvest or as a result of losses, with fertilizers or otherwise.
THE IMPORTANCE OF WATER IN PLANT LIFE. WATER PROPERTIES OF SOIL
Water makes up up to 95% of the mass of plants; all life processes take place in it or with its use. Therefore, water is a necessary condition for the life of the body. When there is a lack of water, the plant's metabolism is disrupted.
·Water ensures the flow of nutrients and minerals through the plant's conducting system.
·Seed germination depends on the availability of water.
·Water is involved in the process of photosynthesis.
·Aqueous solutions filling the cells and intercellular spaces provide the plant with elasticity, thus the plant retains its shape.
The plant must absorb water. Otherwise, sooner or later, his life will be interrupted. Typically, a plant absorbs water exclusively through its root system from the soil. The root hairs of the roots are involved in this. Leaves evaporate water through their stomata.
If the evaporation of water by a plant exceeds the supply of water, the plant will wilt. This often happens during the day when it’s hot. At night, the plant makes up for the deficiency, since evaporation at this time of day is reduced
As a result of the constant absorption and evaporation of water in the plant, there is a constant water exchange, which includes three stages: the absorption of water by the roots, its movement through the vessels of the conductive tissue, and the evaporation of water by the leaves. The flow of water goes through all the organs of the plant. The amount of water a plant absorbs is approximately the amount it evaporates. Only a fraction of a percent of the incoming water is used for the synthesis of substances. These are quite large volumes of water. Water properties of soil. Water (water-physical, hydrophysical) properties are the set of soil properties that determine the behavior of soil water in its thickness. The main water properties of soil are
1) moisture capacity (the ability of soil to absorb and retain a certain amount of water)
2) water permeability (the ability of soils to absorb and pass through water coming from the surface)
3) water-lifting capacity (the ability of the soil to cause upward movement of water through capillary forces)
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