Evaporation of water, or transpiration, is a very important part of plant life. Water is absorbed by the root system along with minerals dissolved in it, which are simply necessary for the normal growth of the body. Most of the absorbed water evaporates by the leaves.
The role of water in the development of the plant organism . Water is a very important element and its role in the life of the plant is difficult to overestimate. Due to water, it supports the turgor of the cells, so that the leaves and stems become elastic and resilient. Without enough fluid, the plant withers quickly.
In addition, together with water, the minerals absorbed by the root are distributed over all the organs of the plant. Moisture also protects the body from overheating. Water evaporation by plants occurs mainly through the stomata - specialized formations on the leaves. To some extent, transpiration is also carried out by the whole body of the plant through the integumentary tissue.
Stomata and their structure . The evaporation of water by leaves occurs mainly through specialized structures called stomata. The stomata consists of two sickle-shaped closure cells, between which there is a small gap. The inner wall of the trailing cells is thicker, and the outer is thin. A small cavity is located under the structure.
The stomata can be located on both sides of the leaf. But in many plants, they are located on its inner part. But in aquatic plants, the leaves of which are in contact with water (for example, water lilies), - on the outside of the leaf.
It is worth noting that stomata are responsible not only for the evaporation of water, but also for gas exchange with the atmosphere - oxygen and carbon dioxide pass through them .
Evaporation of water: how does it occur? As already mentioned, transpiration can also occur through the integument of the whole body of the plant organism - in this case it is called cuticular. The leaves, stem and other organs of a young plant are covered with a single-layer epidermis - moisture is eliminated through it. In more mature plants, a cuticle and wax ball is deposited on the outer surface, which protects the body from excessive moisture loss and drying out. Therefore, cuticular transpiration in mature leaves is minimized.
The main evaporation passes through the stomata. To begin with, the water moves through the vessels of the xylem, then passes along the cell walls into the intercellular spaces, from where it is collected in the submuscular cavity.
Opening and closing of stomata is primarily affected by the amount of water. When moisture accumulates in the closing cells, they stretch and take the shape of a crescent - in this case, the gap opens. If there is not enough water in the cells, they lose turgor, their walls fall off and close the crack.
The content of carbon dioxide also affects the condition of stomata. If its level in plant tissues drops sharply, then the processes of opening stomata are activated. And if the concentration of this gas is too high, the gap closes. That is why the stomata close at night when the processes of photosynthesis cease.
Evaporation of water and its quantitative characteristics . Like any other process, transpiration has its own quantitative indicators, which are used in agriculture, science and other areas of human life.
For example, transpiration rate shows how many grams of water are released by a part of a plant with a certain area per unit time. By measuring the transpiration productivity, we can say how much dry mass was accumulated by the plant during the evaporation of one kilogram of water. And having determined all these indicators, one can find out some individual characteristics of the plant species, establish what conditions are necessary for its productive growth.