The plant, as a rule, occupies two environments – elevated and underground, and necessary for the activity takes all from both environments. Air food is photosynthesis, and soil consists in absorption of water and the dissolved mineral substances root hairs of the soaking-up root zone.
As absorption by a root of water and mineral salts from the soil is carried out
Beginning from a tip, the root consists of four sites: zones of division, stretching zone (growth zones), zones of absorption and zone of carrying out. The absorption zone on a root has length about 2-3 cm. Root hairs – the long outgrowths many times increasing the general soaking-up root surface depart from cages of an external cover of a root.
The root can absorb mineral salts only in the dissolved look. The slime emitted by root hairs dissolves them and makes available to absorption.
Water with the dissolved minerals climbs the carrying-out plant fabrics to a stalk and leaves. The ascending current is so carried out. The organic matter which is formed in leaves in the course of photosynthesis arrives to roots and other bodies of a plant the descending current.
The ascending current goes on tracheitises and vessels of wood, descending – on cribriform tubes of a bass. Wood and a bass – types of the carrying-out fabric.
Features of root food of plants
Root food provides receipt in a vegetable organism of water and mineral salts. The plant gets from the soil of salt of potassium, phosphorus, calcium, magnesium, compound of nitrogen, also other elements are gray. Root hairs of a root system at the same time work as small pumps. The need of a plant for minerals depends on its type, age, intensity of growth and stages of development, properties of the soil, time of day and the nature of weather conditions. The majority of plants need nitrogen, potassium, phosphorus, magnesium, sulfur, however beet and potatoes, for example, demand bigger amount of potassium, and barley and wheat – nitrogen. The lack of nitrogen slows down growth of a plant and promotes formation of small leaves. At the shortage of potassium processes of division and stretching of cages slow down that can cause death of a root tip. Phosphorus is important for a metabolism, and magnesium – for formation of chlorolayers and a chlorophyll. The deficiency of sulfur reduces intensity of photosynthesis.
Circulation of mineral substances
In nature the mineral substances absorbed by plants partially come back to the soil at fall of leaf, branches, needles, flowers, dying off of root hairs. When conducting agricultural works of it does not occur as the harvest is withdrawn by the person. For this reason it is important to use fertilizers to prevent exhaustion of the soil and to keep its high productivity.