active absorption of water from the soil by the root is mainly affected by
SURFACE AREA OF ROOTS ATP
title: Absorption of water text: Absorption of water The absorption of water by plants is essential for various metabolic activities. Terrestrial plants get their water supply from soil which serves as the source of water and [minerals]. The way in which water from soil enters roots, particularly to the root xylem, is called "mechanism of water absorption". Both active and passive absorption have been proposed for mechanism of water absorption.This process is known as Conduction Active absorption refers to the absorption of water by roots with the help of ATP, generated by the root respiration: as the root cells actively take part in the process, title: Absorption of water text: it is called active absorption. According to Renner, active absorption takes place in low transpiring and well-watered plants, and 4% of total water absorption is carried out in this process. The active absorption is carried out by two theories; active osmotic water absorption and Active non-osmotic water absorption. In this process energy is required. This theory was given by Pari (1910) and Priestley (1921). According to this theory, the root cells behave as an ideal osmotic pressure system through which water moves up from the soil solution to the root xylem along an increasing gradient of D.P.D. (suction pressure, which title: Absorption of water text: than the soil water.If stated, water potential is comparatively positive in the soil water. This gradient of water potential causes endosmosis. The endosmosis of water continues till the water potential both in the root and soil becomes equal. It is the absorption of minerals that utilise metabolic energy, but not water absorption. Hence, absorption of water is indirectly an active process in a plant's life.Active transport is in an opposite direction to that of diffusion. This theory was given by Thimann (1951) and Kramer (1959). According to the theory, sometimes water is absorbed against a concentration gradient. This requires expenditure title: Soil text: movement of water in soil is the means by which plants acquire it and their nutrients. Most soil water is taken up by plants as passive absorption caused by the pulling force of water evaporating (transpiring) from the long column of water (xylem sap flow) that leads from the plant's roots to its leaves, according to the cohesion-tension theory. The upward movement of water and solutes (hydraulic lift) is regulated in the roots by the endodermis and in the plant foliage by stomatal conductance, and can be interrupted in root and shoot xylem vessels by cavitation, also called "xylem embolism". title: Absorption of water text: is the real force for water absorption). If solute concentration is high and water potential is low in the root cells, water can enter from soil to root cells through endosmosis. Mineral nutrients are absorbed actively by the root cells due to utilisation of adenosine triphosphate (ATP). As a result, the concentration of ions (osmotica) in the xylem vessels is more in comparison to the soil water. A concentration gradient is established between the root and the soil water. Hence, the solute potential of xylem water is more in comparison to that of soil and correspondingly water potential is low