الفهرس 
Introduction
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Abstract
Water is essential for root growth, as in any other physiological process that depends on cell elongation, to provide a force that causes expansion (Acevedo, 1979). Under normal condition, roots receive the oxygen needed for respiration from the soil. However, when the soil in saturated with water, gas exchange is reduced to only the most superficial portion of the soil, leading to a situation of root anoxia. The available oxygen is quickly consumed by the microbial flora of the soil, stopping the absorption and transport of water and salts into the root (Richards, 1983) and (Azcon-Bieto and Talon, 2000).