8. Write the process of water absorption by roots in plant
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In higher plants, water is absorbed through root hairs from the soil water. The walls of root hairs are permeable to water and are hydrophilic in nature. They contain vacuoles filled with cell sap. Absorption of water by roots takes place by two mechanisms namely, active absorption and passive absorption. During active absorption, the root cells absorb water using metabolic energy released through respi­ration. Active absorption could be either osmotic absorption or non-osmotic absorption. In osmotic absorption, water is absorbed from the soil into the xylem of the roots in the osmotic gradient. In non-osmotic absorption, water is absorbed against the osmotic gradient. In passive absorption, water absorption is due to transpiration. In this, absorption of water into the root is due to conditions that originate in the top of the plant and the root cells play a passive role. Osmotic concentration of the root cells is due to the presence of soluble metabolic products synthesized in the aerial parts of the plants and later translocated downwards to the root cells.

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