Transpiration and Absorption

Transpiration is the process by which water in the form of water vapour is lost from the aerial parts of the plant. + This loss of water tends to lower the concentration of water in the cell sap. * Hence, water from the soil passes through the semipermeable membrane of the root hair into the root hair cell. When water accumulates in the root hair, neighbouring cell of the root cortex has a comparatively lower concentration of water molecules. Hence, water from the root hair diffuses into the cortical cell, and the root hair becomes flaccid (limp). Once again it absorbs water from the soil. Thus, by a cell to cell osmosis, water from the soil passes into the root hair, the cortical cells and finally reaches the xylem vessels through the passage cells and the unthickened areas of the endodermis.