The process by which water enters the cell from a source outside the cell is called water absorption. Higher plants absorb water by roots, lower plants by rhizoids and aquatic plants by whole body. Rhizomes are the main organ of plant water absorption. Rhizomes extend into the spaces between soil particles. On the other hand, there is a large amount of capillary water in the spaces between soil particles. As the concentration of capillary water in the interstices of soil particles is less than that of the root cell sap, the pore pressure deficit occurs. ie DPD decreases. Water enters the rhizome in the process of osmosis to equalize this diffusion pressure deficit. It reduces the density of mullein and root cells. But cortex cells have higher cell density. Due to this, there is a diffusion pressure deficit between the cortex and cortex cells. To equalize this diffusion pressure deficit, water moves from the root into the first cells of the cortex. Then the water passes through the second, third, fourth, fifth etc. cells of the cortex and finally reaches the intestine. This results in a decrease in endodermal cell density, but a higher pericycle cell density. As a result a diffusion pressure deficiency occurs. To equalize this pressure deficit, water enters the xylem vessel cavity from the endoderm through the pericycle by the process of osmosis. Later, the water reaches the necessary parts of the plant through the xylem.