Root hairs are in contact with soil particles. These provide a large surface area for water absorption. Water diffuses into the root hairs as a result of diffusion pressure deficit gradient. Water enters as long as the DPD of the cell sap is greater. The DPD falls following an increase in TP. The DPD of the adjoining cortical cells being higher and water moves from root hairs into cortical cells.
The DPD of the next inner cells being higher, water moves into them. In this way, water moves from one cortical cell to the other along a DPD gradient till it reaches the passage cells in the endodermis. Through the radial and inner tangential walls of the passage cell water enters the pericycle and then to the protoxylem element.
