Transpiration

• Epidermal cells bear a fine tubular outgrowth called root hair, which grows in between soil particles and is in contact with soil solution
• A thin film of liquid surrounding soil particles is a diluted solution of mineral salts
• The cell sap of the root hair cell, concentrated with sugars and dissolved salts, has a lower potential than the soil solution
• Water molecules enter the root hair cell by osmosis through the partially permeable membrane
• The entry of water dilutes the cell sap, and the root hair cell has a higher water potential compared to the surrounding soil
• Water molecules pass by osmosis from the root hair cell into inner cells
• Water molecules pass by osmosis from the outermost cell to the inner cells in the cortex, and the process continues until water enters xylem vessels and moves up the plant