Hint: Root hairs are present only in the maturation zone of the root. Maximum water absorption occurs via root hair cells only. Root hairs are long, thin, and can easily penetrate between tiny soil particles.
Complete answer: Root hairs prevent bacterial entry in xylem sap. Root hairs cover a large surface area for water absorption. The absorption of water takes place by the process known as osmosis. Osmosis is the process in which movement of water i.e., movement of solvent takes place from high water concentration to low water concentration through a semipermeable membrane. The absorbed water is transported through the roots to other parts of the plant. Adsorbed water reaches leaves and is used in the process of photosynthesis. It acts as one of the reactants in photosynthesis. Also, it helps leaves and shoots cells to maintain rigidity. The absorbed water is used to maintain the internal environment of the leaf. Evaporation causes cooling in leaves. Some dissolved minerals are transported in plants via the water transportation pathway. Water molecules present in between soil particles enter the root hair cell via osmosis. It reaches the cell cytoplasm and is further passed into the xylem cells.
Note: The concentration of water is more in the soil as compared to root cells hence, movement of water occurs from soil to root hair cells only. Water potential i.e. ability to give solvent [water] is more of soil particles than that of root hair cells.