why negative root pressure develops due to excessive transpiration
- Root pressure is the positive pressure that develops in the roots of plants by the active absorption of nutrients from the soil.
- Root pressure develops because of active absorption which depends on the active accumulation of solute in xylem sap.
- Root pressure usually develops during the night when absorption is maximum and transpiration is minimum.
- During day time, transpiration is maximum. The water lost through transpiration causes the guard cells and other epidermal cells to become flaccid. They in turn take up water from the xylem. This creates a negative pressure or tension in the xylem vessels, from the surfaces of the leaves to the tips of the roots, through the stem.