Biology – 8.1 Transport in plants | e-Consult

Wilting occurs when the water potential in the plant's cells is lower than the water potential in the surrounding environment. This leads to a net loss of water from the cells, causing them to lose turgor pressure. Turgor pressure is the pressure exerted by the cell contents against the cell wall, which keeps the plant cells firm and the plant upright.

Water potential is a measure of the tendency of water to move from one area to another. Water moves from areas of high water potential (less negative) to areas of low water potential (more negative). In a healthy plant, the water potential inside the cells is higher than that of the soil. This difference in water potential drives water uptake by the roots.

When the water potential in the soil is lower than that in the roots, the rate of water uptake decreases. This is because the water potential gradient is reduced. The plant's cells lose water through transpiration, and if the rate of water uptake is insufficient to replace this loss, the turgor pressure decreases. As turgor pressure falls, the cells become flaccid, and the plant begins to wilt.

Factors influencing water potential include:

• Soil water potential: Drier soil leads to lower water potential.
• Transpiration rate: Higher transpiration rates increase the demand for water, potentially lowering the water potential in the plant.
• Temperature: Higher temperatures increase transpiration rates.
• Humidity: Lower humidity increases transpiration rates.
• Wind: Increased wind speeds increase transpiration rates.