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loss of turgor (tension of tissues) by plants due to disruption of the water balance; it occurs when the transpiration of water by leaves exceeds the amount entering the tissues. Wilting is manifested externally by a drooping of the leaves and tops of the stems. Various plant species wilt after different degrees of water loss. Sunflowers and potatoes wilt after a loss of more than 30 percent of the water in the leaves, and some shade-loving plants wilt after a water loss of 2-3 percent.
Wilting may be temporary or prolonged. Temporary wilting (temporary water deficiency) occurs when the water entering from the soil cannot compensate for the amount expended by the plant; but after reduced transpiration—for example, toward evening—the water balance is restored, and the plant returns to normal. Prolonged wilting (residual water deficiency) occurs when there is little or no moisture available to the plant in the soil, and the water balance is not restored even during the night.
As plants wilt, their growth halts, and as dehydration intensifies, photosynthesis is disrupted, the energy efficiency of respiraton diminishes, and starch, proteins, and other high-molecular compounds in the tissues break down, resulting in death of the cells. Wilting in arid regions can be prevented by irrigating, improving the mineral nutrition of the plants, hardening seeds before sowing, and planting drought-resistant varieties.
T. F. KORETSKAIA