BOTANY

Detailed explanation-1: -The point at which matric forces hold water too tightly for plant extraction (-1.5 MPa) is termed the permanent wilting point. The amount of water held between field capacity and permanent wilting point is considered plant available water (PAW) (Figure 2).

Detailed explanation-2: -The permanent wilting point is the point when there is no water available to the plant. The permanent wilting point depends on plant variety, but it is usually around 1500 kPa (15 bars). At this stage, the soil still contains some water, but it is difficult for the roots to extract from the soil.

Detailed explanation-3: -Usually the basal leaves wilt first (Taylor and Ashcroft, 1972, p. 303), so one can refer to the “first permanent wilting point, ”, at which the basal leaves do not recover, and the “ultimate per-manent wilting point, ”, at which the apical leaves do not recover. The permanent WP depends upon plant osmotic adjustment.

Detailed explanation-4: -On a hot, dry day (or after several days with no rain or watering), transpiration causes more water to be lost than is coming in, and the water balance within the plant can get thrown off. The dehydrated collapsing cells in the leaves and stems can no longer remain erect, and the plant begins to wilt.

Detailed explanation-5: -Ultimate wilting point: Point after which plant is not able to extract any water from the soil and gets wilted and dies.