Wilting refers to the loss of rigidity or structure of non-woody parts of plants (Figure 6.26). It
occurs when turgidity of plant cells is lost. When a cell absorbs water, the cell membrane
pushes against the cell wall. The rigid cell wall pushes back on the cell making the cell
turgid. If there is not enough water in the plant, the large central vacuole of the cell shrinks
and the cytoplasm decreases, resulting in decreased pressure being exerted on the cell mem-
brane, and in turn, on the cell wall. This results in the cell becoming flaccid (floppy). When
the cells of a plant are flaccid, the entire plant begins to wilt.
Figure 6.26: Crops wilt due to a lack of water.Wilting occurs due to lower availability of water which may be due to:
- Drought conditions: where the soil moisture drops below conditions that allow plants
to grow. - Low temperatures: which prevent the plants vascular transport system from function-
ing; - High salinity(salt concentration): which causes water to diffuse from plant cells to the
soil, thus inducing shrinking of cells. - Saturated soil conditions: where roots are unable to obtain sufficient oxygen for cel-
lular respiration and so are unable to transport water into the plant. - Bacterial or fungal infections: that block the plant’s vascular system.
Guttation
Guttation is the ”oozing out” or exuding of drops of water on the tips or edges of leaves of
some vascular plants such as grasses visible in Figure 6.27.
Figure 6.27: Guttation in plant leavesChapter 6. Support and transport systems in plants 179