Wall pressure will______________ with rise in turgidity

The correct option is decrease.

To understand why wall pressure decreases as turgidity rises, we must examine the physiological mechanisms of cell wall relaxation during cell expansion. Turgidity represents the state of a cell being distended due to the internal pressure of water. As water enters the cell, it exerts turgor pressure against the cell wall.

For the cell to expand and accommodate this influx of water, the cell wall must undergo a process called wall loosening. This enzymatic relaxation reduces the rigid structure of the cell wall, thereby decreasing the resistance or counter-pressure it exerts back onto the cell contents. This counter-pressure is known as the wall pressure.

During cellular expansion, the effective wall pressure can be represented as:

$$\mathrm{WP}=\mathrm{TP}-Y$$

where WP is the wall pressure, TP is the turgor pressure, and Y is the yield threshold of the cell wall. As turgidity rises and the wall loosens to yield to the pressure, the resistance (wall pressure) decreases to facilitate expansion.