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Q.
On the walls of the cells, the pressure exerted by the swelling protoplast is_________.
NTA AbhyasNTA Abhyas 2020
Solution:
When a plant cell is placed in pure water, due to the entry of water inside the cell by endosmosis, the cell swells but never bursts. Due to the entry of water the plasma membrane exerts some pressure on the cell wall. Such hydrostatic pressure is called as Turgor Pressure (TP). This pressure, in simpler words, is due to an increase in the Turgidity of the cell, when the cell absorbs water from the surrounding medium.
Significance of TP can be the following:
1. It provides stability to the cell.
2. All cellular organelles, like Plastids, Mitochondria, etc. remain distended, which is needed for normal plant growth and development, due to TP.
3. TP also provides sufficient mechanical support to non-woody plants, as in the case of Maize, Sugarcane, etc.
4. Several physiological movements in plants are due to change in TP, like stomatal movement, Nastic movement in Touch-me-Not.
5. Radicles and Plumules emerge out due to TP.
To counter-balance, the cell wall of the cell, whose TP has increased, exert equal and opposite pressure. This is called as Wall Pressure (WP).
Suction Pressure (or DPD) is the thirst of the cell.
OP prevents the movement of water across a membrane.