Question

When a cell is fully turgid, which of the following will be zero
(a)Turgor pressure or pressure potential
(b)Wall pressure
(c) Suction pressure/DPD/Water potential
(d) Osmotic pressure (solute pressure)

Answer 1

Hint: As the cell becomes fully turgid the value of turgor pressure becomes equal to that of solute potential (Ψs) so that the potential energy of water becomes either zero or equal to that of external hypotonic solution. When the cell is fully turgid the pressure difference between pure water and solution becomes zero and as a result, the entry of water will Stop.

Complete answer:
When a cell is fully turgid its water potential or DPD becomes zero. When a plant cell is placed in a hypotonic solution, water enters into a cell by osmosis, and as a result turgor pressure develops in the cell which is in solution. The cell membrane becomes stretched and the osmotic pressure of the cell decreases. As the cell absorbs more and more water its Turgor Pressure increases and Osmotic Pressure decreases. When a cell is fully turgid, its osmotic pressure is equal to turgor pressure and DPD is zero. Turgid cells cannot absorb any more water. Thus, with reference to plant cells, the DPD can be described as the actual thirst of a cell for water. Simply DPD of a cell is the thirst of the cell for water. It is zero for a fully turgid cell and maximum for a plasmolyzed cell. When DPD is zero, the entry of water will stop. Thus it is DPD that tends to equate and represents the water-absorbing ability of a cell, it is also called suction force or suction pressure.

Additional Information: -DPD is directly proportional to the height of the plant, tree, or organism. DPD is governed by two factors i.e. turgor pressure and osmotic pressure.
-When a cell is fully turgid, its walls and membranes are completely stretched. At this time osmotic pressure of the cell will be equal to turgor pressure and so water potential becomes zero. A turgid cell cannot absorb any more water.
-The internal water potential of a plant cell is more negative than pure water because of the cytoplasm’s high solute content. Because of this difference in water potential, water will move from the soil into a plant’s root cells via the process of osmosis.
So, the correct answer is ‘suction pressure / DPD / water potential’.

Note: -Turgor, Pressure exerted by fluid in a cell that presses the cell membrane against the cell wall. Turgor is what makes living plant tissue rigid.
-Loss of turgor, resulting from the loss of water from plant cells, causes flowers and leaves to wilt.
-Diffusion Pressure Deficit(DPD) is the pressure difference between pure water and solution or simply DPD of a cell is the thirst of the cell for water.