Question

In actively growing plant cells (rice, wheat, groundnut etc.), this component of water potential becomes negligible
(A) Solute potential
(B) Pressure potential
(C) Matric potential
(D) Gravitational potential
Choose the correct answer from the options given below:

• (A) and (B) only
• (B) and (C) only
• (C) and (D) only
• (B) and (D) only

Hint:

For well-hydrated, growing cells, simplify the water potential equation to:
\[ \Psi_w = \Psi_s + \Psi_p \]
Always assume matric potential ($\Psi_m$) is only significant in dry seeds, soils, or wood, while gravitational potential ($\Psi_g$) is only significant in tall trees over $10\text{ meters}$ in height.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
The total water potential ($\Psi_w$) of a plant cell is a measure of the free energy of water per unit volume relative to pure water.
It is determined by several contributing components: solute (osmotic) potential ($\Psi_s$), pressure (turgor) potential ($\Psi_p$), matric potential ($\Psi_m$), and gravitational potential ($\Psi_g$).
The equation representing this relationship is:
\[ \Psi_w = \Psi_s + \Psi_p + \Psi_m + \Psi_g \]
Depending on the physiological state and physical scale of the plant cell, certain components exert a dominant influence while others become negligible.

Step 2: Detailed Explanation:
Let us analyze each of the water potential components in actively growing, herbaceous plant cells:
Solute potential ($\Psi_s$) is always significant because growing cells maintain a high concentration of dissolved solutes to drive water uptake.
Pressure potential ($\Psi_p$) is also highly significant because turgor pressure is required to stretch the cell wall during cell expansion and growth.
Matric potential ($\Psi_m$) represents the binding of water to insoluble cellular matrices such as cell walls and organelles.
While $\Psi_m$ is dominant in dry seeds or highly dehydrated soils, it becomes negligible in well-hydrated, actively growing vegetative plant cells where free water is abundant.
Gravitational potential ($\Psi_g$) depends on the height of the water column relative to a reference level.
At the single-cell level, the vertical distance is extremely small, making the gravitational contribution negligible.
Therefore, both matric potential ($\Psi_m$) and gravitational potential ($\Psi_g$) are negligible in actively growing cells.

Step 3: Final Answer:
The components that become negligible in actively growing plant cells are (C) and (D) only.
This corresponds to Option (C).