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Botany Question 20 – AP-EAMCET 2025

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Choose the correct statements among the following I. Movement of water through apoplast involves crossing the cell membrane. II. Movement of water through apoplast is dependent on the gradient. III. In symplast, water travels in the cells through plasmodesmata. IV. Transpiration pull has lesser significance than root pressure for water transport in tall plants.

Understand the two main pathways for water movement in plants: apoplast and symplast, and the forces driving them.

Step 1: Evaluate Statement I: Apoplast Pathway and Cell Membrane✦ Active

The apoplast pathway involves the movement of water through the cell walls and intercellular spaces of adjacent cells. This pathway does not require water to cross the cell membrane, as it bypasses the cytoplasm. Water only crosses the cell membrane when entering the symplast pathway or the cell itself. Therefore, statement I is incorrect.

💡 Teacher's Secret Hint

Remember that the apoplast is the non-living part of the plant, primarily cell walls and intercellular spaces, allowing for rapid, unimpeded water flow.

Step 2: Evaluate Statement II: Apoplast Pathway and Gradient○ Expand

Water movement through the apoplast is primarily driven by a water potential gradient. Transpiration from leaves creates a negative pressure (tension) that pulls water up through the xylem and the apoplast, moving from areas of higher water potential to lower water potential. Therefore, statement II is correct.

💡 Teacher's Secret Hint

All passive water movement in plants, whether apoplastic or symplastic, is ultimately driven by differences in water potential.

Step 3: Evaluate Statement III: Symplast Pathway and Plasmodesmata○ Expand

The symplast pathway involves the movement of water through the cytoplasm of cells. Adjacent cells are connected by plasmodesmata, which are small channels that allow for the direct flow of cytoplasm and dissolved substances, including water, between cells. Therefore, statement III is correct.

💡 Teacher's Secret Hint

The symplast pathway is the living part of the plant, involving the cytoplasm and its connections, the plasmodesmata.

Step 4: Evaluate Statement IV: Transpiration Pull vs. Root Pressure○ Expand

Transpiration pull is the major driving force for water transport in tall plants. It creates a strong negative pressure (tension) that pulls water column upwards against gravity. Root pressure, on the other hand, is a relatively weak positive pressure generated by the active transport of ions into the xylem, causing water to move in. Its role is minor in tall plants and is more significant in shorter plants or during periods of low transpiration (e.g., at night). Therefore, statement IV is incorrect.

💡 Teacher's Secret Hint

Transpiration pull is a 'pulling' force, while root pressure is a 'pushing' force. The pulling force is far more significant for moving water over long distances in tall plants.

Step 5: Identify the Correct Option○ Expand

Based on the evaluation, statements II and III are correct. Option 2 combines these two correct statements.

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