Question:
In the roots of plants, casparian strip made of suberin forms a ring around the cells of the endodermis. It effectively blocks the entry of water and mineral ions into the stele via the apoplast. A defect in the casparian strip leads to
In the roots of plants, casparian strip made of suberin forms a ring around the cells of the endodermis. It effectively blocks the entry of water and mineral ions into the stele via the apoplast. A defect in the casparian strip leads to
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Think of the Casparian strip as a "one-way check valve" for solutes in the root. If this valve leaks, solutes slip back out, and the root loses its ability to build up the osmotic pressure needed to draw water in, lowering hydraulic conductivity.
Updated On: Jun 16, 2026
- increased solute leakage and reduced root hydraulic conductivity.
- decreased solute leakage and increased root hydraulic conductivity.
- increased solute leakage and increased root hydraulic conductivity.
- decreased solute leakage and reduced root hydraulic conductivity.
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The Correct Option is A
Solution and Explanation
Step 1: Understanding the Question:
The question asks about the physiological consequences of a defect in the Casparian strip of plant roots.
Step 2: Detailed Explanation:
• The Casparian strip is a band of cell wall material deposited in the radial and transverse walls of the endodermis in plant roots.
• It is made of suberin, a hydrophobic, waxy substance that is impermeable to water and dissolved solutes.
• Physiologically, the Casparian strip blocks the apoplastic pathway, preventing water and mineral ions from diffusing passively into the vascular cylinder (stele).
• This forces all water and solutes to cross the selectively permeable plasma membranes of endodermal cells via the symplastic pathway.
• This mechanism allows the plant to selectively uptake nutrients and maintain a high concentration of solutes inside the stele, creating an osmotic gradient that drives root pressure.
• If the Casparian strip is defective, the barrier is compromised.
• Consequently, solutes accumulated in the stele can leak back into the cortex apoplast (increased solute leakage).
• Additionally, the root cannot maintain the osmotic pressure gradient required for the active transport and upward movement of water.
• This leads to a significant reduction in the root's hydraulic conductivity, which is its capacity to transport water from the soil to the xylem.
Step 3: Final Answer:
Therefore, a defect in the Casparian strip leads to increased solute leakage and reduced root hydraulic conductivity.
The question asks about the physiological consequences of a defect in the Casparian strip of plant roots.
Step 2: Detailed Explanation:
• The Casparian strip is a band of cell wall material deposited in the radial and transverse walls of the endodermis in plant roots.
• It is made of suberin, a hydrophobic, waxy substance that is impermeable to water and dissolved solutes.
• Physiologically, the Casparian strip blocks the apoplastic pathway, preventing water and mineral ions from diffusing passively into the vascular cylinder (stele).
• This forces all water and solutes to cross the selectively permeable plasma membranes of endodermal cells via the symplastic pathway.
• This mechanism allows the plant to selectively uptake nutrients and maintain a high concentration of solutes inside the stele, creating an osmotic gradient that drives root pressure.
• If the Casparian strip is defective, the barrier is compromised.
• Consequently, solutes accumulated in the stele can leak back into the cortex apoplast (increased solute leakage).
• Additionally, the root cannot maintain the osmotic pressure gradient required for the active transport and upward movement of water.
• This leads to a significant reduction in the root's hydraulic conductivity, which is its capacity to transport water from the soil to the xylem.
Step 3: Final Answer:
Therefore, a defect in the Casparian strip leads to increased solute leakage and reduced root hydraulic conductivity.
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