The Question is from neet-botany plant-physiology , and it was created by the author B VENKAT

Question

A plant exposed to a fungal toxin exhibits significantly reduced translocation of potassium ions ($K^+$) despite normal transpiration rates. The toxin MOST likely affects which process?

B VENKAT · Accepted Answer

## CORE INFORMATION
✓ **Answer**: C
## CONCEPT FRAMEWORK
 **Primary Concept**: Plant Transpiration and Ion Transport
 **Related Topics**: Xylem transport, Potassium ion uptake, Membrane proteins, Fungal toxins
 **Prerequisites**: Understanding of transpiration pull, xylem function, and the role of potassium ions in plant physiology.
## SOLUTION PATHWAY
**Given Information**:
  * Reduced $K^+$ translocation
  * Normal transpiration rates
  * Fungal toxin exposure
**Method & Steps**:
 1. Analyze the given information: The problem states that transpiration (water movement) is normal, but potassium ion ($K^+$) transport is reduced. This suggests the issue is specifically with $K^+$ transport, not the overall water transport mechanism.
  Reasoning: Transpiration is driven by the water potential gradient, and it involves the cohesion-tension theory. If transpiration were affected, we would expect a change in water movement.
  Formula/Rule:  No specific formula is directly applicable here. The problem relies on understanding the process of water and ion movement in plants.
 2. Consider the options:  The options explore different aspects of water and ion transport in plants.
  Working: Let's examine each option:
  A. Stomatal opening and closing affects transpiration rates. Since transpiration is normal, this is unlikely.
  B. Water potential gradient affects transpiration. Since transpiration is normal, this is also unlikely.
  C. Membrane transport proteins are crucial for the active transport of ions like $K^+$ into the xylem. A fungal toxin could directly inhibit these proteins.
  D. Root pressure contributes to water movement but is less significant than transpiration pull. It's less likely to be the primary cause of reduced $K^+$ translocation.
 3. Final step: The most plausible explanation is that the fungal toxin directly inhibits the activity of membrane transport proteins responsible for $K^+$ uptake into the xylem.
  Result: Option C
  Verification: The explanation aligns with the given information. Reduced $K^+$ translocation despite normal transpiration points to a problem with $K^+$ transport itself, not the water transport system.  A fungal toxin impacting membrane proteins is a logical mechanism.
 ## OPTION ANALYSIS
A :x: Stomatal function is directly related to transpiration rate. Since transpiration is normal, this is not the likely cause of reduced $K^+$ translocation.
B :x: The water potential gradient is the driving force for transpiration. If this were affected, transpiration would also be affected, which it is not.
C ✓: Membrane transport proteins are essential for the active uptake of $K^+$ into the xylem. A fungal toxin could easily inhibit these proteins, leading to reduced $K^+$ translocation.
D :x: Root pressure contributes to water movement, but its effect is less significant than transpiration pull.  It is unlikely to be the primary reason for reduced $K^+$ translocation.
 ## LEARNING AIDS
 **Common Mistakes**:
  1.Confusing transpiration with ion transport:  These are related but distinct processes.
  How to avoid: Carefully distinguish between the movement of water and the movement of ions in the plant.
  2.Focusing solely on transpiration: The problem highlights a specific issue with ion transport, so don't get sidetracked by the normal transpiration rate.
  How to avoid:  Analyze the problem statement carefully to identify the key issue.
 **Quick Tips**:
  1. Understand the role of membrane proteins in active transport.
  2. Remember that fungal toxins can target specific cellular processes.

B VENKAT · Answer

Stomatal opening and closing

B VENKAT · Answer

Water potential gradient in the xylem

B VENKAT · Answer

The correct Option is "Activity of membrane transport proteins involved in $K^+$ uptake into xylem"

B VENKAT · Answer

Root pressure generation

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