The Question is from neet-botany mineral-nutrition , and it was created by the author K SURESH KUMAR

Question

Certain halophytes can tolerate high salinity by accumulating ions like $Na^+$ and $Cl^-$ in their vacuoles.  Which membrane transport protein is MOST directly involved in this process?

K SURESH KUMAR · Accepted Answer

## CORE INFORMATION
✓ **Answer**: B
## CONCEPT FRAMEWORK
 **Primary Concept**: Membrane transport in halophytes
 **Related Topics**: Ion homeostasis, vacuolar compartmentalization, salt tolerance mechanisms in plants
 **Prerequisites**: Understanding of membrane transport proteins,  plant cell structure (vacuoles, tonoplast), and the role of proton gradients in secondary active transport.
## SOLUTION PATHWAY
**Given Information**:
  Halophytes accumulate $Na^+$ and $Cl^-$ ions in their vacuoles to tolerate high salinity.
  We need to identify the membrane protein directly involved.
**Method & Steps**:
 1. Identify the location of ion accumulation: The question states that $Na^+$ and $Cl^-$ ions are accumulated in the vacuoles.
  Reasoning: Vacuoles are enclosed by a membrane called the tonoplast.
 2. Consider the mechanism of ion transport:  The transport of ions against their concentration gradient (into the vacuole) requires energy.  Secondary active transport, often coupled to a proton gradient, is a common mechanism for this.
  Working: A proton pump (H+-ATPase) creates a proton gradient across the tonoplast.  A $Na^+/H^+$ antiporter then uses this gradient to move $Na^+$ into the vacuole in exchange for $H^+$. $Cl^-$ can follow passively or through other secondary active transport mechanisms.
  Key Point:  The question asks for the *most directly* involved protein.  While the $H^+-ATPase$ is crucial in establishing the proton gradient, the $Na^+/H^+$ antiporter directly transports $Na^+$.
 3. Identify the correct protein: The tonoplast $Na^+/H^+$ antiporter is the membrane protein most directly involved in transporting $Na^+$ into the vacuole.
  Result: Option B, Tonoplast $Na^+/H^+$ antiporter.
  Verification: The other options are not directly involved in transporting $Na^+$ and $Cl^-$ into the vacuole.  The plasma membrane $H^+-ATPase$ establishes the proton gradient, but doesn't directly transport the ions. The plasma membrane $K^+$ channel and tonoplast aquaporin are involved in other transport processes (K+ transport and water transport, respectively).
 ## OPTION ANALYSIS
A :x: Plasma membrane $H^+$-ATPase: This protein establishes the proton gradient for secondary active transport, but doesn't directly transport $Na^+$.
B ✓: Tonoplast $Na^+/H^+$ antiporter: This protein directly transports $Na^+$ into the vacuole using the proton gradient.
C :x: Plasma membrane $K^+$ channel: This protein is involved in potassium transport, not sodium transport into the vacuole.
D :x: Tonoplast aquaporin: This protein is involved in water transport, not ion transport.
 ## LEARNING AIDS
 **Common Mistakes**:
  1.Confusing the roles of the $H^+-ATPase$ and the $Na^+/H^+$ antiporter: Remember that the $H^+-ATPase$ creates the gradient, while the antiporter uses the gradient for ion transport.
  2.Focusing on $Cl^-$ transport: While crucial, the question focuses on the protein most directly involved in $Na^+$ transport.
 **Quick Tips**:
  1.Halophytes and vacuolar ion accumulation usually involve $Na^+/H^+$ antiporters.
  2.Remember the function of key membrane proteins in plant cells.

K SURESH KUMAR · Answer

Plasma membrane $H^+$-ATPase

K SURESH KUMAR · Answer

The correct Option is "Tonoplast $Na^+/H^+$ antiporter"

K SURESH KUMAR · Answer

Plasma membrane $K^+$ channel

K SURESH KUMAR · Answer

Tonoplast aquaporin

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