Question

Theory of proton transport concept given by Levitt in 1974 related to

• A. Mechanism of opening and closing of stomata
• B. Energy assimilation in photosynthesis
• C. Diffusion through stomatal pores
• D. Mechanism of guttation in plant

Hint:

Levitt's Theory (1974) = Active $K^+/H^+$ proton transport for stomatal opening and closing.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Stomatal movement is regulated by turgor pressure changes in guard cells governed by active proton-potassium ionic exchange.
Key Formula or Approach:
\[ \text{Proton Pump: } \text{H}^+\text{-ATPase pumps } \text{H}^+ \text{ out} \implies \text{Inward } \text{K}^+ \text{ uptake} \implies \text{Turgor increases} \]

Step 2: Detailed Explanation:
In 1974, J. Levitt proposed the Active Potassium ($K^+$) and Proton ($H^+$) Transport Theory for stomatal regulation.
According to this theory:
- In daylight, guard cell phosphoenolpyruvate (PEP) carboxylase produces malic acid, which dissociates into malate and $H^+$ ions.
- An active proton pump ($H^+$-ATPase) expels $H^+$ out of guard cells in exchange for $K^+$ and $Cl^-$ ions.
- Accumulation of potassium malate lowers guard cell osmotic potential, drawing in water by endosmosis, increasing guard cell turgidity and opening the stomatal pore.

Step 3: Final Answer:
Thus, Levitt's proton transport concept explains the Mechanism of opening and closing of stomata, matching option (A).