Question

The process of the discharge of liquid from the tip of a healthy leaf under humid conditions is called guttation, and this process occurs through specialized pores called

• A. Pneumatophores
• B. Lenticell
• C. Hydathodes
• D. Stomata

Hint:

Distinguish clearly between Transpiration and Guttation:
Transpiration: Loss of water vapor via regulated Stomata, driven by solar energy.
Guttation: Loss of liquid water via permanently open Hydathodes, driven by positive Root Pressure.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
Under conditions of high soil moisture and high relative humidity, transpiration rates are low.
However, active absorption of mineral nutrients by roots continues, which lowers the water potential of root cells and draws water into the xylem.
This generates a positive hydrostatic pressure, known as root pressure, which pushes water up the xylem column, resulting in the exudation of water droplets from leaves.

Step 2: Detailed Explanation:
Let us evaluate each of the listed structures:
1. Guttation and Hydathodes (C): The exudation of liquid water droplets from leaves is called guttation.
Unlike transpiration (which releases pure water vapor), guttation water contains dissolved minerals, organic acids, and sugars.
Guttation occurs through specialized, permanently open pores located at the margins or tips of leaves, called hydathodes.
Underneath the pore of a hydathode is a group of loosely packed parenchyma cells called epithem, which is in direct contact with the terminal tracheids of xylem vessels.
2. Pneumatophores (A): These are specialized breathing roots found in mangrove plants that grow upward out of the water and mud to facilitate oxygen intake.
3. Lenticels (B): These are porous tissues consisting of cells with large intercellular spaces in the periderm of woody stems and roots, facilitating gaseous exchange in woody plants.
4. Stomata (D): These are microscopic pores regulated by guard cells that control the release of water vapor during transpiration and the uptake of \( \text{CO}_2 \) during photosynthesis.

Step 3: Final Answer:
The specialized pores through which guttation occurs are hydathodes, corresponding to option (C).