Question

Cytokinin treatment extends the life span of detached Xanthium leaves by delaying chlorophyll and protein degradation. This experiment is called:

• A. Richmond-Lang effect
• B. Nyctinastic effect
• C. Epinasty
• D. Depot effect

Hint:

Associate keywords with hormone effects. For cytokinins, the key association is "delay of senescence" or "anti-aging," which is scientifically termed the Richmond-Lang effect.

Answer 1

The Correct Option is A

Step 1: Concept Overview:
The question identifies a phenomenon where the plant hormone cytokinin inhibits senescence (aging) in detached leaves, specifically the breakdown of chlorophyll and protein, and asks for its specific name.
Step 2: Detailed Explanation:
Definitions of the terms are provided below:

Richmond-Lang effect: This term specifically describes the cytokinin-induced delay of leaf senescence. Richmond and Lang discovered that cytokinins could prolong the greenness of detached leaves by inhibiting chlorophyll and protein degradation. This aligns perfectly with the question's description.

Nyctinastic effect: This refers to plant "sleep movements," where leaves or petals fold in response to darkness, and is unrelated to senescence.

Epinasty: This is the downward bending of leaves or other plant parts, often induced by ethylene, representing a growth response, not directly related to senescence delay.

Depot effect: This is a broader term referring to cytokinins' ability to mobilize nutrients towards the application site, creating a nutrient "sink." While nutrient mobilization contributes to delaying senescence, the specific phenomenon is called the Richmond-Lang effect.

Step 3: Conclusion:
The experiment and the observed phenomenon are widely recognized as the Richmond-Lang effect.