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: Understanding the Concept:
The question asks for the specific name of the phenomenon where the plant hormone cytokinin delays senescence (aging) in detached leaves, specifically the breakdown of chlorophyll and protein.
Step 2: Detailed Explanation:
Let's define the given terms:

Richmond-Lang effect: This is the specific term used to describe the delay of senescence in leaves by the application of cytokinins. This effect was demonstrated by scientists Richmond and Lang, who observed that cytokinins could keep detached leaves green for a longer period by inhibiting the degradation of chlorophyll and proteins. This perfectly matches the description in the question.

Nyctinastic effect: This refers to the "sleep movements" of plants, where leaves or petals fold in response to the onset of darkness. It is unrelated to senescence.

Epinasty: This is the downward bending of leaves or other plant parts, often caused by the hormone ethylene. It is a growth response, not directly related to delaying senescence.

Depot effect: This is a more general term that refers to the ability of cytokinins to mobilize nutrients towards the area of application, creating a nutrient "sink" or "depot." While this nutrient mobilization is part of the mechanism behind delaying senescence, the specific phenomenon itself is named the Richmond-Lang effect.

Step 3: Final Answer:
The experiment and the observed phenomenon are famously known as the Richmond-Lang effect.