Question

The regulation of plant development by light is termed as

• A. Photomorphogenesis
• B. Photosynthesis
• C. Differentiation
• D. Photorespiration

Hint:

"Photo-" means light and "morphogenesis" means creation of form. Therefore, "Photomorphogenesis" literally translates to the regulation of a plant's physical form and developmental stages by light signals.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Light acts not only as an energy source for plants but also as a highly informative environmental signal.
Plants perceive light signals via specialized photoreceptors (such as phytochromes, cryptochromes, and phototropins) to regulate their growth, development, and morphology.

Step 2: Detailed Explanation:
Let us define each of the listed physiological processes:
Photomorphogenesis (A): This is the growth and development of plants directly regulated by light signals (separate from photosynthesis).
It controls critical transitions in the plant life cycle, such as seed germination, seedling de-etiolation (development of green leaves and short stems), chloroplast development, and the transition to flowering.
These processes are mediated by photoreceptors that detect changes in light quality, intensity, direction, and duration.
Photosynthesis (B): This is the metabolic process where light energy is captured and stored as chemical energy (sugars) by converting \(\text{CO}_2\) and water.
Differentiation (C): This is the developmental process where unspecialized cells acquire distinct structural and functional identities.
Photorespiration (D): This is an energy-consuming metabolic pathway where Rubisco fixes oxygen instead of \(\text{CO}_2\) under hot, dry conditions.

Step 3: Final Answer:
The light-regulated growth and development of plants is termed Photomorphogenesis, corresponding to option (A).