Question

Which phytohormone is regarded as an anti-stress promoter and growth bio-stimulator?

• A. Jasmonic acid
• B. 1-MCP
• C. Melatonin
• D. Prohexadione -- Ca

Hint:

Melatonin in plants is emerging as a key molecule that:
Enhances tolerance to various stresses (anti-stress).
Promotes growth and development (growth bio-stimulator).
Jasmonic acid: Primarily defense.
1-MCP: Ethylene inhibitor.
Prohexadione-Ca: Growth retardant.

Answer 1

The Correct Option is C

The question asks for a phytohormone that acts as both an anti-stress promoter and a growth bio-stimulator.
(1) Jasmonic acid (JA): A phytohormone primarily involved in plant defense responses against herbivores and pathogens, and also in some developmental processes. While it helps plants cope with certain stresses, it's not primarily viewed as a broad growth bio-stimulator in the same way as others.
(2) 1-MCP (1-Methylcyclopropene): An ethylene action inhibitor, used to delay ripening and senescence in fruits and flowers. It's not a growth promoter or a broad anti-stress agent itself.
(3) Melatonin (N-acetyl-5-methoxytryptamine): Originally known for its role in animals, melatonin has been identified as a ubiquitous molecule in plants with diverse functions. It is increasingly recognized as a potent anti-stress compound in plants, helping them tolerate various abiotic stresses (drought, salinity, cold, heat, heavy metals) and biotic stresses. Furthermore, melatonin acts as a growth bio-stimulator, promoting seed germination, root growth, vegetative growth, flowering, and fruit development. It influences many physiological processes and interacts with other phytohormones.
(4) Prohexadione-Ca: A plant growth regulator that inhibits gibberellin biosynthesis, thus acting as a growth retardant, not a bio-stimulator in the sense of promoting overall growth. Therefore, melatonin fits the description of being both an anti-stress promoter and a growth bio-stimulator in plants very well. Melatonin