Question

Which phytohormone is called secondary hormone?

• A. Cytokinins
• B. Auxins
• C. Gibberellins
• D. Ethylene

Hint:

Ethylene is the only gaseous plant hormone and plays a key role in fruit ripening.

Answer 1

The Correct Option is D

Step 1: Understanding primary and secondary hormones.
Plant hormones are classified based on their broad physiological roles. Auxins, gibberellins, and cytokinins are considered primary growth hormones.
Step 2: Nature of ethylene.
Ethylene is a gaseous phytohormone involved mainly in fruit ripening, senescence, and abscission rather than primary growth promotion.
Step 3: Analysis of options.
(A) Cytokinins: Primary growth hormone.
(B) Auxins: Primary growth hormone.
(C) Gibberellins: Primary growth hormone.
(D) Ethylene: Correct — regarded as a secondary hormone.
Step 4: Conclusion.
The phytohormone called secondary hormone is ethylene.