21.Spermidine represents which of the following group of compounds.
(1) jasmonic acid     (2) polyamine
(3) auxin                (4) strigolactone

Correct answer: (2) polyamine

Explanation:

• Spermidine is a naturally occurring organic compound classified as a polyamine. It is derived biosynthetically from putrescine by adding an aminopropyl group and plays important roles in cellular growth, nucleic acid stabilization, and signaling in plants and other organisms.

• Jasmonic acid is a plant hormone involved in defense and stress responses but not structurally related to spermidine.

• Auxin is a class of plant hormones derived from tryptophan, regulating growth and development.

• Strigolactones are plant hormones involved in symbiotic interactions and shoot branching regulation.

Option-wise:

• (1) Jasmonic acid — Incorrect.

• (2) Polyamine — Correct.

• (3) Auxin — Incorrect.

• (4) Strigolactone — Incorrect.

Spermidine is an aliphatic polyamine synthesized from putrescine, involved in diverse biological activities including growth regulation and nucleic acid stabilization in plants, highlighting its critical role among plant secondary metabolites.