62. Programmed cell death (PCD) plays an important role in development of barley aleurone. The following statements are made with respect to involvement of various phytohormones and signaling molecules.
A Gibberellic and promotes PCD.
B. Abscisic acid postpones PCD.
C. Cyclic GMP signaling postpones PCD.
D. Nitric oxide scavenger delays PCD.
Which one of the following combinations of statements is correct?
(1) A and C          (2) B and D
(3) A and B          (4) C and D

Correct answer: (3) A and B

Explanation:

• (A) Gibberellic acid (GA) promotes programmed cell death (PCD) in barley aleurone cells, which is essential for seed germination as PCD helps in the mobilization of nutrient reserves.

• (B) Abscisic acid (ABA) postpones or delays PCD, acting as a protective hormone during seed dormancy and stress conditions, thereby maintaining aleurone cell viability longer.

• (C) Cyclic GMP (cGMP) signaling is involved in various plant processes but its direct role in postponing PCD in aleurone cells is not well supported; usually cGMP acts as a secondary messenger in signaling cascades.

• (D) Nitric oxide scavenger delays PCD is incorrect because nitric oxide (NO) itself is often involved in signaling pathways that regulate PCD; scavenging NO would tend to inhibit processes needing NO rather than delaying PCD; the exact effect depends on experimental context but is not conventionally understood as delaying PCD in aleurone.

Option-wise:

• (1) A and C — C questionable.

• (2) B and D — D questionable.

• (3) A and B — correct.

• (4) C and D — both questionable.

  Programmed cell death in barley aleurone is tightly regulated by hormones where gibberellins stimulate PCD facilitating nutrient mobilization during germination, while abscisic acid delays PCD to maintain cell viability under stress.