28. Gibberellic acid (GA) controls seed germination by directing breakdown of the stored starch. In which one of the following tissues of the barley seed, alpha-amylase gene is induced in response to GA?
(1) Endosperm                (2) Coleoptile
(3) Aleurone layer           (4) Embryo

Correct answer: (3) Aleurone layer

Explanation:

• Gibberellic acid (GA) produced by the embryo diffuses to the aleurone layer in barley seeds.

• GA induces the aleurone cells to transcribe and synthesize alpha-amylase and other hydrolytic enzymes.

• These enzymes are secreted into the endosperm where they break down stored starch into sugars for embryo nourishment.

• The endosperm is the storage tissue, not where alpha-amylase synthesis is induced.

• The coleoptile and embryo do not produce alpha-amylase in response to GA.