34. Plant hormone responsible fruit ripening is
(1) Auxin                                   (2) Gibberellic acid
(3) Abscisic acid                         (4) Ethylene

Correct answer: (4) Ethylene

Explanation:

• Ethylene is the primary plant hormone responsible for fruit ripening. It is a gaseous hormone that triggers various physiological and biochemical changes in fruits such as softening, color change, and aroma development.

• Auxin mainly regulates growth and development but is not the main fruit ripening hormone.

• Gibberellic acid mainly promotes growth processes including stem elongation and seed germination, but not ripening.

• Abscisic acid is more associated with seed dormancy and stress responses, not fruit ripening.

Option-wise:

• (1) Auxin – growth regulator, not ripening hormone.

• (2) Gibberellic acid – growth and germination hormone, not key for ripening.

• (3) Abscisic acid – stress hormone, involved in seed dormancy, not primary ripening hormone.

• (4) Ethylene – correct; principal hormone driving fruit ripening.

• Ethylene is widely recognized as the hormonal signal that initiates and coordinates the fruit ripening process for many fruit species, thereby determining fruit quality and shelf life.