Read the following statements regarding the plant growth regulator that is synthesised in large amounts by tissues undergoing senescence and ripening fruits: (I) It enhances the respiration rate during the ripening of fruits. (II) It promotes female flowers in cucumbers, thereby increasing the yield. (III) It is chemically a derivative of terpenes. (IV) It promotes horizontal growth of seedlings, swelling of the axis

Step-by-step solution

The plant growth regulator synthesised in large amounts by tissues undergoing senescence and ripening fruits is ethylene. Statement (I) is correct: Ethylene enhances the respiration rate during fruit ripening, a phenomenon known as respiratory climactic. Statement (II) is correct: Ethylene promotes female flowers in cucumbers, which increases the yield. Statement (III) is incorrect: Ethylene is a simple gaseous plant growth regulator. Gibberellins, not ethylene, are derivatives of terpenes. Statement (IV) is correc