Gibberellin is a gaseous hormone involved in fruit ripening and senescence

Question

BlackTom AI · Accepted Answer

Gibberellins are not gaseous hormones; they are diterpenoid plant growth regulators synthesized in plant tissues and transported in solution. Key concepts: plant hormones (phytohormones) differ by chemical nature and primary functions—ethylene is a gaseous hormone central to fruit ripening and senescence, while gibberellins (GAs) are soluble diterpenoid molecules involved mainly in stem elongation, seed germination, flowering induction, and fruit growth.

Step-by-step reasoning:
1. Chemical identity and physical state: Gibberellins are a class of diterpenoid acids (small organic molecules) produced in plastids and cytosol and move through the plant in the xylem and phloem sap. They are not gases at physiological conditions. Ethylene (C2H4), by contrast, is a simple hydrocarbon gas produced enzymatically from S-adenosylmethionine via ACC synthase and ACC oxidase.
2. Functional roles: Gibberellins promote stem elongation (cell elongation and division), break seed dormancy by inducing hydrolytic enzymes (e.g., α‑amylase in cereal aleurone), and can stimulate fruit set and growth (parthenocarpy in some species). They are not the primary hormonal signal for ripening and programmed senescence.
3. Ripening and senescence: Ethylene is the principal hormone triggering climacteric fruit ripening and many aspects of senescence and abscission. Abscisic acid and other signals also play roles in senescence, but gibberellins are not the gaseous ripening hormone.

Why the statement is false: It combines two incorrect assertions—calling gibberellin gaseous and attributing the ripening/senescence role primarily to it. The correct gaseous ripening hormone is ethylene, not gibberellin.

Why the other option (True) is incorrect: Choosing True would conflate gibberellins with ethylene, ignoring differences in chemical state and primary physiological roles.

Conclusion: The correct answer is False, which matches the provided answer.

Gibberellin is a gaseous hormone involved in fruit ripening and senescenceTrue/False

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