Q.Name the only plant growth regulator that occurs naturally in the gaseous state, and state one of its commercially important physiological effects.

Ethylene is a multi-functional gaseous hormone; it produces the triple response (with horizontal growth), triggers abscission, and ripens fruit — so all three listed effects are genuine ethylene functions.

Ethylene (C₂H₄) is synthesised in large amounts by tissues undergoing senescence and fruit ripening, and it diffuses easily as a gas. Its documented effects in NCERT Class 11 Biology include:

1. Horizontal growth of seedlings — in etiolated pea seedlings, ethylene produces the 'triple response': inhibition of stem elongation, promotion of stem/lateral swelling, and horizontal (diageotropic) growth of the stem.
2. Abscission of leaves, flowers and fruits — ethylene promotes the formation of the abscission zone and hastens senescence, causing shedding of leaves and flowers. …

Ethylene is widely used commercially to speed up (hasten) the ripening of fruits such as tomatoes and apples, not to slow it down.

Ethylene is a simple gaseous hormone synthesised in large amounts by tissues undergoning senescence and ripening fruits. It influences fruit ripening, senescence and abscission of plant organs, and promotes horizontal growth of seedlings, breaking of seed and bud dormancy, initiation of flowering in some plants (e.g. mango), and promotes 'triple response' (reduced stem elongation, increased stem thickening, and horizontal growth). Its most important commercial application …

Ethylene is the only major plant hormone that exists as a gas, and it is best known for triggering fruit ripening and senescence.

Of the five classical groups of plant growth regulators, auxins, gibberellins, cytokinins and abscisic acid are all organic compounds that act in solution within plant tissues, but ethylene (C2H4) is a simple, small hydrocarbon gas synthesised by plant tissues, particularly in ripening fruits. It diffuses readily through plant tissues and t …

Correct answer: (c) Ethylene.

Ethylene is the only plant growth regulator that exists and acts naturally as a gas.

Among the five major classes of plant hormones (auxins, gibberellins, cytokinins, abscisic acid and ethylene), only ethylene is a simple, volatile hydrocarbon gas (C2H4) at physiological temperature and pressure. It is synthesised by almost all plant tissues, especially during senescence and fruit ripening …

Ethylene is the only gaseous plant growth regulator among the five classical groups.

The five major classes of plant growth regulators/hormones are auxins, gibberellins, cytokinins, ethylene, and abscisic acid. Of these, auxins, gibberellins, cytokinins, and abscisic acid are all organic compounds active in liquid/solid form within plant tissue. Ethylene (C2H4) is unique -- it is a simple, small hydrocarbon gas, synthesised especially in tissues undergoing senescence and in ripening fruits. It plays key roles in fru …

Ethylene is the only major plant hormone that is a gas at normal temperature.

Of the five classical groups of plant hormones (auxins, gibberellins, cytokinins, abscisic acid, and ethylene), ethylene (C2H4) is unique in being a simple gaseous hydrocarbon. It is synthesised by plant tissues, especially during fruit ripening, and diffuses readily through air and plant tissue. Ethylene promotes fruit ri …

Ethylene is the plant hormone that promotes fruit ripening.

Ethylene is a simple gaseous hormone synthesised in large amounts by tissues undergoing senescence and by ripening fruits. It hastens fruit ripening by promoting breakdown of cell-wall components (softening), conversion of starch to sugars, and degradation of chlorophyll — giving ripe fruits their characterist …

Ethylene (C₂H₄) is the only plant growth regulator that is a gas at normal temperature and pressure.

Among the five classical groups of plant growth regulators — auxins, gibberellins, cytokinins, ethylene, and abscisic acid — ethylene is the only one that exists as a simple gaseous hydrocarbon (C₂H₄) under normal physiological conditions. It diffuses easily through plant tissues and even through the air between neighbouring plants/fruits. Ethylene is widely used commercially to hasten the ripening of fruits (e.g., in mangoes, bananas, tomatoes), and it also promotes senescence and abscission of leaves and flowers, and breaks seed/bud dormancy.

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Ethylene is unique among the five major plant growth regulators (auxins, gibberellins, cytokinins, ABA, ethylene) because it exists as a gas at normal temperature and pressure.

Ethylene (C2H4) promotes fruit ripening, senescence, abscission, and triple response in seedlings, and, being volatile, can diffuse through air to affect neighbouring tissues/fruits (which is why one ripe fruit hastens ripening of nearby fruit -- ' …

Ethylene is the plant hormone responsible for fruit ripening.

Ethylene is a simple gaseous hormone synthesized in large amounts by ripening fruits themselves; it triggers the biochemical changes of ripening — starch to sugar conversion, cell-wall softening, chlorophyll breakdown, and pigment (carotenoid/anthocyanin) synthesis.

• (a) Gibberellins — promote stem elongation, seed germination, bolting.
• (b) Ethylene — promotes fruit ripening and senescence. Correct. …