Q.Due to environmental change in area, the fruits were taking more time for ripening. Which gaseous growth regulator can be suggested to fruit merchant? Give the source of the same in plants.
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Ethylene: The Ripening Hormone
Imagine you've bought a bunch of raw bananas. You put them in a paper bag with a ripe apple. The next day, the bananas are noticeably yellower. What happened? The apple released a gas that told the bananas, "It's time to ripen." That gas is ethylene.
Ethylene is the only gaseous plant growth regulator (PGR). It's a simple hydrocarbon — just two carbons and four hydrogens (C2H4) — but its effects are dramatic. Unlike auxins or gibberellins that promote growth, ethylene is largely about finishing things: ripening, aging, and shedding.
The Precise Statement
Ethylene is a gaseous plant hormone that regulates fruit ripening, senescence (aging), abscission (dropping of leaves/fruits), and epinasty (downward curling of leaves). It is produced naturally by most plant tissues, especially in response to stress, wounding, or during ripening.
C2H4
Key Effects Explained
Fruit Ripening — This is ethylene's most famous job. Unripe fruits produce a little ethylene, which triggers more ethylene production in nearby fruits (a positive feedback loop). That's why one rotten apple spoils the barrel — the rotten one releases ethylene that ripens (and then rots) the others. Commercially, fruits like mangoes and tomatoes are picked green, transported, then exposed to ethylene gas in ripening chambers.
Senescence and Abscission — Ethylene accelerates aging. It breaks down chlorophyll (yellowing leaves), weakens cell walls at the abscission zone (where a leaf or fruit attaches to the stem), and promotes dropping. This is why ethylene is used to defoliate cotton plants before mechanical harvesting.
Epinasty — When a plant is flooded or stressed, ethylene causes the upper side of leaf petioles to grow faster than the lower side, making leaves curl downward. This is a visible sign of stress.
A common mistake is thinking ethylene only ripens fruits. It also promotes senescence, abscission, and epinasty — and in some cases (like pineapple flowering) it even promotes flowering.
Practical Applications …
Fruit ripening is driven by a gaseous hormone that a merchant could apply externally to speed up a delayed ripening process, and this same gas is also produced naturally within the fruit's own tissue. …
Ethylene — a gaseous plant hormone that hastens fruit ripening; it is naturally produced within the ripening fruit tissue itself (and other actively metabolising/senescing tissues) from the amino acid methionine.
Ethylene gas speeds fruit ripening and is produced by the fruit's own tissue.
Of the classical plant hormones, ethylene is unique in being a simple gas (C2H4) and is the principal regulator of fruit ripening, especially in climacteric fruits (banana, mango, tomato, apple), where it triggers a burst of respiration and enzymatic changes — softening of the cell wall, starch-to-sugar conversion, chlorophyll breakdown and pigment synthesis, and characteristic aroma development. It is synthesised endogenously within plant tissues (fruit pulp, flowers, nodes, and senescing/wounded/stres …
- CBSE 2026Set ANNUAL1 markMCQQ.The function of ethylene hormone is -(a) Horizontal growth of plants(b) Abscission of leaves(c) Ripening of fruits(d) All of the above
›Reveal solutionSolution
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:
- 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.
- Abscission of leaves, flowers and fruits — ethylene promotes the formation of the abscission zone and hastens senescence, causing shedding of leaves and flowers. …
- CBSE 2024Set ANNUAL1 markMCQQ.Ethylene is used for :(a) Slowing down ripening of Apples(b) Slowing down ripening of Tomato(c) Hastening of ripening in Fruits(d) Both (B) & (C)
›Reveal solutionSolution
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 …
- CBSE 2024Set HALF_YEARLY1 markQ.Match the correct pair. Column 'A' item: 'Gaseous hormones'. Choose its match from Column 'B':(a) 1200 ml.(b) Ethylene(c) 4500 ml.(d) 500 ml.(e) 450 min(f) 1
›Reveal solutionSolution
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 …
- CBSE 2024Set ANNUAL1 markQ.A simple gaseous plant growth regulator is _______
›Reveal solutionSolution
[!TLDR]
Ethylene
Method
Ethylene is the only plant growth regulator that exists as a simple gas at normal temperature/pressure, used to h …
- CBSE 2023Set ANNUAL1 markMCQQ.Which of the following is the only gaseous plant growth regulator?(a) ABA(b) Cytokinin(c) Ethylene(d) Gibberellin
›Reveal solutionSolution
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 …
- CBSE 2022Set TERM11 markMCQQ.Which of the following is a gaseous plant growth regulator?(a) Gibberellin(b) Ethylene(c) Auxin(d) Cytokinin
›Reveal solutionSolution
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 …
- CBSE 2022Set ANNUAL1 markQ.Name the plant hormone found in a gaseous state.
›Reveal solutionSolution
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 …
- CBSE 2021Set ANN1 markQ.Name the plant hormone which helps to the ripening of fruits.
›Reveal solutionSolution
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 …
- CBSE 2021Set ANNUAL1 markMCQQ.Which of the following is the only gaseous plant growth regulator found in plants?(a) Ethylene(b) Abscisic acid(c) Auxin(d) Cytokinin
›Reveal solutionSolution
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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- CBSE 2020Set ANNUAL1 markMCQQ.Which of the following is a gaseous plant growth regulator ?(a) Gibberellin(b) Ethylene(c) Auxin(d) Cytokinin
›Reveal solutionSolution
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 -- ' …
- CBSE 2020Set ANNUAL1 markMCQQ.Hormone that is used in ripening of fruits:(a) Gibberellins(b) Ethylene(c) Indole acetic acid(d) Abscisic acid
›Reveal solutionSolution
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. …
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