Question

One hormone hastens the maturity period in juvenile conifers, a second hormone controls xylem differentiation while the third increases the tolerance of plants to various stresses. They are respectively

• A. Gibberellin, Auxin and Cytokinin.
• B. Gibberellin, Auxin and Ethylene.
• C. Gibberellin, Auxin, and ABA
• D. Auxin, Gibberellin, and ABA.

Answer 1

The correct option is C

Gibberellin, Auxin, and ABA

The correct option is C.

Explanation for the correct option:

Gibberellins:

1. Gibberellins promote fruit and flower ripening, shoot elongation, and seed germination.
2. Young leaves, seed embryos, and stem and foundation apical meristems are where these are produced.
3. GAs induce germination in plant seeds that need to be exposed to cold or light.
4. The development of seedless fruit, gender expression, and the delay of senescence in leaves and fruit are all impacted by gas.

Auxins:

1. The primary hormones responsible for cell elongation in phototropism and gravitropism are auxins.
2. They encourage leaf development and layout and regulate how the meristem differentiates into the structure of the plant.
3. The only naturally occurring auxin that exhibits physiological activity is indole acetic acid (IAA), despite the fact that various synthetic auxins are utilized as herbicides.
4. Other plant responses under the direct or indirect regulation of auxins include flowering, fruit set, ripening, and prevention of abscission (leaf falling).

ABA:

1. ABA and cytokinin share a chemical family.
2. It is found throughout all higher plants and has a number of effects, including promoting abscission (leaf fall), the establishment of dormancy in buds, and the growth of potato tubers.
3. Abscisic acid directly inhibits the synthesis of RNA and proteins as part of its mode of action.

Explanation for the incorrect options:

Ethylene:

1. It largely acts as an inhibitor of growth activities.
2. It regulates a number of physiological processes thus used as a plant growth regulator.
3. Ethylene lamps could be used for color development and for the ripening of fruits such as bananas, mango, apple, etc.
4. It also induces a feminizing effect in plants, which means used to increase the number of female flowers in a plant to induce fruiting.
5. It is applied to rhizomes, tubers, and seeds to induce early sprouting in them.
6. It is used for thinning excess flowers and young fruits such as walnuts, cherry, cotton, etc.

Final answer: One hormone hastens the maturity period in juvenile conifers, a second hormone controls xylem differentiation while the third increases the tolerance of plants to various stresses. They are respectively Gibberellin, Auxin, and ABA.