Plant hormones govern diverse growth and developmental mechanisms. Of the provided choices, gibberellin is the principal agent for enhancing cell elongation in stems, thereby facilitating stem extension and overall plant development. Gibberellins incite both cell division and elongation, with a notable impact on stem internodes, and are frequently employed to augment stem length in cultivars such as dwarf varieties.
The functions of the remaining hormones are as follows:
- Cytokinin: Facilitates cell division and retards senescence, but is not the primary driver of cell elongation.
- Abscisic acid: Suppresses growth and induces dormancy and stress acclimations, exemplified by stomatal closure during periods of water scarcity.
- Ethylene: Accelerates fruit maturation and senescence, and in certain contexts, may impede elongation.
Consequently, gibberellin stands as the hormone principally responsible for promoting cell elongation in stems.