Which hormone is mainly responsible for stem elongation in plants?

The hormone responsible for stem elongation in plants is gibberellin. Gibberellins are a group of plant hormones that play a crucial role in various developmental processes, particularly elongation of stems and internodes. They promote cell division and elongation, allowing plants to grow taller and developing into a more robust structure. This action is particularly evident in conditions that require rapid growth, such as the transition from a juvenile to an adult stage in a plant.

While auxins also contribute to growth and are involved in cellular elongation, they primarily affect the direction of growth (such as phototropism) rather than facilitating general elongation in the same way gibberellins do. Other hormones like cytokinin and ethylene play different roles; cytokinin primarily influences cell division and growth in shoots and roots, while ethylene is involved in processes like fruit ripening and responses to stress. Thus, gibberellin stands out as the key hormone for promoting stem elongation specifically.