What hormone is involved in promoting root formation and bud growth in plants?

The hormone responsible for promoting root formation and bud growth in plants is auxin. This hormone plays a crucial role in various aspects of plant development. It is primarily involved in stimulating cell elongation and differentiation, which leads to the formation of roots and the development of buds. Auxins are typically distributed unevenly in plant tissues, which can result in directional growth—a phenomenon known as tropism.

Auxins facilitate the process of rooting by enhancing the growth of root primordia, which leads to the development of new roots from stem cuttings and existing root systems. The hormone also influences the growth of lateral buds, promoting branching and a fuller plant structure. Its ability to coordinate various growth responses makes it integral to the overall health and development of plants.

In contrast, other hormones like cytokinin primarily promote cell division and shoot development, ethylene is involved in fruit ripening and responses to stress, and gibberellin promotes stem elongation and germination but is not specifically linked to root formation. Hence, auxin is the primary hormone for the aspects mentioned in the question.