Which plant hormone is responsible for promoting seed germination?

Gibberellin is the plant hormone primarily responsible for promoting seed germination. This hormone plays a crucial role in breaking seed dormancy, which is an essential step that allows seeds to sprout under favorable environmental conditions. Gibberellins stimulate the production of enzymes that facilitate the breakdown of stored food within the seed, making nutrients available for growth. This process involves the activation of enzymes such as alpha-amylase, which helps in converting starches into sugars, providing the energy necessary for the seedling to emerge and begin its growth.

Gibberellins also influence other stages of plant growth, including stem elongation and flowering, but their key role in seed germination sets them apart from other hormones. While auxin is involved in various growth processes such as cell elongation and apical dominance, and cytokinins promote cell division and shoot formation, neither primarily focuses on the germination process. Ethylene is known for regulating fruit ripening and responses to stress but does not play a direct role in seed germination. Therefore, gibberellin's specific action on promoting the sprouting of seeds firmly establishes it as the correct answer in this context.