Plant hormones diffuse throughout plants and regulate growth and development. The five major plant hormones are auxin, cytokinin, gibberellin, abscisic acid, and ethylene. Auxin promotes root growth and cell elongation. Cytokinin stimulates cell division and new shoot growth. Gibberellin causes internode elongation and controls yearly flowering cycles. Abscisic acid induces dormancy, and ethylene stimulates fruit ripening and flower senescence. The hormones interact to balance shoot and root growth in response to environmental changes throughout the seasons.