Biology · Reproduction

Abscisic acid promotes senescence.

Gibberellins delay leaf senescence (aging). They help in stem elongation, seed germination, and retaining chlorophyll in leaves. Therefore, they act as anti-senescence hormones.

Cytokinins are known to delay leaf senescence. They maintain protein and chlorophyll content, keeping leaves green and active for a longer time. Commonly used to preserve the freshness of cut flowers and leaves.

Auxins generally delay senescence in most plants. They promote growth and cell elongation, helping the leaf remain functional longer. In some species, their effect might vary, but they do not promote senescence.

Abscisic acid is the only major hormone that promotes leaf senescence. It is also called the stress hormone because it helps plants cope with water stress, drought, and cold. ABA induces stomatal closure, leaf yellowing, and abscission (leaf fall). Hence, it promotes aging and the death of leaves.