giberelinas

Gibberellins are a large family of plant hormones, known as gibberellins or giberelinas, that regulate growth and development in many plant species. They were first identified from the fungus Gibberella fujikuroi, which caused the foolish seedling disease in rice; the name derives from that organism. Gibberellins are diterpenoid acids produced in various tissues, including young leaves, stems, seeds, and roots.

Most higher plants synthesize gibberellins through a pathway beginning in plastids and continuing in the cytosol, producing several bioactive forms such as GA1, GA3, GA4, and GA7. The precise complement of active gibberellins varies by species and tissue. Exogenous gibberellins, especially gibberellic acid (GA3), are widely used in agriculture and horticulture.

Functions and mechanism: Gibberellins promote stem elongation and leaf expansion, stimulate seed germination by triggering the production of hydrolytic enzymes (for example, amylases in cereal grains), and influence flowering and fruit development. They can also break seed and bud dormancy and, in some crops, induce parthenocarpic (seedless) fruit set. The molecular mechanism involves binding to the GID1 receptor; the GA–GID1 complex promotes degradation of DELLA proteins, which are growth repressors, thereby enabling growth processes.

Applications and regulation: Exogenous gibberellins are used to improve germination of dormant seeds, increase fruit size and uniformity, promote seedless fruit production, and enhance malting in cereals. Because their effects can be species- and context-dependent, their use is subject to regulatory guidelines and careful timing and dosage.