Giberellic acid is a growth hormone present in various amounts in plants, most commonly discussed is giberellic acid-3 (GA-3). It is formed by cells in the elongating region of stems and to a limited amount in leaves. It is a stimulant for physiological processes, including flowering, stem growth and seed production. It also is involved in sex expression, development of seedless fruits and retention of foliage.
The hormone gibberellic acid is used by plants to induce growth and, in some cases, flowering and seed germination. Growth is regarded as the elongation of plant cells, which is most profound at the tips of stem shoots. As days lengthen, gibberellic acid acts to induce flowering, as in the case of plants in the mustard family like radish, cauliflower and broccoli. This hormone also plays the central role in breaking seed dormancy in plant species that require their seeds to be exposed to light or their seed coats to be cracked before germination. Thus, the new seedling begins growth and breaks out of the seed.
Presence of gibberellic acid is needed for male flower parts, the anther with its stamen, pollen and filament, to be formed in the developing flower bud. This is the case for plants with perfect flowers, those that have both male and female parts in the same blossom, as well as for plants that form single-sexed male flowers.
The presence of gibberellic acid, depending on specific plant species, can have secondary effects. One is the prevention of seeds in fruits, or the fleshy swelling of the ovary without forming seeds, such as in modern bananas. An abundance of this hormone can retard the dropping of dying leaves or the ripe fruits of citrus, a process called senescence.