1. Promote the elongation and growth of stems
The most prominent effect of gibberellin on plants is to stimulate the elongation of stems, so that the height of plants increases significantly, especially on the elongation of flower stems. Gibberellin does not change the number of internodes, but stimulates the elongation of plant cells and promotes cell division. Just like a giraffe's neck is very long, but its cervical vertebrae have the same number of cervical vertebrae as we humans, only seven, but each cervical vertebrae are exceptionally long.
2. Promote leaf growth
Gibberellin not only promotes stem elongation, but also promotes leaf growth and expansion, and even changes leaf shape. Gibberellin negatively regulates the complexity of leaf structure, for example, the up-regulation of gibberellin level makes tomato only grow a single leaf with smooth edges, while the spraying of gibberellin at the topping stage of tobacco leaves has a great impact on the opening of parietal leaves in the later stage. It can promote the stretching and smoothing of the top tobacco leaves, reduce wrinkles, and increase the width of the top tobacco leaves, so as to promote the increase of yield.
3. Improve resilience
Gibberellin is also involved in the process of plant tolerance to many abiotic stresses. For example, under environmental stresses such as low temperature, high salinity, drought and hyperosmosis, plants can adapt to the external environment by slowing down their growth by reducing gibberellin, and conversely, plants will also produce escape mechanisms through the increase of gibberellin, so as to get rid of environmental stresses such as flooding.
4. Promote germination and break dormancy
The seeds of lettuce, tobacco and begonia, which can only germinate in the presence of light, are called light-needed seeds. Treating these light-demanding seeds with gibberellin can germinate in dark conditions. On the contrary, for those seeds that germinate in dark conditions, it is easy to germinate under light conditions after applying gibberellin, such as ginseng soaked in 20ppm gibberellin for 15 minutes, which can emerge 2 days earlier, and the germination rate is also significantly increased.
Gibberellin has a certain effect on the release of dormancy, and the main mechanism is that gibberellin can hinder the degradation of plasmodesmata callosum, which is the signal of intercellular dormancy and release signaling, so that the signaling substance is transported to the apical meristem, thereby relieving dormancy. From a biological point of view, gibberellin treatment can activate redox metabolic enzymes and energy metabolism early, and relieve dormancy early. The most obvious example of the effect of gibberellin on relieving dormancy is breaking the dormancy of potato tubers.
5. Replace the needs of plants for light, low temperature, etc
Under the short day of less than 10~12 hours, long-day plants can only stay in vegetative growth and cannot turn to the reproductive growth stage. Treating these long-day plants in short-day sunlight with gibberellin allowed them to form stems and flower normally. Biennials such as cabbage, beets, turnips, and carrots need to go through a long winter and receive enough low temperatures to form stems and flower and bear fruit in the second year. If they are treated with gibberellin in the year of their growth without vernalization at low temperatures, it can replace part of the effect of low temperature and help flowering and fruiting.