Gibberellin/Gibberellic Acid

1. Physiological function of gibberellin

Gibberellin is a kind of widely used plant growth promoter with high performance. It can promote plant cell elongation, stem elongation, leaf expansion, accelerate growth and development, make crops mature early, and increase yield or improve quality; Can break dormancy, promote germination; Reduce organ shedding, improve fruit setting rate or form seedless fruit; It can also change the sex and ratio of some plants, and cause certain biennial plants to flower in the current year.

(1) Gibberellin is associated with cell division and stem and leaf elongation

Gibberellin can stimulate internode elongation of the stem, and the effect is more significant than auxin, but the number of internode does not change, and the increase of internode length is due to cell elongation and cell division. Gibberellin can also elongate the stems of dwarf mutant or physiologically dwarf plants to reach the height of normal growth. For dwarf mutant species such as maize, wheat and pea, treatment with 1mg/ kg gibberellin can significantly increase the length of internode and reach the normal height, which also indicates that the main reason for the dwarf mutant species is the lack of gibberellin.

Gibberellin treatment of whole plants can cause the rapid growth of original internode cells, accelerate the mitosis of stem subapical region, and increase the number of original cells in each internode. Gibberellin differs from auxin in promoting elongation and growth. Gibberellin had no obvious effect on the elongation of the isolated organs. Gibberellin is also used to promote the elongation of the grape stem, make it loose, prevent mold infection, generally sprayed twice, once when flowering, once when fruit set.

(2) Gibberellin and seed germination

Gibberellin can effectively break the dormancy of seeds, roots, tubers and buds and promote germination. For most light-requiring seeds, exogenous gibberellin could induce dark germination instead of red light. Low temperature treatment can relieve the dormancy of some plant seeds, and exogenous gibberellin treatment can achieve the same effect instead of low temperature. For example, 0.5 ~ 1mg/ kg of gibberellin can break the dormancy of potatoes.

(3) Gibberellin and flowering

The effect of gibberellin on plant flowering is complex, and its actual effect varies with plant species, application method, type and concentration of gibberellin. Some plants need to experience a period of low temperature and long sunshine before flowering, and gibberellin treatment can replace low temperature or long sunshine to make it bloom, such as radish, cabbage, beet, lettuce and other biennial plants. However, gibberellin could not induce the formation of flower buds in short-day plants under non-induced conditions, and had an inhibitory effect on the flowering of some woody fruit trees, such as citrus.

(4) Gibberellin and sex differentiation

The effect of gibberellin on the sex differentiation of monoecious plants varies with species. Gibberellin has a female promoting effect on corn of gramineae family. The treatment of gibberellin at different developmental stages of young inflorescence can make the male ear female or male flower sterile respectively. In melons, gibberellin can promote the differentiation of male flowers, while in bitter melon and some varieties of loofah, gibberellin can promote the differentiation of female flowers. Treatment with gibberellin can induce parthenocarpy of grapes, strawberries, apricots, pears, tomatoes, etc., and produce seedless fruits.

(5) Gibberellin and fruit development

Gibberellin is one of the essential hormones for fruit growth, which can promote the synthesis and secretion of hydrolase, hydrolyze starch, protein and other storage substances for fruit growth. Gibberellin can also delay fruit ripening and regulate the supply and storage time of fruits and vegetables. In addition, gibberellin can stimulate a variety of plants to produce parthenocarpy and can also promote fruit setting

2, the application of gibberellin in production

(1) Promote growth, early maturity and increase production

Many green leafy vegetables treated with gibberellin can accelerate growth and increase yield. Celery is sprayed with 30~ 50mg/ kg liquid about half a month after harvesting, increasing production by more than 25%, hypertrophy of stems and leaves, and 5~ 6d early market. Spinach, purse purse, crowndaisy, leek, lettuce, etc., with 1.5 to 20mg/ kg liquid spray leaves, the effect of increasing production is also significant.

For edible fungi such as mushrooms, when the primordium is formed, dipping the lump with 400mg/ kg liquid can promote the enlargement of the fruiting body. Vegetable soybeans and dwarf beans, sprayed with 20~ 500mg/ kg liquid, can promote early ripening and increase yield. Leek, at a height of 10cm or 3d after harvest, sprayed with 20mg/ kg liquid, increased production by more than 15%.

(2) Break dormancy and promote germination

The vegetative organs of potato and some vegetable seeds have dormant periods, which affect reproduction. Treat potato slices with 5-10mg/kg solution for 15min, or whole potato blocks with 5-15mg/kg solution for 15min. Dutch beans, cowpeas, green beans and other seeds, with 2.5 mg/ kg liquid soaked for 24 hours, can promote germination, the effect is very obvious. The dormancy of lettuce seeds could be broken successfully by soaking the seeds with 200mg/ kg gibberellin at 30~ 40 ° C for 24h after germination. In strawberry greenhouse promoted cultivation and semi-promoted cultivation, after covering the shelter for 3d, that is, when the buds appeared more than 30%, each plant was sprayed with 5~ 10mg/ kg gibberellin solution 5mL, focusing on the heart leaves, which could make the top inflorescence bloom early, promote growth, and mature early.

(3) Promote fruit growth

Melon vegetables in the young melon stage with 2 to 3mg/ kg liquid spray fruit once, can promote the growth of young melons, but do not spray the leaves, so as to avoid the number of male flowers increased. Tomato, flowering period with 25~ 35mg/ kg flower spray, can promote fruit set, bomb shelter fruit. Eggplant, flowering period 25~ 35mg/ kg, spray flowers once, promote fruit setting, increase production. Pepper, flowering period 20~ 40mg/ kg spray flowers once, promote fruit setting, increase production. Watermelon, flowering period 20mg/ kg spray flowers once to promote fruit setting and increase production, or young melon spray young melon once to promote young melon growth and increase production.

(4) Prolong the storage period

For melons, spraying the fruit with 2.5 ~ 3.5 mg/ kg liquid before harvest can extend the storage time. Spraying bananas with 50~ 60mg/ kg liquid before harvest has a certain effect on extending the storage period of bananas. Gibberellin used in jujube and longan can also delay senescence and prolong storage period.

(5) Change the ratio of male and female flowers to improve seed yield

Using female cucumber line for seed production, spraying 50~ 100mg/ kg liquid on 2~ 6 true leaves of seedlings can make female cucumber become unisecious, complete pollination and improve seed yield.

(6) Promote stem flowering and improve the breeding coefficient of improved varieties

Gibberellin can induce early flowering of long-day vegetables. Spraying plants or dropping growing points with 50 to 500mg/ kg of gibberellin can make 2a growing sunshine crops such as carrots, kale, radish, celery and Chinese cabbage boll under short-day conditions before overwintering.

(7) To relieve the drug damage caused by other hormones

After the vegetable is overmedicated, it can be treated with 2.5 ~ 5mg/ kg liquid to relieve the drug damage of polyplobulozole and butenin. Treatment with 2mg/ kg liquid can relieve ethylene damage. Tomatoes caused by excessive use of loxacin can be relieved by 20mg/ kg gibberellin.

3. Precautions

In the application of growth regulators should pay attention to:

First, to use drugs strictly according to technology, it is necessary to make clear the period of drug use, concentration, drug application site, frequency, etc

Second, it is necessary to cooperate with external conditions, because light, temperature, humidity, soil factors, as well as varieties, fertilization, density and other agronomic measures will have different degrees of influence on drugs, and it is necessary to combine the application of growth regulators with conventional agronomic measures

Do not abuse plant growth regulators. Each plant growth regulator has its biological principle of action, and each drug has certain limitations, do not think that no matter what kind of drug is used to increase production and efficiency;

Four can not be mixed with alkaline substances, and gibberellin is easily neutralized by alkali. However, it can be mixed with acidic and neutral fertilizers and pesticides, and the effect of increasing production is better when mixed with urea. The aqueous solution is easy to decompose and should not be put away for a long time. It should be used now, and can also be mixed with calcium persulfate, ammonium sulfate and other fertilizers

Fifth, gibberellin is a white or yellowish powder, insoluble in water, insoluble in benzene, chloroform, soluble in phenols, acetic acid, ethyl acetate pH6.2 phosphate buffer. Therefore, when preparing an aqueous solution, you should first pour gibberellin powder into a beaker, add a small amount of alcohol or high liquor, acetone or ice acetic acid, stir it fully to dissolve it completely, avoid heating, and then pour a certain amount of water according to the concentration requirements, stir well.