Gibberellin is widely used in the production of fruit trees as an effective measure to increase the yield of fruit trees. Gibberellin exists in almost all tissues and organs of fruit trees and basically participates in every link of fruit tree growth and development.
In fruit tree production, external application of gibberellin can break seed dormancy, induce seedless fruit formation, increase fruit setting rate, thin flowers and fruit, delay fruit tree flowering, and increase fruit storage capacity.
Effect of Gibberellin on Grape Fruit Development
Large grain, the seedless grape is the main development direction of table grapes. Seedless grapes can be obtained by processing seeded grapes, or through genetic breeding methods to select grape varieties with degraded seeds.
In practice, it is found that seedless grapes cannot form normal seeds and lack the endogenous hormones that promote fruit setting and swelling. This results in a low fruit setting rate and thin fruit grains of seedless grapes, which affects the appearance and quality of the fruit. Therefore, the seedless varieties of table grapes have small berries, while large berries have pits.
A large number of experiments have shown that the application of gibberellin can induce parthenocarpy grapes and form seedless fruits. Generally, 7-14 days before the full blooming period, external application of gibberellin can increase abnormal embryos, inhibit pollination and fertilization, and hinder seed formation.
The formation rate of seedless fruits treated with gibberellin 10-16 days before the full flowering period is as high as 98-99%. Too early or too late applying can lead to the appearance of seeded grapes.
Kyoho grapes 4-6 days before the first flowering and 10 days before the full bloom, apply with 50mg/l GA4+7, can make more than 95% of the Kyoho grapes become seedless.
Because the main physiological function of gibberellin is to promote cell division and make cells elongate and grow. The use of gibberellin can also promote the swelling of grapes. The development of young grapes is mainly dependent on stored nutrients. External application of gibberellin will induce an increase in the content of auxin, increase the absorption of nutrients by the young fruit, and promote the size of the fruit.
Effect of Gibberellin on Grape Fruit Quality
Fruit quality is mainly composed of appearance quality and internal quality, which is one of the main factors that determine the commercial nature of the fruit. The appearance quality mainly includes fruit size, shape, and color. Intrinsic quality is mainly affected by sugar, acid content, and sugar-acid ratio, and aroma occupies an important position in grape flavor quality.
1. Effect of gibberellin on grape fruit size
Fruit enlargement can be divided into two stages: early cell division and late cell enlargement. The early stage of young fruit is mainly cell division, and then it enters the process of cell volume increase.
Fruit enlargement can be divided into two stages: early cell division and late cell enlargement. The early stage of young fruit is mainly cell division, and then it enters the process of cell volume increase.
Because gibberellin can induce the synthesis of α-amylase and cause starch hydrolysis, this increases the concentration of sugar and increases the osmotic pressure of the cell sap, allowing water to enter the cells and make them grow longitudinally.
The effect of gibberellin on fruit enlargement is mainly in the rapid growth period of the first stage of the fruit. During this period, the increase of gibberellin content promotes the change of cell division to cell enlargement, and at the same time mobilizes the transportation and accumulation of nutrients to the fruit. Increase the content of the pulp cell, thereby increasing the size of the fruit.
For seedless grape varieties, in the full flowering period, 7-10 days after flowering, dip the fruit cluster and grains with gibberellin to increase the weight by 0.5-3 times, and mature one week in advance.
2. Effect of gibberellin on grape color
The color of the fruit is one of the important indicators for the quality identification of grapefruit, and the color of the grape skin is a concrete manifestation of the value of the commodity. Grapefruit contains a lot of natural anthocyanins. Anthocyanin pigments are derivatives of anthocyanins and can impart multiple colors to plant organs.
The accumulation of anthocyanins generally starts at the beginning of color change and reaches a maximum in the mature period. In addition to environmental influences such as light, temperature, and cultivation techniques, the coloration of grape berries also has a great influence on it by plant exogenous hormones.
After a gibberellin treatment of Kyoho grape berries, the berry coloring period is 9-11 days earlier, and the coloring speed is also accelerated. According to the test on Kyoho grapes, the treatment group started coloring early after spraying gibberellin. When the fruits of the treatment group turned red, the control fruits were only half red, and the harvest time of the treatment group was 15-30 days earlier.
3. Effect of gibberellin on grape organic acids
The organic acid is one of the important factors that determine the flavor quality of fruit. The taste of the fruit mainly depends on the balance between sweetness, sourness, and bitterness. The content of organic acids in fruits is regulated by variety differences, environmental factors, and cultivation management measures.
In addition, plant growth regulators can also regulate the content of organic acids in grape berries. Gibberellin can promote the conversion of sugars to organic acids in the young fruit stage, so applying gibberellin in the early stage of fruit development can promote the rapid decline of total acid content in the later stage of fruit development.
Gibberellin has a regulatory effect on the sugar metabolism and ripening of grapefruits, which can promote the conversion of organic acids to sugars and reduce the total acid content. The ripening of the fruit also promotes the consumption of acid by respiration and increases malic enzyme and malic acid. The activity of dehydrogenase promotes the decomposition of malic acid.
4. Effect of gibberellin on grape sugar content
The fruit develops from early bitterness and astringency to maturity and has excellent color and flavor quality, and the role of sugar is very large. Sugar is the most important component of fruit quality and flavor substances. The quality of fruit mainly depends on the amount and type of sugar in the fruit.
Plant hormones also play a very important role in regulating fruit sugar accumulation. Exogenous plant hormones can be used in production to promote fruit sugar accumulation at different developmental stages.
In the young fruit stage, gibberellin can promote the conversion of sugar to organic acid and can inhibit the conversion of sugar into organic acid in the slow growth period. At the same time, gibberellin can also promote the absorption of sucrose in grapefruit.
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