How to apply plant growth regulators to fruits and vegetables
Scientific and rational use of several plant growth regulators can effectively control the growth of fruit trees and vegetables at different stages, improve their quality and yield, and increase economic benefits. 1. Ethephon 1. Physical and chemical properties. The pure product is a white crystalline solid, easily soluble in water and ethanol, poorly soluble in benzene and dichloroethane, and in acidic solution...
Scientific and rational use of several plant growth regulators can effectively control the growth of fruit trees and vegetables at different stages, improve their quality and yield, and increase economic benefits.
1. Ethephon
1. Physical and chemical properties. The pure product is a white crystalline solid, easily soluble in water and ethanol, poorly soluble in benzene and dichloroethane. In acidic solution (pH < 3.5) it is stable; above pH 4.5 it gradually decomposes and releases ethylene, and the decomposition rate accelerates as the pH value increases.
2. Formulations. 40% aqueous solution.
3. Scope of application and methods of use. Ethephon is a low-toxicity plant growth regulator. After application, it can enter the plant body through the stems, leaves, flowers and fruits, and release ethylene under the action of cell sap; this exogenous ethylene performs the same physiological functions as the endogenous hormone ethylene in plants. It has effects such as breaking seed dormancy, controlling apical dominance, promoting female flower development, promoting fruit ripening and organ abscission, thereby shortening the crop growth period, dwarfing crops, preventing lodging, hastening ripening and increasing yield, and improving quality.
Ethephon can be applied by spraying the leaves, fruits or the whole plant, or by dipping the fruits, depending on the crop and purpose. (1) For ripening apples and pears, spray an 800-1000 times dilution of the 40% aqueous solution 3-4 weeks before the fruit ripens. (2) For ripening tomatoes, when the fruits are fully grown but still green and not yet red, spray an 800-1000 mg/kg solution. (3) To increase female flowers in cucumbers and pumpkins, spray a 100-250 mg/kg solution 1-2 times starting from the 3-4 leaf stage, with an interval of 10 days. (4) For ripening and de-astringency of persimmons, after harvest dip the fruits in a 250-1000 mg/kg solution.
4. Precautions. Ethephon has strong physiological activity; improper use may not only fail to achieve results but may also cause phytotoxicity. Therefore, the dosage used should vary with the variety, temperature, fertility and other conditions. If there is drought, insufficient soil fertility, or the plants are stunted for other reasons, the concentration used should be appropriately reduced; conversely, if there is abundant rain, sufficient fertility and low temperatures so that normal ripening cannot occur, the concentration used should be appropriately increased.
2. Paclobutrazol
1. Physical and chemical properties. The technical material is a white solid, poorly soluble in water, soluble in organic solvents. It is stable to light, acid and alkali.
2. Formulations. 25% emulsifiable concentrate, 15% wettable powder.
3. Scope of application and methods of use. Paclobutrazol is an inhibitor of endogenous gibberellin synthesis, and has the effects of controlling crop growth, shortening internodes, reducing lodging, promoting tillering, controlling shoots and preserving fruits, and increasing yield. It is suitable for crops such as wheat, cotton, fruit trees, vegetables and rapeseed. (1) For shoot control in fruit trees, on peach trees within 1 week after half of the flowers have fallen, spray a 400-800 mg/kg solution, which has a significant dwarfing and shoot-controlling effect. For apple trees, open a ring-shaped trench under the canopy, 30 cm wide and 20 cm deep, following the principle of exposing roots without injuring them, and apply 1-1.5 g of active ingredient per square meter of canopy by broadcasting it into the trench and covering with soil; irrigate before or after application and keep the soil moist. For grapes, apply 2-3 g of active ingredient per mature vine in a ring-shaped trench, or spray a 1500 mg/kg solution, which can inhibit new shoot growth and increase yield. (2) For greenhouse vegetables, it has a clear seedling-strengthening effect. For ornamental plants, it can adjust plant shape and make them more ornamental; the concentration used is 100-300 mg/kg.
3. Gibberellin
1. Physical and chemical properties. The industrial product is a white crystalline powder, poorly soluble in water, benzene, nitrogen and the like, and soluble in methanol, ethanol, acetone and phosphate buffer at pH 6.2. In the dry state it is not easily decomposed; its aqueous solution is easily destroyed and becomes ineffective above 5°C. It decomposes readily on contact with alkali.
2. Formulations. 85% technical powder, 4% emulsifiable concentrate.
3. Scope of application and methods of use. Gibberellin is a highly effective growth stimulant, an exogenous gibberellin that enters the plant body through seeds, leaves, young shoots, flowers and fruits and performs the same physiological functions as endogenous gibberellin. It can promote plant cell growth, accelerate growth and development, hasten maturity and increase yield; break seed dormancy and promote germination; change the ratio of female to male flowers, affect flowering time and reduce flower and fruit drop. It is an antagonist of growth inhibitors such as paclobutrazol and chlormequat. It is suitable for many crops such as grain, cotton, fruit trees and vegetables. (1) For grapes, 7-10 days after full bloom, when the young fruits begin to grow, spray the fruit clusters; for the seedless Purple grape, spray a 200 mg/kg solution, and for Kyoho and Muscat Hamburg grapes, spray a 200-400 mg/kg solution, which can increase the fruit-setting rate, enlarge the fruits and significantly increase yield. Never use it before or during flowering. (2) For watermelon, at the 2-leaf 1-heart stage, spray a 5 mg/kg solution 1-2 times to induce female flowers. (3) For cucumber, at the 1-leaf stage, spray a 50-100 mg/kg solution 1-2 times to induce female flowers. (4) For sweet potato, soak the root and stem portions of the vine cuttings in a 20 mg/kg solution for 10 minutes and plant immediately, which can increase yield. (5) For potato, soak the tubers in a 0.5-1 mg/kg solution for 10 minutes, remove and air-dry before planting; for spring-planted seed potatoes this makes emergence early and uniform, and for summer-planted seed potatoes it can promote sprouting of dormant buds. Soaking for too long or using too high a concentration will produce an inhibitory effect. (6) For strawberry, 2 weeks before flower bud differentiation, spray a 20-50 mg/kg solution 2 times, with an interval of 5 days each time, which can elongate the flower stalks and advance flowering.
4. Precautions. Gibberellin is poorly soluble in water; before use, dissolve it first in a small amount of alcohol, then add water to dilute to the required concentration. The aqueous solution cannot be stored for long. When gibberellin is used to promote fruit setting and stimulate growth, water and fertilizer must keep up in order to exert its yield-increasing effect.
4. 4-CPA (Fangluosu)
1. Physical and chemical properties. The technical powder is a white crystalline solid with a slightly irritating sour odor, and can dissolve in water and most organic solvents.
2. Formulations. Technical powder, 10% emulsifiable concentrate.
3. Scope of application and methods of use. 4-CPA is a plant growth regulator. It can effectively inhibit the production of abscisic acid in crops, so that a separation layer is not easily formed between the fruit stalk and the fruit, preventing flower and fruit drop, increasing the fruit-setting rate, promoting young fruit development and hastening maturity. It is suitable for melons and fruits. (1) For fruit trees, spray apple trees once each at the flowering stage, the young fruit growth stage, the fruit drop stage and 1 month before harvest with a 25-35 mg/kg solution. For grapes, spray 30 mg/kg at the flowering stage to increase the fruit-setting rate. (2) For tomato and eggplant, spray a 25-30 mg/kg solution at the flowering stage, directing it at the flowers and avoiding the young leaves. (3) For pepper, at the flowering stage, spray a 20 mg/kg solution on the flowers to preserve flowers and fruits.
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