In agricultural production, plant growth regulators, as a type of high-efficiency and low-consumption agricultural inputs, have become an important part of modern planting technology. These artificially synthesized compounds precisely regulate the growth and development process of crops by simulating the mechanism of action of endogenous plant hormones, significantly improving the yield and quality of agricultural products. According to their physiological functions and application characteristics, the growth regulators widely used in current agricultural production are mainly divided into the following five categories:
- Growth promoters: growth engines that break natural limits
a. Gibberellic acid (GA)
As a naturally occurring diterpenoid compound in plants, artificially synthesized gibberellins (such as GA3) show multiple effects in agricultural production. In rice cultivation, gibberellins can break seed dormancy, allowing the flowering period of parents to meet during hybrid rice seed production, and increase the yield of hybrid seeds by more than 30%. In citrus cultivation, spraying 10-20ppm gibberellin solution during the flowering period can significantly reduce physiological fruit drop, and using it during the fruit expansion period can delay the aging of the peel and extend the harvest period. It is worth noting that the combination of gibberellins and cytokinins can induce the formation of seedless grapes. Its application in the seedless white grape producing areas of Xinjiang can increase the yield by 40%.
b. Auxins
Naphthaleneacetic acid (NAA), as a highly stable synthetic auxin, performs outstandingly in fruit tree cutting propagation. When cutting apple hardwoods, the rooting rate can be increased from 15% in the natural state to more than 85% by rapid dipping with 2000ppm NAA. Indolebutyric acid (IBA) has become the first choice for inducing rooting of explants in tissue culture due to its poor mobility in the plant body. In the tissue culture of blueberry and other difficult-to-root crops, 0.5-1.0mg/L IBA can make the rooting rate exceed 90%. 2,4-D, as an auxin with herbicide concentration, is still used in tomato flower and fruit preservation, but it needs to be strictly controlled in the concentration range of 5-10ppm to prevent phytotoxicity.
- Growth inhibitors: a precisely controlled “brake system”
a. Paclobutrazol (PP333)
This triazole compound shortens the internodes of rice seedlings by 40%-50% by inhibiting the activity of kaurene oxidase, a key enzyme in GA biosynthesis. In the southern double-season rice area, spraying 300ppm paclobutrazol at the 1-leaf 1-heart stage of seedlings can reduce the height of the plant by 10-15cm and improve the lodging resistance by 3 levels. After application to young apple trees, the growth of new shoots decreased by 60%, and the proportion of short branches increased to 75%, significantly promoting early fruiting and high yield. It should be noted that paclobutrazol can remain in the soil for up to 2-3 years, and continuous use may lead to growth inhibition of subsequent crops.
b. Chlormequat (CCC)
As a quaternary ammonium salt regulator, chlormequat shortens the internodes of wheat base by 30%-40% by competitively inhibiting geranyl pyrophosphate synthase in the GA synthesis pathway. Spraying 0.3% dwarfing solution at the beginning of jointing in the Huanghuaihai wheat region can reduce plant height by 15-20cm and increase yield by 8%-12%. In potted flower applications, CCC can make poinsettia, chrysanthemum and other plants compact, and increase ornamental value by 2 levels.
- Maturation regulator: the “biological clock” that controls the time of listing of agricultural products
a. Ethephon
This ethylene releaser decomposes to produce ethylene when pH>4, and has a significant ripening effect. Bananas are treated with 500-1000ppm ethephon after harvest, and the entire warehouse can be uniformly yellowed within 72 hours, and the commodity rate is increased to more than 95%. Spraying 300 times of 40% ethephon solution during the cotton boll opening period can increase the boll opening concentration by 50% and the proportion of pre-frost flowers by 35 percentage points. It is worth noting that ethephon is stable in solutions with pH<3.5, so an acidic buffer must be added during configuration to maintain activity.
b. Abscisic acid (ABA)
As a “stress hormone” of plants, exogenous ABA can induce the upregulation of anthocyanin synthesis-related genes in fruits such as grapes. Spraying 200ppm ABA on the leaves of Ningxia wine grapes during the color change period can increase the anthocyanin content of the peel by 2-3 times and improve the wine quality score by 15 points. In the cold-resistant training of fruit trees, spraying 50ppm ABA in autumn can increase the lignification degree of apple branches by 40% and increase the winter survival rate to more than 90%.
- Growth retardant: a “metabolic switch” that regulates the growth rhythm of crops
a. Ethinazole (S3307)
Compared with paclobutrazol, Ethinazole is 4-10 times more active and has a soil residual period of only 3-6 months. Spraying 50ppm Ethinazole during the flowering period of peanuts can reduce the growth of stems and leaves by 25%, increase the fullness of pods by 20%, and increase the yield by 50-80kg per mu. As a seed treatment agent, wheat seeds can be treated with 10-20mg/kg of tebuconazole to optimize the root-crown ratio of seedlings to 1:1.5, significantly enhancing drought resistance.
b. Antinexamethasone (TE)
This type of cyclohexanecarboxylic acid ester compound regulates plant height by inhibiting cell elongation rather than division. Spraying antinexamethasone before winter wheat jointing can increase the stem thickness by 0.2-0.3mm, increase mechanical strength by 50%, and reduce the lodging area by 80% when encountering a force 8 gale. When mixed with insecticides and fungicides, it can improve the spread of the liquid on the crop surface and increase the prevention effect by 15%-20%.
- Functional regulators: “targeted drugs” to solve specific problems
a. Sodium nitrophenolate
As a nitrophenolate compound, it can activate multiple plant enzyme systems at an extremely low concentration of 0.2-0.5ppm. Spraying 1.8% sodium nitrophenolate 6000 times solution during the seedling stage of vegetables can shorten the seedling period by 3-5 days and increase the survival rate by 30%. When mixed with herbicides, it can alleviate the symptoms of pesticide damage and increase the safety factor of corn field herbicides by 2 levels.
b. Brassinolide (BR)
This sterol substance enhances crop stress resistance by activating the activity of cell membrane ATPase. Spraying 0.01% brassinolide 1000 times solution during the tillering period of rice when encountering low temperature can increase the number of tillers by 35% and reduce the yield reduction from 30% to 10%. In the post-harvest preservation of fruits and vegetables, 1-2ppm BR treatment can maintain SOD enzyme activity and reduce the rot rate of strawberries during storage by 60%.
