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. According to their physiological functions and application characteristics, the growth regulators widely used in current agricultural production are mainly divided into the following categories:
- Gibberellic acid (GA)
As a naturally occurring diterpenoid compound in plants, synthetic 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 area of Xinjiang can increase the yield by 40%.
- Auxins
Naphthaleneacetic acid (NAA), as a highly stable synthetic auxin, performs well 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 tissue culture of difficult-to-root crops such as blueberries, 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 the concentration must be strictly controlled in the range of 5-10ppm to prevent phytotoxicity.
- 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 plant height by 10-15cm and increase 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.
- 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% chlormequat solution at the early stage of jointing in the Huanghuaihai wheat area 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 improve the ornamental value by 2 levels.
- Ethephon
This ethylene-releasing agent decomposes to produce ethylene when pH>4, and has a significant ripening effect. Bananas treated with 500-1000ppm ethephon after harvest can turn yellow evenly in the entire warehouse within 72 hours, and the commercial rate can be 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 preparation to maintain its activity.
- Abscisic acid (ABA)
As a “stress hormone” of plants, exogenous ABA can induce the upregulation of genes related to anthocyanin synthesis 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 increase the wine quality score by 15 points. In the cold-resistance training of fruit trees, spraying 50ppm ABA in autumn can increase the lignification degree of apple branches by 40% and the winter survival rate to more than 90%.
These plant growth regulators precisely regulate the growth and development process of crops by simulating the action mechanism of plant endogenous hormones, significantly improving the yield and quality of agricultural products.
