Plant Growth Regulators Demonstrate Significant Efficacy in HighTemperature Summer Environments

Adverse conditions typical of summer—such as high temperatures, intense sunlight, and drought—often lead to excessive vegetative growth (etiolation) and physiological dysfunction in crops. Plant growth regulators address these issues by modulating the balance of endogenous hormones; this enhances stress tolerance, curbs rampant growth, and promotes reproductive growth, thereby stabilizing both yield and quality.

1. Controlling Excessive Growth and Preventing Etiolation
In the high-temperature, high-humidity conditions of summer, crops (such as corn, cotton, and wheat) are prone to stem elongation, internode stretching, and an increased risk of lodging (falling over). Applying growth retardants—such as Mepiquat chloride, Paclobutrazol (Paclo), or Chlormequat chloride—at this stage effectively inhibits gibberellin synthesis and slows cell elongation. This shortens internodes, resulting in sturdier, more compact plants with well-developed root systems, thereby significantly improving their resistance to lodging.

Key Application Practice: Taking cotton as an example, chemical regulation should be initiated when the daily growth increment of the main stem exceeds 0.8 cm. Apply 0.5–2 grams of 98% Mepiquat chloride per *mu* (approx. 0.067 hectares) during the late evening or on overcast days, ensuring thorough coverage of the growing points and the tender upper leaves.

2. Enhancing Tolerance to High Temperatures and Drought
High temperatures and drought conditions can exacerbate crop transpiration, diminish photosynthetic efficiency, and lead to premature senescence and wilting. The application of regulators such as Brassinolide and Gibberellin helps stabilize cell membranes, boost the activity of antioxidant enzymes, and delay the degradation of chloroplasts, thereby enhancing the crops' tolerance to both heat and drought.

Recommended Strategy:Spraying 0.01–0.1 mg/L Brassinolide prior to the onset of heat stress can significantly improve the heat tolerance of crops such as cucumbers. For drought-affected crops, a low-concentration mixture of Gibberellin and Brassinolide can be applied via drip irrigation to aid in the recovery of physiological functions and prevent widespread crop mortality.

3. Promoting Nutrient Conversion and Reproductive Growth
Summer marks a critical period for grain filling and fruit setting in most crops. By employing the "Triple Protection Spray" technique—a combined application of insecticides, fungicides, and plant growth regulators—growers can effectively promote robust grain filling in crops like wheat, thereby enhancing overall grain quality. Common Combinations:
Brassinolide + Monopotassium Phosphate: Enhances photosynthetic efficiency and promotes the translocation of nutrients to the fruit.

Gibberellin + Foliar Fertilizer: Promotes fruit setting and enlargement, and improves marketability.