Optimizing the Use of Plant Growth Regulators to Stabilize and Boost Crop Yields

1. Cultivating Robust Seedlings and Preventing Legginess:Under adverse climatic conditions, vegetable seedlings are prone to developing into "leggy seedlings" (characterized by excessive stem elongation), which compromises their overall quality. To address this, a soil drench using Chlormequat Chloride at a concentration of 250–500 ppm can be applied to inhibit legginess in cucumbers and tomatoes, thereby fostering the growth of sturdy seedlings. Alternatively, foliar sprays of Daminozide (B-9) at a concentration of 1000–4000 ppm, or Paclobutrazol (Paclo) at 100–200 ppm, can be applied during the seedling stage to prevent excessive stem elongation.


2. Preventing Flower and Fruit Drop and Improving Fruit Setting Rates: When vegetables encounter high temperatures, drought, or prolonged overcast and rainy weather during the flowering period, significant flower and fruit drop often ensues. Chemical regulation can be employed using 2,4-D or Tomato Spirit (4-CPA) to mitigate this issue. Recommended concentrations are 10–20 ppm for tomatoes, 30–40 ppm for eggplants, and 20–30 ppm for peppers. The prepared solution can be placed in a small cup or bowl, into which the flowers are dipped directly, or it can be applied to the flower stalks using a fine-tipped brush.

3. Promoting Stem and Leaf Growth and Increasing Yields: Prior to flowering, applying a 400–600-fold dilution of the cytokinin-based regulator "5406" (KT-30) or a 50–100 ppm solution of Sodium Bisulfite to vegetables can enhance photosynthetic activity. This accelerates the growth of stems and leaves, thereby stimulating flowering, fruit setting, and the rapid enlargement and early maturation of produce. Additionally, spraying Gibberellic Acid (GA3) on crops such as celery, spinach, and garland chrysanthemum 10–20 days prior to harvest can increase yields by 10%–30%.

4. Inhibiting Sprouting and Prolonging Dormancy: Treating potatoes with 0.01% Methyl 1-Naphthaleneacetate (MENA) effectively inhibits sprouting during storage. For crops such as onions and garlic, a foliar spray of Maleic Hydrazide (MH) applied 15–20 days prior to harvest can significantly reduce their tendency to sprout during storage. Conversely, if cut potato seed tubers are soaked in a 0.5–1 ppm solution of Gibberellic Acid (GA3) for 10 minutes—then removed, air-dried, and placed on a moist sand bed for sprouting—this process can effectively break the tubers' dormancy and promote germination.


5. Regulating the Differentiation of Male and Female Flowers in Cucurbits: Treating seedlings with Ethephon can alter the sex expression of cucurbits, thereby increasing the production of female flowers. For instance, spraying cucumber seedlings possessing 2 to 4 true leaves with a 100–200 ppm Ethephon solution can increase the number of female flowers within the first 20 nodes. Furthermore, spraying cucumber seedlings at the stage when their first true leaf is fully expanded can induce the continuous formation of female flowers—without the appearance of male flowers—along the basal and middle sections of the stem. Consequently, Ethephon plays a particularly significant role in cucumber production.