Plant hormones and plant growth regulators precisely regulate crop growth, development, and stress resistance in modern agricultural production. Simultaneously, plant hormones and plant growth regulators exhibit complex synergistic and antagonistic relationships, jointly regulating the entire plant life cycle. For example, the ratio of auxin to cytokinin determines the direction of tissue differentiation; ethylene and abscisic acid jointly promote senescence, etc.
Sowing and Seedling Stages: Laying the Foundation for High Yields
1. Breaking Dormancy and Promoting Uniform and Strong Seedlings. Some seeds (such as potato tubers, rice, and wheat seeds) have long dormancy periods, which can delay planting. Soaking seeds or tubers in gibberellic acid can effectively break dormancy, promote seed germination, and result in rapid and uniform emergence.
2. Promoting Rooting and Accelerating Propagation. Treating the base of cuttings with auxin-based regulators such as naphthaleneacetic acid (NAA) or indolebutyric acid (IBA) (commonly known as rooting powder) can significantly promote the formation of adventitious roots, allowing plants that are previously difficult to root, such as cucumbers and roses, to easily survive, greatly improving propagation efficiency.
Vegetative Growth Stage: Regulating Growth and Shaping Ideal Plant Shape
1. Regulating Growth, Increasing Yield and Income. In vegetable production, the application of growth regulators such as gibberellin and aminoethyl ester can promote the growth of crops like Chinese cabbage and increase yield. In cotton cultivation, the use of mepiquat chloride is mainly used to inhibit vegetative growth, prevent excessive vegetative growth, and concentrate nutrients to supply the cotton bolls, thereby increasing yield and income.
Controlling Excessive Growth and Preventing Lodging. Crops such as corn and rice are prone to excessive vegetative growth when fertilizer and water are applied excessively, leading to lodging or nutrient waste. Farmers often use growth retardants such as chlormequat chloride, paclobutrazol, and uniconazole, which are foliar sprayed during key growth stages (such as the early jointing stage) to inhibit stem elongation, promote thicker stems, develop a strong root system, enhance lodging resistance, and shape an ideal plant shape.
Flowering and Fruit Setting Stage: Protecting Flowers and Fruits, Determining Yield
1. Inducing Flowering and Regulating Flowering Period. Gibberellin is a well-known "flowering inducer." For plants that require low temperatures or long days to flower (such as certain vegetables and flowers), spraying gibberellic acid under unnatural conditions can induce flowering, enabling off-season production. Ethephon, on the other hand, promotes female flower differentiation in some plants (such as melons and solanaceous fruits), increasing the number of fruits. In tomato production, ethephon treatment can uniformly induce flowering, resulting in consistent fruit ripening and facilitating management and harvesting.
2. Flower and fruit preservation, and thinning. Under adverse environmental conditions (such as low temperatures and drought), eggplants and citrus fruits are prone to flower and fruit drop. Spraying with auxin-based (2,4-D) or gibberellic acid regulators during the flowering or young fruit stage can prevent the formation of an abscission layer on the flower stalk or fruit stalk, thus retaining flowers and fruits on the plant and improving fruit set. Excessive flowering and fruiting in fruits and vegetables can lead to smaller fruits and decreased quality. Applying regulators such as naphthaleneacetic acid (NAA) and abscisic acid (ABA) during the peak flowering or young fruit stage can promote the shedding of some underdeveloped young fruits, achieving a reasonable "family planning" approach and ensuring that the remaining fruits are large, of high quality, and maintain stable yield.
Fruit Development and Maturation: Enhancing Quality and Value
1. Promoting Fruit Enlargement: Utilizing the synergistic effect of cytokinins and gibberellins can promote cell division and elongation, resulting in rapid fruit enlargement. In fruits such as grapes, kiwifruit, and watermelons, treatment of young fruits with chlorpyrifos or thidiazuron can promote cell division, increase fruit size, and may even produce seedless fruits.
2. Promoting Fruit Ripening and Coloring: During the fruit ripening stage or after harvest, soaking or spraying with ethephon releases ethylene gas, which accelerates the conversion of starch into sugars, the decomposition of organic acids, and the degradation of chlorophyll, leading to the formation of pigments (such as lycopene and anthocyanins), thereby achieving the purpose of ripening and uniform coloring. Ethephon is commonly used to promote the ripening of fruits such as tomatoes, bananas, and citrus fruits. For example, bananas are often harvested when unripe and then ripened to yellow using ethephon after transportation to the sales area.
3. Promoting Preservation and Delaying Senescence. Cytokinin regulators (such as benzylaminopurine) are commonly used. Post-harvest spraying or soaking of leafy vegetables (such as celery and lettuce) and flowers can inhibit chlorophyll degradation and protein decomposition, maintaining the product's fresh green color and crispness, and extending shelf life.
Enhancing Stress Resistance: The "Guardian Angel" of Crops
Plant hormones and plant growth regulators can also help crops cope with adverse environments. Although abscisic acid promotes senescence, it is also a "stress resistance signal" for plants. Spraying before adverse conditions occur can activate the crop's self-protection mechanisms, such as closing stomata and accumulating osmotic regulators, thereby improving its resistance to cold, drought, and salinity. When herbicides are used improperly, spraying brassinolide and other similar products can regulate the crop's physiological state, helping it to recover growth quickly and reducing herbicide damage.
Of course, plant hormones and plant growth regulators offer many benefits in crop production, but the following points should be noted:
1. Dual Nature: Plant regulators are like "medicines," and their concentration and timing are extremely critical. Low concentrations promote growth, while high concentrations may inhibit or even kill plants.
2. Strict Use: They must be used according to the instructions regarding crops, timing, concentration, and method. Indiscriminate use is strictly prohibited.
3. Supplementary Role: They cannot replace basic growth conditions such as fertilizer, water, light, and temperature; they are merely "icing on the cake" for good cultivation management.
4. Safe Interval: Use is prohibited for a period before harvest to ensure that residues in agricultural products meet safety standards.
In short, plant hormones and plant growth regulators are the "magic wand" of modern precision agriculture. We need to learn how to use them rationally and scientifically to achieve precise management of the crop life cycle, ultimately achieving increased yield, improved quality, increased efficiency, and cost reduction.
