How are plant growth regulators applied to pollution-free agricultural products?
How are plant growth regulators applied to pollution-free agricultural products? Please explain that plant growth regulators are physiologically active substances that are artificially synthesized or extracted from microorganisms and have a significant regulatory effect on plant growth and development. Here we collectively refer to the trace chemical substances that regulate plant growth and development as plant hormones or plant growth regulators...
How are plant growth regulators applied to pollution-free agricultural products? Please explain
Plant growth regulators are physiologically active substances that are artificially synthesized or extracted from microorganisms and have a significant regulatory effect on plant growth and development. Here we collectively refer to the trace chemical substances that regulate plant growth and development as plant hormones or plant growth regulators.
Regarding the use of plant hormones, several theoretical issues must first be clarified: First, plant hormones are different from fertilizers. Plant hormones are not nutrients; they only regulate and control plant growth and development and cannot replace the role of fertilizers. Second, externally applied plant hormones must be absorbed by the plant, participate in plant metabolism, and affect the balance of endogenous hormones within the plant in order to take effect. Third, the sensitivity of plants to plant hormones varies depending on the plant species, the type of organ, and the developmental stage.
The use of plant hormones should strictly comply with the production technical regulations for pollution-free agricultural products and green agricultural products and the guidelines for pesticide use, and low-toxicity, low-residue plant growth regulators should be used in limited amounts. The use of plant hormones should not affect the excellent traits of green agricultural product quality.
I. Selection of plant growth regulators
(1) Choose legally produced varieties of plant growth regulators
In China, the production and use management of plant growth regulators falls under the category of "pesticides," and products used to regulate plant growth must be registered as "pesticides." For the legal production of plant growth regulators, there must be a "pesticide registration certificate" issued by the Ministry of Agriculture, a production license or production approval document issued by the industrial products licensing department of the State Council, and a "product enterprise standard" reviewed and filed by the provincial chemical industry department and the technical supervision bureau, as well as product quality standards and a quality control certificate attached after quality inspection.
Plant growth regulator products must have a label or instruction sheet. It should indicate the name of the plant growth regulator, enterprise name, product batch number, regulator registration certificate number (temporary registration certificate number), regulator production license number or production approval document number, regulator active ingredient, content, weight, product performance, toxicity, uses, application technology, application method, production date, expiration date, and precautions during use. Repackaged products should also indicate the repackaging unit. (2) Have clear production and control objectives
The use of plant growth regulators must have clear regulatory objectives, such as solving production problems such as excessive vegetative growth, abscission, reducing labor intensity, regulating flowering period and flowering time, and improving quality. According to the regulatory objectives, effective regulator products should be selected and not abused. Different plant growth regulators have different regulatory effects on plants; some promote growth, some inhibit growth, some delay growth, some promote abscission, and some inhibit abscission. The appropriate type of regulator should be selected according to the problems that need to be solved in production, the properties, functions, and economic conditions of the regulator.
II. Key technologies for the use of plant growth regulators
(1) Control the use concentration and dosage
In the application of plant growth regulators, attention must be paid to the issue of dosage. The issue of dosage involves the effectiveness of plant growth regulator use, cost, and the safety of agricultural products and the environment. Some regulators may have completely opposite effects at different concentrations. For example, auxins promote growth at low concentrations, inhibit growth at high concentrations, and may even kill plants. When using plant growth regulators, the concentration and amount of solution must be strictly controlled. On the premise of achieving the regulatory objective, the dosage should be reduced as much as possible to lower costs and reduce residues. Usually, applying a plant growth regulator once at a critical period will have an obvious effect; applying it multiple times not only wastes labor and chemicals, but the effect may not necessarily be better than a single application. However, when using plant growth retardants, low-concentration multiple applications are more effective than a single high-concentration application. This is because low-concentration multiple applications can not only maintain a continuous inhibitory effect, but also avoid toxic side effects on plants.
(2) Master the period and time of use
The physiological effects of plant growth regulators are often associated with a certain growth and development period; too early or too late will not achieve the desired effect. Use at different periods may even produce completely opposite results. For example, naphthaleneacetic acid used on young fruit has a fruit-thinning effect, while use before harvest can prevent pre-harvest fruit drop. Therefore, the appropriate period must be selected for application, and attention must also be paid to the time of use. Generally, it is better before 10 a.m. on a clear, windless day. Do not use it on rainy days. If it rains within 4 hours after application, it must be reapplied.
(3) Select and use according to the responses of different crops, different varieties, and different organs to plant growth regulators
Different crops, varieties, and organs have different degrees of sensitivity to regulators, so different types of regulators and use concentrations should be selected accordingly. For example: apricot trees are sensitive to paclobutrazol, so the dosage should be increased. Another example is when using paclobutrazol on plum trees; Chinese plum is not suitable. Therefore, selection must be based on the responses of the tree species and variety.
(4) Use appropriate formulations and application methods
Plant growth regulators include technical materials and formulations such as aqueous solutions, powders, oils, and fumigants. Application methods usually include spraying, soaking, smearing, pouring, dripping, and fumigation. Technical materials are usually difficult to dissolve in water, so a corresponding solvent must be selected before dilution and use. When using aqueous solutions for foliar spraying, a certain amount of surfactant is usually added (such as soapy water, washing powder, etc., but the pH of the solution must not change too much) to make it easy to adhere to and spread on the leaf surface. Suspensions prepared from wettable powders are less uniform than aqueous solutions; when spraying, care should be taken to shake to prevent precipitation. The application method should be selected according to the pathway by which the regulator enters the plant to take effect. For example, paclobutrazol is absorbed through the roots and can be applied to the soil; when using 2,4-D to prevent flower and fruit drop, the agent should be applied to the flowers to inhibit the formation of the abscission layer. If 2,4-D is used to treat young leaves, it is likely to cause damage. Another example is using naphthaleneacetic acid or ethephon to stimulate pineapple flowering; the solution can be poured into the cup-shaped central leaf whorl to directly stimulate inflorescence differentiation, rather than soil irrigation or spraying. However, because our city's agricultural products are exported to countries such as Japan, daminozide (butyrylhydrazide) is a type that must not be detected, so it absolutely must not be used in production.
(5) The containers used to prepare the agents must be washed clean
Different regulators have different physical and chemical properties such as pH, so the containers used to prepare the agents must be clean and sanitary. A container that has held alkaline agents will become ineffective if used to hold acidic agents without cleaning; after holding a growth-inhibiting regulator, it also cannot exert its effect if used to hold a growth-promoting agent. For example, when maleic hydrazide is used in production, the concentration is generally relatively high. If residue remains and it is not cleaned, using it to treat at low dosage to prevent fruit drop will cause fruit trees to drop leaves and fruit, producing the opposite effect.
(6) Pay attention to plant growth vigor and climate changes
Generally speaking, for plants with good growth vigor, the concentration can be slightly higher, while for weak growth vigor, the concentration should be slightly lower. Temperature also has a great influence on regulators; the response is fast at high temperature and slow at low temperature, so the concentration used in winter and summer should differ. Under drought conditions, the solution concentration should be reduced. Conversely, when used in conditions with sufficient rain, the concentration should be appropriately increased.
(7) Cleverly and cautiously mix and use multiple agents
Mixing several plant growth regulators or mixing them with pesticides and fertilizers can produce comprehensive effects and solve several production problems at the same time. For example: to advance the supply period of pears, when using ethephon for ripening, it can be mixed with naphthaleneacetic acid to avoid causing fruit drop. However, when mixing several plant growth regulators or mixing them with pesticides and fertilizers, it is necessary to fully understand whether there is enhancement or antagonism among the mixed plant growth regulators or between plant growth regulators and other pesticides. For example, Yemianbao and Penshibao are acidic and cannot be mixed with alkaline pesticides or fertilizers; gibberellin easily decomposes when encountering alkali. When maleic hydrazide is mixed with cytokinin, their effects will cancel each other out.
(8) Conduct small-scale trials
Due to the influence of various factors such as climate, quality of growth regulators, and formulations, a uniform standard cannot be applied during use. Different crop types and varieties, and even the same crop and same variety, may differ due to different climate and soil. Before large-scale treatment, small-scale trials must first be conducted to determine the appropriate regulator type, concentration, and formulation, so as to achieve scientific and rational use.
(9) Combine with improved varieties and various cultivation techniques
Plant growth regulators only play a role at a certain link in plant growth and development. They cannot be separated from improved varieties, nor can they replace fertilizers, pesticides, and other cultivation measures. To achieve ideal results in their application in agricultural production, they must be coordinated with other agricultural technical measures. For example: when using naphthaleneacetic acid and indoleacetic acid to treat cuttings to promote rooting, a certain humidity and temperature in the seedbed must be maintained; otherwise, rooting is difficult to ensure. Plant growth regulators are regulatory substances within organisms; the use of plant growth regulators cannot replace fertilizer and water. Even growth-promoting regulators must have sufficient fertilizer and water conditions to take effect.
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