Video: Application Of Growth Regulators In Garden Plots
2023 Author: Sebastian Paterson | [email protected]. Last modified: 2023-11-26 20:34
Measure seven times …
Currently, plant growth regulators are widely used in plant growing practice. They are used to accelerate plant growth or slow it down, root cuttings, when transplanting trees, to increase crop yields, to remove seeds from dormancy, to obtain seedless fruits …
I would like to dwell not on advertising this or that drug in this series, but on the mechanism of action of this class of biological compounds. In order for the amateur gardener to imagine the mechanism of action of one or another drug that has a certain commercial name, because the active substance included in it will belong to one of those considered in the article.
Chemical processes in the cell proceed at high speed due to the action of biological catalysts - enzymes or enzymes. The speed and direction of enzymatic reactions in the cell depends on the amount of enzyme, temperature and pH. Each enzyme has its own pH optimum at which its activity is best manifested.
Natural growth regulators - phytohormones are formed in the plants themselves in small quantities and are necessary for their vital activity. These include auxins, gibberellins, brassinosteroids and a number of other substances that stimulate plant growth and development. The balanced development of plants includes both the stimulation of plant growth and the inhibition of growth.
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So, growth regulators are formed in the process of plant metabolism and exert, in very small amounts, a regulatory and coordinating effect on physiological processes in various plant organs. Distinguish between stimulants and inhibitors (inhibitors) of growth.
Growth stimulants, used in super-optimal doses, are capable of suppressing growth processes and acting as inhibitors. I would like to draw the attention of readers to this. It is known from plant physiology that the main representative of auxins in plants is indolyl-3-acetic acid (IAA). It is synthesized from tryptophan at the tip of the shoot.
Auxin stimulates cell division and elongation, it is necessary for the formation of vascular bundles and roots. It is noticed that damaged roots or branches thicken much worse. The reason for this is the low ability of these organs to synthesize hormones.
Cytokinins are formed by condensation of adenosine-5-monophosphate and isopentenyl pyrophosphate in the apical (apical) meristem of the root. There are many cytokinins in developing seeds and fruits. Cytokinins induce cell division in the presence of auxin, activate differentiation, promote the release of buds, seeds and tubers from dormancy, prevent chlorophyll breakdown and degradation of cell organelles, and activate protein synthesis.
Currently, more than 100 gibberellins of acidic and neutral nature are known. The best known and most common gibberellin is gibberellic acid. The discovery of its physiological properties as a growth regulator took place in Japan. Rice disease is widespread there, which the locals call "bakanoe - mad rice", "bad sprouts." Seedlings of diseased plants outpace healthy rice in growth, but the ears grow ugly and there is no grain.
In 1926, the Japanese botanist Kurosawa isolated and described the causative agent of the disease - the fungus Gibberella fujikuroi (now this fungus has been transferred to the genus Fusarium). It soon became clear that many of the "mad rice" symptoms could be caused by the culture broth in which the fungus grew. This means that the fungus secretes some water-soluble substance that enhances the growth of the rice. According to the generic name of the fungus, the substance was named gibberellin.
Gibberellins are synthesized from acetylcoenzyme A in leaves and roots. Gibberellins promote stem elongation, seed release from dormancy, peduncle formation and flowering, activate cell division, increase the activity of phospholipid synthesis enzymes.
Abscisic acid is synthesized in the leaves and root cap. Abscisic acid (ABA) inhibits plant growth and is an antagonist of growth stimulants. ABA accumulates in cells under unfavorable environmental conditions, in aging leaves, dormant seeds, in the separating layer of leaf petioles and peduncles.
Ethylene gas is synthesized from methionine or by reduction of acetylene. A lot of it accumulates in aging leaves and ripening fruits. It inhibits the growth of stems and leaves. Ethylene treatment induces root formation, accelerates fruit ripening, germination of pollen, seeds, tubers and bulbs.
Brassinosteroids are found in various plant organs, but they are especially abundant in pollen. They stimulate growth in length and thickness of seedlings, enhancing both cell division and expansion.
I would like to note that the action of enzymes has the character of a catalytic process and is part of an integral mechanism of action. For example, active root formation requires a complex of factors that can simultaneously provide the maximum reduction in transpiration, intensive assimilation and hormonal activity of the leaves. These primarily include the temperature and humidity of the soil and air, as well as the illumination mode. Therefore, without creating the necessary conditions for complex plant nutrition, the additional use of growth stimulants will only lead to their depletion and death.
A bit of history. In 1880, Charles Darwin and his son Francis Darwin set themselves the task of determining which organ of the plant perceives light. Plants standing on the windowsill turn towards the sun, shoots and leaves bend towards the greatest illumination. The Darwin's results indisputably indicated that the direction of light is perceived by the apex of the seedling and transmits information about the direction of light to the underlying zone. Darwin's hypothetical substance was called auxin (from the Greek auxo - grow).
So, auxins are hormones produced in the apical (apical) meristems of the shoots. For the plant as a whole, the auxin signal means that the shoot is growing intensively and it is necessary to provide for its needs, and each plant cell, depending on its position, performs this task. Auxin affects the arrangement of leaves on the plant. Each young leaf, while growing, serves as a source of auxins. For the surrounding cells, this means that the place is occupied; it is no longer possible to lay a new leaf nearby. A large number of auxins is a signal for the growth of shoots; in order to ensure their growth, the plant must form an additional number of roots.
Auxin treatment causes the formation of adventitious roots on the stem and lateral roots on the main root. This effect is used by treating difficult-to-rooted cuttings with auxin solutions. As I have already noted, when additional treatment of plants with growth stimulants, it is necessary to strictly follow the recommended concentrations. If the recommended concentration of the drug or the treatment time is exceeded, the plants synthesize ethylene, which adversely affects their own state.
Cytokinins are called "rejuvenation" hormones of plant tissues. If you treat a leaf preparing for leaf fall with cytokinin, it will remain green for a long time. But in fact, cytokinin does not rejuvenate the leaf, but simply does not allow it to die from exhaustion, attracting and retaining nutrients in the tissues.
Attempts are under way to use one of the synthetic cytokinins, benzyladenine, as an aging inhibitor for many green vegetables such as lettuce, broccoli and celery. Note that auxins and cytokinins are antagonists in the regulation of lateral kidney development. Many of the fungi that cause plant disease have learned to make cytokinins. In the affected area, a tumor appears, from which numerous thin shoots grow in all directions. The people called this structure "the witch's broom".
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As you can see, the effect of phytohormones on plants is diverse and very significant. Florigen and vernalin are considered flowering hormones. The assumption about the existence of a special flowering factor was expressed in 1937 by the Russian researcher M. Chailakhyan. The chemical basis of the action of phytohormones in plant cells has not yet been sufficiently studied.
Currently, it is believed that one of the points of application of their action is close to the gene, and hormones stimulate the formation of specific messenger RNA here. This RNA, in turn, is involved as a mediator in the synthesis of specific enzymes - protein compounds that control biochemical and physiological processes. Fungi and bacteria have learned the physiology of plants much better over millions of years of coexistence with plants. Many of the fungi that cause plant disease have learned to make cytokinins.
Agrobacterium tumefaciens surpassed all in the "study of physiology" and hormonal balance. The cells of these bacteria are able to transfer their DNA to the nuclei of plant cells. The transmitted DNA fragment contains information on the biosynthesis of auxins, cytokinins and special substances - opines. Opines cannot be utilized by plant cells, but serve as a source of carbon and nitrogen for bacterial growth. Plant cells that have received such DNA begin tumor growth. Even if bacteria are destroyed (antibiotic treatment), the tumor continues to grow as cells continue to produce auxins and cytokinins due to inserted bacterial genes. This is where genetic engineering is in its purest form, without human intervention.
I gave this example so that the readers will understand that plant hormones control the development and growth of plants. And their indiscriminate application does not always lead to positive results.
At present, synthetic growth regulators are used in agriculture.
Retardants inhibit stem growth by inhibiting cell elongation and suppressing gibberellin synthesis. The stems become shorter and thicker, resulting in increased plant resistance to lodging. In fruit growing and in the cultivation of flowers in greenhouses, three such substances are widely used - phosphon, cicocel and alar.
Morfactins prevent seed germination, formation and growth of shoots, weaken apical dominance in shoots and enhance it in roots.
Herbicides are used to destroy vegetation. There are general herbicides, when all plants die, and selective herbicides, for the selective destruction of certain classes of plants. They can inhibit photosynthetic or oxidative phosphorylation.
Defoliants accelerate leaf fall in plants, which activates the maturation of seeds and fruits and facilitates mechanized harvesting.
Desiccants cause accelerated drying of leaves and stems, which makes it possible to collect seeds of legumes and harvest potatoes with combines.
Senicants are a mixture of physiologically active substances that accelerate the maturation and aging of agricultural plants.
Now there are many different drugs on sale to improve the growth and development of plants. When using growth stimulants, the general provisions are: good plant nutrition and compliance with all rules of agricultural technology. There is a good folk wisdom: "Measure seven times - cut once." It can be fully attributed to the topic we are discussing.
It is very important to follow the rules for the use of growth stimulants, especially with regard to avoiding overestimation of the concentration of solutions, so as not to destroy the plants. Plant growth stimulants are not a panacea for all ills. Only in experienced hands are they useful.
Along the way, I want to note that our gardeners have long been using homemade growth stimulants. These are infusions of weeds, when using them, gardeners get very good results. I will not single out any one of the commercial preparations, this is a matter of the practical experience of every gardener or gardener.
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