Auxin
Auxin is a class of endogenous hormones containing an unsaturated aromatic ring and an acetic acid side chain, including indole acetic acid (IAA), 4-chloro-IAA, 5-hydroxy-IAA, naphthalene acetic acid, and the like. In 1872 Polish horticulturist Shelensky studied the growth of root elongation in the root tip. Later Darwin and his father studied the photosynthesis of the grass coleoptile. In 1928, Wenter first isolated the chemical messenger that causes the coleoptiles to bend, and named it auxin. In 1934, Keg et al. determined that it was indole acetic acid, so it was customary to use acetic acid as a synonym for auxin. Auxin is synthesized in expanded young leaves and apical meristems and is transported from the phloem over long distances, accumulating from the top down to the base. The auxin in plants is formed by tryptophan through a series of intermediate products. Its main route is through indole acetaldehyde. Indole acetaldehyde can be decarboxylated from tryptophan by oxidative deamination to oxime pyruvate, and can also be formed by decarboxylation of tryptophan to tryptophan before oxidative deamination. The acetaldehyde is then reoxidized to indole acetic acid. Another possible synthetic route is the conversion of tryptophan to indole acetic acid by oxime acetonitrile. In plants, indole acetic acid can combine with other substances to lose its activity, such as combining aspartic acid with indole acetylaspartate, inositol in combination with inositol acetate, and glucose into glucoside, and The protein binds to indole acetic acid-protein complexes and the like. Conjugated indole acetic acid can often account for 50-90% of indole acetic acid in plants, and may be a storage form of auxins in plant tissues. They can be hydrolyzed to produce free indole acetic acid. The indole acetic acid oxidase commonly found in plant tissues can oxidatively decompose acetic acid. Auxin has many physiological effects, which are related to its concentration. At low concentrations, growth can be promoted. At high concentrations, growth is inhibited and plants die. This inhibition is associated with its ability to induce the formation of ethylene. The physiological effects of auxin appear on two levels. At the cellular level, auxin stimulates cell division in stratum formation, stimulates cell elongation in shoots, inhibits root cell growth, promotes cell division in xylem and phloem, promotes rooting of cuttings, and regulates callus morphogenesis. At the level of organs and whole plants, auxin works from seedlings to fruit ripening. The auxin controls the reversible red light suppression of the hypocotyl elongation of the seedlings; when the indole acetic acid is transferred to the underside of the shoots, the zonality of the shoots is generated; when the indole acetic acid is transferred to the backlight side of the shoots, the tropism of the shoots is generated. Indole acetic acid causes apical dominance; delays leaf senescence; auxin applied to the leaves inhibits shedding, and auxin applied to the paraxial extremities of the detachment promotes shedding; auxin promotes flowering, induces unisexual fruit development, and delays fruit ripening. The concept of hormone receptors has been proposed in recent years. The hormone receptor is a macromolecular cell component that can specifically bind to the corresponding hormone and then initiate a series of reactions. Complexes of indole acetic acid and receptors have two effects: one is that they act on membrane proteins, affect media acidification, ion pump transport, and tension changes, which are fast reactions (<10 minutes); second, they act on nucleic acids, causing Cell wall changes and protein synthesis are slow reactions () 10 minutes). Media acidification is an important condition for cell growth. Indole acetic acid activates the ATP (adenosine triphosphate) enzyme on the plasma membrane, stimulates hydrogen ions to flow out of the cell, and lowers the pH of the medium. The relevant enzyme is then activated, hydrolyzing the polysaccharides in the cell wall, and softening the cell wall and allowing the cells to expand. Administration of indole acetic acid resulted in the appearance of specific messenger RNA (mRNA) sequences, which altered protein synthesis. Indole acetic acid treatment also changes the elasticity of the cell wall, allowing cell growth to proceed. Gibberellin Gibberellins are a class of plant hormones that are biguanide compounds. In 1926, the Japanese pathologist Kurosawa discovered that rice plant growth was caused by the secretion of Gibberella in the study of rice bastard disease. In 1935, Sakata Japan separated an active product from Gibberella zeae and obtained crystallization, which was named Gibberellin (GA). The first isolated gibberellin was identified as gibberellic acid (GA3), and more than 70 gibberellins have been isolated from higher plants and microorganisms. Since gibberellins contain carboxyl groups, they are acidic. Endogenous gibberellins exist in both free and bound forms and can be transformed into each other. The gibberellin pH 3 ~ 4 solution is the most stable, pH value is too high or too low will make gibberellin become physiologically active pseudo gibberellin or Gibbimalic acid. The precursor of gibberellin is kafomene. Certain growth retardants, such as amo-1618 and chlormecurine, inhibit the formation of kauriene, and Flowserve-D inhibits the conversion of kaurene to gibberellin. The site of formation of gibberellins in plants is generally young tissues such as young leaves, buds, young roots, and immature seeds. Different gibberellins are present in different organs of various plants. The gibberellin formed at the apex of young leaves and shoots is exported through the phloem, and the gibberellin produced in the roots is transported upwards through the xylem. GA3 has the strongest physiological activity and the most studied GA3, which can significantly promote the growth of stems and leaves of plants, especially for genetic and physiological dwarf plants; it can replace some seeds germination. Required light and low temperature conditions to promote germination; long daylight plants can bloom under short day conditions, shorten life cycle; can induce flowering, increase the number of male flowers in melons, induce parthenocarpy, increase fruit set rate, promote fruit Growth retards fruit aging. In addition, GA3 can also be used to prevent skin rot; spraying at the flowering stage of cotton can reduce the shedding of bells; potato soaking can break the dormancy; barley soaking can increase maltose production and so on. Many of the physiological effects of gibberellic acid are related to its regulation of nucleic acids and proteins in plant tissues. Not only does it activate multiple hydrolytic enzymes in seeds, but it also promotes the synthesis of new enzymes. The most studied is the significant effect of GA3-induced alpha-amylase production in barley kernels. In addition, the synthesis of protease, β-1,3-glucosidase, and ribonuclease was induced. Gibberellin-induced stem elongation is associated with nucleic acid metabolism. It acts on DNA first, activates DNA, and then transcribes messenger RNA (mRNA), which translates from mRNA to a specific protein. Cytokinin Cytokinins are a class of plant hormones that have an adenine ring structure. The common feature is that there is a specific substitution at the 6th position of the adenine ring. Their physiological functions are prominent in promoting cell division and inducing bud formation. In 1948, American Skog and China Cui? discovered that adenine could induce the differentiation of tobacco marrow into buds in tobacco tissue culture. In 1955, Miller et al. isolated and purified the deoxyribonucleic acid of yeast DNA and the deoxyribonucleic acid of spermatozoa to obtain a substance that promotes cell division. The substance was named kinetin (KT) and its chemical structure was 6-furylmethyladenine. Also known as thiol adenine. In 1963 Latham isolated the first natural cytokinin found in higher plants from maize tender seeds 11 to 16 days fertilized and named it Zeatin (Z). More than 20 adenine derivatives have been obtained from higher plants. Such as dihydrozeatin, zeatin riboside (ZR) and isopentenyl adenine. In modern times, a variety of similar substances have been synthetically synthesized, such as 6-benzyladenine (BA) and tetrahydropyranylbenzyladenine (PBA). They are called cytokinins (CTK). The root tissue (apical root) synthesizes cytokinins most actively, transporting them from roots to stems over long distances through the xylem. Seedlings, shoots, young fruits, and developing seeds also form cytokinins, which were first obtained in corn seeds that were not mature. Cytokinins can be produced by the cleavage of transfer ribonucleic acid (tRNA) and can also be synthesized from mevalonate and adenine as precursors. Cytokinins have a variety of physiological effects. One is cell division. There are two processes for cell division: one is the process of nuclear division and the other is the process of cytoplasmic division. Cytokinin promotes cytokinesis. In the absence of cytokinins, cells do not normally divide to form multinucleated cells. The second is to induce bud formation. Some isolated leaves can produce shoots at both the base of the main vein and the leaf margin after being treated with kinetin. The third is anti-aging. Treatment of isolated leaves with kinetin can reverse protein and chlorophyll degradation in the treated area. The fourth is to overcome the top advantage. Administration of kinetin to lateral shoots inhibited by auxin, which is transported by the apical polarity of the stem, allows sprouting of lateral buds. Cytokinin inhibits the formation of lateral roots and adventitious roots. Cytokinins can genetically transform male grape varieties into hermaphroditic plants. The use of cytokinin and auxin in appropriate proportions can promote the differentiation of shoots and roots into a complete plant. Abscisic acid Abscisic acid is a plant hormone with a sesquiterpene structure. In 1963, American Idikotte et al. purified a substance from cotton bolls to significantly promote shedding of petiole explants, known as shedding hormone II. Wellin et al. also purified a substance from the leaves of eucalyptus under short-day conditions to control dormancy of deciduous trees called dormant hormones. In 1965, it was confirmed that shedding hormone II and dormant hormone are the same substance, and they are collectively named as abscisic acid. Abscisic acid forms in many parts such as senescent leaf tissue, mature fruit, seeds, stems, and roots. Water deficit can promote abscisic acid formation. Abscisic acid is rapidly redistributed in plants and is present in the phloem and xylem fluid. The precursor for the synthesis of abscisic acid is mevalonate and there are two ways to go after it produces farnesyl pyrophosphate. One is the common C15 direct pathway in fungi. One is the C40 indirect pathway in higher plants. The latter first forms carotenoids (violaxanthin), which are oxidized to lightly or biologically oxidized cyloxanthin of C15 and then converted to abscisic acid. Abscisic acid can be metabolized by oxidation and binding. Abscisic acid stimulates ethylene production and promotes fruit ripening. It inhibits the synthesis of deoxyribonucleic acids and proteins. Abscisic acid has the following physiological functions: 1. Inhibit and promote growth. When the concentration of abscisic acid applied is large, growth of stems, hypocotyls, roots, coleoptiles, or leaves is inhibited. When the concentration is low, it promotes the growth of roots and hypocotyls of the isolated cucumber cotyledon, accelerates the breeding of duckweed, and stimulates the development of parthenocarpic seeds. 2. Maintain bud and seed dormancy. Dormancy is related to the balance between gibberellin and abscisic acid in the body. 3. Promote the shedding of fruits and leaves. 4. Promote stomatal closure. Abscisic acid can quickly close the stomata, and it is not poisonous to plants. It is a good anti-transpiration agent. A biological test to test the concentration of abscisic acid is to float the epidermis of isolated leaves on the surface of various concentrations of abscisic acid solution. In a certain range, the degree of opening and closing of the stomata is inversely proportional to the concentration of abscisic acid. 5. Affect the flowering. Under long-day conditions, abscisic acid can make strawberry and blackberry apical buds dormant and promote flowering. 6. Affect sexual differentiation. Gibberellin can cause female plants of hemp to form male flowers. This effect can be reversed by abscisic acid, but abscisic acid cannot make female plants form female flowers. Vinyl In 1964 Lieberman proposed that ethylene be derived from methionine. In 1979, Adams and Yang discovered that 1-aminocyclopropyl carboxylic acid (ACC) is a precursor of ethylene production and determined that the ethylene synthesis pathway is: methionine→adenosylmethionine (SAM)→ACC→ethylene. The ACC synthase that catalyzes the formation of ACC by SAM is a major rate-limiting factor in ethylene synthesis. Aminoethoxyethylene glycine (AVG), aminoxyacetic acid (AOA) and other substances can effectively inhibit this reaction. Almost all higher plant tissues can produce trace amounts of ethylene. Drought, waterlogging, extreme temperatures, chemical damage, and mechanical damage can all stimulate the increase of ethylene in the plant. This is known as “adversity ethylene†and will accelerate organ aging and shedding. Germination of seeds, fruits and other organs mature, aging and shedding when the content of ethylene in the tissue is high. High concentrations of auxin promote ethylene production. Ethylene inhibits the synthesis and transport of auxin. The inhibition of elongating growth of yellow pea seedlings, promotion of thickening and change of tropism (triple reactions) and overlying responses of leaves are ethylene-specific biological effects, often used as bioassays. It is the most important physiological role of ethylene to initiate and promote the maturation, senescence, wilting and shedding of plant organs and tissues such as fruits, corollas and leaves. As the fruit matures, ethylene increases its ability to synthesize ribonucleic acids and promote protein synthesis. In addition, it can promote the activation of many enzymes such as peroxidase, phospholipase, and so on, so it has a ripening effect. In the formation of the separated layer, ethylene promotes the synthesis of protein in the layered area, increases the activity of the cellulase in the layered area, thereby accelerating the formation of the separation layer and causing the organ to fall off. Ethylene promotes flowering, induces the formation of female flowers; breaks the dormancy of some seeds; inhibits the opening of hooks on the top of the seedlings; inhibits root growth; induces formation of adventitious roots and root hairs; promotes porcine hyperplasia; and increases plant excretion. Brassin Brassica, also known as alfalfa. This is a type of plant endogenous steroidal physiologically active substance with sterols as the backbone. In 1970, the United States agronomist Mitchell and others extracted from rape pollen to obtain a significant promotion of the growth of soybean seedlings, known as Brassica. Britain's Mandala is equal to the 1978 refined brassine crystals, the chemical structure belongs to sterol lactones, it was named brassinolide (BR). Later, more than a dozen biologically active brassinosteroids were purified from other plants, of which brassinolide has the strongest physiological activity and is considered to be a new plant hormone. Brassinolide has a dual role in promoting cell division and elongation in kidney bean seedlings, and can promote whole plant growth, including plant height, plant weight, and barnyard weight; and it not only promotes stem growth, but also leaves and Increased number of lateral shoots; decreased extracellular ion exudation in rice cells at low temperatures, indicating that it has a protective effect on the cell membrane and can improve crop cold tolerance. Elevator Guide Rails And Accessories Guide Rail Accessories,Elevator Accessories Of Guide Rail,, YC PRECISION TECHNOLOGY & MACHINERY CO.,LTD , https://www.yc-technology.com
Ethylene is a gaseous hormone. In the middle of the 19th century, it was discovered that leaked lighting gas can affect plant growth and development. In 1901, Russian scholar Nyurovov confirmed the role of ethylene in lighting gas and found that plants had a "triple reaction" to ethylene. From 20 to 30 years, the extensive effects of ethylene on plants have been identified and used as fruit ripening agents. In 1934, the American Bois Thomson Institute Clark proposed that ethylene is the concept of mature hormones. In the late 1950s, Berger et al introduced gas chromatography into ethylene studies to accurately determine trace amounts of ethylene and its changes in traced tissues. In the late 1960s, ethylene was recognized as a plant endogenous hormone.