Auxins


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Related to Auxins: callus, Plant hormones, Cytokinins

Auxins

 

substances produced in plant cells that stimulate the growth processes (growth of roots in cuttings, elongation of cells in stem segments, cell division in plant tissue culture); a group of plant hormones. At low concentrations auxins accelerate plant growth, but at high concentrations they inhibit it. Judging by their structure, auxins are probably monobasic hydroxy acids. Beta-indolylacetic acid (called heteroauxin), which is most widespread in plants, and some of its derivatives which are formed in plants during oxidative deamination of tryptophan are similar to auxins. Auxins are formed in young, vigorously growing parts of higher plants—growing points in stems, in root tips, in young leaves and buds, in fungi, and so on. The high content of auxins in growing organs stimulates the inflow of nutrients from other parts of the plant. Auxins are capable of moving down the stem and up the root. Growth movements in the plant and various tropisms are due to the uneven distribution of auxins in the axial organs. Auxins are found in free or bound states in plant tissues; only free auxins are biologically active. Auxins interact both with other plant hormones (gibberellins and kinins) and with metabolic products. Their mechanism of action is varied and still not completely elucidated. Auxins are assumed to stimulate the biosynthesis of some protein-enzymes involved in the formation of the structural components of cell walls or to form unstable complexes with ribonucleic acid, thereby regulating cell division. Many synthetic organic substances (for example, betaindolebutyric acid) have the same action as auxins. Auxins are used in plant-growing to hasten the rooting of cuttings and the like.

REFERENCES

Boysen-Jensen, P. Rostovye gormony rastenii. Moscow-Leningrad, 1938. (Translated from English).
Kholodnyi, N. G. Fitogormony. Kiev, 1939.
Zöding, H. Rostovye veshchestva rastenii. Moscow, 1955. (Translated from German.)
Reguliatory rosta rastenii v sel’skom khoziaistve. Moscow, 1958. (Translated from English.)
Mel’nikov, N. N., and Iu. A. Baskakov. Khimiia gerbitsidov i regu-liatorov rosta rastenii. Moscow, 1962.
Leopold, A. Rost i razvitie rastenii. Moscow, 1968. (Translated from English.)
Went, F. W., and K. V. Thimann. Phytohormones. New York, 1937.
Pilet, P. E. Les phytohormones de croissance. Paris, 1961.

R. KH. TURETSKAIA and V. I. KEFELI

References in periodicals archive ?
Whereas tissue cultures of normal, healthy plant cells cultured in vitro need an exogenous supply of auxins and cytokinins as plant hormones for continued growth, some cells lose this requirement during subculturing and become able to grow on hormone-free media.
Because increasing of methanol can influence of methylotrophs bacteria on the phylosphere and these bacterial accumulation is caused plant regulators production like auxins that led to develop of leaf area [49 and 50].
These data suggest a model in which basipetal auxin transport from a leaf either blocks movement of a growth-stimulatory signal (possibly cytokinin in nature) or initiates a movement of a growth inhibitory signal into the leaf from lower plant organs.
Role of cytokinin and auxin in shaping root architecture: regulating vascular differentiation, lateral root initiation, root apical dominance and root gravitropism.
In summary, the bacteria-associated plant growth properties shown in our experiments suggested that PGPR bacteria were able to produce phytohormone auxin (IAA) that stimulated the growth of maize and wheat crops.
Ecker, a professor in Salk's Plant Molecular and Cellular Biology Laboratory, used biochemical and genomic analyses to identify PIF7, as the key molecular link between a plant's light sensors and production of auxins.
2,4-D is most commonly used for weed control in lawns and other turf, No2-till burndown, Control of weeds and brush along fences and highway and railroad rights of way, Conifer release (control of broad-leaf trees in conifer plantings), Grass hayfields and pastures, Cereal grains, Corn and sorghum (occasionally), and as a synthetic auxin analogue
Effects of sucrose, inoculum density, auxins, and aeration volume on cell growth of Gymnema sylvestre.
In micropropagation, the general principle is that high concentration of cytokinin and low concentration of auxin in the medium promote the induction of shoot morphogenesis [8,9].
To assess the effect of auxin in combination with cytokinin on callus induction, eight different medium formulations were used.
However, not much is known about the complex molecular network operating during cell proliferation and morphogenesis triggered by auxins and NO in that process.