auxin


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auxin

(awk′sĭn) [Gr. auxe, increase]
A substance that promotes growth in plant cells and tissues.

auxin

a type of plant growth-regulating substance involved in the growth of cells and several other functions. The most important auxin is indolacetic acid (IAA; see Fig. 194 ), but many other substances have been classified as auxins, using a BIO-ASSAY method developed by Fritz WENT.

The effects of auxins depend on their concentration in the plant. They are most concentrated at the shoot tip and least concentrated in the root, except for small amounts at the root tip. The major effects of auxin are summarized below:

  1. Encourages cell growth by elongation, producing a softening of the MIDDLE LAMELLAE of cell walls.
  2. Stimulates cell division in the PHLOEM of the VASCULAR BUNDLES, so encouraging new growth.
  3. Promotes positive PHOTOTROPISM in shoots by growth of tissues towards the light source.
  4. Promotes GEOTROPISM in all parts of the plant (positive in roots, negative in shoots, due to unequal distributions of the hormone).
  5. Induces APICAL DOMINANCE by suppressing lateral buds.
  6. Induces lateral root formation.
  7. Stimulates fruit development, enabling seedless fruits to be produced artificially. (h) Suppresses ABSCISSION in leaves and fruit. (i) Encourages the formation of wound tissues in injured or diseased plants.

    Auxins have a number of commercial uses, e.g. to promote the rooting of cuttings, regulate plant height, induce flower formation and control fruit set and fruit drop.

auxin

plant hormone.
References in periodicals archive ?
The effect of auxins and cytokinins and their combinations on callus fresh and dry weight indicated that kin concentration outweighs the 2,4-D in the medium.
Sixty bacterial isolates showing growth and having different morphological appearance (colony shape, colony lustre, shape of boundary, colony size) on agar medium were selected and further used for studying auxin biosynthesis in vitro.
Estelle maintains that identifying these proteins is important because "understanding how auxin works may allow us to manipulate plant growth in desirable ways.
If we can determine how auxin is made in a plant, then we can change the concentration, or level.
These pathways have been studied and most of the components that transmit the signal from perception site to chromatin have been identified for the major plant hormones, such as auxin, gibberellins, cytokinins, ethylene, and abscisic acid as well as for brassionosteroids, jasmonic and salicylic acid (Santner & Estelle, 2009, Wang & Irving, 2011).
The most important proteins in this process are the export proteins known as "PINs," which regulate the direction of the auxin flow.
Effect of ethanol, methanol and acetone on rooting etiolated cuttings of Vigna radiata in presence of sucrose and auxin.
Physical Indicators of Barium Titanate Products of Auxin Technology
25] Prokryl Z, Vancura V and M Wurst Auxin formation by rhizosphere bacteria as a factor of root growth.
We already knew that auxin is made in the leaves and travels to the stem to stimulate growth," said Chory.
Here biologists in various specialties report on recent findings regarding the control of auxin synthesis and transport, mechanisms of cellular responses, auxin-dependent plant growth and development, and signal integration.
Good growth of calluses were seen when the concentrations of both the auxins were high.