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 hormone rooting powder is more important on the geranium than the fuchsia, but both benefit from its use.
Dip the end in hormone rooting powder then insert the cuttings in pots of compost.
Rooting powder isn't usually necessary, though its dual fungicidal action ups the success rate.
Dip the shoots into enough hormone rooting powder to cover the wounds where leaves have been removed.
love of is once that dies' Take some hormone rooting powder and dip the bottom of the cutting into it, then place it in a small pot of compost about 1in deep.
Dip the base of the cutting in rooting powder or gel - this is a hormonal powder that will stimulate and increase the quality of the roots.
After dipping in hormone rooting powder they can be inserted in the trench 6ins apart, only a third of each cutting protruding above the surface before treading firmly and watering regularly, especially during dry spells.
In future, dip your cuttings in a rooting powder that contains fungicide and root them in a warm place.
Snip non-flowering, 8-10cm shoots just below a node and dip them in rooting powder.
N Dip the cut end in hormone rooting powder or liquid, covering the lower 6mm, (1/4in), before inserting it in a pot filled with seed compost.
Use hormone rooting powder for a faster result and keep the cuttings in a bright but not sunny place until they are rooted (2-3 weeks).
Remove all but two or three leaves at the top, snip off the thorns from the bottom, dip the base in rooting powder and insert cuttings 6in deep in light soil with some bonemeal added.