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.
Don't forget to buy some rooting powder whilst you are at the garden centre.
Trim them just below a leaf joint, treat the cut end with hormone rooting powder and root them in pots in a propagator or under a polythene tent on the windowsill.
Dip the shoots into enough hormone rooting powder to cover the wounds where leaves have been removed.
Remove the bottom leaves, dip in rooting powder and plant half inch into pots of seed and cutting compost.
And you don't need special equipment, bar some hormone rooting powder.
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).
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.
When the shoots emerge, make a clean cut below a leaf joint and dip the base of each in hormone 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.
Dip the cut end in hormone rooting powder or liquid,covering the lower 6 mm (1/4in)of the cutting before inserting it in a pot filled with seed compost.
Remove the thorns and lower leaves and dip in hormone rooting powder.