auxin

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auxin

(ôk`sĭn), plant hormone that regulates the amount, type, and direction of plant growth. Auxins include both naturally occurring substances and related synthetic compounds that have similar effects. Auxins are found in all members of the plant kingdom. They are most abundantly produced in growth areas (meristem), e.g., root and shoot tips, but are also produced elsewhere, e.g., in the stems and leaves. The method of dispersal throughout the plant body is not yet fully understood. Auxins affect numerous plant processes, e.g., cell division and elongation, autumnal loss of leaves, and the formation of buds, roots, flowers, and fruit. They are also responsible for many forms of tropismtropism
, involuntary response of an organism, or part of an organism, involving orientation toward (positive tropism) or away from (negative tropism) one or more external stimuli.
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. It is known that phototropism is due to the inhibition of auxins by light; the cells on that side of a plant exposed to light do not divide or grow as quickly as those on the shaded side, and thus the plant grows toward the light source. Auxins are widely used commercially to produce more vigorous growth, to promote flowering and fruiting and also root formation in plants not easily propagated by stem cuttings, to retard fruit drop, and to produce seedless varieties (e.g., of tomatoes) by parthenogenetic fruiting. Only minute amounts of auxins occur naturally, and synthetic auxins (e.g., 2,4-D) must be administered in carefully prescribed doses, since excessive concentration produces usually fatal abnormalities. However, different species of plants react to different amounts of auxins, a fact used to advantage as a method of weedweed,
common term for any wild plant, particularly an undesired plant, growing in cultivated ground, where it competes with crop plants for soil nutrients and water. In their natural habitat, wildflowers and herbs not only provide beauty but function in many useful ways, e.g.
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 control. The principal natural auxin is indoleacetic acid; other common but less frequent plant hormones include the gibberellins, lactones, and kinins.

auxin

[′ȯk·sən]
(biochemistry)
Any organic compound which promotes plant growth along the longitudinal axis when applied to shoots free from indigenous growth-promoting substances.
References in periodicals archive ?
Brush the wound with rooting hormone compound and wedge a matchstick into the cut, then tape a sleeve of polythene around the bottom of the cut, plugging the sleeve with sphagnum moss for the roots to grow into and then seal the top.
Try treatments with and without rooting hormone, mist, and bottom heat.
Set the cutting about 2 inches deep in the prepared planting hole (C); if using the powder or gel form of rooting hormone, avoid brushing it off as you do this.
You just need to be a little bit organized and have appropriate compost, sharp knives, maybe some rooting hormone, some clean pots or trays, or even a cold frame.
In view of the increasing demand of soil bioengineering techniques, there is a need to select new species and effective rooting hormone for vegetative propagation through stem cutting.
Remember, take 10 cm cuttings from the new growth, trim off the bottom leaves, dip in rooting hormone, pop three to four into a pot of potting compost and keep moist.
Though the Fultons occasionally make new plants by pushing hydrangea sticks into garden soil, they get better results when they are a bit more scientific about it and start cuttings in small pots using rooting hormone.
Tear off a small shoot with a heel of old wood, dip it in rooting hormone, and pop it in good quality compost in a 3in pot.
You'll need sharp, clean secateurs, rooting hormone powder, containers and a free-draining cuttings compost.
3) and root dry weight (62 mg) per cutting was obtained from the cuttings of deep shade to full sun regime followed by deep shade and the lowest was in full sun regime without application of any rooting hormone.
Dust the wound with rooting hormone, press branch into an adjacent shallow hole amended with compost, and cover with 3 inches of soil.