Why is auxin included in the powder

What are the effects of auxin on plants? The following sections break down these questions so that this valuable plant growth hormone can be better understood. Answer: Auxin is a plant growth hormone that can be created chemically or produced biologically by the plant. In biological synthesis, the natural hormone is represented by the symbol IAA, standing for indoleacetic acid.

What are the major functions? Answer: Auxin promotes cell growth and elongation of the plant. In the elongation process, auxin alters the plant wall plasticity making it easier for the plant to grow upwards. Auxin also influences rooting formations. What are the effects? Indole acetic acid IAA is the naturally occurring auxin found in plants. IAA is involved in nearly every aspect of plant growth and development. Some of the processes regulated by IAA include formation of embryo in development, induction of cell division, stem and cleoptile elongation, apical dominance, induction of rooting, vascular tissue differentiation, fruit development, and tropic movements such as bending toward light.

Commercial preference given to these synthetic compounds and less to IAA is illustrated by the large number of rooting products available containing one or both of them see Figure 2, page Plant response to rooting hormones varies with each species, but before rooting hormones are introduced, growers should implement a few simple cultural practices to reduce the number of propagation challenges.

Cuttings, whether they are grown from on-site or off-shore stock plants, should be thoroughly inspected before planting. Softwood cuttings that have an actively growing shoot tip should be selected. Tissues that are too young or too old will root more slowly than cuttings that are at the proper stage of maturity. Cuttings that are too old also tend not to branch as well as younger, softer tissue. Therefore, it is important to visually inspect the lower portion of the cutting to check for woody tissue that is brown or grayish-brown in color.

Cuttings that exhibit this hardwood tissue may need to be trimmed closer to the shoot tip. Fully developed flowers on cuttings are sometimes another sign that tissue may be too old to root optimally.

Generally speaking, auxin- based rooting products are applied at concentrations of , ppm for herbaceous and softwood cuttings. In addition, rates between 1, and 3, ppm may be used for woodier tissue, but the maximum recommended concentrations are not more than 5, and 10, ppm for semi-hardwood and hardwood cuttings, respectively.

When optimal treatments are applied, cuttings will tend to have the following characteristics: Basal portion of cutting shows some swelling, callus tissue forms and root initials emerge just above the cutting base.

Care should be taken with rooting hormones because over- application of some formulations can cause damage to the cutting base. Formulations dissolved in alcohol are more prone to cause burn or dehydrate plant tissue. Auxin in excessive concentrations may result in inhibition of bud development, yellowing of leaves, leaf abscission, blackening of stems and even death of cuttings. It has also been reported that misapplication to leaves may result in curling or other distortion of plant growth.

There are several accepted methods of application for growers wishing to utilize rooting hormones in their propagation practices. When dipping cutting bases into a rooting hormone, better efficiency is maintained with dipping several cuttings at once, rather than dipping them individually. It is also better to use a small portion of the hormone mixture in a separate container, away from the stock batch with frequent changes. This will minimize the potential for disease spread and cross contamination.

Auxin-based rooting hormones may be mixed with talc and applied to the base of cuttings. The cuttings are dipped in the powder, then lightly tapped to remove excess chemical. To increase adhesion of powder to cutting bases, stem tissue can be re-cut or dipped in water or alcohol before application. However, this will lead to a more rapid deterioration of the rooting hormone batch and may increase the potential for disease spread. Powdered forms of rooting hormones are generally less effective than liquid formulations applied at the same concentration.

Auxins were the first class of plant hormones to be discovered. Their main function is to help plants grow and auxin stimulates plant cells to elongate. The tips of the growing stems and roots apical meristem of a plant is one of the main places where auxin is produced. The apical meristem is also the location that all other parts of a plant grow from - the stem, leaves and flowers. Auxins are one specific group of hormones that are used:. Selective weedkillers kill some plants, but not others.

This can be useful for getting rid of dandelions in a lawn without killing the grass, or weeds that compete with crops such as wheat. The selective weedkiller contains a growth hormone that causes the weeds to grow too quickly and die.