Last updated: May 21, 2021

What Does Auxins Mean?

An auxin is a plant hormone that is primarily involved in regulating plant growth. Auxins are the main cause behind the elongation of cells in plants. Auxins also control the pattern of epidermal cells in a leaf.

Auxins, however, have different effects on the roots and the shoots of a plant. A high auxin concentration in the shoot can cause the shoot's cells to grow faster whereas a high auxin concentration in the root can cause the cells in the shoots to grow slowly.

Knowing about auxins can help a grower direct a plant's growth in a certain direction.


Maximum Yield Explains Auxins

There are four auxins that exist in nature and are synthesized by plants. Since their discovery, more auxins have been derived from existing ones and others have been synthesized in the laboratory. The most prevalent of the natural auxins is indole-3-acetic acid (IAA), which is produced by algae, plants, bacteria, and fungi. IAA thickens the cambium layer of plants by actually enlarging xylem cells.

Another agriculturally significant auxin is indole-3-butyric acid (IBA), a synthetic form of which is used in a variety of products available to boost propagation rates. If you have used a rooting hormone product on your cuttings to make clones, it is highly likely you were using IBA to initiate adventitious root production. Since IAA is not suitable for long-term packaging storage, the majority of commercial rooting hormone products contain either IBA or a synthetic auxin, such as NAA (1-Naphthaleneacetic Acid).

The concentration of auxins in a plant's roots and shoots determine how they react to gravity and light. The auxin in plant shoots cause them to grow away from gravity or upwards, while the auxins in roots cause them to grow towards gravity or downwards. For example, plant shoots typically grow towards light. In this scenario, the side of the plant that is not facing the light has a higher concentration of auxin. The shaded side grows longer as the auxin causes the cells to multiply, and hence the plant grows toward the light. Blue light is the most effective stimulant for shoot growth.

Knowing how auxins affect cannabis plants, and where auxins are primarily found within the plant, can help growers manipulate the way in which their plants grow. For example, removing the top growth tip or bud, which removes the IAA that that area of the marijuana plant was producing, gives the lower bud nodes room to multiply and develop larger. (This technique is called pinching-off, but in practice sharp objects should be used to remove the top growth tip, rather than pinching fingers.)

It is important to note that some synthetic auxins are used as herbicides. Oddly enough, these auxins cause the plant to have a rapid, uncontrollable growth spurt. The plant can not keep up and eventually dies.

There are four other classic types of hormones aside from auxins: cytokinins, gibberellins, ethylene, and abscisic acid, with new classes still being discovered and synthesized.


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