Auxin, << AWK sihn, >> is the name of a group of hormones that help control plant growth. Plant embryos, young leaves, and the tips of stems and roots produce auxins that influence the growth of different parts of plants. Auxins play an important role in plant tropisms (bending movements). For example, the stems or leaves of many plants bend toward light. Such movement, called positive phototropism, occurs because auxins accumulate on the dark side of the stem or leaf stalk, causing the cells on that side to lengthen. This elongation gradually bends the stem or leaf toward the light.
It is almost impossible to extract large amounts of auxins from plants. Artificially produced auxins are widely used in weedkillers. They are also used to promote root formation on plant cuttings, to stimulate the growth of seedless fruits, and to prevent sprouting in stored potatoes and onions.
