Auxins
Auxins are a group of plant hormones or growth regulators that are naturally produced by plants and exhibit certain traits of morphogenetics. They support cell division, stem and root growth, and are found in the tips of roots and branches. In the course of a plant's life cycle, auxins play a crucial role in coordinating a variety of growth and behavioral activities, including cell division and differentiation, fruit development, cutting root formation, prevention of lateral branching (apical dominance), and defoliation (abscission). They can also greatly influence plant orientation by promoting cell division on one side of the plant in response to sunlight and gravity.
Applications
Auxin is a growth-promoting substance that helps in the elongation of shoots. There are four key effects of auxin on plant growth.
- Stimulation of Branch Elongation: Growth hormone positively affects gibberellin, which promotes cell elongation. This increases the length of the plant. Essentially, gibberellin and growth hormone increase the distance between nodes and thus between branching points.
- Control of Seedling Orientation: Whether new shoots grow in the soil or toward the light depends on the location of the growth hormones and how they affect the cells within the plant. Growth hormones move down and laterally away from the light by gravity. Cells grow more in areas of the plant where there is a high concentration of growth hormones.
- Stimulation of Root Branching: When growth hormone is applied to a cut stem, the stem will root at the cut.
- Promotes Fruit Development: Growth hormone in flowers promotes maturation of the ovary wall and facilitates the step of full fruit development.
However, in high concentrations, auxins can prevent the development of lateral shoots. Auxins have the ability to act as both pesticides and plant growth regulators. The herbicide 2-4-D is a phytochemical-based pesticide that is intended to cause dicotyledonous plants to grow rapidly and uncontrollably, ultimately killing the plant.