auxín

Auxin is a class of plant hormones that plays a crucial role in various aspects of plant growth and development. It is one of the five major classes of plant hormones, along with gibberellins, cytokinins, abscisic acid, and ethylene. Auxins are primarily responsible for the regulation of cell elongation and differentiation, which are essential for processes such as phototropism, gravitropism, and apical dominance.

The term "auxin" was coined by French botanist François Dherbecourt in 1897, derived from the Greek word "auxein," meaning "to increase." The first identified auxin was indole-3-acetic acid (IAA), which was discovered by Japanese scientist Fujio Watanabe in 1926. Since then, numerous other auxins have been identified, including indole-3-butyric acid (IBA), naphthalene acetic acid (NAA), and 2,4-dichlorophenoxyacetic acid (2,4-D).

Auxins are synthesized in the root and shoot meristems, and they are transported throughout the plant via the vascular system. The primary role of auxins is to promote cell elongation, which is essential for the growth of stems, roots, and leaves. In addition, auxins play a crucial role in the regulation of apical dominance, a process by which the growing tip of a plant inhibits the growth of lateral buds.

Auxins also influence plant responses to environmental stimuli, such as light and gravity. For example, auxins promote phototropism, the growth of plants towards light, by inhibiting the growth of cells on the shaded side of the plant. Similarly, auxins play a role in gravitropism, the growth of plants towards or away from gravity, by regulating the distribution of auxins within the plant.

Auxins are also involved in the regulation of plant defense mechanisms, such as the induction of systemic acquired resistance (SAR). In response to pathogen infection, plants produce salicylic acid, which is transported throughout the plant and induces the production of defense-related genes, including those involved in the synthesis of auxins.

In agricultural applications, auxins are used as growth regulators to promote plant growth and development. They are also used in the production of fruit and vegetables, where they help to regulate the size and shape of the produce. However, the use of auxins in agriculture has been controversial due to concerns about their potential environmental impact and human health risks.