Auxins are a class of plant hormones that play a fundamental role in various aspects of plant growth and development. These hormones are essential for coordinating processes like cell elongation, root and shoot growth, and the response to light and gravity. Here are key points about auxins:

• Cell Elongation: One of the primary functions of auxins is to stimulate cell elongation, primarily in the stem and coleoptiles (the protective sheath covering the emerging shoot) of plants. This elongation is crucial for plant growth, as it enables them to reach light sources and compete for sunlight.
• Tropisms: Auxins are involved in various tropisms, including phototropism (growth towards light) and gravitropism (response to gravity). In phototropism, auxins accumulate on the shaded side of a stem or shoot, promoting cell elongation on that side and causing the plant part to bend toward the light source.
• Role in Root Growth: In roots, auxins inhibit cell elongation and promote root growth. They help the roots navigate through the soil to access water and nutrients by growing in the direction of higher moisture and nutrient concentrations.
• Propagation: Auxins are used in horticulture and agriculture to stimulate root development in cuttings and promote the growth of adventitious roots in plant propagation.
• Apical Dominance: Auxins are responsible for apical dominance, which means that the terminal bud at the top of a shoot suppresses the growth of lateral buds. This allows the plant to allocate resources efficiently.
• Seed Germination: Auxins are involved in seed germination, helping the embryonic shoot (plumule) break through the seed coat and grow towards the soil surface.
• Synthetic Auxins: Synthetic auxins like indole-3-acetic acid (IAA) and 2,4-dichlorophenoxyacetic acid (2,4-D) are used as herbicides to control weed growth.
• Transport: Auxins are transported within the plant from the apical meristem (the growing tip) downwards through the stem. This transport is typically polar, moving from the apical meristem towards the base.