1. A plant hormone that promotes cell elongation and growth, especially in stems and roots.
Usage: biology; commonly used in botany and plant science

Examples

• Auxin is produced in the tip of a plant shoot and moves downward to regulate growth.
• The concentration of auxin determines whether a plant root grows downward or upward.
• Scientists use synthetic auxin to stimulate root development in plant cuttings.
• Auxin helps plants respond to light by promoting cell elongation on the shaded side.
• High levels of auxin can inhibit growth in lateral buds, keeping the plant's main stem dominant.
• Gardeners sometimes apply auxin-based rooting hormones to help new plants establish themselves.