What does auxin mean?
Auxin is any of a group of plant hormones — the most important being indole-3-acetic acid (IAA) — that regulates growth and development. Produced mainly in the tips of young shoots and leaves, auxin travels downward through the stem, stimulating cell elongation and coordinating processes such as bending toward light (phototropism), upward root growth, and apical dominance, whereby the main central stem suppresses branching below it. Gardeners exploit this effect by pruning growing tips to encourage bushier plants. Synthetic auxins are widely used in agriculture as rooting compounds for cuttings and as herbicides. The term derives from the Greek 'auxein', meaning 'to increase'. Though technical, auxin is essential vocabulary in botany and horticulture.
nounAny of a class of plant hormones that promote cell elongation and growth, particularly indole-3-acetic acid (IAA) produced naturally in the tips of shoots.
- Any of a class of plant hormones that stimulate cell elongation, root formation, and other growth responses; specifically indole-3-acetic acid (IAA), produced chiefly in shoot tips.
"The gardener pruned the top of the hedge, knowing that removing the growing tip would reduce auxin production and encourage bushier side growth."
"Auxin accumulates on the shaded side of a stem, causing those cells to elongate and the plant to bend toward the light."
"Commercial rooting powders contain synthetic auxins that encourage cuttings to develop new roots."
Used when referring to multiple molecules of the hormone or to different members of the auxin class of plant hormones.
"Synthetic auxins such as 2,4-D are widely deployed as selective herbicides."
Auxin is why your houseplant bends toward the window — Charles Darwin's own experiments on this 'bending' phenomenon laid the groundwork for its discovery decades later.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of auxin
The word 'auxin' was coined in the early twentieth century from the Greek 'auxein', meaning 'to grow' or 'to increase', reflecting the substance's role in promoting plant growth. The name emerged during the period when scientists were identifying the chemical messengers responsible for phototropic responses first studied experimentally by Charles Darwin in the 1880s. It shares its Greek root with related botanical terms such as 'auxetic' and 'auxanometer', an instrument for measuring plant growth.
How auxin is actually used
A technical term used primarily in botany, horticulture, agriculture, and biology education. It appears rarely in casual conversation but frequently in scientific writing and gardening literature. Plural 'auxins' refers to multiple members of the class or different types.
Easily confused with auxin
A toxin is a poisonous substance harmful to living organisms, whereas auxin is a natural plant growth hormone.