A light-induced auxin-inhibitory substance, indolylacetonitrile (IAN), was isolated from light-grown cabbage (Brassica oleocea L.) shoots. The IAN content in cabbage shoots increased in response to light. Cabbage hypocotyl elongation is inhibited by 10-5M of IAN in 90 min but promoted after 48 hr. Light-induced growth inhibition is caused by the denudation of 3- indolylmethylglucosnolathe (IMG) to IAN which is, in turn, converted to the growth hormone indole-3-acetic acid (IAA).
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