(ethene) A gaseous hydrocarbon, formula C2
, that is produced in small quantities by many plants and that can be considered to act as a plant growth substance. The production of ethylene is frequently stimulated by *auxins
and the ethylene so produced acts, by a feedback mechanism, to inhibit auxin synthesis. Ethylene production also increases after wounding and exposure to disease. Ethylene may enhance an auxin response but it normally inhibits longitudinal growth and causes radial expansion of tissues. It can promote flowering in certain species, e.g. pineapple (Ananas comosus), and speeds up the ripening of fruit, an effect that has been put to commercial use in the citrus industry. Other effects mediated by ethylene include: the induction of epinasty; the induction of root hairs; the stimulation of seed germination in certain species; the promotion of leaf abscission; and the inhibition of auxin transport.
The route of ethylene synthesis in plants is uncertain though the amino acid methionine has been suggested as a precursor.