A new inhibitor of auxin-induced growth, 5-chloro-6methoxy-2-benzoxazolinone, from light-grown shoots of maize seedlings

A new inhibitor of auxin-induced growth was isolated from light-grown shoots of maize seedlings (Zea mays L.) and its chemical structure was determined by spectral data as 5-chloro-6-methoxy-2-benzoxazolinone. It inhibited the auxin-induced growth of coleoptile sections of Avena seedlings, and the growth of shoots and roots of maize seedlings at concentrations higher than 1 and 3 and 10 μmol/L, respectively; the doses required for 20 % growth inhibition were 14.7, 15.8 and 292 μmol/L, respectively. The activity of the inhibitor was higher than that of its analogue, 6-methoxy-2-benzoxazolinone. These results suggest that a new growth inhibitor, 5-chloro-6-methoxy-2-benzoxazolinone, may be involved in the inhibition of auxin-induced growth, which may be one of the causes of inhibition of the growth of maize seedlings.