Specific Inhibition of Phototropism in Corn Seedlings

Abstract

Geotropism was used as a control for the specificity of potential inhibitors of phototropism by the coleoptiles of corn (Zea mays) seedlings. The compounds tested fall into 3 categories showing: no inhibition of either phototropism or geotropism (KCl); nonspecific inhibition of phototropism and geotropism (KCN); and specific inhibition of phototropism (KI, NaN3 and phenylacetic acid). Simultaneous irradiation of coleoptiles with phototropically inert light in addition to the phototropically active blue light also results in an inhibition of phototropism. Since azide, iodide and phenylacetic acid are known to interact with flavins while a simultaneous irradiation with a phototropically inert light may depopulate the 1st triplet state of flavins, the hypothesis that the photoreceptor pigment for phototropism in corn is a flavin was supported.