[Decarboxylation of indolyl-acetic acid in relation to phototropism inAvena coleoptiles].

3-Indolyl[1-(14)C]acetic acid (IAA) or 1-naphthyl[1-(14)C]acetic acid (NAA) was applied toAvena coleoptiles and the output of(14)CO2 was measured afterwards. In the dark the applied IAA was decarboxylated by the coleoptiles. The decarboxylation rate increased for 3h after addition of IAA. Under the same conditions NAA was not decarboxylated by the coleoptiles. When the coleoptiles were illuminated before application of IAA, the kinetics of(14)CO2-output did not change, a finding which shows that the IAA decarboxylating enzyme system is not induced or activated by light. In order to study decarboxylation of IAA in relation to phototropism coleoptiles were illuminated unilaterally during the measurement of(14)CO2-output. Blue light and white light within the range of phototropically active intensities do not cause any increase of the IAA decarboxylated rate after the onset of illumination. There is a difference between NAA and IAA concerning the behaviour in vivo and in vitro. NAA is decarboxylatedin vitro as well asin vivo. IAA, however, is found to be photosensitive invitro but seems to be protected against light destruction invivo.