Studies on the Auxin Metabolism of Some Cereal Crops under Germination and Seedling Growth : III. Some experiments in vitro on the IAA-destroying system in the wheat seedling

[摘要] The mechanism of IAA-destroying system in the wheat seedling is discussed in this paper. The IAA-oxidase activity in the crude homogenate of dark-grown wheat seedlings is masked by the existence of the IAA-oxidase inhibitors in the homogenate, but the addition of H2O2 to the homogenate removes this masking and the high IAA-oxidase activity becomes visible. Then, the ferulic acid, one of the IAA-oxidase inhibitors, H2O2 and the dialysed enzyme solution from whet coleoptile were mixed and incubated for detecting the changes in UV-absorption spectrum of the mixture. As a result, it was observed that the ferulic acid in the mixture was oxidized by the H2O2-peroxidase system. The masking of IAA-oxidase activity in the crude homogenate is also removed by the addition of riboflavin (FR) or flavin mononucleotide (FMN) and light instead of H2O2, but the enhancement of IAA-destroying action by FR (FMN) and light is observed without enzyme preparation in the mixture. This sesult suggests that it is the non-enzymatic destruction of IAA. It was also observed that this non-enzymatic destruction of IAA by FR (FMN) and light is inhibited by IAA-oxidase inhibitors, phenolics, contained in wheat seedlings. From the above-mentioned results, the authors have supposed the scheme of IAA-destroying system in wheat seedling as shown in Fig. 5.

[学科分类] 农业科学（综合）