Peroxidase activities in the floral tissues of Tradescantia clone BNL 4430 treated with maleic hydrazide alone, X rays alone, or in combinations.

Abstract

Changes in peroxidase activity in young inflorescences of Tradescantia clone BNL 4430 were investigated after treating with maleic hydrazide (MH) alone, X rays alone, or MH and X rays in combinations. MH is a promutagen known to be activated into a mutagen in plant cells. The treatments with MH were conducted for 4 h at a fixed concentration of 1 mM, and the X-ray doses applied were 768 to 882 mGy. For the combined treatments, X rays were delivered either 20 h before starting, or 2 or 20 h after completing the 4-h MH treatments. The treatments with MH alone and X rays alone both increased peroxidase activity, as compared with the controls. The combined treatments of delivering X rays 20 h before starting the MH treatments resulted in marked increases in the activity of this enzyme. However, the increases in peroxidase activity after the combined treatments of X-raying 2 h after completing the MH treatments were small, and the activity rather decreased by X-raying 20 h after completing the MH treatments. These results are consistent with our earlier findings that clear synergistic effects of MH and X rays in inducing somatic pink mutations in the stamen hairs of clone BNL 4430 were detected by treating with X rays before MH treatments, whereas antagonistic effects of MH and X rays were often observed by delivering X rays during or after MH treatments (Xiao and Ichikawa, 1995). It is therefore highly likely that peroxidase is certainly involved in the activation of MH into a mutagen, and that the increases and decreases in peroxidase activity after different combined treatments are related to the occurrences of synergism and antagonism, respectively, between MH and X rays.