摘要
The post-embryonic growth of the Arabidopsis thaliana root system can be modified by different types of stress,such as sublethal concentrations of metals,which may induce the production of reactive oxygen species(ROS).In this study,the effects of different concentrations of potassium chromate(K_(2)CrO_(4))on the distribution and relative quantity of hydrogen peroxide(H_(2)O_(2))were determined in primary and adventitious roots in A.thaliana HyPer line seedlings.This line has a biosensor that specifically reports H_(2)O_(2) levels within tissues as fluorescence.Primary root growth was inhibited at 100μM Cr(VI);in contrast,adventitious root formation was induced over the main root growth axis.These structures proliferated from 100-160μM Cr(VI),and much higher concentrations(180-200μM)of K_(2)CrO_(4) were required to affect their growth.The H_(2)O_(2) distributions were observed in the columella and lateral root cap of primary roots of plants grown in medium lacking dichromate,but following the development of toxicity symptoms,H_(2)O_(2) changed its distribution to the meristem and differentiation zones.Conversely,adventitious roots had comparable H_(2)O_(2) distribution patterns in untreated plants and those exposed to Cr(VI)supplementation.Thus,differential H_(2)O_(2) distribution correlates with the resistance of adventitious roots,but not primary roots,to dichromate and underlies cell reorganization at the apex to support growth.
