Physiological Response And Mechanism Of Regulation By Endogenous Nitric Oxide And Hydrogen Sulfide In Chinese Cabbage Under Selenium Stress

Selenium?Se?has been becoming an emergent pollutant in the agricultural environment.In order to explore the variation of Nitric oxide?NO?and Hydrogen sulfide?H₂S?and the mechanism of Se-induced stress responses in Brassica rapa,pharmacy test and fluorescent probe technique are used to find the correlation among NO,H₂S,ROS and root length.This result will contribute the environmental assessment of Se pollution and studying how to improving plant resistance on excess Se.The results are shown below:Firstly,chlorophyll and water content in Brassica rapa increased under lower concentration of Na₂SeO₃ and they decreases distinctly when exposed to higher concentration of Na2SeO3,while MDA has an opposite trend.This phenomenon means that selenium has a role of protection to plant at a fit concentration.In this experience,the fresh weight of all treatments is lower than that of the control which may be result of plant seeding has a poor resistance to Se.Another result is that the Se content are different in root,leaf and stem,the raw of Se content from highest to lowest is root,leaf and stem.Secondly,in order to study how to induces reactive oxygen species?ROS?burst and role of NO in this process,some signs are recorded and analysed the relationship amomg NO,root length and ROS content,even the NADPH oxidase.The results indicates that Se-induced faster accumulation of NO than ROS.Both NO and ROS accumulation were positively correlated with Se-induced inhibition of root growth.The removal of NO by L-NMMA?Tungstate and cPTIO could alleviate Se-induced expression of Br Rbohs coding for NADPH oxidase and the following ROS accumulation in roots,which further resulted in the amelioration of Se-induced oxidative injury and growth inhibition.Thirdly,in this work,a self-developed specific fluorescent probe?WSP-1?was applied to track endogenous H₂S in situ in the roots of Brassica rapa under Se stress.Se-induced root growth stunt was closely correlated with the inhibition of endogenous H₂S generation in root tips.Se stress dampened the expression of most Br LCDs and Br DCDs homologues in the roots of Brassica rapa.The increase in endogenous H₂S by the application of H₂S donor NaHS could significantly alleviate Se-induced ROS over-accumulation,oxidative impairment,and cell death in root tips,which further resulted in the recovery of root growth under Se stress.However,dampening the endogenous H₂S could block the alleviated effect of NaHS on Se-induced phytotoxicity.And also,the increase in endogenous H₂S resulted in the enhancement of GSH in Se-treated roots.Finally,the endogenous H₂S are detected in Brassica rapa root which are treated with Se,L-NMMA,Tungstate,and cPTIO,and it get rising after NO content decrease.It is means that NO maybe is an upstream signaling which regulate the H₂S production.