Exogenous Nitric Oxide Alleviates Oxidative Damage And Promotes Lateral Roots Growth Of Wheat Seedlings Under Drought Stress

Nitric oxide (NO) is a novel regulation material of plant growth, which particiates inthe physiological processs of growth, development, tolerance to biotic and abiotic stress ofplants. In this study, the wheat was selected as experiment material and 15ï¼…PEG was usedto mimic drought stress, then the effects of NO donor sodium nitropusside (SNP) on theleaves and root growth of wheat seedlings under drought stress were investigated, and therelated mechanism was analyzed in the process of actions of SNP at adaptive concentration.Results showed that the membrane permeability, malondialdehyde (MDA) content,generation rate of superoxide anion (O₂^.-) and hydrogen peroxide (H₂O₂) content were allincreased during the period of drought stress for 4ds. After addition of 0.1 mmol/L or 0.5mmol/L SNP, there existed different effects in wheat seedling leaves under drought stress.Application of 0.5 mmol/L SNP exhibited a similar effect as drought stress on the changesof membrane lipid peroxidation products; Addition of 0.1 mmol/L SNP could markedlydecreased generation rate of O₂^.- and MDA content etc, inhibited LOX activity, promotedSOD activity and changed the activities of CAT. This showed that the membrane lipidperoxidation-related enzymes were regulated in different manners with application of SNPat low concentration: LOX activity was always inhibited; SOD activity was progressivelypromoted; the activities of CAT was firstly inhibited and then promoted. This indicated thatthe alleviation of membrane lipid peroxidation induced by drought stress in wheat seedlingleaves was due to the SNP-induced variation of LOX, SOD and CAT activities in leaves ofwheat seedlings under drought stress.It was found that that the LR growth of wheat seedlings grown normally was alsopromoted by the treatmentwith PEG plus SNP at adaptive concentration, and 25μmol/L was the adaptive concentration of SNP. By application of CPTIO, this LR promotion wasconfirmed to NO actions. It was further tested that NO-induced LR and root hairdevelopment of wheat seedlings with PEG-treatment was mediated by jasmonates (JAs).Because NDGA is a special inhibitor of LOX, a crucial JAs synthesis enzyme, that theaddition of NDGA affected the endogenous JAs content and lateral roots growth mediatedby JAs was regulated by LOX. Two wheat (Yangmai No. 158 cv., sensitive to drought;Yumai No. 18 cv., tolerant to drought) seedlings grown in the dark were treated with 15ï¼…polyethylene glycol (PEG-6000, to mimic drought stress) and sodium nitroprusside (SNP)at different concentration (0, 25, 50, 100, 200, 400μmol/L), it was found that lateral root(LR) development of the wheat seedlings under drought stress was promoted by NO andthe promotion role of NO was not only related to the concentration of its donor SNP, butalso related to the wheat species with different tolerance to drought stress. And LOXactivity expressed changes in same conditions, it implied that LOX played roles in theprocess. 200μmol/L SNP was adaptive tO promote LR development of drought-sensitivewheat seedlings, and 100μmol/L SNP was adaptive to promote that of drought-tolerantwheat seedlings. These results indicated that the application of SNP could promote LRgrowth of wheat seedlings under drought tress and drought-sensitive wheat seedlingsneeded higher concentration of SNP to promote LR growth than drought-tolerant ones, thissuggested that the concentration of SNP added for NO application under drought conditionslied on the sensitivity of plant materials to drought stress. All results suggested that thedifference of action concentration of exogenous NO was due to the difference of growthperiods and conditions and species of plant materials, and the NO application of adaptiveconcentration could alleviate membrane lipid peroxidation of leaves and promote rootgrowth of wheat seedlings subjected to drought stress to enhance tolerance of wheatseedlings to drought stress.