Effect of Different Concentrations of Exogenous ZnONPs on the Heat Tolerance of Snapdragon
Using snapdragon seedlings as test materials,this study investigated the effects of foliar spraying of different concentrations(0,50,100,200 mg/L)of zinc oxide nanoparticles(ZnONPs)on the growth,chlorophyll content,osmotic regulation substances,and enzyme activity and related substances in the AsA-GSH cycle of snapdragon seedlings under day/night temperatures of 25℃/20℃,35℃/30℃,and 40℃/35℃stress,in order to explore the role of ZnONPs in alleviating heat stress in snapdragon seedlings.The results showed that under high temperature stress,the height,stem thickness,leaf length,leaf width,and biomass of snapdragon significantly decreased.Applying different concentrations of ZnONPs could alleviate the growth inhibition of snapdragon.Under 40℃/35℃stress,compared with the treatment of spraying 0 mg/L ZnONPs,the treatment of spraying 50-200 mg/L ZnONPs increased the total chlorophyll content and carotenoid content of snapdragon by 3.8%—7.7% and 4.9%—11.7%,respectively.The soluble sugar content and proline content of osmotic regulating substances increased by 12.7%—44.8% and 18.2%—32.9%,respectively.Under 40℃/35℃stress,the activities of ascorbate peroxidase(APX),dehydroascorbate reductase(DHAR),monodehydroascorbate reductase(MDHAR),and glutathione reductase(GR)in the AsA-GSH cycle of snapdragon continuously decreased.After spraying different concentrations of ZnONPs,the activities of APX,DHAR,MDHAR,and GR in snapdragon increased by 35.3%—86.3%,13.5%—24.6%,58.5%—81.5%,and 8.6%—19.7%,respectively.The content of ascorbic acid(AsA),glutathion(GSH),ascorbic acid/dehydroascorbate(AsA/DHA),and glutathione/reduced glutathione(GSH/GSSG)increased by 5.9%—11.7%,9.9%—16.5%,14.4%—31.1%,and 19.5%—37.7%,respectively,while the malondialdehyde(MDA)content,relative conductivity,O2-·production rate,and hydrogen peroxide(H2O2)content of snapdragon seedlings continued to decrease.The conclusion is that different treatments with ZnONPs can improve the heat tolerance of snapdragon,among which spraying 100 mg/L ZnONPs treatment has the best effect on improving the heat tolerance of snapdragon seedlings.
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