Effects of Exogenous Nitric Oxide and Putrescine on Drought Resistance of Strawberry Seedlings
The present study aimed to investigate the effects of exogenous nitric oxide(NO)and putrescine(Put)on enhancing drought resistance of strawberry seedlings.'Benihoppe'strawberry was used as experimental material,and 10％PEG-6000 was used to simulate drought stress.The pharmacological experiments were performed by foliar application of distilled water(H2O),Put,sodium nitroprusside(SNP)as a NO donor,DL-α-difluoromethylarginine(DFMA)as an inhibitor of arginine decarboxylase synthesis pathway of Put,and NG-Nitro-L-arginine Methyl Ester(L-NAME)as an inhibitor of nitric oxide synthase(NOS).The results showed that the drought stress significantly decreased the net photosynthetic rate(Pn),transpiration rate(Tr),stomatal conductance(Gs),and maximum photochemical efficiency of PS Ⅱ(Fv/Fm)in strawberry leaves,but led to a dramatic increase in malondialdehyde(MDA)levels in both roots and leaves of strawberry plants.Compared with drought stress alone,the hydrogen peroxide(H2O2)levels decreased by 25.57％and 16.62％in leaves,and by 35.38％and 40.09％in roots on the fifth day of treatment for Put and NO,respectively.Exogenous Put treatment induced a significant increase in proline(Pro)content and catalase(CAT)activity,however,exogenous NO treatment significantly boosted the activities of superoxide dismutase(SOD),peroxidase(POD),and CAT in leaves and roots.Additionally,both Put and NO treatments can markedly increase the activities of NOS and diamine oxidase(DAO),reduce polyamine oxidase(PAO)activity.As a result of increased NOS and reduced PAO activities,the application of both Put and NO on the leaves promoted the accumulation of NO,spermidine(Spd),and spermine(Spm),enhanced the levels of endogenous hormones,osmoregulation substances,and signaling molecules,as well as antioxidant enzyme activities in strawberry plants,thereby improving the drought resistance of strawberry seedlings.
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