| Waterlogging is one of the most common natural disasters.Much more continuous rainy days are the main reason for waterlogging.A long-term waterlogging can inhibit the growth of wheat,decrease the factors of yield,furthermore result in the death of wheat.So it is necessary to find ways to improve wheat waterlogging tolerance.In our experiment wheat seeding was pretreated with exogenous ethylene and H2O2 in order to explored the physiological characteristics and mechanism of alleviation during waterlogging.We also sprayed exogenous ethylene and H2O2 after anthesis.after harvest we kept the seeds for germination and growth under waterlogging,explored the physiological characteristics and mechanism of alleviation,and provide a theoretical basis of improving wheat waterlogging tolerance.The main results were summarized as follows:1.Wheat pretreated with ethylene and H2O2 showed more secondary roots than non-treatment under waterlogging,as well as root length.These results suggested that ethylene and H2O2 pretreatment can promote roots growth under waterlogging.Ethylene and H2O2 pretreatment can up-regulate ACS2 significantly,but little effects on NADPH oxidase.Ethylene treatment up-regulate MT while H2O2 down-regulate MT.Waterlogging induced PCD in roots and caused aerenchyma formation,but with ethylene and H2O2 pretreatment there were much more PCD and aerenchyma formation in roots.These suggested that ethylene and H2O2 pretreatment can significantly induce aerenchyma formation during waterlogging.2.Compared with non-treatment,ethylene and H2O2 pretreatment induced endogenous ethylenen and H2O2 accumulation.Ethylene and H2O2 pretreatment showed higher SPAD and photosynthetic rate under waterlogging.After waterlogging,in the wheat which was pretreated with ethylene and H2O2 showed less ROS accumulation and MDA content while the antioxidant enzyme SOD,CAT,APX,GR activity was higher than non-treatment under waterlogging.These results indicated that ethylene and H2O2 pretreatment reduced membrane lipid peroxidation and increased the antioxidant enzyme activity,improved the wheat waterlogging tolerance.3.There is no difference between ethylene and H2O2 treatments and control of the seed size in seed germination of neat generation,but in germination index and mean germination time,H2O2 treatment showed a lower level.During germination,starch content consumption was faster and the amylase activity was higher and the soluble sugar content increased faster in the seed with ethylene and H2O2 treatments in last generation during filling stage.For the seminal root growth,the seed with ethylene and H2O2 treatments in last generation showed faster root elongation than the seed with no treatment.But this advantage disappeared gradually when wheat grew up in normal condition.Interestingly,when waterlogging appended the wheat with ethylene and H2O2 treatments showed long root length,more secondary roots and more arenchyma formation.4.Membrane lipid peroxidation ROS,MDA was decreased while antioxidant enzyme SOD,CAT,APX,GR activity and rubisco content was more and chlorophyll fluorescence was higher in the wheat seedlings with ethylene and H2O2 treatments in last generation during filling stage under waterlogging.In summary,exogenous ethylene and H2O2 pretreatments promoted wheat differentiation of secondary roots,increased root elongation,and induced PCD to form aerenchyma,maintained the gas exchange between shoot and root during waterlogging,and reduced the damage caused by waterlogging.After waterlogging membrane lipid peroxidation increased slightly and antioxidant enzyme activity increased significantly and as well as SPAD,Photosynthesis in the wheat which was treated with exogenous ethylene and H2O2.Another experiment found that seed germination characteristics were effected by ethylene and H2O2 treatments in last generation during filling stage.The roots of treated seeds elongated faster than the non-treated,besides,when the treated seeds grew up,the roots of them elongated more and developed more secondary roots,as well as arenchyma,and decreased the membrane lipid peroxidation,increased the antioxidant enzyme activity and photosynthesis under waterlogging.In addition,the seeds treated with waterlogging in last generation during filling stage grew better than treated with exogenous ethylene and H2O2. |
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