| Preliminary studies indicated that the development of wheat endosperm cells belongs to a programming cell death(PCD)progress,and waterlogging could accelerate the progress(Fan et al 2013).In order to describe the specific mechanism mentioned above,we took highly waterlogging tolerant cultivar Hua 8 and waterlogging susceptible cultivar Hua 9 as material in this study.The main results were as follow:1.The results of Evans Blue staning showed that,the PCD phenomenon can be observed in wheat endosperm cells after flowering 15 days under normal development,and the PCD progress can be accelerated after waterlogging,especially more significant in Hua 9 which is sensitive to waterlogging treatment.Results showed that starch grains and protein bodies were increased with the development of two varieties of wheat endosperm cell,and it could be accelerated after waterlogging.Nuclear degradation of Hua 8 and Hua 9 endosperm were occurred after flowering 12 d and 15 d under normal development,respectively.It could be aggravated by waterlogging,while occurred earlier in Hua 9 endosperm.2.Contents of MDA,O2-,H2O2,soluble sugar,soluble protein and proline could be increased at early development of Hua 8 endosperm under water stress.Compared with the control,SOD activity was increased by waterlogging treatment,and the POD activity showed the trend of first decrease and then rise with the devolpment of Hua 8 wheat endosperms,while the CAT activity showed a trend from rise to decline.Accroding to the isozymes electrophoresis technique,we found that a new band(SOD1)and two bands(CAT2,CAT5)added on SOD and CAT isozyme spectrogram of Hua 8 endosperm after waterlogging respectively,and activities of all CAT isozymes enhanced compared to control group.The water content of Hua 9 caryopsis was also decreased after waterlogging treatment,and contents of MDA,O2-,H2O2,soluble protein in Hua 9 endosperms were increased significantly after waterlogging treatment,while the activities of SOD and POD increased slightly.Unlike Hua 8,the CAT activity showed a trend from decline to rise then decrease.It showed little change on the activies of SOD isozymes in Hua 9 endosperm after waterlogging treatment,except the SOD2 activity showed increased after waterlogging treatment,and all kinds of CAT isozymes activities increased.3.With the development of endosperm cells,the fluorescence signals of tubulins gradually increased,and distributed along the cell membrane.In the early stage of the development of wheat endosperms,most of the tubulins distributed in amyloplasts and cytoplasmic vesicles.The number of colloidal gold particles in dorsal endosperm cells was significantly increased after flowering 12 days under waterlogging treatment.The colloidal gold particles were distributed in the mitochondria of dorsal endosperm cells after flowering 15 days,while distributed mainly around amyloplasts.The fluorescence signals of actins were also gradually increased with the development of endosperm cells.The number of colloidal gold particles in abnominal endosperm cells was significantly increased after flowering 12 days under waterlogging treatment,and distributed in the cytoplasm and cytoplasmic organelles,while mainly distributed in amyloplasts.The colloidal gold particles were distributed in the cytoplasm of dorsal endosperm cells after flowering 15 days,while decreased in mitochondrias and amyloplasts.Above all,the changes of physiological and biochemical characteristics of endosperm after waterlogging treatment differ from different moisture resistant wheat cultivars.The MDA and O2-content in both wheat endosperms were increased under waterlogging treatment,while the ability in clearing up oxygen free radical of Hua 8 endosperm is stronger than Hua 9,so that the PCD phenomenon induced by waterlogging in Hua 9 endosperm is earliar than Hua 8.After the waterlogging,the rapid accumulation of nutrients in amyloplasts,intracellular microtubule cytoskeleton as transport track,assists in endosperm cell life to reduce the damage caused by flooding.Cytoskeleton may also be involved in the flood emergency response stress,regulation of endosperm cell PCD process. |
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