| With the ever-increasing world population, rapid development of economy and global climate change, the living environment of plants is also changing greatly. In all of the adverse of non-biotic stresses to plant, drought is one of the factors that serious influences world agricultural production through affecting plants growth and development, gene expression, distribution and production quality. As a variety of eximious forage grass, Chamaecrista rotundifolia cv Wynn was introduced from Australian by the Fujian Agricultural sciences academy in 1987, and have become an important local legume forage crop resource since they grow successfully in the red soil area of the north Fujian Province. Whereas there have seen occurrence of frequent seasonal drought at the red soil area in recent years, and it has a serious impact on the mountain prataculture. Therefore, breeding of drought-tolerant varieties of legumes have been marked very important,agricultural ecology institute (Fujian Academy of Agricultural Sciences)bred a new radiant line (86134R1) of the Chamaecrista rotundifolia with adaptability, Compared with CPI86134,resistance and high yield characteristics which have shown significant differences through eradiating of 60Co-γray. As an improved high-quality green manure and forage crop, the"86134R1"line is worth intensive study and wide promotion.The drought stress simulation of Polyethylene glycol-6000 (PEG-6000) and soil drought stress were combined in this experiment to systematically study the impact of drought stress on Chameacrista rotundifolia(86134R1) seed germination, plant growth, biological yield, nutritional quality and proteomics, to explore the physiological metabolism, feeding value and protein changes and performance under drought stress.(1) In this study, PEG-6000 solution was used to simulate the drought condition. The CPI86134 and 86134R1 seeds were treated with six different stress gradients of normal water supplication (contrast), 5%, 10%, 15%, 20%, and 25% (w/v, PEG-6000), respectively. Parameters the targets such as seed germination rate, termination energy, relative termination energy, germination index and vigor index were comprehensively assessed to establish the drought resistant characters of the legume. The results showed that seed germination were significant at the different concentrations of PEG-6000. The inhibition of seed germination increased with an increase in drought stress. The seed germination inhibitions of CPI86134 and 86134R1 as affected by drought stress were different. Compared with CPI86134, at the early period of germination, the germination rate, relative germination rate, germination energy, the relative germination energy and germination index of 86134R1 have shown a higher value.(2) With increasing drought stress, the biomass gradually decreased. After 20d of drought stress, the biomass of CPI86134 decreased by 16.76%, 37.63% and 52.79%, respectively, as compared to the control, and that of 86134R1 decreased by 15.46%,31.31% and 43.04%. For forage, the crude protein and crude fiber contents were two important indices of forage quality. An increase in crude protein content and a decrease in the crude fiber content played a key role in improving forage quality. In this study, the crude protein content of Chamaecrista rotundifolia showed a downward trend along with increasing drought stress. The cellulose content increased, and the crude fiber content also decreased along with the decrease in water content. The content of water soluble vitamins presented an irreversible growth tendency along with the increasing drought stress. The crude protein content and the crude fiber content of 86134R1 were higher than CPI86134 at different moisture levels, and the cellulose content was aways lower than CPI86134.The nutritional quality of 86134R1 was high and less influenced by drought whether under normal moisture condition or drought stress.(3) The resistant response of Chamaecresta rotundifolia to drought stress increased with increasing drought stress. Chamaecrista rotundifolia leaf relative water contention (RWC) decreased while leaf water retention capacity increased. The contents of free proline (Pro) accumulated and soluble protein decreased. Under drought stress, the production ratio of reactive oxygen radical increased, which led to membrane lipid peroxidation. Malonidaldehyde (MDA) content increased; at the same time, the activities of cell protective enzymes (SOD, POD, and CAT) increased in order to eliminate free radicals and reduce the level of membrane lipid peroxidation. However, when the stress duration lasted to the 15th day, the activities of cell protective enzymes POD and CAT decreased, which illustrated that continuous of drought stress reduced or inactivated the activities of the active oxygen scavenging enzymes. The two strains of Chamaecrista rotundifolia CPI86134 and 86134R1, showed certain drought tolerance in the course of drought stress. Under the same level and same time stress, the leaf relative water content, water holding capacity, chlorophyll content, free proline content, soluble protein content and POD, SOD, CAT activities of 86134R1 were higher than CPI86134. After comprehensive assessment, the relative value of targets which were determined in this study could be used as general identification of Chamaecrista rotundifolia's drought resistance. The determined drought resistance of 86134R1 was stronger than CPI86134.(4) In this study, it was found that 21 proteins expressed differentially and all of them were identified by mass spectrometry and bioinformatics. By appraising these proteins, it was realized that drought stress affected the plant genetics and metabolism.in DNA, RNA synthesis of transcription, DNA binding, transporting ATP,and participation in energy conversion to impact and adjustment the energy metabolism in plants, affecting plant photosynthetic carbon metabolism by directly impacting on carbon assimilation rate of photosynthesis; affecting the normal protein synthesis in plant by influencing protein synthesis ,translation, and enzyme-related protein interactions; affecting the nitrogen metabolism by promoting the plant nitrogen assimilation. In addition, the results also showed that drought stress affected plant pigments, synthetics of aroma-related enzymes, plant disease resistance, cell power, synthesis of phytohormones, electron transport, photophosphorylation, and free radical scavenging. Through the changes in protein spots, enzyme protein and structural proteins were the focus of its impact. By comparing CPI86134 and 86134R1,it was found that rapamycin kinase, disease resistance protein, retrotransposon protein, and putative Ty3-gypsy subclass were the enzymes only found in 86134R1 leaves. In drought stress, basic metabolism of plants maintenance of balance, and resistance to adversity, induced by a number of new enzyme or protein are subject to interference. The inductions of these new proteins were possibly closely related to enhancing the plant drought performance. |
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