| Soybean is the important economic crop. In soybean, the yield that reduced by drought induced is the total caused by other abiotic stresses. So the research on drought resistant of soybean is a hot spot on botany studying. And the researches will be a very significance in theory and practice.The seven lines of soybean including Jindoul7, Jidoul2, Zho-nghuang30, Zhonghuang39, Jindou23, Jindoul9and Youheil were used to screen the materials. Seven soybeans were treated with0,5,10,15,20%PEG. The relative ion leakage markedly increased, and the relative water content significantly decreased. Jindou23and Jindou17had the best drought resistance, Jindou19had the worst drought resistant, and the drought resistance of4varieties was Jindoul2, Jindou30, Jindou39and Youheil, orderly. So we choose Jindou23and Jindoul9in further research because there were the most differences between them. The relative ion leakage markedly increased in soybean leaf under different concentrations of PEG treatments for48h, and the relative water content significantly decreased. The Jindoul9leaves appeared wilting in20%PEG treatment, so we choose15%PEG treatment in our research. The relative ion leakage and O2-?content of Jindou23leaf under15%PEG treatments for0,24,36,48,60h was lower than that in Jindoul9leaf. And the contents of relative water and soluble sugar were higher than in Jindoul9leaf. These results showed that Jindou23in drought stress could maintain normal osmotic pressure to reduce the water loss of cell and the damage of plant. Meanwhile, the chlorophyll contents decreased in both Jindou23and Jindou19. But the chlorophyll content in Jindou23deceased the less than that in Jindou19. The data indicated that Jidou23could maintain the relative better photosynthesis in drought stress to alleviate the adverse effect of drought stress.The MDA content accumulated in Jindou23root under the same concentration of PEG treatment for48h was marked higher than that in Jindou19root and the difference between the MDA contents in two soybeans reached the very significant level (p<0.01). The MDA content in Jindou23and Jindou19roots under25%PEG treatment was markedly increased and the difference between in two soybeans had almost no difference (p>0.05). Others, the effects of differents concentrations of PEG treatments on the relative water contents in both soybean roots were almost no difference. So20%PEG was used in next experiments. The MDA contents in both Jindou23and Jindou19root under differents concentrations of PEG treatments were increased with the time treatments extension. And the differences of MDA contents in between Jindou23and Jindoul9showed the very siganificance at24h,36h,48h and60h treatments (p<0.05). Therefore,0,24and48h were as the trcament times in further study. The Pro content and the soluble sugar content in Jindou23and Jindoul9under drought stress were increased and their contents in Jindou23were higher than that in Jindou19. Further-more the H2O2content in Jindou23under drought stress was lower than that in Jindou19. So Jindou23in drought condition did better in containing osmosis and produce less H2O2than jindou19and reduced the damage to root by drought induced.Under drought condition, the exogenous application of NaHS (H2S donor) could effectively relieve the effects of PEG on the MDA content in two soybean roots. Furthermore, the effects of NaHS on drought stress showed a dose-dependent.40μM NaHS was the optimal concentration. So in fouther research, we choose40μM NaHS. The exogenous application of NaHS in drought condition could effectively increase the Pro content and the soluble sugar content, and decrease the H2O2content in these two soybean roots to maintain osmosis, produce less H2O2and protect the soybean seedlings. Meanwhile, the exogenous application of NaHS could increase APX, CAT, POD and SOD activities in the two soybean roots and eliminate the ROS level to protect soybean under drought condition. |
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