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为探索苏云金芽胞杆菌(Bacillus thuringiensis,Bt)对重金属镉胁迫下水稻(Oryza sativa)种苗生长及生理生化指标的影响,本研究分别采用直接测量法、表观观察法和紫外分光光度法测定其对镉胁迫下水稻种苗苗高、根长、水稻种子发芽率、剑叶枯黄率与褐斑率以及叶绿素含量的影响。利用原子力显微镜观察镉处理前后的苏云金芽胞杆菌表面的变化。结果表明,经过镉处理的Bt菌的表面出现一些颗粒物,说明镉在细菌表面存在吸附的过程,暗示该菌在水稻田镉污染生物修复中具有潜在的应用前景。此外,在镉胁迫下,水稻种苗的生长受到抑制,其抑制作用随镉胁迫浓度的增大而增强。在50和400 mg/L Cd2+处理组中,根长与苗高的Cd处理与Cd+Bt处理的差异不显著(P>0.05),表明,镉胁迫下Bt菌处理的水稻种苗苗高和根长变化较小。在100和400 mg/L Cd2+处理组中,叶绿素a和叶绿素b的Cd+Bt处理较Cd处理显著提高(P<0.05);在200 mg/L Cd2+处理组中,Cd+Bt处理较Cd处理水稻种子发芽率显著提高(P<0.05)。施用Bt菌前后镉对水稻枯黄率与褐斑率的影响研究发现,50和400 mg/L Cd2+处理组中,Cd+Bt处理较Cd处理枯黄率显著下降(P<0.05);50 mg/L Cd2+处理组中未出现褐斑,400 mg/L Cd2+处理组中Cd+Bt处理较Cd处理褐斑率显著下降(P<0.05),表明,经Bt菌处理后水稻的剑叶枯黄率与褐斑率均低于未加菌的处理。本研究结果表明,Bt菌可以通过对重金属镉的吸附,减少水稻土中的游离镉的含量,从而减少了水稻种苗对重金属镉的吸附量,缓解镉对水稻的胁迫作用,并提高幼苗叶绿素的含量。本研究为Bt菌株在实际镉污染农田中的应用提供理论基础。
In order to explore the effects of Bacillus thuringiensis (Bt) on the growth and physiological and biochemical indexes of rice (Oryza sativa) seedlings under the stress of heavy metal cadmium, the direct measurement method, the visual observation method and the ultraviolet spectrophotometry Effects of cadmium stress on seedling height, root length, seed germination rate, flag leaf withered rate and brown spot rate and chlorophyll content in rice seedlings. Atomic force microscopy was used to observe the changes of Bacillus thuringiensis surface before and after cadmium treatment. The results showed that some particles appeared on the surface of Bt-cadmium-treated bacteria, indicating that there was adsorption of cadmium on the surface of bacteria, suggesting that the bacteria had potential application in the bioremediation of cadmium pollution in paddy fields. In addition, the growth of rice seedling was inhibited under cadmium stress, and its inhibition increased with the increase of cadmium stress. There was no significant difference between Cd treatment and Cd + Bt treatment for root length and seedling height in 50 and 400 mg / L Cd2 + treatment groups (P> 0.05), indicating that seedling height and Root length changes smaller. Cd + Bt treatments of chlorophyll a and chlorophyll b were significantly increased (P <0.05) in 100 and 400 mg / L Cd2 + treatment groups compared with Cd treatment; Cd + Bt treatment was more effective than Cd treatment in 200 mg / L Cd2 + treatment group The germination rate of rice seeds increased significantly (P <0.05). The effect of cadmium on browning rate and brown spot rate of rice before and after the application of Bt was studied. The results showed that the browning rate of Cd + Bt was significantly decreased (P <0.05) compared with Cd treatment at 50 and 400 mg / L Cd2 + treatment (P <0.05) Brown spots were not found in Cd2 + treatment group, but the Cd spotting rate in Cd + Bt treatment group was significantly decreased (P <0.05) compared with Cd treatment in 400 mg / L Cd2 + treatment group, indicating that browning rate and browning rate The spot rate was lower than the non-added treatment. The results showed that Bt could reduce the amount of free cadmium in paddy soil through the adsorption of heavy metal cadmium so as to reduce the amount of heavy metal cadmium adsorbed by rice seedlings and alleviate the stress effect of cadmium on rice and increase the chlorophyll Content. This study provides a theoretical basis for the application of Bt strain in the actual cadmium contaminated farmland.