pb2+/Cd2+处理对冬小麦幼苗根际微生物种群数量的影响

摘要

采用盆栽试验培育冬小麦幼苗,待幼苗生长3周、7周和12周时,收集根系土,进行根际土壤细菌、真菌、放线菌、亚硝化菌和自生固氮菌数量的测定.结果表明:冬小麦幼苗生长3周时,pb2+/Cd2+对根际细菌、自生固氮菌和亚硝化菌表现为显著(P＜0.05)抑制作用,平均抑制率分别为20.41％ ～49.79％、26.62％～76.99％和87.15％～95.88％,而真菌、放线菌数量主要表现为增加,平均增加率分别为0.31％～38.88％和19.58％～113.64％,但微生物总数减少,而多样性指数增加,真菌/细菌比值升高；幼苗生长7周时,放线菌、自生固氮菌和亚硝化菌数量主要表现为增加现象,平均增加率分别为18.16％～19.72％、13.71％～24.59％、2.09％～519.29％,真菌数量降低,平均降低率为9.59％～39.46％,细菌数量在低浓度时增加,高浓度时减少,微生物总数增加,多样性指数主要表现为降低,真菌/细菌比值降低；幼苗生长12周时,pb2+/Cd2+处理下细菌数量极显著(p＜0.01)增加,真菌、放线菌、固氮菌和亚硝化细菌数量降低,平均降低率分别为12.05％～44.66％、1.94％～ 15.51％、12.44％～55.72％和97.88％～99.00％,微生物总数主要表现为增加,多样性指数降低,真菌/细菌比值极显著降低(P＜0.01).pb2+/Cd2+处理对冬小麦幼苗根际各类微生物数量、微生物总数和多样性指数及真菌/细菌比值影响显著(p＜0.05),且微生物多样性指数的变化主要取决于放线菌数量的变化；pb2+/Cd2+对冬小麦根际固氮菌和亚硝化菌数量的影响规律不稳定,预示着pb2+/Cd2+污染将影响其根际土壤N的固定和转化能力,且N源的可利用率不稳定.%Pot experiments were conducted to culture winter wheat seedlings. The rhizosphere soil was collected to determine the number of bacteria, fungi, actinoplanes, nitrogen-fixing bacterial, and nitrosobacterial when seedlings had grown for three weeks, seven weeks, and twelve weeks, respectively. The number of bacteria, nitrogen-fixing bacteria, and nitrosobacteria in Pb27Cd2+ significantly (p<0.05) decreased by 20.41 %-49.79%, 26.62%-76.99%, and 87.15%-95.88%, respectively, and the number of fungi and actinoplanes increased by 0.31%-38.88% and 19.58%-113.64%, respectively at the third week. Moreover, the total number of microorganisms decreased and the diversity and the ratio of fungi / bacteria increased in Pb2+/Cd2+ at the third week. When winter wheat seedlings grew for seven weeks, the number of actinoplanes, nitrogen-fixing bacteria, and nitrosobacterial mainly increased by 18.16%-19.72%, 13.71%-24.59%, and 2.09%-519.29%, respectively and that of fungi decreased by 9.59%-39.46%. Moreover, the number bacterial increased in low doses of Pb2+/Cd2+ and decreased in high doses of Pb2+/Cd2*. At the same time, the total number of microorganisms increased and the diversity and the ratio of fungi/bacteria decreased in the stress of Pb2+/Cd2+. When winter wheat seedlings grew for twelve weeks in Pb22+/Cd2*, the number of bacteria significantly (p<0.01) increased, and the number of fungi, actinoplanes, nitrosobacterial, and nitrogen-fixing bacterial decreased by 12.05%-44.66%, 1.94%-15.51%, 12.44%-55.72%, and 97.88%-99.00%, respectively. At the same time, the total of microorganism mainly increased, the diversity reduced, and the ratio of fungi / bacterial significantly (p<0.01) decreased. The effect of Pb2+/Cd2* on the number of rhizosphere microorganisms, diversities, and the ratio of fungi/bacteria was significant (p<0.05) and the shift of the diversity was mainly due to the change of the number of actinoplanes. The irregular change of nitrosobacterial and nitrogen-fixing bacteria indicated that the nitrogen fixed capacity of soil in the rhizosphere of winter wheat seedlings was affected by Pb2+/Cd2* in the future. Moreover, the utilization of nitrogen resource was also affected.