Abstract:

The number of microorganisms from winter wheat rhizospheric soil under Cd2+ pollution (0.0, 5.0, 10.0, 20.0, 50.0, 70.0 mg/kg dry soil) was studied using pot experiment. The results indicated that the number of bacterial, fungi, nitrogen-fixing bacterial, and nitrosobacterial mainly decreased significantly (P<0.05), however the number of actinoplanes increased significantly (P<0.01) at three weeks after winter wheat seedlings emerged under Cd2+. At the same time, the ratio of bacterial in microorganism communities decreased and that of fungi and actinoplanes increased, however the total number of microorganism reduced, the Shannon-Wiener diversity index increased, and the ratio of fungi/bacterial rise under Cd2+. After seven weeks when winter wheat seedlings emerged, the number of bacterial and nitrosobacterial increased significantly (P<0.01) and the number of fungi, actinoplanes, and nitrogen-fixing bacterial decreased. At the same time, the ratio of bacterial in microorganism communities increased and that of fungi and actinoplanes decreased. The total number of microorganism went up, but the Shannon-Wiener diversity index reduced and the ratio of fungi/bacterial reduced insignificantly (P<0.01) under Cd2+. After twelve weeks when winter wheat seedlings emerged, the number of bacterial and fungi increased significantly (P<0.01) and that of actinoplanes, nitrosobacterial, and nitrogen-fixing bacterial mainly decreased. At the same time, the ratio of bacterial and fungi in microorganism communities increased and that of actinoplanes decreased. The total of microorganism mainly increased, the Shannon-Wiener diversity index mainly reduced and the ratio of fungi/bacterial changed unregularly under Cd2+. On the whole, the amount of microorganism decreased and the Shannon-Wiener diversity index increased under Cd2+ during early winter wheat seedling growth, but the amount of microorganism increased and the Shannon-Wiener diversity index decreased under Cd2+ during later seedling growth compared to 0.0 mg/kg dry soil.