青蒿素对根瘤菌化感效应研究

目的:研究黄花蒿释放的化感物质——青蒿素对根瘤菌的化感效应.方法:试验选用快生型和慢生型2株菜豆根瘤菌,在青蒿素质量浓度为0,20,40,80 mg·L-的根瘤菌液体培养基中培养,分别测定在不同青蒿素浓度下根瘤菌的生长曲线、碳源利用率、胞外蛋白酶、酸性磷酸酶和根瘤的固氮酶活性.结果:青蒿素极显著的抑制根瘤菌的繁殖生长,在培养液中加入40 mg.L-1青蒿素培养8h,根瘤菌的数目不到正常培养的一半.随着青蒿素浓度的增加,根瘤菌对蔗糖和葡萄糖的利用速率显著降低,青蒿素妨碍根瘤菌对碳源的吸收利用可能是抑制它们繁殖生长的重要原因之一.此外,根瘤菌胞外蛋白酶和磷酸酶的活性随青蒿素浓度的增加而降低,说明黄花蒿释放的青蒿素可能抑制根瘤形成,并干扰类菌体和寄主细胞之间的能量供需关系.固氮酶活性(y)与培养基中的青蒿素浓度(x)可用y=e-ax+b表示.当培养基中的青蒿素浓度达到48 mg·L-1时,固氮酶的活性几乎为0.因此,在形成根瘤后,土壤中的青蒿素也可能使根瘤丧失固氮活性.结论:在黄花篙种植的土壤中,它们释放的青蒿素对根瘤菌繁殖生长、根瘤形成和生物固氮的抑制作用可能进一步影响菜豆的氮源供应和生长发育,造成减产.

Studies on allelopathic effect of artemisinin on rhizobium

Two strains of bean rhizobia, Rhizobium vigna 01 (slow-growing Rhizobium) and Rh. vigna 03 (fast-growing Rhizobium),were adopted to study allelopathic effect of artemisinin on the rhizobia. The results showed a significant inhibition of the reproduction and growth of rhizobium by artemisinin. After about 8 hours by adding 40 mg·L^-1 artemisinin into the culture medium, the number of rhizobia was less than half of those in normal culture. The utilization of sucrose and glucose by rhizobia decreased significantly as the concentration of artemisinin increased in the culture medium, which could be one of the main reasons for the inhibition of reproduction and growth of rhizobia by artemisinin. In addition, the activities of extracellular protease and acid phosphatase released from rhizobia decreased significantly as the concentrations of artemisinin increased. Artemisinin refluxed from Artemisia annua could thus inhibit the formation of root nodules and interfered with energy supply and reception between bacteroid and host cells. y=e^-ax+b reflected the relationships between nitrogenase activities (y) and concentrations of artemisinin (x). In the culture medium with 48 mg·L^-1 of artemisinin, nitrogenase activities were about zero, resulting in the inactivation of nitrogenase in nodules formed. In general, artemisin in A. annua grown soils may inhibit the reproduction and growth of rhizobia, nodule formation and nitrogen biofixation, leading to less nitrogen supply, poor growth and development, and low yields of beans.