Effect of Parthenium hysterophorus on nitrogen-fixing and nitrifying bacteria

Abstract

Root or leaf extract of Parthenium hysterophorus L. inhibited the growth of Rhizobium phaseoli and Azotobacter vinelandii. Similar inhibition was caused by parthenin, caffeic acid, and anisic acid, the important inhibitors isolated from the weed. Leghaemoglobin content in the root nodules of the bean plants grown in soil mixed with Parthenium leaf was reduced significantly as compared with the control. Nitrosomonas activity was progressively lowered with decreasing distance from the plant and also in leaf- or root-mixed soil. Leaf and root leachate, parthenin, anisic acid, vanillic acid, and fumaric acid inhibited nitrite production to varying degrees.