Inhibition of nitrite oxidizers by roots of grass.
A heat-labile substance in surface sterilized pieces of Hyparrhenia filipendula roots was toxic to nitrite oxidizers in a soil enrichment culture; it occurred all the year in the outer root tissues and in summer in the stele. Its action was bactericidal. It was probably water-soluble. There was no proof that the inhibitor was excreted by the grass roots in vivo or that it was responsible for the low concentration of mineral N in soil under grass.