Exudation of nitrogenous compounds by clover and ryegrass in sterile and non-sterile micro-lysimeters

Abstract

Exudation of ammonium and amino acids from white clover and perennial ryegrass roots was investigated in a microlysimeter system. A higher proportion of ammonium than amino acids was observed in the exudate. The most abundant amino acids in both clover and ryegrass exudates were serine and glycine. There was no correlation between amino acid profiles of exudates and root extracts: asparagine was the major amino acid in clover roots and glutamine in ryegrass roots. The presence of micro-organisms in the growth medium had no effect on the amounts of ammonium, serine and glycine measured in exudates, while amounts of glutamate and aspartate were increased in non-sterile clover exudates. It is proposed that bacteria have no substantial effect on the N-exudation in sand by young clover and ryegrass plants.