Experiments to examine the significance of ammonia evolution from barley seedlings infected with the powdery mildew fungus, Erysiphe graminis f.sp. hordei

Experiments using intact seedlings and detached leaves failed to confirm previous reports that ammonia gas is evolved from barley leaves during the establishment of infection by the powdery mildew fungus Erysiphe graminis f.sp. hordei.

In the experiments using intact seedlings infection did, however, lead to greater concentrations of ammonium nitrogen in the senescing leaves and, in one experiment, the subsequent evolution of ammonia gas from these seedlings. Losses of nitrogen as ammonia gas from crops are probably small, but it is possible that under some circumstances they may represent a significant proportion of the otherwise unexplained nitrogen losses and hence be important in experiments which aim to study the nitrogen balance of crop-soil systems.