Abstract

The effects of gramine on the bacterium Pseudomonas syringae in culture and on barley leaf disks were studied. Gramine prolonged the lag phase of growth and decreased the size of the population at stationary phase at concentrations similar to those found in barley leaves. Gramine (2 mM) increased the basal respiration rate ca 21 % and inhibited bacterial growth. Higher gramine concentrations decreased both coupled and basal respiration rates. The bacteria caused 80% damage (necrotic area) on leaf disks without gramine, but they caused only 36% damage on leaf disks with natural gramine. It is suggested that gramine, which is present in epidermis and mesophyll parenchyma cells, may decrease infection and damage in barley leaves.