EARLY RESPONSES DURING PLANT-BACTERIA INTERACTIONS IN TOBACCO CELL-SUSPENSIONS

Bacteria that induce a hypersensitive response in tobacco leaves initiate a net uptake of extracellular H+ and a net increase in extracellular K+ in tobacco suspension cells. Other studies have shown that these interactions also result in a transient increase in lipid peroxidation and O2- production. The relationships between these early plant responses were studied simultaneously using suspension-cultured tobacco cells and compatible, incompatible, and saprophytic bacteria. The bathing medium was monitored during a 6-h period for pH, conductivity, [K+], and luminol-dependent chemiluminescence. In all bacterial treatments, an immediate increase in chemiluminescence and pH occurred within 30 min after addition of the bacteria. After about 2 h a second increase in pH, conductivity, [K+], and chemiluminescence occurred with incompatible bacteria. The first response appears nonspecific, while the second response appears to depend on the host/pathogen incompatibility.