Alfalfa and tobacco cells react differently to chitin oligosaccharides andSinorhizobium meliloti nodulation factors

Alfalfa (Medicago sativa L.) suspension cultures respond to yeast elicitors with a strong alkalinization of the culture medium, a transient synthesis of activated oxygen species, and typical late defence reactions such as phy toalexin accumulation and increased peroxidase activity. The alkalinization reaction as well as the oxidative burst were also observed when tobacco (N icotiana tabacum L.) cell-suspension cultures were treated with yeast elici tors. Depending on the degree of polymerization, N-acetyl chitin oligomers induced the alkalinization response in both plant cell-suspension cultures, while only tobacco cell cultures developed an oxidative burst. Suspension- cultured tobacco cells responded to Sinorhizobium meliloti nodulation facto rs with a maximal alkalinization of 0.25 pH units and a remarkable oxidativ e burst. In contrast, addition of Sinorhizobium meliloti nodulation factors to suspension-cultured alfalfa cells induced a slight acidificatiton of th e culture medium, instead of an alkalinization, but no oxidative burst.