Enhancement of phytoalexin accumulation in cultured plant cells by oxalate

Oxalate (0.2-2.0 mM), a compound which induces systemic resistance, can enhance secondary product synthesis 10-fold in cotton cell suspension cultures. To accomplish this, cells require induction with a low level (10 μ of protein per 15 ml incubation) of elicitor from Verticillium dahliae. In the presence of oxalate, these minimal concentrations of elicitor required to induce phytoalexin formation did not have any necrotic effect on the growth of the cotton cultures. Even at higher concentrations of elicitor (80 μg of protein per 15 ml incubation), oxalate was able to reduce the detrimental effect of elicitor on cell suspension growth rates indicating oxalate may have a direct effect on growth. Therefore, in cotton cell suspension cultures the addition of an enhancer of elicitor-induced phytoalexin formation allows optimum stimulation of secondary metabolite formation without affecting cell mass accumulation.