Abstract
Physiological effects of alternaric acid, a toxic compound produced by Alternaria solani on hypersensitive cell death of potato cells were studied. Treatment of potato shoot slices with 50μM alternaric acid depolarized more than half of the respiration-dependent component of membrane potential. Depolarization of the component was almost completed when treated with 100μM alternaric acid. In these treatments, the diffusion potential was not affected at an early stage after treatment. In potato tuber slices treated with alternaric acid, cell death was delayed when potato cells were penetrated by an incompatible race of Phytophthora infestans, though the growth of intracellular hyphae was not affected, at least, until 7hr after inoculation. These results suggested that the toxic compounds, which are produced by a parasitic fungus, help its infection by prolonging the time interval between penetration and death of the penetrated cell of its host plant.
