The effect of light wavelength on the susceptibility of plants to virus infection

Plants exposed for 24–72 h to light of different wavelengths differed in their subsequent susceptibility to virus infection. French bean leaves were less susceptible to infection by tobacco necrosis virus and Nicotiana glutinosa leaves were less susceptible to infection by tobacco mosaic virus when previously exposed to blue or red light than when exposed to green light. These differences were most pronounced at low energy levels. Leaves exposed to each kind of light were less susceptible than those kept in darkness.