The effect of infection with tobacco etch virus on the rates of respiration and photosynthesis of tobacco leaves

Unlike tobacco mosaic virus, which increases the respiration of tobacco leaves Within an hour of their being inoculated, a virulent strain of tobacco etch virus did not change respiration rates until leaves showed external symptoms. The respiration rates of inoculated or systemically infected leaves with symptoms rose to 40 % above that of healthy leaves, three times the increase produced by tobacco mosaic virus. The increased respiration rate occurred at all times of the year and was maintained through the life of the leaves. Leaves infected with tobacco etch virus and showing symptoms had a photosynthetic rate 20 % lower than that of healthy leaves.