The Respiration of Tobacco Leaves in the 20‐hour Period Following Inoculation With Tobacco Mosaic Virus

The effect of infection with tobacco mosaic virus on the respiration rates of detached tobacco leaves in the period immediately after inoculation differed in plants grown at different times of the year. During winter, infection increased respiration rates, and in summer decreased them. In winter‐grown plants, increasing the light intensity during the period before inoculation decreased respiration rates after infection. Extending the day length for winter‐grown plants did not alter the effect of infection on respiration. Respiration rates began to change in less than 1 hr. after inoculation and are unlikely to be associated with the formation of new virus.