Respiration of tobacco leaves infected with different strains of potato virus X

A study was made of the effects on respiration by four strains of potato virus X varying in the severity of symptoms they produce on tobacco leaves. No effects on respiration rates were observed in either inoculated or systemically infected but symptomless leaves, even though there was a significant increase in virus concentration during the experimental period. However, a significant increase was detected in any leaves on which symptoms developed, this increase being directly correlated with the severity of symptom expression. At the same time a great increase in virus concentration was found. Measurement of respiration patterns of single local lesions showed that an increase in respiration occurred each time a chlorotic and necrotic ring formed in the tissues. The use of metabolic inhibitors indicated that metabolic controls are different in the leaves infected with latent or mild strains, as compared to those infected with the severe, necrotizing strains.