Effect of temperature on peroxidase activity, isozyme patterns and concentration of threadlike particles in tristeza—infected citrus plants

Abstract

Peroxidase activity (PA) in various tristeza-infected citrus varieties was significantly higher than in healthy controls. In leaves and bark of Egyptian sour lime and Palestine sweet lime, PA was correlated with symptom severity and content of threadlike particles (TLP). In infected roots of Egyptian sour lime, there was an increase in PA but TLP content was minimal.

Temperatures above 22°C caused a gradual decrease in PA in both healthy and infected leaves of Egyptian sour lime trees. At 36°C, no differences in PA between infected and healthy samples were observed. In these plants TLP content was minimal and almost no symptoms were observed.

No new isozymes were found in various host tissues infected with tristeza, psorosis, exocortis or impietratura. One isozyme appeared earlier in tristeza-infected plants than in healthy controls, suggesting that isozymes associated with senescence are activated at an earlier stage in infected plants than in healthy ones.