Antioxidative Capacity and Electrolyte Leakage in Healthy Versus Phytoplasma Infected Tissues of Euphorbia coerulescens and Orbea gigantea

The present study reports on reactive oxygen species (ROS), antioxidant enzyme activities, electrolyte leakage and levels of abscisic acid (ABA) in healthy and phytoplasma infected (PI) tissues of Euphorbia coerulescens and Orbea gigantea. Histochemical staining for ROS indicated that PI tissues possess higher levels of hydrogen peroxide (H2O2) rather than superoxide (O2 ·-) as compared with healthy tissues in both plant species. The results indicated that superoxide dismutase (SOD) is not playing an important role in eliminating O2− in PI tissues. This was confirmed by a significantly decreased activity of SOD and a non-significant difference in O2 ·- content in PI tissues as compared to healthy tissues in both plant species. Peroxidase (POX) activity was significantly decreased while polyphenol oxidase (PPO) significantly increased in PI tissues compared with healthy tissues in both plant species. PI tissues was associated with a significant increase in catalase (CAT) and ascorbate peroxidase (APX) activity in E. coerulescens and a significant increase in glutathione reductase (GR) activity in O. gigantea. However, other antioxidant enzymes were lower compared with the healthy tissues. In both plant species, electrolyte leakage was significantly increased in PI tissues compared to healthy tissues.ABA level was decreased in PI tissues as compared to healthy tissues.