Severe leaf-vein infestation upregulates antioxidant and photosynthetic activities in the lamina of Ficus religiosa

Pipaldiplosis pipaldiplosis forms galls on the midribs and veins of the leaves of Ficus religiosa, but how these leaf-vein infestations can affect the antioxidant defense mechanism and photosynthetic performance of the interveinal lamina is unknown. Therefore, we investigated ROS, antioxidant potential and photosynthesis in the lamina of F. religiosa infected by leaf-vein gall P. pipaldiplosis. The H2O2 content rose rapidly upon mild infection and thereafter decreased with increasing the intensity of infection. Severe leaf-vein infestation significantly up-regulated the activities of superoxide dismutase, catalase and guaiacol peroxidase. Correlation between H2O2 and antioxidant enzymes clearly indicates that ROS plays a crucial role in plant defense mechanism against P. pipaldiplosis. Leaf-vein galls remarkably altered the minimum and maximal fluorescence intensities, density of active reaction centers, light harvesting efficiency, electron transfer rate, dissipation energy, maximum quantum yield of primary PSII photochemistry, quantum yield of electron transport and performance index on cross section basis in the lamina of infected leaves. The results indicate that during the mild infection, reaction centers act as energy dissipating units (inactive form) to prevent photoinactivation and reconvert to energy conserving units (active form) during the severe infection. More severe infection results in complete obstruction of leaf-veins which ultimately cause death of the leaves. In conclusion, P. pipaldiplosis-induced oxidative stress decreases photosynthesis in leaf lamina during the mild infection. In contrast, the rate of photosynthesis increased during the severe leaf vein infestation to compensate the loss of photo-assimilates caused by P. pipaldiplosis.

Automated summary

Leaf-vein gall infestation affects the antioxidant defense mechanism and photosynthetic performance of Ficus religiosa leaves. Mild infection leads to oxidative stress and decreased photosynthesis, while severe infection increases photosynthesis to compensate for lost photo-assimilates.