Effect of Fungicide (Maneb) on Antioxydant System and Carbon Assimilation in Leaves of Sorghum Plants

The effects of Maneb on antioxidant potentials and carbon assimilation were studied in leaves sorghum (Sorghum bicolor L.) plants (C₄ species). The plants were sprayed by three doses; recommended dose (2.5 g/L), twice and three times higher at 25, 40 and 55 days after planting (DAP). The leaves were harvested at 5, 10 and 15 days after treatment (DAT) and proteins content, activities of antioxidative enzymes catalase (CAT), guaiacol peroxidase (POD), glutathione reductase (GR), glutathione-S-transferases (GST) and glyoxalase I (GlyI) as well as activity of key enzyme in primary fixation of atmospheric CO₂ phosphoenolpyruvate carboxylase (PEPC) and chlorophyll content were estimated. The protein content was found increased under Maneb treatment. While the POD and GR activities appear unaffected, CAT activity increased at 10 and 15 DAT. Whereas the GST activity increased significantly in plants treated with 5 g/L at 5 DAT and in plant exposed to 2.5 g/L at 10 DAT. The activity and proteins levels of GlyI were increased progressively with increasing fungicide treatment. This increase was more pronounced at 5 DAT; being 1.7 and 1.5 fold for 5 and 7.5 g/L, respectively. However, both PEPC activity and chlorophyll content seem unchanged in presence of fungicide even at high concentration. These results indicate that sorghum leaves have a well-developed systems of protection from carbonyl stress.