Antioxidant metabolism in coffee (Coffea arabica L.) plants in response to nitrogen supply

Nitrogen (N) is the main element required for plant development. N fertilization interferes directly in N content in tissues, antioxidant systems, chlorophyll content and photosynthesis. We investigated the action of three levels of N (0, 150 and 300 kg N ha(-1)) in coffee (Coffea arabica L.) cv. Catuai Vermelho IAC 44 leaves of plants during distinct fruit development stages (from pinhead drop to dried fruit). Leaf N content, net photosynthesis, chlorophyll content, total soluble protein and the activities of catalase, superoxide dismutase, guaiacol peroxidase and ascorbate peroxidase were analyzed. Leaf N content, net photosynthesis, chlorophyll and protein content increased significantly with N supply (N deficient plants exhibited visual symptoms of chlorosis). Antioxidant enzymes showed increased specific activities during fruit development, and decreases with N fertilization, being higher in absence of N. We identified two bands of Mn-SOD with increased activities and one of Fe-SOD, but they did not exhibit high SOD activity remaining essentially constant. Curiously, Cu/Zn-SOD isoenzymes were not detected, despite the fact that they are frequently abundant in plants. A relationship between N fertilization and antioxidant enzyme activities were founded in coffee leaves during fruit development indicating high activity of enzymatic antioxidant system during the coffee fruit ripening stage.