Anatomical and physiological aspects of coffee seedlings (Coffea arabica L.) with brown eye spot (Cercospora coffeicola Berk. & Cook.) cultivated with silicic acid

Abstract

Our objective was to verify how silicic acid can influence physiological and anatomical characteristics of coffee (Coffea arabica L.) seedlings inoculated with Cercospora coffeicola Berk. & Cook.. The treatments were six silicic acid doses amended to the soil (0, 0.5, 1, 2, 4 and 6 g kg ^–1 of soil) using a complete randomized block experimental design with four replicates. The experimental unit was composed of 12 coffee seedlings from the cultivar Catuaí Vermelho IAC 99. We evaluated the leaves by their chlorophyll a, b, carotenoids and lignin content as well as by the presence of epicuticular wax. The photosynthetic potential was evaluated in seedling with and without  symptoms of brown eye spot in the highest silicic acid dose (6.0 g kg^-1) and control. Transversal stem cuts were performed for measurements of the epidermal, cambium, xylem, phloem and spongy parenchyma thickness. The content of leaf pigments and lignin as well as the stem’s anatomical characteristics were not influenced by the increasing silicic acid amendment. The presence of epicuticular wax was observed in leaves of plants grown in the 2g and 6g silicic acid. The highest silicic acid dose showed the lowest photosynthetic potential capacity in seedlings without symptoms of brown eye spot.