Distribuicao da assimilacao de nitrato e de matéria seca em plantas jovens de café cultivadas em diferentes níveis de nitrogenio

Nitrate assimilation and plant growth were examined in young coffee plants cultivated in sand in the greenhouse. The plants were supplied with nutrient solutions containing 3.75, 7.5 and 15mM of nitrate. The distribution among the roots and shoots was assessed. Leaf area and leaf dry weight increased with nitrate concentration, while root dry weight and leaf pair number remained constant. The in vivo nitrate reductase activity, assayed with and without exogenous nitrate in root tips was higher than in recently expanded leaves, and increased with nitrate concentration. The highest nitrate reductase activity, assayed with exogenous nitrate, revealed limitation to nitrate assimilation by substrate availability in both leaves and roots. Shoot growth was higher than root growth as a function of increasing nitrogen levels