Abstract
The addition of 1 mM cysteine, 2 % casein and 1010 polyvinylpyrrolidon (PVP) as protectants in the extraction (NRA) solution produced the highest nitrate reductase activity (EC 1.6.6.1) in tomato plants (Lycopersicon esculentum Mill. cv. Carmelo). The extraction medium was buffered at pH 7.7. NRA and nitrate concentration were higher in roots than in leaves. The opposite was observed for the insoluble-N fraction. A decrease of NRA in leaves and roots after 6 h of boron starvation was observed. The decay of the enzyme activity was higher in roots than in leaves. NRA was not affected by high concentrations of ammonia and glutamine in the incubation medium. Alterations observed in the concentrations of N-fractions might suggest an indirect effect of B deficiency on nitrate uptake and translocation of different Nsolutes in tomato plants.
Published Version
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