Nitrate reductase activity in sugarcane leaves in function of variations in the assay conditions.

Abstract

The most appropriate conditions for in vitro nitrato reductase activity (NRA) assay in leaf tissue of two sugarcane varieties (NA 56 - 79 and CB 47 - 355) were studied. Above 50 mM NO-₃, the NRA declined considerably. Such effect of high KNO₃ levels on NRA was probably not related to the osmotic potential of the medium. In the absence of exogeneous NO-₃, the NRA was negligible. Maximal NRA was obtained at pHs 7,5 and 8,5 for the varieties CB 47-355 and NA 56- 79, respectively. Maximal reduction of nitrate to nitrite was observed at 32° C for NA 56-79 and between 32°C and 37° C for CB 47 - 355. The maximal NRA occurred in the +3, +4 and +5 leaf (fully expanded leaves).