| Popis: |
Light affects assimilation of nitrate via nitrate reductase in many ways. Two prominent examples are: an effect on uptake and movement of nitrate between storage and metabolic pools; and production and distribution of reducing power and generation of carbon skeletons via photosynthesis. Nitrate reductase activity (NRA) correlates more closely with nitrate flux into leaf tissue than leaf nitrate concentration. The possibility that nitrate “flux” through a pool may regulate NRA fits well with the postulation that NO3 − exists in “metabolic” (active) pools, and “storage” (inactive) pools, where only the active pool is available for induction of NRA and for use as a substrate. The existence of “storage” and “metabolic” pools has been demonstrated in tobacco cells (Heimer and Filner, 1971; Ferrari et al., 1973), corn roots (Aslam and Oaks, 1975) and etiolated barley leaves (Aslam et al., 1976). |
