Nitrogen limitation compromises the realization of yield potential in cereals more than any other single factor. In
rice, the world's most important crop species, the assumption has long been that only ammonium-N is efficiently
utilized. Consequently, nitrate utilization has been largely ignored, although fragmentary data have suggested that
growth could be substantial on nitrate. Using the short-lived radiotracer 13N, we here provide direct comparisons
of root transmembrane fluxes and cytoplasmic pool sizes for nitrate- and ammonium-N in a major variety of Indica
rice (Oryza sativa), and show that nitrate acquisition is not only of high capacity and efficiency but is superior to
that of ammonium. We believe our results have implications for rice breeding and molecular genetics as well as
the design of water-management and fertilization regimes. Potential strategies to harness this hitherto unexplored
N-utilization potential are proposed.