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Comparative kinetic analysis of ammonium and nitrate acquisition by tropical lowland rice: implications for rice cultivation and yield potential

Published online by Cambridge University Press:  01 March 2000

H. J. KRONZUCKER
Affiliation:
Department of Plant Sciences, University of Western Ontario, London, ON, Canada, N6A 5B7 Soil and Water Sciences Division, International Rice Research Institute (IRRI), P. O. Box 933, Manila, Philippines
A. D. M. GLASS
Affiliation:
Department of Botany, University of British Columbia, Vancouver, BC, Canada, V6T 1Z4
M. Y. SIDDIQI
Affiliation:
Department of Botany, University of British Columbia, Vancouver, BC, Canada, V6T 1Z4
G. J. D. KIRK
Affiliation:
Soil and Water Sciences Division, International Rice Research Institute (IRRI), P. O. Box 933, Manila, Philippines
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Abstract

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.

Type
Research Article
Copyright
© Trustees of the New Phytologist 2000

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