The Effect of Tungstate on Nitrate Assimilation in Higher Plant Tissues

Tungstate is not only a competitive inhibitor of molybdate uptake and utilization in Azotobacter vinelandii, but also inhibits growth of this organism when nitrate or nitrogen is the sole nitrogen source. The effect of tungstate on the formation of active nitrate reductase in suspension cultures of tobacco XD cells and intact barley shoots was examined. In both cases tungstate prevented the formation of active enzyme. Because of its broad biological spectrum of action, tungstate may be used to selectively prevent nitrate reduction. It will now be possible to examine the regulation of nitrate uptake and of other steps of the nitrate assimilation pathway in higher plants without the complications introduced by the functioning of the pathway. 13 references, 2 figures, 2 table.