Nitrate Reduction in the First Leaf and Roots of Barley Seedlings Grown in Sand and in Culture Solution

The in vivo method has been used to determine activity of nitratereductase in Hiproly and Proctor barley. Differences in activitybetween the cultivars were small and less than those due togrowing conditions. Activity in plants grown in culture solutionwas greater than that for sand-grown plants, especially in theroot The in vivo method gave values for nitrate reductase activitywhich are less than those found by the in vitro method, andevidence is presented to show that the in vivo method underestimatesthe rate of formation of organic nitrogen in barley seedlings.It is shown that significant nitrate reductase activity occursin roots but it is nevertheless concluded that the main siteof nitrate assimilation is in the leaves of this material.