Nitrate Reductase Activity of Grain Sorghum Leaves as Related to Yields of Grain, Dry Matter, and Nitrogen¹

Abstract

Eleven grain sorghum ( Sorghum bicolor L. Moench) hybrids were grown in the field and growth chamber. Leaf blade samples were assayed by in vitro and in vivo procedures for nitrate reductase activity (NRA) to i)termine NRA of the hybrids, ii) examine relationships between NRA and grain and N yields, and iii) determine whether NRA of growth chamber‐grown plants are indicative of those of field‐grown plants. Among hybrids, differences in yields of grain, dry matter, and grain protein and in in vitro NRA were significant though comparatively small. Seven hybrids had similar N input: accumulation ratios while four had lower ratios. This variation in N input:accumulation ratios, precludes the use of NRA, as assayed here, as a criterion for screening grain sorghum cultivars for N accumulation ability. Also, NRA values of young growth chamber‐grown plants were not indicative of those of field‐grown plants.