Dynamics of Shoot Nitrogen and Ureide Concentrations During Crop Development Among Diverse Soybean Genotypes.

Previous research indicates that sensitivity of dinitrogen fixation to water-deficit stress differs among soybean genotypes and that genotypic differences may be influenced by concentrations of total N and ureides in plant shoot under well-watered conditions. It has also been documented that shoot N and ureide concentrations are influenced by soybean developmental stage. This research evaluates the relationship between shoot nitrogen and ureide concentrations during crop development for 22 MG IV soybean genotypes from diverse genetic backgrounds. Under conditions of low soil N, preliminary results indicate little change in shoot N and ureides in response to developmental stage between late vegetative and early seedfilling. During the first half of seedfill, shoot ureides increased approximately three fold and, concomitantly, total shoot N declined approximately 30 percent. This trend reversed during late seedfill coinciding with the onset of senescence.