Genotypic Variation for Shoot N Concentration and Response to Water Deficits in Soybean
- C. Andy King and
- Larry C. Purcell *
For soybean [Glycine max (L.) Merr.], reports differ as to the degree to which accumulation of shoot biomass and N are inhibited by water deficit (WD). Our first objective was to evaluate responses of shoot biomass and shoot N to WD for soybean genotypes from diverse genetic backgrounds. The second objective was to determine if the severity of WD affected the response of N accumulation relative to biomass accumulation among genotypes. In a 2-yr field study of 15 genotypes, shoot N concentrations ranged from 25 to 33 mg N kg−1 for plants from well-watered (WW) treatments harvested around 60 d after planting, and N2 fixation accounted for 68% of the N accumulated. Following a 16- to 22-d WD period, shoot N concentrations were similar to that of WW plants for genotypes with low WW N concentrations but decreased for genotypes with high WW N. As a result, the shoot N concentration range among genotypes decreased following WD stress. In a greenhouse study where essentially all of the plant N accumulated was from N2 fixation, shoot N concentration increased across a range of WD levels for six genotypes with low WW N concentrations but decreased for two genotypes with high WW N. These results indicate that changes in shoot N concentration in response to WD depend on both the inherent N concentration of a given genotype and the severity of the WD stress.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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