Measurement of Instantaneous Nitrogen Use Efficiency among Pearl Millet Genotypes uri icon

abstract

  • Nitrogen is often a limiting factor in pearl millet (Penuisetum glaucum( L.) R. Br.) production. Genotypesa re knownth at differ their responset o N. In this study four pearl millet genotypes,w hich werep reviouslyi dentified as extremesi n N use efficiency (total above ground biomass/unit of N absorbed) in the field, were comparedi nnutrient solution culture for their responset o N supply and the instantaneous measuremenot f photosynthetic N efficiency (~tmol CO2 g-~ N s-a). The latter componenpt ossibly contributes to N use efficiencyN-efficient genotypes, ?Souna B? and 700112, and N-inefficient genotypes, ?BK560a? nd ?B J104?, were growna t four N levels containing 60, 120, 180, and 240 mg N plant-~. Specific leaf area (cm2 g-a) was calculated from an accompanyingg rowth analysis. Leaf CO2 exchange rate was measured on several leaves as they became fully expanded. Photosynthetic N efficiency was derived usingvalues of leaf N concentration. Nitrogen-efficient genotypesmaintained thicker leaves (316.1 vs. 332.5 cm2 g-l) and were generally less responsive in terms of leaf N concentrations and leaf COs exchanger ate (CER)t o the N available in solution as comparetdo the N-inefficient genotypes. Souna B, the most efficient genotype,maintained a stable CER across all N levels. Photosynthetic N efficiency was similar for all genotypese xcept BK560w, hich was ~)0 to 15% less efficient. The small difference in photosynthetic N efficiency among genotypes coupled with relatively high photosynthetic N efficiency values of BJI04 (N-inefficient genotype) suggests that differences in instantaneous measures of N use efficiency occurringduring photosynthesios ffer little explanationf or overall differences in N use efficiency among these genotypes in a previous field study. Nitrogen use efficiency was more related to the partitioning of N resources available into additional leaf area

publication date

  • 1988