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This article in CS

  1. Vol. 28 No. 4, p. 681-685
     
    Received: June 22, 1987
    Published: July, 1988


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doi:10.2135/cropsci1988.0011183X002800040025x

Measurement of Instantaneous Nitrogen Use Efficiency among Pearl Millet Genotypes

  1. G. Alagarswamy,
  2. J. C. Gardner,
  3. J. W. Maranville  and
  4. R. B. Clark
  1. I CRISAT, Patancheru, India 502324
    N orth Dakota State Univ. Carrington Res. Ext. Ctr., Carrington, ND 58421
    D ep. of Agronomy Univ. of Nebraska, Lincoln, NE 68583
    D ep. of Agronomy and USDA-ARS, Univ. of Nebraska, Lincoln, NE 68583

Abstract

Abstract

Nitrogen is often a limiting factor in pearl millet [Pennisetum glaucum (L.) R. Br.] production. Genotypes are known that differ their response to N. In this study four pearl millet genotypes, which were previously identified as extremes in N use efficiency (total above ground biomass/unit of N absorbed) in the field, were compared in nutrient solution culture for their response to N supply and the instantaneous measurement of photosynthetic N efficiency (μmol CO2 g−1 N s−1). The latter component possibly contributes to N use efficiency. N-efficient genotypes, ‘Souna B’ and 700112, and N-inefficient genotypes, ‘BK560’ and ‘BJ104’, were grown at four N levels containing 60, 120, 180, and 240 mg N plant−1. Specific leaf area (cm2 g−1) was calculated from an accompanying growth analysis. Leaf CO2 exchange rate was measured on several leaves as they became fully expanded. Photosynthetic N efficiency was derived using values of leaf N concentration. Nitrogen-efficient genotypes maintained thicker leaves (316.1 vs. 332.5 cm2 g−1) and were generally less responsive in terms of leaf N concentrations and leaf CO2 exchanger ate (CER) to the N available in solution as compared to 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 genotypes except BK560, which was 10 to 15% less efficient. The small difference in photosynthetic N efficiency among genotypes coupled with relatively high photosynthetic N efficiency values of BJ104 (N-inefficient genotype) suggests that differences in instantaneous measures of N use efficiency occurring during photosynthesis offer little explanation for 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.

Published as Paper no. 8372, Journal Series, Nebraska Agric. Exp. Stn. Work supported in part by a grant from the International Sorghum/Millet Cooperative Research Support Program (INTSORMIL).

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