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This article in AJ

  1. Vol. 87 No. 6, p. 1221-1225
    Received: May 27, 1994

    * Corresponding author(s): dwyerl@ncccot.agr.ca
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Changes in Maize Hybrid Photosynthetic Response to Leaf Nitrogen, from Pre-Anthesis to Grain Fill

  1. Lianne M. Dwyer ,
  2. Anne M. Anderson,
  3. Douglas W. Stewart,
  4. B. L. Ma and
  5. Matthijs Tollenaar
  1. A gric. and Agri-Food Canada, Ctr. for Land and Biological Resources Res. (CLBRR), Ottawa, ON KIA OC6, Canada
    U niv. of Guelph, ON NIG 2W1
    U niv. of Guelph, ON NIG 2W1, Canada



Improvement of nitrogen use efficiency in maize production requires quantifying genotypic variability in response to soil N. The objective of this field study was to quantify the relationship between leaf N concentration and leaf photosynthetic rate from pre-anthesis to grain fill for six maize (Zea mays L.) hybrids. Maize hybrids were grown at the Central Experimental Farm at Ottawa in Ontario (45°23′ N, 75°43′ W) in 1991, 1992, and 1993 at three N fertilizer rates (0, 100, and 200 kg N ha−1). A method of analysis was developed to relate leaf photosynthesis measurements at comparable irradiance levels to leaf N concentration measurements. Photosynthetic response to leaf N was characterized by two fitted coefficients, N0, threshold leaf N concentration for photosynthesis, and P3, photosynthetic rate at high (30 g N kg−1 dry weight) leaf N concentration. There were no hybrid differences in N0 (P > 0.05). There were differences in P3, notably a significantly lower P3 value at anthesis for an old hybrid compared with recent commercial hybrids. In 1992, a recent commercial hybrid, Pioneer 3902, had the highest P3 value, the second highest crop growth rate (CGR) and the highest grain yield, but hybrid differences in P3 were not generally correlated with CGR or grain yield (P > 0.05). Growth stage had a significant effect on both N0 and P3; both declined at later growth stages (P ≤ 0.05). The decline in P3 was greatest in Pride 5 in 1993. Photosynthate production during grain fill was potentially limited in all hybrids by a decline in P3 as the season progressed, although the degree of decline varied with year and hybrid. This analysis quantified the relationships between leaf N concentration and leaf photosynthetic rate for different growth stages and hybrids for evaluation of hybrid N use efficiency.

CLBRR Contribution no. 94-56.

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