在国际水稻研究所（IRRI）农场试验条件下，选用6个不同的热带水稻材料，其中包括2个常规籼稻、2个杂交籼稻和2个新株型稻（NPT），研究氮肥农学利用率（AE）和氮素光合效率（PNUE）及其相关叶片参数的基因型差异，并探讨了它们之间的关系。结果表明，新株型稻的净光合速率(Pn)大于常规籼稻，杂交籼稻居中。各基因型间的气孔导度(Gs)、胞间CO2浓度(Ci)、蒸腾速率(Tr)和Ci/Gs的差异趋势不同。不同基因型叶片的氮浓度（N%）和比叶重（SLW）存在一定的差异。常规籼稻的单位叶绿素的净光合速率（Pn/Chl）较NPT低，杂交籼稻为中间类型；叶片净光合速率和单位面积含氮量（Na）之间存在显著的正相关；本研究所选用的热带杂交籼稻的PFP（氮肥偏生产力）和AE比新株型稻和常规籼稻高，两者最低的均为常规籼稻。氮素光合效率与AE间存在显著正相关，表明后期的氮素光合效率对氮肥利用率具有一定的指示和预测作用，这对于判断水稻品种氮肥利用率将具有重要的应用价值。
Photosynthetic characteristics are considered to be significant in nitrogen use efficiency (NUE) in view of their close associations with dry matter production and grain yield in cereal crops. Photosynthetic nitrogen use efficiency (PNUE) and photosynthetic characteristics were investigated using six tropical rice (Oryza sativa L.) genotypes including two indica inbreds, two indica hybrids, and two NPT (new plant type) lines under field-grown conditions. The objectives of this study were to compare genotypic variations in agronomic efficiency (AE), PNUE, and related leaf parameters and their correlations among six rice genotypes. The results indicated that net photosynthetic rate (Pn) was higher for NPT lines than for indica inbreds, while it was mediate for indica hybrids. Variations were observed in stomatal conductance (Gs), inter CO2 concentration (Ci), transpiration rate (Tr), and the ratio of Ci to Gs among all rice genotypes. Differences in leaf nitrogen concentration (N%) and specific leaf weight (SLW) were also found among all genotypes. The Pn per Chlorophyll unit (Pn/Chl) was lower in indica inbreds than in NPT lines while indica hybrids appeared to be middle types. There was a significantly positive correlation between Pn and leaf N content per unit leaf area (Na). Generally, both partial factor productivity of applied N (PFP) and AE of indica hybrids were higher than those of both NPT lines and indica inbreds. However, the lowest PFP and AE were observed in PSBRc18 and IR72903-121-2-1-2, respectively. PNUE was positively and significantly correlated with AE in all genotypes, suggesting that the PNUE at reproductive growth stage of rice might be a good indicator for NUE and could be utilized in evaluating genotypes with high NUE in rice.
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