Measured leaf photosynthetic light response (PLR) curves at different positions were fitted by non-rectangular hyperbola (NRH) equation to characterize vertical profile of parameters in NRH equation, namely maximum net photosynthetic rate P nmax , initial quantum yield of assimilation φ , dark respiration rate R d , and convexity of the curve k , at both jointing and heading stages within rice canopy. And leaf-position-specific and canopy average NRH equations were constructed respectively based on measured PLR curves at each specific leaf position and all measured PLR curves within rice canopy. The results showed that the P nmax , φ , and R d reached the maximum at the top second leaf and then decreased at jointing stage and decreased in downward leaves at heading stage. The k increased with lowering leaf position at both stages. The leaf-position-specific NRH equation performed well in estimating net photosynthetic rate P n for all leaves at different positions and stages, while the canopy average NRH equation underestimated leaf P n at upper canopy and overestimated P n at lower canopy. The top fourth leaf was suitable for estimating photosynthetic parameters at canopy scale, as the P nmax , φ , R d , and k of the top fourth leaf were near to these parameters of rice canopy, and the canopy average NRH equation performed well in estimating leaf P n for the top fourth leaf. The results will provide basic information for upscaling leaf photosynthesis to canopy scale.

中文翻译：

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水稻冠层内光合光响应的垂直剖面

用非矩形双曲线(NRH)方程拟合测量不同位置的叶片光合光响应(PLR)曲线，表征NRH方程中参数的垂直剖面，即最大净光合速率P nmax 、同化初始量子产率φ 、暗呼吸率 R d 和曲线 k 的凸度，在水稻冠层内的拔节和抽穗阶段。并基于每个特定叶位实测PLR曲线和水稻冠层内所有实测PLR曲线分别构建叶位特异性和冠层平均NRH方程。结果表明，P nmax 、φ 和R d 在顶部第二叶达到最大值，然后在拔节期降低，在抽穗期向下叶片降低。k 在两个阶段都随着叶片位置的降低而增加。叶位特定NRH方程在估计不同位置和阶段所有叶片的净光合速率P n 方面表现良好，而冠层平均NRH方程低估了上部冠层的叶片P n ，高估了下部冠层的P n 。顶四叶适合于估计冠层尺度的光合参数，因为顶四叶的 P nmax 、 φ 、 R d 和 k 接近水稻冠层的这些参数，并且冠层平均 NRH 方程在估计中表现良好叶子 P n 为顶部第四片叶子。结果将为将叶片光合作用升级到冠层规模提供基本信息。而冠层平均 NRH 方程低估了上部冠层的叶 Pn，高估了下部冠层的 Pn。顶四叶适合于估计冠层尺度的光合参数，因为顶四叶的 P nmax 、 φ 、 R d 和 k 接近水稻冠层的这些参数，并且冠层平均 NRH 方程在估计中表现良好叶子 P n 为顶部第四片叶子。结果将为将叶片光合作用升级到冠层规模提供基本信息。而冠层平均 NRH 方程低估了上部冠层的叶 Pn，高估了下部冠层的 Pn。顶四叶适合于估计冠层尺度的光合参数，因为顶四叶的 P nmax 、 φ 、 R d 和 k 接近水稻冠层的这些参数，并且冠层平均 NRH 方程在估计中表现良好叶子 P n 为顶部第四片叶子。结果将为将叶片光合作用升级到冠层规模提供基本信息。