Vertical profile of photosynthetic light response within rice canopy
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ORIGINAL PAPER
Vertical profile of photosynthetic light response within rice canopy Yuping Lv 1 & Junzeng Xu 2,3
&
Xiaoyin Liu 2,3 & Haiyu Wang 2,3
Received: 15 October 2019 / Revised: 15 March 2020 / Accepted: 29 March 2020 # ISB 2020
Abstract 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 Pnmax, initial quantum yield of assimilation φ, dark respiration rate Rd, 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 Pnmax, φ, and Rd 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 Pn for all leaves at different positions and stages, while the canopy average NRH equation underestimated leaf Pn at upper canopy and overestimated Pn at lower canopy. The top fourth leaf was suitable for estimating photosynthetic parameters at canopy scale, as the Pnmax, φ, Rd, 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 Pn for the top fourth leaf. The results will provide basic information for upscaling leaf photosynthesis to canopy scale. Keywords Photosynthetic light response . Parameters in non-rectangular hyperbola equation . Leaf position . Rice
Introduction Determining leaf photosynthetic light response (PLR) curves is essential to understand both the relationship between irradiance and photosynthetic rate driven by photon energy and the photochemical efficiency of photosynthetic process, which provide a scientific basis for simulating crop production (Ye and Zhao 2010; Lachapelle and Shipley 2012; Qian et al. 2012; Flanagan et al. 2015). Numerous mathematical functions have been used to describe the PLR curves, such as Michaelis-Menten, Mitscherlich, hyperbolic tangent,
* Junzeng Xu [email protected] 1
College of Hydraulic Science and Engineering, Yangzhou University, Yangzhou 225009, Jiangsu, China
2
State Key Laboratory of Hydrology-Water Resources and Hydraulic Engineering, Hohai University, Nanjing 210098, Jiangsu, China
3
College of Agricultural Engineering, Hohai University, Nanjing 210098, Jiangsu, China
rectangular hyperbola, and non-rectangular hyperbola (NRH) equations (Vervuren et al. 1999; Lobo et al. 2013), and these functions have been applied widely in biochemical or conceptual photosynthetic models (Morecroft et al. 2003; Halfhide et al. 2015; Zvalinsky and Tishchenko 2016). As one of the most popular functions for describing the
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