基于三维冠层模型的玉米光合作用和光能利用模拟

Modelling maize photosynthesis and light utilization based on a 3D maize canopy model

光线分布和叶片光合特征在冠层内部具有极强的时空异质性,基于三维冠层模型的玉米光合模型是精确评估品种高光效的重要手段。该研究将作物三维冠层模型、光线分布模型、光合模型与光能利用模型相耦合,建立了玉米冠层光合生产模型3DMaizeCaP,设置3个不同株型的玉米品种(矮单268、京科968和郑单958),2种不同光照条件(晴天和阴天),通过大田试验与模型模拟研究揭示了玉米冠层光合速率和光能利用效率对品种和环境的响应。结果表明,矮单268、京科968和郑单958的叶片最大光合速率和暗呼吸速率均随节位下降呈线性降低的垂直分布规律,各品种中矮单268的最大光合速率最大,而暗呼吸速率最小;冠层净光合速率日变化趋势明显,矮单268在阴天和晴天下的冠层最大净光合速率(以CO2计)为21.6和26.2μmol/(m^2·s),均显著(P<0.05)高于京科968(20.8和24.9μmol/(m^2·s))和郑单958(19.6和24.4μmol/(m2·s));矮单268的日CO2净同化量在阴天和晴天下均显著(P<0.05)高于郑单958,增幅分别高达14.8%和12.4%,各品种间株型虽有显著差异(P<0.05),但冠层日累积光截获并无显著差异(P>0.05);单叶尺度上,各叶片中第16节位的单叶日净同化量达到最大;矮单268的光能利用效率最大,在阴天和晴天下分别为3.22和3.03 g/MJ,比京科968分别高4.5%和5.6%,比郑单958分别高7.7%和7.8%;初始光量子效率对玉米冠层光能利用效率的敏感性显著高于最大光合速率(P<0.05)。从提高玉米冠层光能利用效率考虑,建议设计株型紧凑、叶片光合性能强的玉米品种。研究可为定量研究玉米冠层光合速率提供估算方法,也可为高光效品种选育提供评价依据和鉴定技术。

Light distribution and leaf photosynthesis characteristics are highly heterogeneous within a crop canopy.Maize canopy photosynthesis model based on a 3D canopy structure is an important approach to accurately evaluating radiation use efficiency for cultivars.In this study,we built a maize photosynthetic production model 3DMaizeCaP via coupling canopy 3D architecture model,radiative flux distribution model,leaf photosynthesis model and radiation utilization model.In this study,three cultivars with different plant architecture,i.e.,AD268,JK968 and ZD958,and two typical weather conditions,i.e.,a sunny day and an overcast day were used.In order to unravel the responses of canopy photosynthesis rate and radiation use efficiency to cultivar and environment,a simulation study combined with field experiment was performed.The results showed that the maximum photosynthesis rate and dark respiration rate decreased linearly with decreasing leaf rank for AD268,JK968 and ZD958.The distribution of both the maximum photosynthesis rate and dark respiration rate of individual leaves showed a vertical profile from the top to the bottom of the maize canopy.The AD268 had the highest maximum photosynthesis rate and the lowest dark respiration rate among three cultivars.The diurnal course of canopy photosynthesis rate was characterized evidently that canopy photosynthesis rate increased in the morning and reached the maximum value at 12:00 of noon on an overcast day and at 11:00 on a sunny day and then decreased in the afternoon for all cultivars.The maximum canopy photosynthesis rate of AD268 was 21.6μmol CO2/(m2·s)on an overcast day and was 26.2μmol CO2/(m2·s)on a sunny day,which were significantly higher than that of JK968(20.8μmol CO2/(m2·s)and 24.9μmol CO2/(m2·s))and of ZD958(19.6μmol CO2/(m2·s)and 24.4μmol CO2/(m2·s)).The daily net assimilated CO2 of AD268 was significantly(P<0.05)higher than that of ZD958.In comparison with ZD958,the daily net assimilated CO2 increased by 14.8%and 12.4%on a sunny and an overcast day respectively.The plant architecture of AD268 was significantly different with other cultivars(P<0.05).However,there was no significant difference in the daily intercepted photosynthetic absorbed radiation between cultivars(P>0.05).The leaf at 16th main stem phytomer rank produced the highest daily net assimilated CO2 among individual leaves at the leaf level.The radiation use efficiency of AD268 was 3.22 and 3.03 g/MJ under a sunny and an overcast condition,respectively,indicating a 4.5%and a 5.6%increase compared to JK968 and a 7.7%and a 7.8%compared to ZD958.The canopy radiation use efficiency of maize was more sensitive to the initial slope of light response curve than to the maximum photosynthesis rate(P<0.05).From the point view of improving canopy radiation use efficiency for maize,designing a maize ideotype that has a more compact plant architecture and higher leaf photosynthetic capacity was suggested for breeding in the future.This study could provide not only an approach for quantitatively estimating canopy photosynthesis rate of maize but also an evaluation basis as well as a phenotyping technique for breeding cultivars with high photosynthetic efficiency.