Transfer characteristics of canopy photo-synthetically active radiation in different rice cultivars under different cultural conditions | 不同品种和栽培条件下水稻冠层光合有效辐射传输特征

Chinese. 【目的】揭示水稻冠层光合有效辐射（PAR）传输特征在不同栽培条件下的变化规律。【方法】以2个不同株型水稻品种为材料，于2009―2010年分别设置不同栽插密度和施氮水平的田间试验，系统测定水稻主要生育时期的冠层结构和PAR传输参数，分析冠层结构和PAR传输参数随生育进程的动态变化规律以及PAR传输参数的日变化规律，并研究入射光散射比例对冠层PAR传输的影响。【结果】栽插密度和施氮量对水稻叶面积指数 （LAI）、冠层平均叶倾角和株高有显著影响。冠层PAR透过率、反射率随生育进程先减后增，最小值出现在孕穗至抽穗期；提高施氮量减少了冠层PAR反射率。随生育进程的推进，水稻冠层消光系数（K）逐渐增加，并随栽插密度和施氮量增加而增加，不同条件下的K值随移栽后天数的变化可以用指数递增方程来描述。冠层PAR反射率、截获率和K值的日变化呈向下抛物线状，以正午时刻最小；而PAR透过率则呈相反模式；灌浆期PAR透过率、截获率和K值的日变化幅度明显小于分蘖期和拔节期。消光系数随太阳高度角的变化可以用Doseresp曲线来描述，但受到品种特性和冠层结构的影响。随着入射光散射比例的增加，PAR透过率逐渐减少，K值逐渐增加。【结论】水稻冠层PAR传输特征受栽插密度和施氮量的调控，并存在显著的生育时期变化和日变化规律，同时受入射光散射比例的影响。

English. 【Objective】 The objective of this study was to explore the dynamic transfer characteristics of canopy photosynthetically active radiation (PAR) in different rice cultivars and under different cultural conditions.【Method】Field experiments were conducted in Nanjing in 2009 and in Yizheng in 2010, involving two cultivars with different plant types, three planting densities and five nitrogen rates. During rice growing periods, the dynamics of canopy structure and the daily changes in PAR transfer parameters were measured, and the effects of proportion of diffuse radiation on canopy PAR transfer characteristics were analyzed. 【Result】 The results indicated that canopy leaf area index (LAI), average leaf inclination and plant height of rice were affected significantly by planting densities and nitrogen rates. Dynamics of canopy PAR transmittance and reflectance firstly decreased and then increased over growing progress of rice, with the minimum value appeared during booting to heading stages. Canopy PAR reflectance decreased with enhancing nitrogen rates. Extinction coefficient (K) in canopy increased over growing progress of rice and with increasing planting densities and nitrogen rates. The dynamics of K with the days after transplanting could be described with the upward exponential equation. The daily change patterns of canopy PAR reflectance and interceptance, and K values could be described with downward parabolic curves, reaching the minimum values at noon, while opposite patterns were seen /in the PAR transmittance. The ranges of daily variation in canopy PAR transmittance and interceptance, and K values at grain filling stage were obviously lower than those at tillering stage. The dynamics of K with the solar angle could be described with the Doseresp curve, which was affected by the canopy structure and cultivar genetic characteristics. Canopy PAR transmittance decreased and K value enhanced with reduced proportion of diffuse radiation.【Conclusion】The dynamic characteristics of canopy PAR transfer in rice were regulated by planting densities and nitrogen rates, exhibiting marked changes over daily times and growth stages, and affected by the proportion of diffuse radiation. These results will provide experimental supports for precision simulation of canopy photosynthesis and productivity in rice.