不同氮素水平下双季稻株型与冠层内光截获特征研究

本文旨在阐明双季稻株型与冠层内光合有效辐射截获的时空分布特征。选用4个不同株型早、晚稻品种,设置4个不同施氮水平,系统观测其植株形态和冠层内光合有效辐射截获率(IPAR)的时空分布状况。结果表明,施氮水平对早、晚稻株高、穗长、叶长和叶基角均有显著影响,均表现为随施氮水平的增加而增大;早、晚稻孕穗期的分层叶面积指数(LAI)和向上累积LAI大于抽穗后12 d,分层LAI呈冠层中部大于上部和下部的分布特征,最大分层LAI出现在0.58相对高度处;冠层上中部分层LAI和向上累积LAI随施氮水平的增加而增大;向上累积LAI随相对高度呈S型曲线分布,可用Logistic方程定量描述(R~2 0.99);早、晚稻孕穗期的冠层IPAR大于抽穗后12 d,且随施氮水平的增加而增大,其日变化表现为正午较小,早晚较大;株型紧凑的早、晚稻品种,冠层IPAR低;冠层IPAR与向下累积LAI之间的关系可用方程IPAR=a (1-e~(-b×LAI))定量描述(R~2 0.88);冠层内IPAR的三维空间分布表现为冠层上中部水平面上IPAR较低,光斑变化大,冠层下部水平面上IPAR较高,光斑变化较平缓,同一冠层高度水平面上的IPAR呈不均匀分布。研究结果可为双季稻高产栽培及理想株型的优化设计提供支撑。

Plant type and canopy light interception characteristics in double cropping rice canopy under different nitrogen rates

The interception of photosynthetically active radiation (PAR) within canopy direct affects double cropping rice photosynthesis and yield formation. The objective of this study was to elucidate the spatial and temporal distribution characteristics of plant type and canopy interception of PAR in double cropping rice under different development stages, cultivar types and nitrogen rates. Field experiments were conducted using four early and late rice cultivars with four nitrogen application rates at Jiangxi in 2016 and 2017. The plant morphology and canopy interception rate of PAR (IPAR) in different canopy heights at different development stages were measured. The nitrogen application rate had significant effects on the plant height, ear length, leaf length and basic leaf angle. All of them increased with increasing nitrogen application rate. The layer leaf area index (LAI) and upward accumulated LAI of early and late rice were greater at booting stage than at 12 d after heading. The layer LAI was greater in mid canopy than in upper and basal canopy. The maximum layer LAI appeared at 0.58 of relative canopy height. The layer LAI and upward accumulated LAI in upper and mid canopy of early and late rice increased with increasing nitrogen application rate. The distribution of upward accumulated LAI followed sigmoid curve with relative height, which could be quantitatively described with Logistic equation (R ² > 0.99). The canopy IPAR of early and late rice was greater at booting stage than at 12 d after heading, and increased with increasing nitrogen application rate. The diurnal variation of IPAR was smaller at noon than in the morning and afternoon. Lower canopy IPAR was observed for the compact plant type of early and late rice cultivars. The relationship between canopy IPAR and downward accumulated LAI could be quantitatively described with an equation of IPAR = a (1-e ^{- b ×LAI}) (R ²> 0.88). IPAR on horizontal plane of the three-dimensional distribution was smaller, with a greater variation of light flecks in upper and mid canopy than in basal canopy. The IPAR at the same canopy height was non-uniform on the horizontal plane. These results would provide a support on cultivation for high yield and optimal design of plant type in double cropping rice.