夏玉米冠层叶片表观自由空间的差异研究

叶片自由空间在环境与冠层养分交换间具有重要作用，是目前植物营养学研究的重要领域之一。通过盆栽试验，以不同株型夏玉米为试材，研究了不同施氮水平（N 0、0.15和0.30 g /kg）下玉米冠层叶片表观自由空间（AFS）的差异。结果表明，不同生育期叶片AFS差异极显著（P0.01），表现为随生育期推进，叶片AFS、生物量和全氮含量均逐渐降低；除成熟期，其它各生育期品种与施氮水平对叶片AFS的影响均存在显著的交互作用。施氮对叶片生物量的影响不显著，但施氮后叶片全氮含量显著增加。不同施氮水平下，植株冠层叶片AFS也存在显著差异，中量施氮处理（即N 0.15 g /kg）植株叶片AFS值（9.49 %）明显高于与不施氮处理（9.03 %），但随施氮量进一步增加，叶片AFS下降，施氮量为N 0.30 g /kg时，叶片AFS为8.62 %；不同施氮水平各生育期不同叶层间叶片AFS、生物量和全氮含量差异显著（P0.05）。不同品种间叶片全氮含量和AFS存在显著差异（P0.05），以紧凑型品种陕单902叶片AFS最大，平均为9.24 %，显著高于其它品种；中间型品种农大108与平展型品种陕单9号间差异不显著，二者平均分别为9.06 %和8.85 %；不同株型品种各生育期不同叶层间叶片全氮含量和AFS缺乏规律性。相关分析表明，叶片全氮与叶片AFS存在极显著正相关（R=0.9481），说明植物冠层叶片AFS大小除受遗传特性影响外，植物体和介质氮素营养水平不同，AFS也存在差异，且这些差异随生育期变化而不同。

Differences in apparent free space (AFS) of summer maize canopy leaves

Leaf free space plays an important role in nutrient exchange between environment and plant canopy, and is a major field of plant nutritional research. A pot experiment was carried out with different plant types of maize to study the differences of leaf apparent free space (AFS) at different layers of canopy under different nitrogen (N) fertilization treatments. The plant types of summer maize were plate conformation Shandan 9, middle conformation Nongda 108 and compact conformation Shandan 902. The N rates were N 0, 0.15 and 0.30 g/kg. The results showed that AFS of canopy leaf was significantly different at different growth stages, and decreased gradually with growth, as well as the biomass and total N content. The interaction between variety and N rates was significant for AFS, biomass and total nitrogen content across the whole growing period, except the interaction for AFS at maturity stage. There was not a significant effect of N fertilization on biomass, but total leaf N content increased significantly with N rate. AFS of canopy leaf was significantly different among different N rates, with AFS of mid-level N fertilization treatment being larger than either no or higher N fertilization treatment. Leaf AFS, biomass and total N content differed with different layers of plant canopy, N fertilization rates and varieties across different growth stages. Among different maize plant type, AFS of compact middle conformation Nongda 108 and plate conformation Shandan 9, and the average were 9.06% and 8.85%, respectively. Correlation analysis showed that there was a significantly positive correlation between total N content and AFS. The research indicated that AFS of canopy leaf was not only controlled by genetic characteristics of plant, but also affected by nutrition of plant and medium. AFS was significantly affected by the nutrient levels of plant and medium and growth stages.