Anten N P R, Schieving F, Werger M J A
Department of Plant Ecology and Evolutionary Biology, Utrecht University, P.O. Box 800.84, 3508 TB, Utrecht, The Netherlands.
Centro de Ecología y Ciencias Ambientales, Instituto Venezolano de Investigaciones Cientificas, Aptdo. 21827, 1020 A, Caracas, Venezuela.
Oecologia. 1995 Apr;101(4):504-513. doi: 10.1007/BF00329431.
An analytical model was used to describe the optimal nitrogen distribution. From this model, it was hypothesized that the non-uniformity of the nitrogen distribution increases with the canopy extinction rate for light and the total amount of free nitrogen in the canopy, and that it is independent of the slope of the relation between light saturated photosynthesis (P) and leaf nitrogen content (n). These hypotheses were tested experimentally for plants with inherently different architectures and different photosynthetic modes. A garden experiment was carried out with a C monocot [rice, Oryza sativa (L.)], a C dicot [soybean, Glycine max (L.) Merr] a C monocot [sorghum, Sorghum bicolor (L.) Moensch] and a C dicot [amarantus, Amaranthus cruentus (L.)]. Leaf photosynthetic characteristics as well as light and nitrogen distribution in the canopies of dense stands of these species were measured. The dicot stands were found to have higher extinction coefficients for light than the monocot stands. Dicots also had more non-uniform N distribution patterns. The main difference between the C and C species was that the C species were found to have a greater slope value of the leaf-level P-n relation. Patterns of N distribution were similar in stands of the C and C species. In general, these experimental results were in accordance with the model predictions, in that the pattern of nitrogen allocation in the canopy is mainly determined by the extinction coefficient for light and the total amount of free nitrogen.
使用一个分析模型来描述最佳氮素分布。基于该模型，推测氮素分布的不均匀性会随着冠层对光的消光率以及冠层中游离氮的总量增加而增大，并且它与光饱和光合作用（P）和叶片氮含量（n）之间关系的斜率无关。针对具有本质上不同结构和不同光合模式的植物，对这些假设进行了实验验证。开展了一项园田试验，涉及一种C3单子叶植物[水稻，稻（L.）]、一种C3双子叶植物[大豆，大豆（L.）Merr]、一种C4单子叶植物[高粱，双色高粱（L.）Moensch]和一种C4双子叶植物[苋菜，尾穗苋（L.）]。测量了这些物种密植林冠层中的叶片光合特性以及光和氮的分布。发现双子叶植物林冠层对光的消光系数高于单子叶植物林冠层。双子叶植物的氮分布模式也更不均匀。C3和C4物种之间的主要差异在于，发现C4物种叶片水平的P-n关系斜率值更大。C3和C4物种林分中的氮分布模式相似。总体而言，这些实验结果与模型预测相符，即冠层中氮素分配模式主要由光消光系数和游离氮总量决定。
