Westbeek Milka H M, Pons Thijs L, Cambridge Marion L, Atkin Owen K
Department of Plant Ecology and Evolutionary Biology, Utrecht University, P.O. Box 800.84, 3508 TB Utrecht, The Netherlands e-mail:
Oecologia. 1999 Jul;120(1):19-26. doi: 10.1007/s004420050828.
This study investigates factors determining variation in photosynthetic nitrogen use efficiency (φ) in seven slow- and fast-growing Poa species from altitudinally contrasting sites. The species and their environmental origin were (in order of increasing relative growth rate): two alpine (Poa fawcettiae and P. costiniana), one sub-alpine (P. alpina) and three temperate lowland perennials (P. pratensis, P. compressa and P. trivialis), as well as one temperate lowland annual (P. annua). Plants were grown hydroponically under identical conditions with free access to nutrients in a growth room. Photosynthesis per unit leaf area measured at growth irradiance (500 μmol m s) was slightly higher in the slow-growing alpine species. At saturating light intensities, photosynthesis was considerably higher in the alpine species than in the lowland species. Carboxylation capacity and Rubisco content per unit leaf area were also greater in the alpine species. Despite variation between the species, the in vivo specific activity of Rubisco showed little relationship to relative growth rate or photosynthetic rate. Both at light saturation and at the growth irradiance, φ was lowest in the slow-growing alpine species P. fawcettiae, P. costiniana and P. alpina, and highest in the fast-growing P. compressa and P. annua. The proportion of leaf nitrogen that was allocated to photosynthetic capacity and the in vivo catalytic constant of Rubisco accounted for most of the variation in φ at light saturation. Minor variations in intercellular CO partial pressure also contributed to some extent to the variations in φ at light saturation. The low φ values at growth irradiance exhibited by the alpine species were additionally due to a lower percentage utilisation of their high photosynthetic capacity compared to the lowland species.
本研究调查了决定来自海拔差异较大地区的七种生长速度快慢不同的早熟禾物种光合氮利用效率（φ）变化的因素。这些物种及其环境来源（按相对生长速率递增顺序）为：两种高山物种（福氏早熟禾和柯氏早熟禾）、一种亚高山物种（高山早熟禾）、三种温带低地多年生植物（草地早熟禾、扁秆早熟禾和普通早熟禾）以及一种温带低地一年生植物（一年生早熟禾）。将植物在生长室内相同条件下进行水培，使其能自由获取养分。在生长光强（500 μmol m⁻² s⁻¹）下测量的单位叶面积光合作用，在生长缓慢的高山物种中略高。在饱和光强下，高山物种的光合作用比低地物种高得多。单位叶面积的羧化能力和 Rubisco 含量在高山物种中也更高。尽管物种间存在差异，但 Rubisco 的体内比活性与相对生长速率或光合速率关系不大。在光饱和以及生长光强条件下，φ 在生长缓慢的高山物种福氏早熟禾、柯氏早熟禾和高山早熟禾中最低，在生长迅速的扁秆早熟禾和一年生早熟禾中最高。在光饱和时，分配到光合能力的叶氮比例和 Rubisco 的体内催化常数占 φ 变化的大部分。胞间 CO₂ 分压的微小变化在一定程度上也导致了光饱和时 φ 的变化。高山物种在生长光强下较低的 φ 值还归因于与低地物种相比，它们对高光合能力的利用率较低。
