Fredeen Arthur L, Griffin Kevin, Field Christopher B
Department of Plant Biology, Carnegie Institution of Washington, 290 Panama Street, 94305, Stanford, CA, USA.
Oecologia. 1991 May;86(3):441-446. doi: 10.1007/BF00317614.
We studied nitrate reductase (NR) activity in six species of the genus Piper (Piperaceae) growing under a broad range of light availabilities. Field measurements were made on plants growing naturally in rainforest at the Los Tuxtlas Tropical Biological Preserve, Veracruz, Mexico at high- and lowlight extremes for each species. Foliar nitrogen on an area basis was positively related to the average daily photosynthetically active photon flux density (PFD) received by the leaf (r=0.76, p<0.01). In vivo NR activity was highly correlated with PFD (r=0.95, p<0.001) and less so with total leaf nitrogen (r=0.68, p<0.05). In vivo NR activity was always higher in high-light plants than in low-light plants within a species. Similarly, gap species such as P. auritum had much higher in vivo NR activities than shade species such as P. aequale. Soil NO and NH pools and nitrogen-mineralization rates at Los Tuxtlas were similar between high- and low-light sites, indicating that the elevated NR activities in high-light plants were not the result of higher NO availabilities in high-light microsites. We performed additional experiments at Stanford, California, USA on Piper plants grown at high- and low-light. Foliar NR was highly inducible by nitrate in the gap species (auritum) but not in the generalist (hispidum) or shade (aequale) species. Root NR activities were, in general, an order of magnitude lower than foliar activities. In total, these studies suggest that Piper gap species are inherently more competent to assimilate NO and are better able to respond to sudden increases in NO availability than are shade species.
我们研究了胡椒属（胡椒科）六种植物在广泛光照条件下的硝酸还原酶（NR）活性。在墨西哥韦拉克鲁斯洛斯图斯特拉斯热带生物保护区的雨林中，对自然生长的每种植物在高光和低光极端条件下进行了实地测量。以面积为基础的叶片氮含量与叶片接收到的平均每日光合有效光子通量密度（PFD）呈正相关（r = 0.76，p < 0.01）。体内NR活性与PFD高度相关（r = 0.95，p < 0.001），与叶片总氮含量的相关性较低（r = 0.68，p < 0.05）。在一个物种内，高光植物的体内NR活性总是高于低光植物。同样，诸如金胡椒等林窗物种的体内NR活性比诸如平胡椒等耐荫物种高得多。洛斯图斯特拉斯高光和低光地点的土壤NO₃⁻和NH₄⁺库以及氮矿化率相似，这表明高光植物中NR活性的升高不是高光微生境中NO₃⁻可用性较高的结果。我们在美国加利福尼亚州斯坦福对在高光和低光条件下生长的胡椒属植物进行了额外的实验。林窗物种（金胡椒）的叶片NR对硝酸盐高度可诱导，而广适性物种（糙果胡椒）或耐荫物种（平胡椒）则不然。一般来说，根NR活性比叶活性低一个数量级。总的来说，这些研究表明，胡椒属林窗物种在固氮能力上天生比耐荫物种更强，并且在NO₃⁻可用性突然增加时能做出更好的反应。
