Pearcy Robert W, Calkin Howard W
Department of Botany, University of California, 95616, Davis, CA, USA.
Oecologia. 1983 Apr;58(1):26-32. doi: 10.1007/BF00384538.
Field measurements of photosynthetic CO exchange were made on saplings of a C tree species, Euphorbia forbesii, and a C tree species, Claoxylon sandwicense, in a shaded mesic forest on Oahu, Hawaii. Both species had light responses typical of those generally found in shade plants. Light saturated photosynthetic rates were 7.15 and 4.09 μmol m s and light compensation points were 6.3 and 1.7 μmol m s in E. forbesii and C. sandwicense, respectively. E. forbesii maintained a higher mesophyll conductance and a higher water use efficiency than C. sandwicense as is typically found in comparisons of C and C plants. Under natural light regimes, both species maintained positive CO uptake rates over essentially the entire day because of low respiration rates and light compensation points. However, photosynthesis during sunflecks accounted for a large fraction of the daily carbon gain. The results show that the carbon-gaining capacity of E. forbesii is comparable to that of a C species in a moderately cool, shaded forest environment. There appears to be no particular advantage or disadvantage associated with the C photosynthetic pathway of E. forbesii in this environment.
在夏威夷瓦胡岛一片阴凉湿润的森林中，对一种C₃树种福布斯大戟（Euphorbia forbesii）和一种C₄树种檀香铁苋菜（Claoxylon sandwicense）的树苗进行了光合CO₂交换的实地测量。这两个物种都具有一般在阴生植物中常见的典型光响应。福布斯大戟和檀香铁苋菜的光饱和光合速率分别为7.15和4.09 μmol m⁻² s⁻¹，光补偿点分别为6.3和1.7 μmol m⁻² s⁻¹。正如在C₃和C₄植物比较中通常发现的那样，福布斯大戟比檀香铁苋菜维持着更高的叶肉导度和更高的水分利用效率。在自然光条件下，由于呼吸速率和光补偿点较低，这两个物种在基本上一整天内都保持着正的CO₂吸收速率。然而，光斑期间的光合作用占每日碳增益的很大一部分。结果表明，在适度凉爽、阴凉的森林环境中，福布斯大戟的碳获取能力与C₃物种相当。在这种环境下，福布斯大戟的C₃光合途径似乎没有特别的优势或劣势。
