Norby Richard J, O'Neill E G
Environmental Sciences Division, Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, Tennessee 37831-6034, USA.
New Phytol. 1989 Mar;111(3):491-500. doi: 10.1111/j.1469-8137.1989.tb00712.x.
White oak (Quercus alba L.) seedlings were grown from a half-sib collection of acorns in pots containing a nutrient-Poor forest soil and maintained in controlled-environment chambers having mean atmospheric CO concentrations of 389, 496, and 793 cm m . Additions of nitrogen and phosphorus to the soil increased plant growth, indicating that the unfertilized plants were nutrient deficient. Despite the nutrient deficiency, the plants grown in elevated concentrations of CO., generally were larger than those in ambient CO , but dry weight data from harvests at 5, 12, 24, and 36 weeks provided insufficient evidence of an effect of CO because of the high variability associated with the recurrently-Hushing habit of these seedlings. Mathematical growth analysis based on periodic non-destructive measurements allowed comparisons of the continuous growth patterns of the plants and avoided the problems of ontogenetic variation. CO , enrichment was thus shown to increase plant growth rate primarily through increased unit leaf rate rather than increased leaf area production. Unit leaf rate during the second half of the experiment was 22 and 27% higher in the medium and high concentrations of CO compared with that in low CO instantaneous measurements of foliar gas exchange also showed that CO , assimilation increased with CO , enrichment. The most pronounced effect of CO , enrichment was increased water-use efficiency, which was shown both through whole-plant gravimetric analysis and instantaneous gas exchange measurements. Whole-plant water-use efficiency for the duration of the experiment was increased by 52 and 82% by the mdium and high concentrations of CO . Limitations of resources, including water and nutrients, do not preclude plant growth responses to CO enrichment of the atmosphere.
白栎（Quercus alba L.）幼苗由橡子的半同胞群体培育而来，种植于装有贫瘠森林土壤的花盆中，并置于可控环境室内，室内平均大气CO浓度分别为389、496和793 μmol mol⁻¹。向土壤中添加氮和磷可促进植物生长，这表明未施肥的植物存在养分缺乏问题。尽管存在养分缺乏情况，但生长在高浓度CO₂环境中的植物通常比生长在环境CO₂浓度下的植物更大，然而，由于这些幼苗反复落叶习性导致的高变异性，在5、12、24和36周收获时的干重数据不足以证明CO₂有影响。基于定期无损测量的数学生长分析能够比较植物的连续生长模式，并避免个体发育变异问题。因此，CO₂富集主要通过提高单位叶速率而非增加叶面积生产来提高植物生长速率。与低CO₂浓度相比，在实验后半期，中等和高浓度CO₂环境下的单位叶速率分别高出22%和27%。对叶片气体交换的瞬时测量还表明，CO₂同化作用随CO₂富集而增加。CO₂富集最显著的影响是提高了水分利用效率，这在全株重量分析和瞬时气体交换测量中均得到体现。在实验期间，中等和高浓度CO₂使全株水分利用效率分别提高了52%和82%。包括水和养分在内的资源限制并不妨碍植物对大气CO₂富集的生长响应。
