Anderson Paul D, Tomlinson Patricia T
USFS, North Central Forest Experiment Station, Forestry Sciences Laboratory, 5985 Highway K, Rhinelander, WI 54501, USA.
To whom correspondence should be addressed. E-mail: panderso/
New Phytol. 1998 Nov;140(3):477-491. doi: 10.1111/j.1469-8137.1998.00296.x.
The interactive influences of elevated carbon dioxide, water stress, and ontogeny on carbon assimilation and biomass production were investigated in northern red oak, a species having episodic shoot growth characteristics. Seedlings were grown from acorns through three shoot-growth flushes (8-11 wk) in controlled-environment chambers at 400, 530 or 700 μmol mol CO and under well watered or water-stressed soil-moisture regimes. Increasing CO growth concentration from 400 to 700 μmol mol resulted in a 34% increase in net assimilation rate (A), a 31% decrease in stomatal conductance to water vapour (g ) and a 141% increase in water use efficiency (WUE) in well watered seedlings. In contrast, water-stressed seedlings grown at 700 μmol mol CO demonstrated a 69% increase in A, a 23% decrease in g , and a 104% increase in WUE. However, physiological responses to increased CO and water stress were strongly modified by ontogeny. During active third-flush shoot growth, A in first-flush and second-flush foliage of water-stressed seedlings increased relative to the quiescent phase following cessation of second-flush growth by an average of 115%; g increased by an average of 74%. In contrast, neither A nor g in comparable foliage of well watered seedlings changed in response to active third-flush growth. Whereas seedling growth was continuous through three flushes in well watered seedlings, growth of water-stressed seedlings was minimal following the leaf-expansion stage of the third flush. Through three growth flushes total seedling biomass and biomass allocation to root, shoot and foliage components were very similar in water-stressed seedlings grown at 700 μmol mol CO and well watered seedlings grown at 400 μmol mol CO . Enhancement effects of elevated CO on seedling carbon (C) assimilation and biomass production may offset the negative impact of moderate water stress and are likely to be determined by ontogeny and stress impacts on carbon sink demand.
在具有间歇性新梢生长特征的北方红栎中，研究了二氧化碳浓度升高、水分胁迫和个体发育对碳同化和生物量生产的交互影响。将橡子培育成幼苗，在400、530或700 μmol mol CO₂的控制环境舱中，经历三次新梢生长高峰期（8 - 11周），土壤水分状况为充分浇水或水分胁迫。将充分浇水的幼苗的CO₂生长浓度从400 μmol mol增加到700 μmol mol，净同化率（A）增加34%，气孔导度（g）降低31%，水分利用效率（WUE）增加141%。相比之下，在700 μmol mol CO₂浓度下生长的水分胁迫幼苗，A增加69%，g降低23%，WUE增加104%。然而，个体发育强烈改变了对CO₂浓度升高和水分胁迫的生理响应。在活跃的第三次新梢生长期间，水分胁迫幼苗第一和第二次新梢生长期的叶片A相对于第二次新梢生长停止后的静止期平均增加115%；g平均增加74%。相比之下，充分浇水的幼苗的可比叶片中的A和g均未因活跃的第三次新梢生长而发生变化。充分浇水的幼苗在三次新梢生长高峰期持续生长，而水分胁迫幼苗在第三次新梢生长的叶片扩展阶段后生长极少。在经历三次生长高峰期后，在700 μmol mol CO₂浓度下生长的水分胁迫幼苗和在400 μmol mol CO₂浓度下充分浇水的幼苗的总幼苗生物量以及生物量在根、新梢和叶片组分中的分配非常相似。CO₂浓度升高对幼苗碳（C）同化和生物量生产的增强作用可能抵消中度水分胁迫的负面影响，并且很可能由个体发育和胁迫对碳汇需求的影响决定。
