Tomlinson Patricia T, Anderson Paul D
USFS, North Central Forest Experiment Station, 5985, Highway K, Rhinelander, WI 54501, USA.
To whom correspondence should be addressed. E-mail: ptomlins/
New Phytol. 1998 Nov;140(3):493-504. doi: 10.1111/j.1469-8137.1998.00291.x.
Northern red oak in the western Lake States area of the USA exists on the most xeric edge of its distribution range. Future climate-change scenarios for this area predict decreased water availability along with increased atmospheric CO . We examined recent photosynthate distribution and growth in seedlings as a function of CO mole fraction (400, 530 and 700 μmol mol CO ), water regime (well watered and water-stressed), and ontogenic stage. Water stress effects on growth were largely offset by elevated CO . Water stress increased root mass ratio without concurrently increasing allocation of recent photosynthate to the roots. However, apparent sink strength of water-stressed seedlings at the completion of the third growth stage tended to be greater than that of well watered seedlings, as shown by continued high export, which may contribute carbon reserves to support preferential root growth under water-stressed conditions. Elevated CO decreased apparent shoot sink strength associated with the rapid expansion of the third flush. Carbon resources for the observed enhanced growth under elevated CO could be provided by enhanced photosynthetic rate over an increased leaf area (Anderson & Tomlinson, 1998, this volume). Increased sink strength of LG seedlings under water-stressed conditions, together with decreased apparent shoot sink strength associated with growth in elevated CO provide mechanisms for offsetting water stress effects by growth in elevated CO . Careful control of ontogeny was necessary to discern these changes and provides further evidence of the need for such careful control in mechanistic studies.
美国湖泊州西部地区的北方红橡生长在其分布范围最干旱的边缘地带。该地区未来气候变化情景预测，水资源可用性将降低，同时大气中的二氧化碳浓度会升高。我们研究了幼苗中近期光合产物的分配和生长情况，将其作为二氧化碳摩尔分数（400、530和700 μmol/mol二氧化碳）、水分状况（充分浇水和水分胁迫）以及个体发育阶段的函数。二氧化碳浓度升高在很大程度上抵消了水分胁迫对生长的影响。水分胁迫增加了根质量比，但并未同时增加近期光合产物向根的分配。然而，在第三个生长阶段结束时，水分胁迫幼苗的表观库强往往大于充分浇水的幼苗，这表现为持续的高输出，这可能有助于积累碳储备，以支持水分胁迫条件下根系的优先生长。二氧化碳浓度升高降低了与第三次新梢快速生长相关的表观地上部库强。在二氧化碳浓度升高条件下观察到的生长增强所需的碳资源，可通过增加叶面积上的光合速率来提供（安德森和汤姆林森，1998年，本卷）。水分胁迫条件下LG幼苗库强的增加，以及二氧化碳浓度升高条件下与生长相关的表观地上部库强的降低，为通过二氧化碳浓度升高条件下的生长来抵消水分胁迫影响提供了机制。仔细控制个体发育对于识别这些变化是必要的，并进一步证明了在机理研究中进行这种仔细控制的必要性。
