作 者 ：衣英华,樊大勇,谢宗强*,陈芳清
期 刊 ：生态学报 2008年 28卷 12期 页码：6025~6033
Keywords:Taxodium ascendens, Quercus variabilis, simulated waterlogging, eco-physiological process,
摘 要 ：池杉（Taxodium ascendens）和栓皮栎（Quercus variabilis）是我国亚热带河岸带和库塘消落区常见的植物，对于河岸带和库塘消落区的水土保持和水源涵养具有十分重要的作用。研究通过测定二者的最大净光合速率、光饱和曲线、二氧化碳饱和曲线、根/茎/叶的可溶性糖含量、叶片的比叶重（leaf mass per unit area, LMA）和根系活力等指标研究了模拟淹水（50d）对两年生栓皮栎和池杉树苗生理生态过程的影响。在淹水过程中，栓皮栎的最大净光合速率不断下降，到试验结束时淹水处理的最大净光合速率降低为对照的9%，而且处理与对照差异极显著；而在整个淹水过程中池杉则在处理和对照间没有显著差异。淹水胁迫下：（1）淹水导致栓皮栎表观量子效率（φ）不断下降，淹水第6天降为对照的59.9%左右（P<0.001），第26天降为对照的40.9%左右（P<0.001）,而26d的淹水对池杉的光饱和曲线却影响不大; （2）淹水导致栓皮栎羧化效率（CE）的不断下降，在正常生长条件下栓皮栎的CE为(0.331±0.075)μmol m-2s-1Pa-1。淹水第10天栓皮栎的CE下降到对照的22.1％，淹水第30天降到对照的16.8%，且差异均显著（P<0.001）。淹水对池杉的二氧化碳饱和曲线没有造成显著影响；（3）淹水导致两个种的根/茎/叶可溶性糖含量呈现动态变化。50d的淹水导致栓皮栎叶片可溶性糖含量相比于对照略有上升，茎和根可溶性糖含量显著上升。而池杉根/茎/叶可溶性糖含量对照和处理之间差异不显著；（4）淹水导致栓皮栎的比叶重持续升高，池杉的与对照没有显著差异；（5）淹水导致栓皮栎的根系活力持续下降，池杉则开始时下降后又升高，这可能与池杉在淹水过程中产生了有利于吸收氧气的不定根，而栓皮栎没有产生不定根有关。以上实验结果说明相对池杉，栓皮栎应属于对淹水较敏感的树种。短期淹水（1~10d）导致栓皮栎光合速率下降的生理生态原因应该至少包括表观量子效率和羧化效率下降两个原因。而长期淹水条件下，叶片碳水化合物的积累（LMA升高）导致的负反馈效应也可能是光合速率下降的原因之一。
Abstract:Taxodium ascendens and Quercus variabilis (Cork Oak) are very important species distributed in the subtropical riverside and drawdown area of reservoirs and ponds in China. In this study, to investigate the effects of waterlogging on the eco-physiological processes of these two species, the maximum net photosynthesis rate, apparent quantum yield（φ）, apparent carboxylation efficiency（CE）, content of soluble sugar of root/stem/leaf, Leaf Mass per unit Area (LMA) as well as the root activity of these two species under waterlogging conditions were measured. Waterlogging caused a persistent decrease of maximum photosynthetic rate of Cork Oak (on the 50th day of waterlogging, the value was only 9% of control). In contrast, there was no significant difference of maximum photosynthetic rate between waterlogged and control seedlings of Taxodium ascendens. It was shown that: (1) the φ of Cork Oak was decreased by waterlogging (6 days of waterlogging decreased φ to 59.9% of control, 26 days of waterlogging decreased φ to 40.9%), while waterlogging caused no significant change of φ of Taxodium ascendens; (2) under normal conditions, the CE of Cork Oak was approximately (0331±0.075)μmol m-2s-1Pa-1, waterlogging induced a persistent decrease of CE (10 days of waterlogging decreased CE to 221% of control, 30 days decreased to 16.8%), while waterlogging caused no significant changes in the CE of Taxodium ascendens;(3) the soluble sugar content of the root/stem/leaf of both species also showed kinetic responses under waterlogging stress. At the beginning of waterlogging (10th day), the soluble sugar content of the leaf and root of Cork Oak was less than the control; afterwards, it was higher than the control. Comparably, the soluble sugar content of stem of Cork Oak was higher than control during the period of treatment. As for Taxodium ascendens, the soluble sugar content of root/stem/leaf was not significantly different between waterlogging and control; (4) The LMA of waterlogged Cork Oak was higher than control, while there was no difference between control and treatment of Taxodium ascendens; (5) compared with control, the root activity of the waterlogged Cork Oak decreased persistently. While at early stage of waterlogging, the root activity of Taxodium ascendens was reduced to some degree; afterwards, it was higher than control, which might be due to the emergence of adventitious roots. The results above indicate that Cork Oak was more sensitive to waterlogging than Taxodium ascendens. This study indicates the underlying mechanisms contributing to the decreased photosynthesis rate of Cork Oak at the early stage of waterlogging, include the decreased apparent quantum yield and decreased apparent carboxylation efficiency. In addition, the feed-back effect of accumulated carbohydrates in leaves on the photosynthesis rate of Cork Oak may occur during long-term waterlogging.
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