COMPARATIVE KINETICS OF PHOTOSYNTHESIS IN FLOATING AND SUBMERGED POTAMOGETON LEAVES
COMPARATIVE KINETICS OF PHOTOSYNTHESIS IN FLOATING AND SUBMERGED POTAMOGETON LEAVES
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DOI：
10.1016/0304-3770(95)00455-9
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发表时间：
1995-07-01
期刊：
影响因子：
1.8
通讯作者：
SANDJENSEN, K
中科院分区：
文献类型：
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作者：
FROSTCHRISTENSEN, H;SANDJENSEN, K
研究了5种眼子菜属植物漂浮叶和沉水叶的形态和光合性能，以评估与空气接触或完全淹没相关的适应性。浮叶上表面有气孔，比沉水叶厚，单位表面积叶绿素含量高。浮叶的光吸收率较高，且与叶绿素浓度无关，而沉水叶的光吸收率较低，且与叶绿素浓度有较强的依赖关系。这两种叶型的光合速率相对较高，在其自然生长环境和量子产率类似的陆生叶达到的值。漂浮叶在空气中的碳利用表现出典型的C-3植物的CO2补偿点（32-49 mu 11（-1），相当于1.2-1.8 mu M），光合作用在环境大气CO2水平下不饱和。在水中的pH漂移实验中，沉水叶能够提取大部分溶解的无机碳池（82-89%），并获得高pH值（9.95-10.60）和低残留CO2浓度（6-80 nM），可能是HCO 3-利用的结果。浮叶形式的光合作用下降只有四倍时，放置在富含CO2的水（约200亩M）的光合作用的淹没叶形式下降了两倍时，转移到水饱和的空气中，由于高度增加呼吸。眼子菜属植物的漂浮叶比沉水叶能支持更高的光合作用面积速率，并且被认为在具有浑浊沃茨的生境中特别重要，并且作为漂浮平台和气生花的碳源。然而，这两种叶型的成本效益将取决于环境光和碳条件，因为漂浮叶也厚得多，生产成本高得多，并且它们在水面的有限水平位置限制了植物种群的光利用效率。
We examined the morphology and photosynthetic performance of floating and submerged leaves in five Potamogeton species to evaluate the adaptations associated with air contact or full submergence. The floating leaves had stomata on the upper surface, were thicker and contained more chlorophyll per surface area than the submerged leaves. The light absorptance was higher and independent of areal chlorophyll concentration for floating leaves, but lower and strongly chlorophyll dependent for submerged leaves. The photosynthetic rate of both leaf forms was relatively high in their natural growth environment and quantum yields resembled the values attained for terrestrial leaves. Carbon utilization of floating leaves in air showed CO2 compensation points (32-49 mu 11(-1), corresponding to 1.2-1.8 mu M), typical of C-3 plants, and photosynthesis was not saturated at ambient atmospheric CO2 levels. During pH-drift experiments in water, submerged leaves were able to extract the majority of the dissolved inorganic carbon pool (82-89%) and attain high pH values (9.95-10.60) and low residual CO2 concentrations (6-80 nM), presumably as a result of HCO3- utilization. Photosynthesis of floating leaf forms declined only four-fold when placed in CO2 enriched water (approximately 200 mu M) Photosynthesis of submerged leaf forms declined two-fold when transferred to water-saturated air, owing to a highly increased respiration. The floating leaves of Potamogeton can support higher areal rates of photosynthesis than submerged leaves and are believed to be particularly important in habitats with turbid waters, and as floating platforms and carbon sources for the aerial flowers. The cost-efficiency of the two leaf forms will depend, however, on the environmental light and carbon conditions because floating leaves are also much thicker and expensive to produce, and their confined horizontal location at the water surface restricts the efficiency of light utilization in plant populations.