Maximum photosynthetic efficiency of size-fractionated phytoplankton assessed by 14C uptake and fast repetition rate fluorometry
Maximum photosynthetic efficiency of size-fractionated phytoplankton assessed by 14C uptake and fast repetition rate fluorometry
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DOI：
10.4319/lo.2005.50.5.1438
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发表时间：
2005-09-01
影响因子：
4.5
通讯作者：
Fernández, E
中科院分区：
文献类型：
--
作者：
Cermeño, P;Estévez-Blanco, P;Fernández, E
在高营养浓度和充足光照条件下，大型浮游植物可能比小型浮游植物表现出更高的光合作用效率。这是意想不到的，因为较小的浮游植物，因为它们的表面积与体积比较高，拥有更强的吸收养分和吸收光线的能力。为了探讨大型浮游植物光合作用效率提高的原因，我们同时进行了基于C-14的光合作用辐照度实验和快速重复频率荧光测量，评估了3个大小级别(5、5-20和20微米)海岸群落的最大光合作用效率。在冬季混合(2003年3月)和夏季层积(2003年6月)期间，测定了各尺度级的光饱和光合作用(P-max(B))和最大光系统II(PSII)光化学效率(F-v/F-m)。冬季混合时，各粒级的P-max(B)和F-v/F-m相似。相反，在夏季层结期间，20微米大小级的P-max(B)和F-v/F-m显著较高。在整个数据集中，按大小划分的P-max(B)和F-v/F-m没有显著的相关性。然而，对于适应弱光条件的浮游植物，大小分级的P-max(B)和F-v/F-m之间存在显著的关系。在强光下，过剩的PSII能力可能是导致不同粒级的P-max(B)和F-v/F-m测量结果不一致的原因，而在弱光条件下，光合作用电子传递链和PSII下游的成分变得更加平衡，这导致两个变量之间的紧密协变。大型浮游植物的最大光合作用效率较高可能与某些分类类群(如硅藻)具有较高的PSII光化学效率有关。
Under high nutrient concentrations and sufficient light conditions, large phytoplankton may display higher photosynthetic efficiency than smaller cells. This is unexpected since smaller phytoplankton, because of their higher surface to volume ratio, possess a greater ability to take up nutrients and absorb light. In order to investigate the causes of the increased photosynthetic efficiency in larger phytoplankton, we assessed the maximum photosynthetic efficiency of coastal assemblages in three size classes (< 5, 5-20, and > 20 mu m) by concurrently conducting C-14- based photosynthesis-irradiance experiments and fast repetition rate fluorescence measurements. The light-saturated, chlorophyll-specific photosynthesis (P-max(b)) and the maximum photosystem II (PSII) photochemical efficiency (F-v/ F-m) of each size class were determined during winter mixing (March 2003) and summer stratification (June 2003). During winter mixing, size-fractionated P-max(b) and F-v/F-m were similar in all size classes. In contrast, during summer stratification, size-fractionated P-max(b) and F-v/F-m were significantly higher in the > 20-mu m size class. In the entire data set, size-fractionated P-max(b) and F-v/F-m were not significantly correlated. However, a significant relationship was found between size-fractionated P-max(b) and F-v/F-m for phytoplankton assemblages acclimated to low light conditions. Under high light, an excess PSII capacity may be responsible for the discrepancy between size-fractionated P-max(b) and F-v/F-m measurements, whereas under low light conditions, photosynthetic electron transport chain and components downstream of PSII become more balanced, which results in a tight covariation between both variables. Higher maximum photosynthetic efficiencies of large-sized phytoplankton might be associated with a higher PSII photochemical efficiency characteristic of certain taxonomic groups such as diatoms.