State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, Hubei 430072, China.
Aquat Toxicol. 2010 Jun 10;98(2):196-203. doi: 10.1016/j.aquatox.2010.02.011. Epub 2010 Feb 17.
For revealing the mechanism of allelopathic influence on phytoplankton by aquatic macrophytes, the growth and photosynthetic activities of cyanobacteria Microcystis aeruginosa and the chlorophyte Selenastrum capricornutum were investigated when they coexisted with submerged macrophyte Myriophyllum spicatum and were exposed to allelopathic polyphenols: pyrogallic acid (PA), gallic acid (GA), ellagic acid (EA) and (+)-catechin (CA). According to the results of coexistence assays, the non-photochemical quenching (NPQ) and effective quantum efficiency (YII) of M. aeruginosa were affected earlier and more rapidly than the cell density. However, the influence of M. spicatum on S. capricornutum was not found. When the Toxicity Index (TI) was applied to evaluate the combined effects of binary and multiple mixtures of polyphenols, it was found that the four tested polyphenols with the proportion identified in the M. spicatum-cultured solution were observed to present synergistic effect (0.36-0.49) according to the cell density, NPQ and YII of M. aeruginosa. With the combined effects of polyphenols on S. capricornutum, only additive action (0.52-1.62) was found. On the other hand, PA (2.97mgL(-1)), GA (2.65mgL(-1)) caused significant reductions of photosystem II (PSII) and whole electron transport chain activities of M. aeruginosa by 71.43 and 18.37%, 70.95 and 40.77% (P<0.05), respectively, after 24-h exposure, but no inhibition effect was found in S. capricornutum. The dark respiration and photosystem I (PSI) activities of M. aeruginosa were significantly increased by exposure to PA and GA (P<0.05). Nevertheless, EA and CA had no influence on the electron transport activities of the tested organisms. These results indicate that the reduction in photosynthetic activity of M. aeruginosa and the synergistic effect of allelochemicals may be two important causes for the inhibition of undesired phytoplankton by submersed macrophytes in natural aquatic ecosystems, and PSII in cyanobacteria is considered to be one of the target sites attacked by allelopathic polyphenols.
为了揭示水生植物对浮游植物化感作用的机制，研究了水生植物菹草（Myriophyllum spicatum）共存下，微囊藻（Microcystis aeruginosa）和绿藻（Selenastrum capricornutum）的生长和光合作用活性，并暴露于化感多酚：焦性没食子酸（PA）、没食子酸（GA）、鞣花酸（EA）和（+）-儿茶素（CA）。根据共存试验的结果，非光化学猝灭（NPQ）和有效量子效率（YII）比细胞密度更早、更迅速地受到影响。然而，没有发现菹草对绿球藻的影响。当应用毒性指数（TI）来评估多酚的二元和多元混合物的综合效应时，发现根据微囊藻培养液中确定的比例，四种测试多酚对微囊藻的细胞密度、NPQ 和 YII 表现出协同作用（0.36-0.49）。对于多酚对绿球藻的综合效应，只发现了相加作用（0.52-1.62）。另一方面，PA（2.97mgL(-1)）、GA（2.65mgL(-1)）分别使微囊藻的 PSII 和整个电子传递链活性显著降低了 71.43%和 18.37%、70.95%和 40.77%（P<0.05），而绿球藻没有抑制作用。PA 和 GA 暴露 24 小时后，微囊藻的暗呼吸和 PSI 活性显著增加（P<0.05）。然而，EA 和 CA 对测试生物的电子传递活性没有影响。这些结果表明，微囊藻光合作用活性的降低和化感物质的协同作用可能是水生植物在自然水生生态系统中抑制不需要的浮游植物的两个重要原因，并且蓝藻的 PSII 被认为是化感多酚攻击的靶标之一。
