College of Environment Science and Engineering, Xiamen University of Technology, Ligong Road 600, 361024, Xiamen, China.
Ecotoxicology. 2020 Jul;29(5):514-523. doi: 10.1007/s10646-020-02196-2. Epub 2020 Apr 10.
Understanding the growth and development of aquatic plants in eutrophic water is of great significance for the selection of potential candidate plant for use in the phytoremediation of eutrophic aquatic ecosystems. The present study aimed to investigate the chronic effects of microcystin-LR (MC-LR) on photosynthesis in the leaves of Typha angustifolia Linn. Photosynthetic activity was stimulated in the leaves following exposure to 4.6 μg L MC-LR for six weeks based on the enhancement of Ribulose-1, 5-bisphosphate carboxylase/oxygenase (Rubisco) activity and net photosynthetic rate (P). However, P decreased significantly after exposure to 49.1 or 98.3 μg L MC-LR, via non-stomatal limitation by reducing the chlorophyll a and b contents and Rubisco activity. In addition, glycolate oxidase (GO) and serine:glyoxylate aminotransferase (SGAT) activities decreased significantly, indicating that the photorespiration pathway was affected adversely. The intercellular carbon dioxide (C) concentration decreased significantly following exposure to 98.3 μg L MC-LR, accompanied with decreases in P and stomatal conductivity (g), indicating that stomatal limitation on the photosynthesis system in T. angustifolia L. was observed after exposure to 98.3 μg L MC-LR. Under long-term exposure to MC-LR (49.1-98.3 μg L), oxidation stress was severe in the aquatic plant, and non-stomatal limitation or stomatal limitation effects on the photosynthesis system were obvious, resulting in decreases in photosynthesis rates.
了解富营养化水体中水生植物的生长发育对于选择潜在的候选植物用于富营养化水生生态系统的植物修复具有重要意义。本研究旨在研究微囊藻毒素-LR（MC-LR）对香蒲叶片光合作用的慢性影响。根据核酮糖-1,5-二磷酸羧化酶/加氧酶（Rubisco）活性和净光合速率（P）的增强，在暴露于 4.6μg/L MC-LR 六周后，叶片中的光合活性受到刺激。然而，当暴露于 49.1 或 98.3μg/L MC-LR 时，P 显著下降，这是通过降低叶绿素 a 和 b 含量以及 Rubisco 活性来实现的非气孔限制。此外，乙醇酸氧化酶（GO）和丝氨酸：乙醛酸氨基转移酶（SGAT）活性显著降低，表明光呼吸途径受到不利影响。暴露于 98.3μg/L MC-LR 后，细胞间二氧化碳（C）浓度显著下降，伴随着 P 和气孔导度（g）的下降，表明在暴露于 98.3μg/L MC-LR 后，香蒲叶片光合作用系统受到气孔限制。在长期暴露于 MC-LR（49.1-98.3μg/L）下，水生植物的氧化应激严重，非气孔限制或气孔限制对光合作用系统的影响明显，导致光合作用速率下降。
