Effects of environmental stress on characteristics of low molecular weight organic acids secreted by macrophyte roots

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Abstract

本文首次对马来眼子菜（Potamogeton malaianus）、苦草（Vallisneria natans）、芦苇（Phragmites australis）、菖蒲（Acorus calamus）、荇菜（Nymphoides peltatum）和菱角（Trapa incisa）6种水生植物根系小分子量有机酸（Low Molecular Weight Organic Acids，LMWOAs）分泌差异性及其对环境胁迫（温度、缺磷和高铵态氮）响应特征进行研究.结果证实6种受试植物根系分泌LMWOAs组成和含量具有明显的物种差异性；其中，甲酸、乳酸和草酸为主要有机酸.温度可显著影响水生植物根系LMWOAs分泌量而对种类影响不大，高温（30℃）刺激莕菜根系LMWOAs分泌量增加，但却明显抑制苦草和菖蒲根系LMWOAs分泌； 25℃时马来眼子菜、芦苇和菱角根系LMWOAs分泌量最多.缺磷和高铵态氮胁迫均会显著影响水生植物根系LMWOAs分泌量和种类.缺磷胁迫促进苦草、菖蒲和莕菜根系LMWOAs分泌量增加68.68%、55.30%和257.82%，并刺激乙酸和苹果酸等有机酸分泌；而缺磷胁迫可导致马来眼子菜、芦苇和菱角根系LMWOAs分泌量降低38.72%、13.79%和58.99%，且乳酸、甲酸和丁二酸分泌完全被抑制；这表明苦草、菖蒲和莕菜三者能较好的适应缺磷环境.高铵态氮胁迫下苦草根系LMWOAs分泌量和种类增加明显；而其余5种受试植物在高铵态氮胁迫下根系LMWOAs分泌量被明显抑制，尤其是乳酸、苹果酸和酒石酸含量显著降低.综上所述，水生植物分泌LMWOAs特征差异性显著，可在一定程度上反映其耐逆境胁迫能力，本文结果将为水生植物生态修复机理和实践提供重要理论依据.;In this work, six typical aquatic macrophytes, Potamogeton malaianus, Vallisneria natans, Phragmites australis, Acorus calamus, Nymphoides peltatum and Trapa incisa, were selected to investigate their root secretion characteristics of low molecular weight organic acids (LMWOAs) under the stresses of temperature, phosphorus (P) deficiency and high level of ammonia-nitrogen (NH₄+-N). Generally, the compositions and amounts of LMWOAs significantly varied among six species, with formic acid, lactic acid and oxalic acid as the dominate LMWOAs. Temperature didn't change the LMWOAs compositions but had significant effect on LMWOAs amounts. Higher temperature (30℃) was demonstrated to promote LMWOAs secretions for N. peltatum but evidently inhabit that of V. natans and A. calamus. The highest LMWOAs secretion of P. malaianus, P. australis and T. incisa was at 25℃. P deficiency and high level of NH₄+-N could significantly affect the compositions and amounts of LMWOAs. Under P-deficiency stress, the LMWOAs amounts secreted by V. spiralis, A. calamus and N. peltatum were increased by 68.68%, 55.30% and 257.82% respectively, and the acetic acid and malic acid were significantly secreted. In contrast, the LMWOAs amounts secreted by P. malaianus, P. australis and T. incisa were significantly reduced by 38.72%, 13.79% and 58.99% respectively, and the lactic acid, formic and succinic acid were completely inhibited. It indicated that V. natans, A. calamus and N. peltatum were more adaptive to low P sediment. Except for V. spiralis, high level of NH₄+-N significantly reduced the amounts of LMWOAs, especially lactic acid, malic acid and tartaric acid for all the investigated species. In conclusion, significant differences among LMWOAs secreted by macrophytes are closely associated with their tolerances to environmental stress, which will provide important scientific supports for aquatic ecosystem restoration.

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