Australian Rivers Institute & Griffith School of Environment and Science, Griffith University, Nathan, QLD 4111, Australia.
Griffith School of Environment, Environmental Futures Research Institute, Griffith University, Gold Coast Campus, Parklands Drive, Southport, Queensland 4222, Australia.
Sci Total Environ. 2019 Dec 10;695:133901. doi: 10.1016/j.scitotenv.2019.133901. Epub 2019 Aug 13.
Previous studies have shown that under laboratory conditions, dissolved organic matter (DOM) leached from plants can be differentially more phytotoxic to cyanobacteria, compared to green algae. This study examined how DOM source and transformation processes (microbial and photochemical) affect its chemical composition and phytotoxicity towards a cultured species of cyanobacteria (Raphidiopsis raciborskii) using a factorial experimental design. To complement cyanobacterial bioassays, the chemical composition and associated changes in DOM were determined using spectroscopic (nuclear magnetic resonance (NMR) and absorbance) and elemental analyses. Sunlight exposed DOM from leaves of the terrestrial plants, Casuarina cunninghamiana and Eucalyptus tereticornis had the most phytotoxic effect compared to DOM not exposed to sunlight. This phytotoxic DOM was characterised by relatively low nitrogen content, containing highly coloured and relatively high molecular mass constituents. Both mixed effect model and PCA approaches to predict inhibition of photosynthetic yield indicated phytotoxicity could be predicted (P < 0.001) based upon the following parameters: C: N ratio; gilvin, and lignin-derived phenol content of DOM. Parallel proton-detected 1D and 2D NMR techniques showed that glucose anomers were the major constituents of fresh leachate. With ageing, glucose anomers disappeared and products of microbial transformation appeared, but there was no indication of the appearance of additional phytotoxic compounds. This suggests that reactive oxygen species may be responsible, at least partially, for DOM phytotoxicity. This study provides important new information highlighting the characteristics of DOM that link with phytotoxic effects.
先前的研究表明，在实验室条件下，植物浸出的溶解有机质（DOM）对蓝藻的植物毒性比绿藻更为显著。本研究采用析因实验设计，考察了 DOM 的来源和转化过程（微生物和光化学）如何影响其化学成分及其对培养的蓝藻（Raphidiopsis raciborskii）的植物毒性。为了补充蓝藻生物测定，使用光谱（核磁共振（NMR）和吸光度）和元素分析来确定 DOM 的化学组成及其相关变化。与未暴露在阳光下的 DOM 相比，来自陆地植物 Casuarina cunninghamiana 和 Eucalyptus tereticornis 的叶片暴露在阳光下的 DOM 具有最强的植物毒性效应。这种具有植物毒性的 DOM 具有相对较低的氮含量，含有高度着色和相对高分子质量的成分。混合效应模型和 PCA 方法均可预测光合作用产量的抑制，表明可以根据以下参数预测植物毒性（P<0.001）：DOM 的 C:N 比、gilvin 和木质素衍生酚的含量。平行质子检测的 1D 和 2D NMR 技术表明，葡萄糖差向异构体是新鲜浸出液的主要成分。随着老化，葡萄糖差向异构体消失，出现微生物转化产物，但没有出现其他具有植物毒性的化合物的迹象。这表明，至少部分地，活性氧物质可能是 DOM 植物毒性的原因。本研究提供了重要的新信息，强调了与植物毒性效应相关的 DOM 特征。
