Jiang Shan, Xie Feng, Lu Haoliang, Liu Jingchun, Yan Chongling
Key Laboratory of the Ministry of Education for Coastal and Wetland Ecosystems, Xiamen University, Xiamen, 361005, China.
Environ Sci Pollut Res Int. 2017 May;24(13):12484-12493. doi: 10.1007/s11356-017-8845-4. Epub 2017 Mar 30.
Low-molecular-weight organic acids (LMWOAs) represent an important component of root exudates. They play a pivotal role in the degradation of polycyclic aromatic hydrocarbons (PAHs) in sediments as they influence PAH bioavailability and degrader colonization. This study examined variations of LMWOAs in mangrove root exudates (Aegiceras corniculatum and Kandelia obovata) after exposure in phenanthrene and pyrene solution for 7 and 40 days, respectively. After 7 days of treatment, total root exudates and six types of LMWOA in root exudates from both mangrove species were enhanced. The largest increase was found in oxalic acid, i.e., the dominant component in determined LMWOAs. Coupled with the enhancement in LMWOA exudation rates, root metabolism intensities, measured as the dehydrogenase activity, increased. In contrast, after 40 days of exposure, the exudation rate of total LMWOAs had dropped markedly in PAH-contaminated groups compared to the control, indicating that PAHs negatively impacted root metabolism and activities due to their toxicity. The largest decrease was also found in oxalic acid, suggesting that the biological reactions related with oxalic acid are vulnerable under PAH stresses.
低分子量有机酸（LMWOAs）是根系分泌物的重要组成部分。它们在沉积物中多环芳烃（PAHs）的降解过程中起着关键作用，因为它们会影响PAHs的生物可利用性和降解菌的定殖。本研究分别考察了角果木（Aegiceras corniculatum）和秋茄（Kandelia obovata）这两种红树植物的根系分泌物在菲和芘溶液中暴露7天和40天后低分子量有机酸的变化情况。处理7天后，两种红树植物根系分泌物的总量以及根系分泌物中六种低分子量有机酸的含量均有所增加。其中草酸增加幅度最大，草酸是已测定的低分子量有机酸中的主要成分。随着低分子量有机酸分泌速率的增加，以脱氢酶活性衡量的根系代谢强度也增加了。相反，暴露40天后，与对照组相比，多环芳烃污染组中低分子量有机酸的总分泌速率显著下降，这表明多环芳烃因其毒性对根系代谢和活性产生了负面影响。草酸的下降幅度也最大，这表明与草酸相关的生物反应在多环芳烃胁迫下较为脆弱。
