Puzon Juliana Janet M, Rivero Gilda C, Serrano Jocelyn E
Institute of Biology, College of Science, University of the Philipppines Diliman, Quezon City, 1101, Philippines,
Environ Monit Assess. 2014 Oct;186(10):6889-901. doi: 10.1007/s10661-014-3897-0. Epub 2014 Jul 10.
Eichhornia crassipes (Mart.) Solms. plantlets were grown in 0.1 and 1.0 ppm treatment solutions of Hoagland's hydroponic solutions modified with Hg(NO₃)2 in order to examine the specific cellular and biochemical mechanisms involved in the tolerance of this plant exposed to mercury. This study assessed the responses of chloroplast pigments, i.e., carotenoids and chlorophylls, and evaluated the enzymatic and nonenzymatic antioxidant systems. Inductively coupled plasma-atomic emission spectrometry (ICP-AES) revealed varying Hg(2+) levels in the young and mature leaf tissues, with greater amounts of Hg(2+) found in the tissues of the young leaves. Total chlorophyll levels, notably those of chlorophyll a, chlorophyll b, and carotenoids, showed significant elevation in young leaf tissues, while a decrease in their levels was observed in mature leaf tissues in comparison to those of the control plants. These results lend support to the protective role of increased chlorophyll and carotenoid levels in the photosynthetic apparatus of young E. crassipes leaves in the presence of Hg(2+). The antioxidant responses of Hg-treated E. crassipes plants were also measured, revealing a highly significant increase in catalase units, catalase and ascorbate peroxidase activities, and mercury-binding thiols in leaves from Hg-treated plants. Moreover, substantial differences in the degree of oxidative injury between the cells in leaves from the control and Hg-treated plants were evidenced by the lipid peroxidation activities monitored. The Hg-treatment-induced significant decrease in malondialdehyde (MDA) levels was observed in 0.1-ppm Hg(NO₃)2-exposed plants, while a highly significant increase in MDA levels was noted in 1.0-ppm Hg(NO₃)2-exposed plants. The high degree of lipid peroxidation at 1.0-ppm Hg treatment was evidently counteracted by the compensatory protective mechanism brought about by the increased levels in chloroplast pigments and the enhanced activities of the antioxidant systems. E. crassipes responded to mercury treatments by enhancing the synthesis of chlorophyll and carotenoid pigments, enzymatic, and nonenzymatic antioxidant substances, concomitantly increasing the antioxidative activities, thus rendering E. crassipes capable of tolerating Hg-induced stress. The potential of E. crassipes as a phytoremediator is evident.
为了研究凤眼莲（Eichhornia crassipes (Mart.) Solms.）耐受汞的具体细胞和生化机制，将其幼苗培养在添加了Hg(NO₃)₂的改良霍格兰水培溶液的0.1 ppm和1.0 ppm处理溶液中。本研究评估了叶绿体色素（即类胡萝卜素和叶绿素）的反应，并评估了酶促和非酶促抗氧化系统。电感耦合等离子体原子发射光谱法（ICP - AES）显示，幼叶和成熟叶组织中的Hg(2+)水平不同，幼叶组织中的Hg(2+)含量更高。总叶绿素水平，尤其是叶绿素a、叶绿素b和类胡萝卜素的水平，在幼叶组织中显著升高，而与对照植物相比，成熟叶组织中的这些水平则有所下降。这些结果支持了在Hg(2+)存在的情况下，增加叶绿素和类胡萝卜素水平对凤眼莲幼叶光合器官的保护作用。还测量了汞处理的凤眼莲植物的抗氧化反应，结果显示，汞处理植物叶片中的过氧化氢酶单位、过氧化氢酶和抗坏血酸过氧化物酶活性以及汞结合硫醇显著增加。此外，通过监测脂质过氧化活性证明，对照植物和汞处理植物叶片细胞的氧化损伤程度存在显著差异。在暴露于0.1 ppm Hg(NO₃)₂的植物中，观察到汞处理导致丙二醛（MDA）水平显著降低，而在暴露于1.0 ppm Hg(NO₃)₂的植物中，MDA水平显著升高。1.0 ppm汞处理时的高度脂质过氧化显然被叶绿体色素水平增加和抗氧化系统活性增强所带来的补偿性保护机制所抵消。凤眼莲通过增强叶绿素和类胡萝卜素色素、酶促和非酶促抗氧化物质的合成来应对汞处理，同时增加抗氧化活性，从而使凤眼莲能够耐受汞诱导的胁迫。凤眼莲作为植物修复剂的潜力显而易见。
