Cheng Hao, Wang You-Shao, Liu Yong, Ye Zhi-Hong, Wu Mei-Lin, Sun Cui-Ci
State Key Laboratory of Tropical Oceanography and Daya Bay Marine Biology Research Station, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou, 510301, China.
Key Laboratory for Exploitation & Utilization of Marine Fisheries Resource in South China Sea, Ministry of Agriculture, South China Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences, Guangzhou, 510300, China.
Ecotoxicology. 2015 Oct;24(7-8):1650-8. doi: 10.1007/s10646-015-1473-1. Epub 2015 May 9.
Metal pollution has been widely reported in mangrove wetlands; however, the mechanisms involved in metal detoxification by mangroves are still poorly understood. This study aimed to investigate the possible function of root lignification/suberization on Pb uptake and tolerance in mangroves. Two mangroves, Acanthus ilicifolius and Rhizophora stylosa with different root lignification/suberization were selected as plant materials; the former exhibits a thin exodermis and low lignification/suberization, while the latter possesses a thick exodermis and high lignification/suberization. A pot trial with addition of Pb was conducted to investigate the differences in Pb uptake and tolerance between the two mangroves. The experiment of rhizobox was designed to explore Pb dynamics and availabilities in the rhizosphere soils, besides, the ability of Pb uptake by the excised roots and X-ray analysis for Pb distribution within roots were also detected. The results revealed that R. stylosa exhibited relatively higher Pb tolerance together with less Pb accumulations when compared to A. ilicifolius. For both species, lower proportion of exchangeable and Carbonate Pb and higher higher Fe-Mn oxides Pb were observed in the rhizosphere zone when compared to the respective non-rhizosphere zone. The results from metal uptake by the excised roots and X-ray analysis clearly showed that the thick lignified/suberized exodermis of R. stylosa could more efficiently delay Pb entering into the roots, leading to less Pb accumulation. In summary, the present study proposes a barrier property of the lignified/suberized exodermis in dealing with the stresses of Pb.
金属污染在红树林湿地中已有广泛报道；然而，红树林对金属解毒的机制仍知之甚少。本研究旨在探讨根系木质化/栓质化在红树林对铅的吸收和耐受性方面可能发挥的作用。选取两种根系木质化/栓质化程度不同的红树林植物——老鼠簕和红海榄作为实验材料；前者具有较薄的外皮层和较低的木质化/栓质化程度，而后者具有较厚的外皮层和较高的木质化/栓质化程度。进行了添加铅的盆栽试验，以研究这两种红树林在铅吸收和耐受性方面的差异。设计了根箱实验来探究根际土壤中铅的动态变化和有效性，此外，还检测了离体根对铅的吸收能力以及根系内铅分布的X射线分析。结果表明，与老鼠簕相比，红海榄表现出相对较高的铅耐受性，且铅积累较少。对于这两个物种，与各自的非根际区相比，根际区中可交换态和碳酸盐结合态铅的比例较低，而铁锰氧化物结合态铅的比例较高。离体根对金属的吸收结果和X射线分析清楚地表明，红海榄厚的木质化/栓质化外皮层能够更有效地延迟铅进入根系，从而减少铅积累量。总之，本研究提出了木质化/栓质化外皮层在应对铅胁迫方面的屏障特性。
