Cheng Hao, Jiang Zhao-Yu, Liu Yong, Ye Zhi-Hong, Wu Mei-Lin, Sun Cui-Ci, Sun Fu-Lin, Fei Jiao, Wang You-Shao
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.
Tree Physiol. 2014 Jun;34(6):646-56. doi: 10.1093/treephys/tpu042. Epub 2014 Jun 24.
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 anatomy and lignification/suberization on metal uptake and tolerance in seedlings of six species of mangroves. The results revealed that the three rhizophoraceous species (Bruguiera gymnorrhiza (L.) Poir, Kandelia obovata Sheue, Liu & Yong and Rhizophora stylosa Griff) consistently exhibited higher metal tolerances than the three pioneer species (Aegiceras corniculatum (Linn.) Blanco, Acanthus ilicifolius L. and Avicennia marina (Forsk.) Viern.). Moreover, metal-tolerant species often exhibited a thick exodermis with high lignification and suberization. The tolerance indices of the mangroves were found to be positively correlated with the amounts of lignin and suberin deposition within the exodermal cell walls. The observed metal uptake by the excised roots further illustrated that a lignified/suberized exodermis directly delayed the entry of metals into the roots, and thereby contributed to a higher tolerance to heavy metals. In summary, the present study proposes a barrier property of the lignified/suberized exodermis in dealing with the stresses of heavy metals, such that the mangroves which possessed more extensive lignification/suberization within the exodermis appeared to exhibit higher metal tolerance.
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解剖结构以及木质化/栓质化对六种红树林幼苗金属吸收和耐受性的可能作用。结果表明，三种红树科物种（白骨壤、秋茄和红海榄）始终表现出比三种先锋物种（桐花树、老鼠簕和白骨壤）更高的金属耐受性。此外，耐金属物种通常具有一层厚的外皮层，其木质化和栓质化程度较高。发现红树林的耐受性指数与外皮层细胞壁内木质素和栓质素的沉积量呈正相关。对离体根的金属吸收观察进一步表明，木质化/栓质化的外皮层直接延迟了金属进入根部，从而有助于提高对重金属的耐受性。总之，本研究提出了木质化/栓质化外皮层在应对重金属胁迫方面的屏障特性，即在外皮层内具有更广泛木质化/栓质化的红树林似乎表现出更高的金属耐受性。
