Bharali Bhagawan, Bates Jeffrey W
Department of Crop Physiology, Assam Agricultural University, Jorhat-785013, Assam, India.
Ann Bot. 2006 Feb;97(2):257-63. doi: 10.1093/aob/mcj026. Epub 2005 Nov 30.
The widespread calcifuge moss Pleurozium schreberi is moderately tolerant of SO2, whereas Rhytidiadelphus triquetrus is limited to calcareous soils in regions of the UK that were strongly affected by SO2 pollution in the 20th century. The proposition that tolerance of SO2 by these terricolous mosses depends on metabolic detoxification of dissolved bisulfite was investigated.
The capacities of the two mosses to accelerate loss of bisulfite from aqueous solutions of NaHSO3 were studied using DTNB [5, 5-dithio-(2-nitrobenzoic acid)] to assay bisulfite, and HPLC to assay sulfate in the incubation solutions. Incubations were performed for different durations, in the presence and absence of light, at a range of solution pH values, in the presence of metabolic inhibitors and with altered moss apoplastic Ca2+ and Fe3+ levels.
Bisulfite disappearance was markedly stimulated in the light and twice as great for R. triquetrus as for P. schreberi. DCMU, an inhibitor of photosynthetic electron chain transport, significantly reduced bisulfite loss.
Bisulfite (SO2) tolerance in these terricolous mosses involves extracellular oxidation using metabolic (photo-oxidative) energy, passive oxidation by adsorbed Fe3+ (only available to the calcifuge) and probably also internal metabolic detoxification.
广泛分布的嫌钙藓类植物尖叶拟垂枝藓对二氧化硫具有中等耐受性，而三角叶提灯藓则仅生长于英国20世纪受二氧化硫污染严重地区的石灰性土壤中。本研究探讨了这些陆生藓类植物对二氧化硫的耐受性是否取决于溶解亚硫酸氢盐的代谢解毒作用。
使用5,5-二硫代-（2-硝基苯甲酸）（DTNB）测定亚硫酸氢盐，高效液相色谱法测定孵育溶液中的硫酸盐，研究了这两种藓类植物促进亚硫酸氢钠水溶液中亚硫酸氢盐损失的能力。在不同的孵育时间、有无光照、一系列溶液pH值条件下、存在代谢抑制剂以及改变藓类植物质外体Ca2+和Fe3+水平的情况下进行孵育。
光照下亚硫酸氢盐的消失明显加快，三角叶提灯藓的消失速度是尖叶拟垂枝藓的两倍。光合电子链运输抑制剂敌草隆显著降低了亚硫酸氢盐的损失。
这些陆生藓类植物对亚硫酸氢盐（二氧化硫）的耐受性涉及利用代谢（光氧化）能量进行细胞外氧化、被吸附的Fe3+（仅嫌钙藓类植物可利用）进行被动氧化，可能还包括内部代谢解毒。
