UV-B辐射对孔石莼同形世代交替各个阶段发育的影响及响应机制研究

Enhanced UV-B (280nm±320nm) radiation resulting from ozone depletion was one of global environmental problems. Not only terrestrial ecosystems but also marine ecosystems could be affected by enhanced UV-B radiation. The effects of enhanced UV-B radiation on marine macro-algae were exposed to be greatest in shallow intertidal environments because the macro-algae were often at or above the water during low tide. Then enhanced UV-B radiation would affect coastal marine ecosystems. The effects of UV-B radiation on the growth, physiology and biochemistry of macro-algae have been extensively studied. However, few studies have focused on the effects on life history of macro-algae. The effects of UV-B radiation on the growth of sporophyte and gametophyte, the yield of biflagellate gamete and quadriflagellate zoospore were studied, and the changes of the spore and zygote germination rate, germination speed, morphology and aberration were explored using Ulva pertusa Kjellm as the materials in this project. In addition, the response mechanism of UV-B radiation on the photosynthesis, cells ultrastructure, reactive oxygen species generation, antioxidant enzyme system, DNA and protein damage and repair were studied using the sporophyte, gametophyte, biflagellate gamete, quadriflagellate zoospore, different developmental stages of settled spore and zygote on Ulva pertusaje Kjellm. It would clarify the influence of UV-B radiation on the isomorphic alternation of life history of Ulva pertusa Kjellm. The results would provide the fundamental for us to clarify the effects of UV-B radiation on coastal marine ecosystems.

由于臭氧层侵蚀和破坏的日趋加重，使得到达地面的UV-B（280±320nm）辐射增强是当今全球性的重大环境问题之一。潮间带大型海藻由于生长在海洋和陆地的交替区域，直接受到UV-B辐射增强的危害，进而影响近岸海洋生态系统。研究表明UV-B辐射对大型海藻有显著的影响，但对大型海藻生活史不同阶段的影响研究确少见报道。本项目选择潮间带常见的大型海藻孔石莼为研究对象，研究UV-B辐射对其孢子体和配子体生长、游孢子和游配子的产量的影响，并探索孢子和合子萌发率、萌发时长、形态、畸变率的变化；并以孔石莼孢子体、配子体、游孢子、游配子、孢子和合子的不同发育时期为材料，探讨其光合作用、细胞超微结构、活性氧产生、抗氧化酶系统、DNA和蛋白质伤害及修复对UV-B辐射的响应机制。以期阐明UV-B辐射增强对孔石莼同型世代交替生活史的影响，研究结果为研究UV-B辐射增强对近岸海洋生态系统的影响奠定基础。

由于臭氧层衰减导致到达地面的UV-B (280±320nm)辐射增强是全球性环境问题之一。生活在潮间带水域的大型海藻孔石莼（Ulva pertusa Kjellman）不可避免地会受到UV-B辐射增强的影响。因此，项目主要研究了UV-B辐射对孔石莼生活史不同阶段的影响，研究结果为评估UV-B辐射增强对潮间带生态系统的影响提供依据。首先对孔石莼发育的早期情况进行了研究，其发育早期外形主要呈现棒状和蝌蚪状，其中棒状占90.68%±2.50%。UV-B辐射对孔石莼孢子体和配子体的生长和叶绿素a含量均有抑制作用，但孔石莼孢子体和配子体之间的生长和叶绿素a含量均无明显差异，而UV-B辐射处理的孢子体和配子体之间的生长和叶绿素a含量也均无明显差异。UV-B辐射会抑制孔石莼游孢子的释放，使附着孢子的密度降低，同时会降低附着孢子的萌发率。孔石莼幼苗的叶长和叶表面积的发育也会受到UV-B辐射的抑制，随着辐射剂量的增加，抑制作用愈加明显。UV-B辐射会使孔石莼幼苗死亡率上升，幼苗的死亡过程主要表现为细胞收缩和叶绿素的减少。受到UV-B辐射后，幼苗的叶绿素a含量会显著降低，而可溶性蛋白含量会出现增加的现象。UV-B辐射会使幼苗的•O2− 和 H2O2 含量明显增加，进而导致MDA含量的增加；而SOD 和CAT活力也会增加以消除产生的过量的ROS。透射电镜观察发现，UV-B辐射会使幼苗细胞膜出现皱缩，细胞内溶酶体颗粒圆形外观受到破坏。孔石莼成体的生长率和叶绿素a含量会受到UV-B辐射的抑制，而可溶性蛋白含量并没有明显的影响。受到UV-B辐射后，孔石莼成体ROS含量增加， SOD活力也会增加，而CAT活力会出现降低的情况。同时UV-B辐射会使DNA会出现损伤，随着辐射剂量的增加，损伤的更加明显。透射电镜观察发现，UV-B辐射会使孔石莼细胞收缩，细胞器缺失，细胞壁形态出现明显的褶皱，甚至破裂。UV-B辐射也会对孔石莼幼苗和成体的N-NH4+、N-NO3-、P-PO43-的吸收产生影响。最后研究了室外模拟条件下UV-B辐射衰减对孔石莼的影响，UV-B衰减会使孔石莼生长率升高，而叶绿素a、可溶性蛋白和ROS含量均会降低。因此，UV-B辐射会对孔石莼各发育阶段均会出现明显的影响，进而对近岸海洋生态系统和环境造成影响。