【作者】 严雪；

【导师】 于丹；

【作者基本信息】 武汉大学 ， 植物学， 2003， 博士

【摘要】 环境的日益恶化，直接威胁到地球上生物（包括人类）的生存环境与生存空间。地表大气与水体是构成生物圈的两个重要部分，其质量的改变已经引起了广泛的关注。 面积广阔的水体已经成为污染物的主要容纳场所之一，而绝大部分污染物最终沉积在底泥中，通过泥—水界面扩散和释放有害物质，在水体中形成可持续的污染源。不能降解的重金属和具有致癌性的多环芳烃是水体和沉积环境中尤为重要的两类污染物，不仅在发达国家已经引起过严重的生态学灾难，在发展中国家也日益成为环境危机。 大气CO₂含量自1958年开始持续监测以来，发现其浓度以0.45％左右的速率上升，其原因主要来自于人为的影响。目前全球CO₂平均浓度已经超过了360μmol／mol，比工业革命前浓度高出了30％，预测到2100年将超过700μmol／mol。这已经成为全球气候变化，特别是导致地表温度升高（温室效应）的主要原因之一。 本文在实验室模拟水相和沉积相中重金属Pb和多环芳烃蒽的污染逆境和大气CO₂浓度升高（1000μmol／mol）的非污染逆境，通过研究低等水生植物轮藻（Chara globularis）、水网藻（Hydrodictyon reticulatum）和高等水生植物亚洲苦草（Vallisneria asiatica）和刺苦草（Vallisneria spinulosa）对污染物的富集和降解及其在上述环境下的克隆生长、生物量积累、光合作用、风险分摊以及能量代谢，初步探讨了水生植物对污染物的富集能力和在两种逆境下的生理生态学反应与适应策略。主要的研究结果如下： 水生植物能够明显的减缓水相中污染物质向底泥的沉积过程并能够大量吸收水环境中的污染物。苦草和轮藻对Pb的吸收存在明显的时间和浓度效应，随时间增加和环境浓度升高，植物体中积累量也增高，但水网藻对Pb的积累存在饱和现象；蒽在水生植物体内的富集量与植物细胞内疏水性脂类含量有关，水网藻积累量高于苦草和轮藻。随时间延长，蒽在植物体内被转移和降解，浓度降低。 水相污染物对水生植物产生明显的氧化性损伤，并对抗氧化性酶类产生比较复杂的影响，总的趋势是酶活性与污染物浓度升高而降低。通过比较发现，低等植物的抗逆性比高等植物高。三种水生植物中水网藻虽然没有POD活性，但具有较强的SOD活性，所以表现出对Pb有最强的耐受能力。水网藻对蕙胁迫的抗性可能与非酶类防御大分子有关。 沉积污染环境中，刺苦草鳞茎的萌发未受到Pb的影响。原因在于鳞茎作为一种繁殖与营养器官，能够为萌发提供相应的营养，减少了其对外界的环境依赖性。直到幼苗根系形成后，高浓度Pb的毒害作用才表现出来，以至于叶色变黄，组织坏死，生物量积累下降。为了逃避这种有害的生境，刺苦草产生了与对照有一定区别的生长模式。在对照生境中，其生长模式趋向于线状游击型，分枝少，摄食位点散布。在耐受浓度Pb中生长的刺苦草源株产生的子株能在健康与污染生境中以比较松散的线状类型生长，但超过了闽值的高浓度Pb生境中，植株子株不能生存，而在健康生境中形成密集型格局，并“回哺”源株，使其能勉强生存。 一定的数量Pb能由甸旬茎向生长在健康生境中的子株转移，在源株和子株体内产生有害的活性氧和自由基，形成风险分摊。在重金属的胁迫下，植株内部的抗氧化防御体系发生改变。由于克隆体系面临的胁迫程度不同，体内的抗氧化酶类和非酶类小分子物质的含量变化差别很大。160m酬kgPb基本抑制了源株中POD、CAT和SOD等的活性，而40m留kg Pb则刺激了上述酶类的活性增强。在受到风险分摊的子株中，除了SOD略升高外，其余与对照组没有区别。此外，随植株体内Pb浓度的变化，非酶类小分子含量也产生比较明显的改变，有利于提高植株的防御能力。 从表观上看，从含Pb环境中延伸到健康生境中的子株与对照环境没有明显的形态差异，但Pb己从生理上影响了植株的光合色素的合成、荧光产量及激发能在PSI和PSn之间的分配。Pb使源株荧光产量升高，引起植株吸收的光能无效耗能增加，Fv/F。和Fv/Fm的降低表明PSll光合色素复合蛋白活性和PSn原初光能转换效率的下降。Pb对刺苦草能量代谢的影响反应在腺普酸库和能荷值的降低。而高浓度Pb中源株根的能荷小于0.5，说明根发生了生物生存力的不可逆丧失，而植株尚能存活的物质来源有可能与子株“回哺”效应密切相关，其中的原因还有待于进一步的研究。 高浓度CO:有利于刺苦草克隆体系的生长。特别是在源株生长的前期和中期，地上部分的生长速率K远大于对照组。到生长末期，由于光合产物向地下转移储存于鳞茎中，生长速率开始减慢。对于子株生长的促进作用则表现在其整个生长过程中。经过在1 000娜ol/molCOZ下近四个月的培养，生物量增加了1.28倍。这些增加量来源于所有器官的贡献，但贡献率不同。其中鳞茎生物量与对照组相比，增幅虽然高达550%，远大于叶（增幅为206%），但其绝对增加量17.6克却远小于叶（绝对增加量72.9克），所以最大的贡献来源于叶（70%），其次为鳞茎（18%），根和旬甸茎相对较小，分别为7%和5%。 高浓度CO:从克隆体系整体上使鳞茎生物量分配比例增加，而减少了叶的比’例。在子株中鳞茎比例不仅显?更多还原

【Abstract】 The living space and environment of organisms, even those of the human beings, on the earth, are threatened by environmental deterioration. Changes within surface atmosphere and water body, two important parts of the biosphere, have drawn extensive attention from scientists and governments.The vast water-bodies have become the main receiver of contaminants, and most contaminants finally accumulate onto the sediment that in turn becomes a pollution source. As two most important contaminants, heavy metal that can’t be biodegraded and PAHs that typify carcinogenicity have not only brought severe ecocatastrophes in many developed countries, but also caused an ecocrisis in most developing countries.Since 1958, atmospheric concentration of CO2 has shown a steady increase at a rate (~ 0.45 % per year) because of anthropogenic factors. At present, the current atmospheric CO2 concentration, 360 umol/mol, is approximately 30 % higher than the pre-industrial level and conservatively projected to reach about 700 umol/mol by 2100. This becomes one of the prominent and incontrovertible reasons of global climate change, especially, resulting in a significant increase of the average global surface air temperature.In order to analyze the purifying capacity, the ecophysiological response and ecological adaptation of aquatic plants in different stress treatments, in this paper, pollution stress (high concentrations of Pb and PAHs in water phase and sediment) and non-pollution stress (elevated CO2, 1000 umol/mol) were imitated in laboratory and the contamination accumulation and biodegradation, clonal growth", biomass accumulation, photosynthesis, risk spreading and energy metabolism of lower plants. (Chora globular is, Hydrodictyon reticulatum) and vascular plants (Vallisneria asiatica, V. spinulosa), under above environmentwere studied. The main results are as follows:Aquatic plants can remarkably retard the settling process in water phase and greatly absorb contaminants in the aquatic environment. The absorption of Pb by aquatic plant has marked time and concentration effect, the accumulation in the plant increasing with time and concentration; but the accumulation of Pb by H. reticulatum shows the symptom of saturation. The accumulation of anthracene in H. reticulatum is higher than V. asiatica and C. globularis, which is related with the high content of hydrophobicity lipid of cell. With the extension of time, anthracene is transferred and biodegradated in the plant.Contaminants in water phase exerted marked oxidabitlity damage upon aquatic plant, and complex effects on antioxidative enzymes. The general trend being that enzyme activity reduces with the increase of concentration of contaminant. Comparison showed that the hardiness of lower plant is greater than vascular plant. Among the three aquatic plants, although H. reticulatum does not have POD activity, but it has strong SOD activity, and therefore performs greatest tolerance towards Pb. However, tolerance of H. reticulatum to anthracene is probably related to non-enzymic antioxidants.Sprouting of V. spinulosa turion was not affected by heavy metal Pb in sediment. This was explained by the fact that nutrition for seedling depended on the carbohydrate in turion and reduced the dependence of sprouting on environment. After root grew under high concentration of Pb, the seedling developed visible symptoms of toxicity such as chlorosis, necrotic lesions and decline of biomass accumulation. In order to escape the stress habitat, V. spinulosa developed another kind of architecture, which was different from that in the control. The architecture in the control tended to be "guerilla" with few branches and dispersed feeding sites. Ramets reproduced by ortets that grew in low concentration of Pb (below the tolerance threshold value) could grow in both the healthy habitat and low concentration of Pb habitat in linearity pattern. However, ramets didn’t survive in high concentration of Pb but grew in healthy habitat in phalanx pattern and the ortet grew in high concentration更多还原