【作者】 冯丽丽；

【导师】 王希华；

【作者基本信息】 华东师范大学 ， 生态学， 2010， 硕士

【摘要】 近半个世纪以来,随着工业的发展,酸雨污染日益加剧,酸雨对植物特别是森林植被的影响也越来越严重。近年来,国内外许多学者对酸雨在植物生理生态方面的影响做了大量的研究,并取得了显著的成果。随着经济的发展,我国东部地区大气中的NOx排放量已经超过SO2排放量,酸雨的硫氮比值正在逐步减小。而我们过去很多的模拟研究多集中在硫氮比(摩尔比)大于6的硫酸型酸雨,因此深入研究硫氮比值较低的酸雨对植物的影响具有重要的现实意义。通过对我国亚热带典型树种香樟(Cinnamomum camphora)、木荷(Schima superba)、枫香(Liquidambar formosana)、湿地松(Pinus elliottii)和水杉(Metasequoia glyptostroboides)一年生幼苗为期4个月的模拟酸雨处理,以当地水库水为对照,研究硫氮比(摩尔比)为1.58的酸雨胁迫(中度酸雨pH3.5、重度酸雨pH2.5)下,植物茎干生长参数、气体交换参数、质膜透性、养分元素等生理指标的变化规律。研究所取得的主要结论如下：1、低硫氮比酸雨能够引起植物产生一系列的形态和生理生态反应,主要表现在：(1)中度酸雨(pH3.5)对5种植物的茎干生长有一定的抑制作用,但均未出现显著伤害症状。重度酸雨(pH2.5)下,除湿地松外,其余幼苗的叶片均出现退绿、黄化、坏死斑等可见伤害症状；香樟、枫香、湿地松和水杉的茎干生长均有较大幅度的增加。(2)中度酸雨(pH3.5)下,植物的气体交换和光合响应均没有出现明显变化。除水杉外,中度酸雨(pH3.5)对其余幼苗的膜系统伤害较小。高浓度酸雨胁迫(pH2.5)诱导植物气孔部分关闭,引起植物体内外气体交换参数变化,导致叶片净光合速率、蒸腾速率和水分利用效率下降；另一方面,酸雨破坏叶片膜系统,加速脂质过氧化,降低叶绿素光合活性,并最终影响到叶片光合速率。但是重度酸雨(pH2.5)下植物的光合响应参数变化不明显。(3)中等强度的酸雨(pH3.5)对5种幼苗叶片的N、P含量均没有产生显著影响。枫香叶片的K含量和湿地松叶片的Al、Na含量显著上升,其余幼苗叶片的K、Ca、Na、Mg、Al、Mn、Fe、Zn含量均没有产生显著变化。重度酸雨(pH2.5)的氮肥效应使得木荷、枫香、水杉和湿地松的叶片N含量均呈现上升趋势。枫香的Ca、Mg、Mn含量,湿地松的Ca、Mn、Na含量和水杉的Al、Mg、Na含量显著升高。香樟的Al含量和枫香的K含量显著降低。(4)与以往高硫氮比(摩尔比大于6)酸雨研究结果相比发现,低硫氮比在一定程度上增加了植物生长的氮供给,提高了植物叶片的氮含量,在短期内可能会促进植物的茎干生长,减缓酸雨对植物的气体交换和膜系统的负面影响。但是对于较敏感的树种如水杉,中度酸雨(pH3.5)仍然造成植物叶片膜系统损伤。此外,低硫氮比还可能在一定程度上增强植物对酸雨的光合适应性。2、不同植物对低硫氮比酸雨的敏感性存在差异。在实验数据的基础上,综合多项指标发现：湿地松具有更高的抵御环境胁迫的能力,其次是香樟、枫香和木荷,水杉的适应能力较差。更多还原

【Abstract】 The acid rain pollution is worsing increasingly with the development of industry in recent half century, and the impact of acid rain on plant especially forest vegetation have also become more severe. Based on field investigations and experiment results with simulated acid rain, the potential effects of acid rain with higher S/N ratio (molar ration>6) on plants have been shown intensively in China. However, few reports have focus on the effect of acid rain with lower S/N ratio on plants, which has important practical significance with the decreasing of S/N ratio in future.The purpose of this study was to investigate the possible effects of simulated acid rain with lower S/N ratio on five dominant species in subtropical forests. One-year-old seedlings of Cinnamomum camphora, Schima superb, Liquidambar formosana, Pinus elliottii and Metasequoia glyptostroboides were transplanted into pots with the local soil (yellow-red soil) at Tiantong National Station of Forest Ecosystem, Zhejiang Province. The molar ratio of sulfate to nitrate of the simulated acid rain used in our study was 1.58:1, similar to the ratio of NO3- and SO42- in ambient rainfall in Zhejiang. Seedlings were treated with simulated acid rain of pH 2.5 or 3.5, respectively, every other day from April 15 to August 24 in 2009, and local reservoir water of pH 5.0-5.4 as the control. The growth parameters of stem, gas exchange parameters, Photosynthetic pigment contents, membrane penetration, malondialdehyde(MDA) and nutrient elements content in leaves were investigated at the end of the experiment. The results showed that:1、The morphological and physiological changes of seedlings were caused by the simulated acid rain with lower S/N ratio(1) No visible foliar injury was observed, while the growth of stem was inhibited in some degree with the treatment of pH 3.5 acid rain for all five species. The pH2.5 threatment resulted in typical visible foliar injury symptoms, such as etiolation, shrinkages and brown dots, except P. elliottii. The stem growth of C. camphora, S. superb, L. formosana and P. elliottii increased largely.(2) Except M. glyptostroboides, no significant difference was observed in these parameters with the treatment of pH 3.5 acid rain for the species. The pH2.5 treatment altered gas exchange parameters, including net photosynthetic rate(Pn), stomata conductance (Gs), transpiration rate (Tr) and water use efficiency (WUE). Membrane penetration and MDA contents in the seedling leaves of seedlings were increased significantly, suggesting that the decrease of photosynthetic activity was probably caused by non-stomatal factors in combination with stomatal closure. Treated with nitrogen fertilizer, total chlorophyll content of the leaves were increased, and net photosynthetic rate on the basis of chlorophyll content declined significantly under pH 2.5 acid rain treatment. It can be concluded that acid rain treatments can induce partial closing of stomata, damage membrane system and decrease photosynthetic activity of plants(3) Treated with pH3.5 acid rain, the nitrogen (N) and phosphorus (P) content in leaves of five species were not affected significantly. The content of Potassium (K), sodium (Na), Calcium (Ca), Magnesium (Mg), Aluminum(Al), Manganese (Mn), Iron (Fe), Zinc(Zn) in leaves of seedlings did not change significantly at pH3.5, except the K content of L. formosana and Al、Na content of P. elliottii which increased significantly. The N content in leaves of seedlings grew under the pH2.5 treatment owing to the nitrogen fertilizer, except C. camphora. The Ca、Mg、Mn content of L. formosana, the Ca、Mn、Na content of P. elliottii and the Al、Mg、Na content of M. glyptostroboides rised obviously, whereas the Al content of C. camphora and K content of L. formosana reduced significantly.(4) Based on the results, we can conclude that lower S/N ratio increase the supply of nitrogen to plant and improve the N content in leaves, which may promote the stem growth compared with the treatment of higher S/N ratio(molar ration>6). Furthermore, lower S/N ratio may mitigate negative effects of acid rain on photosynthesis and membrane.2、The adaptability to acid rain were various with the speciesWith the parameters measured, it can be found that P. elliottii has the best capacity to acclimate to acid rain stress followed by C. camphora, L. formosana, S. superb and M. glyptostroboides.This study improves our understandings in effects of acid rain on plant growth under lower S/N ratio.更多还原