亚热带常见树种幼苗对酸雨的生理响应及敏感性综合评判

以杨梅（Myrica rubra）、香樟（Cinnamomum camphora）、木荷（Schima superba）、枫香（Liquidambar formosana）、湿地松（Pinus elliottii）和水杉（Metasequoia glyptostroboides）6个亚热带常见树种为试验材料，对其在模拟酸雨胁迫下幼苗叶片光合气体交换参数、叶绿素含量、丙二醛含量和相对电导率等9个生理指标进行测定，以单项指标的耐酸系数为依据，运用主成分分析和隶属函数法对树种耐酸性进行综合评判。结果表明：中度酸雨对植物的气体交换和质膜没有造成明显影响；但在重度酸雨胁迫下，叶片净光合速率、气孔导度、蒸腾速率和水分利用效率等光合气体交换参数明显下降，叶片的相对电导率和丙二醛含量均显著上升。通过主成分分析将与幼苗耐酸性相关的生理指标转化成2个相互独立的综合指标，累积贡献率达88.064%；采用隶属函数法和聚类分析将6个树种按耐酸性强弱划分为3类：杨梅和湿地松为高抗酸树种，香樟、枫香和木荷为中等敏感树种，水杉属敏感型树种。该评价结果与其田间试验结果一致，因此所建立的综合评价方法可用来对幼苗耐酸性强弱进行客观、准确评价

PHYSIOLOGIC RESPONSES OF SEEDLINGS OF SUBTROPICAL SPECIES TO ACID RAIN AND COMPREHENSIVE EVALUATION ON SENSITIVITY

In order to explore the indices and comprehensive evaluation of sensitivity to acid rain,six seedlings of subtropical species,including Myrica rubra,Cinnamomum camphora,Schima superba,Liquidambar formosana,Pinus elliottii and Metasequoia glyptostroboides were taken as test materials and exposed to simulated acid rain (SAR) with different pH values (pH 3.5,pH 2.5,and local reservoir water of pH 50-54 as the control).Gas exchange parameters,the chlorophyll content,membrane penetration and malondialdehyde content(MDA)were determined after treated for four months.The results showed SAR at pH 35 was unlikely to cause significant damage on gas exchange parameters and cell membrane,while pH 25 treatment altered gas exchange parameters significantly,net photosynthetic rate (pn),stomata conductance(gs),transpiration rate(Tr)and water use efficiency(WUE)were significantly declined.Compared with the controls,the membrane penetration and MDA contents in the seedling leaves under pH 25 treatment were increased significantly.The characters of seedlings behaved variously in their susceptibility to acid rain,therefore it was essential to apply more than one index to give a comprehensive evaluation on stress resistant.Principal component analysis could transfer many correlating indices into several independent comprehensive indices with little original information lost.Based on the test results,seven correlated single indices which had very close relationship with the acidic tolerance characters,were transferred into two independent comprehensive,with contribution ratio of accumulative total of 88.064%.Then,according to acidic tolerance coefficients and standardization eigenvector of seven respective charcters of each variety,two comprehensive indices scores could be calculated.The comprehensive evaluation value of each seedling acidic tolerance (D value) could be decuced by weighting sum the subordinative values and weight coefficient of the two comprehensive indices scores.The acidic tolerance of six subtropical species could be distinguished by hierachical cluster analysis,and M.rubra and P.elliottii were the strongest tolerance,followed by C.camphora,L.formosana,S.superba,and M.glyptostroboides was the weakest.The evaluation results accorded with their behavior in the field,which suggested the method could give an objective and precise evaluation on the sensitivity to acid rain between different species of seedlings