O_3浓度升高对桢楠和闽楠幼苗光合作用、抗氧化能力及生物量的影响

Effects of Elevated O_3 Level on Photosynthesis,Antioxidant Capacity and Biomass of Phoebe zhennan and Phoebe bournei Seedlings in Subtropical China

[目的]探讨O_3浓度升高对两种亚热带树木幼苗的影响,并分析其敏感性差异及原因。[方法]本试验以1年生桢楠和闽楠幼苗为材料,采用开顶式气室(OTCs),研究未过滤大气、100 nmol·mol-1(E1)、150 nmol·mol-1(E2)O_3处理对光合作用、抗氧化能力和生物量的影响。[结果]研究表明:(1) O_3熏蒸主要通过非气孔限制因素降低了两树种的净光合速率(Pn)。其中对于桢楠,E2对Pn的不利影响大于E1。而对于闽楠,8月份E2的Pn大于E1,而9月份和10月份小于E1。(2) O_3熏蒸提高了两树种的抗氧化能力,表现为总酚含量和总抗氧化能力随着O_3浓度的升高逐渐升高,而E2的还原型抗坏血酸含量低于E1。(3) O_3熏蒸降低了两树种根、茎、叶及总干质量,及降低了闽楠的根茎比。[结论]O_3熏蒸降低了两树种的光合作用,提高了抗氧化能力,最终减少了生物量。根据Pn和生物量,确定闽楠较桢楠对O_3浓度升高更加敏感。两树种间的O_3敏感性差异与气孔导度和抗氧化物质的背景水平及其对O_3浓度升高的响应有关。

[Objective]Considerable researches have documented the negative effects of O3 on woody species in North America and Europe,however,little is known about how woody tree species respond to elevated O3 in subtropical China. The objectives of this study are to investigate the effects of elevated O3 on two evergreen tree species in subtropical China,and compare the O3 sensitivity between them and explore potential mechanisms on differential responses to O3. [Method]One-year-old seedlings of Phoebe zhennan S. Lee et F. N. Wei and Phoebe bournei（ Hemsl.） Yang were exposed to non-filtered air,100 nmol mol^-1 O3 air（ E1） and 150 nmol mol^-1 O3 air（ E2） to investigate the O3 effects on photosynthesis,antioxidant capacity and biomass of these two species. [Result] The results are as follows：（ 1） O3 fumigation reduced net photosynthesis rate（ Pn） mainly through non-stomatal factorsin both species. Pn was lower under E2 than that under E1 in P. zhennan. Whereas for P. bournei,Pn was greater under E2 than that under E1 in August measurement,while the reverse patterns were observed in the measurements in September and October.（ 2） O3 fumigation increased measured antioxidant substances levels in both species.The levels of total phenols and total antioxidant capacity increased with O3 concentrations increasing. However,reduced ascorbic acid contents were lower under E2 than that under E1.（ 3） O3 fumigation decreased root,stem,foliage and total biomass in both species. The reduced below/above ground biomass ratio was only observed in P.bournei. [Conclusion]O3 fumigation decreases photosynthesis,increases the antioxidant capacity,and ultimately inhibits the growth of the two species. The O3 sensibility of P. bournei is stronger than that of P. zhennan based on Pn and biomass. The differential sensitivity to O3 is related to（ i） stomatal conductance,and（ ii） antioxidant substances responses to elevated O3 and their background level.