大气臭氧浓度增加对湿地松幼苗的影响

Effects of Elevated Ozone Concentration on Slash Pine (Pinus elliottii) Seedlings

采用开顶式气室(open top chambers,OTCs)装置,研究O3浓度增加(E-O3,约150 nL.L-1)对湿地松幼苗的影响,包括伤害症状、植株生长、针叶光合色素含量、气体交换速率与叶绿素荧光、丙二醛(MDA)以及主要抗氧化剂含量变化.经过E-O3处理一个生长季后(AOT40值为38.24μL.L-1.h),湿地松幼苗当年生新叶与老叶呈现出伤害症状,而株高与基径生长、生物量累积与分配未出现显著变化;与对照相比,O3暴露对当年生针叶光合作用具有一定的抑制作用:净光合速率(Pn)、气孔导度(gs)与蒸腾速率(Tr)分别显著降低42.5%、48.2%与46.3%,而胞间CO2浓度(ci)与水分利用效率(WUE)、叶绿素荧光指标无显著变化;叶绿素a、叶绿素b与总叶绿素含量分别降低16.7%、21.1%与17.5%,叶片MDA含量、总还原能力、抗坏血酸与总酚含量均无显著变化.可见,光合色素含量的降低是E-O3引起湿地松幼苗针叶光合速率下降的主要原因.

One-year-old slash pine（Pinus elliottii） seedlings were exposed to charcoal-filtered air（CF） and elevated ozone（E-O3,mean concentration of 150 nL·L-1） for 84 days in six open-top chambers.Growth parameters,pigments content,gas exchange,chlorophyll a fluorescence and antioxidant system were measured after one growing season（AOT40 value of 38.24 μL·L-1·h）.At the end of experiment,both current and old needles showed visible symptoms,and the seedlings were harvested for growth parameters measurement.Elevated O3 did not significantly change height growth,diameter increment,total biomass and biomass partition.E-O3 had negative effects on the photosynthetic parameters,e.g.significant decreases in net photosynthetic rate,stomatal conductance,transpiration rate and pigments content.However,chlorophyll a/b ratio,intercellular CO2 concentration,water use efficiency,and chlorophyll a fluorescence parameters were not affected significantly by E-O3 in comparison with CF.Furthermore,E-O3 induced slight increase in MDA content,total ascorbate and total phenolic compound contents,and reduction in total antioxidant capacity.The results suggested that O3-induced significant reduction in pigments content contributed to lower photosynthetic rate in slash pine exposed to E-O3.