巨桉和天竺桂幼树对不同浓度SO_2的光合生理响应

Photosynthetic Physiological Responses of Saplings of Eucalyptus grandis and Cinnamomum pedunculatumto Sulfur Dioxide Stress

二氧化硫是大气主要污染物之一,可对植物的关键生理过程光合作用产生重要影响。利用密闭环境控制室熏气处理,研究不同浓度(自然状态下浓度、0.5mg·L-1、1.5mg·L-1、3.0mg·L-1)SO2对盆栽巨桉和天竺桂幼树叶绿素含量、光响应曲线、光合特征参数、光合日变化及硫含量的影响。结果表明:(1)SO2胁迫显著减少了巨桉叶绿素a、b含量,且叶绿素a/b值显著降低,而天竺桂在SO2胁迫下叶绿素a、b含量显著增加,叶绿素a/b值无显著影响。(2)SO2胁迫显著抑制了两树种的净光合速率(Pn);在SO2胁迫下巨桉气孔导度(Gs)、胞间CO2浓度(Ci)和蒸腾速率(Tr)显著上升,而天竺桂的Gs和Tr显著被SO2抑制,Ci随SO2浓度的增加先升高后降低。(3)巨桉表观量子效率(AQY)、暗呼吸速率(Rd)、光补偿点(LCP)和光饱和点(LSP)及天竺桂Rd和LCP均随着SO2浓度的增加而先升高后降低,而天竺桂的AQY和LSP逐渐降低。(4)一天中,SO2胁迫显著提高了巨桉Pn、Gs和Tr,而对天竺桂Pn无显著影响,较低浓度SO2胁迫显著促进了天竺桂Gs和Tr,高浓度SO2胁迫则显著抑制其Gs和Tr;SO2胁迫显著抑制了两种植物的Ci。(5)SO2胁迫下,巨桉和天竺桂幼树叶片硫含量均显著增加。研究认为,巨桉对较低浓度的SO2胁迫有一定的适应能力,但对高浓度SO2胁迫的抗性不如天竺桂强,这可能与二者不同的叶片形态及生理特性有关。

Sulphur dioxide （SO2） is one of the main atmospheric pollutants. It can seriously affected plants photosynthesis which is the key physiological processes of plants. Using fumigation treatment in sealed environmental control chambers, we studied the effect of different levels （concentration in natural condition, 0.5 mg. L^-1 ,1.5 mg .L^- 1 and 3.0 mg .L^- 1） of SO2 on content of chlorophyll,the photoresponse curve, photosynthetic parameters, diurnal variation of photosynthesis and sulfur concentration of potted saplings of Eucalyptus grandis and Cinnamomum pedunculatum. The results showed that： （1） SO2 stress signifi- cantly decreased the content of chlorophyll a and chlorophyll b in E. grandis, while remarkably increased in C. pedunculatum. SO2 stress made chlorophyll a/b ratio of E. grandis was significantly lowered, for C. pe- dunculatum no significant effect on the ratio. （2）SO2 stress significantly inhibited the net photosynthetic rate （Pn） Of the two species. Stomatal conductance （Gs）,intercellular CO2 concentration （Ci） and transpi-ration rate （Tr） of E. grandis rose remarkably under SO2 stress, and G, and Tr of C. pedunculatum was significantly inhibited by SOe, Ci firstly increased and then decreased. （3）Apparent quantum efficiency （AQY）, dark respiration rate （Re） ,light compensation point （LCP） and light saturation point （LSP） of E. grandis as well as Rd and LCP of C. pedunculatum first increased and then decreased with increasing concentration of SO2 ,however,AQY and LSP of C. pedunculatum decreased. （4）In a day,SO2 stress signifi- cantly increased Pn ,Gs and Tr of E. grandis,and have no significant effect on Pn Of C. pedunculatum,but lower concentrations of SOe stress significantly promoted Gs and Tr of C. pedunculatum. It was significantly restrained under high concentrations of SO2 stress. Ci of both species were significantly inhibited under SO2 stress. Sulfur content of both species showed an increasing trend under SO2 stress. Overall,E. grandis may have a certain ability to adapt to lower concentration of SO2 stress,but its resistance to high concentration of SO2 stress is not as good as C. pedunculatum,which may be related to their different leaf morphology and physiological characteristics.