两种不同生态型麻疯树夏季光合特性的比较

Comparison of photosynthetic characteristics in two ecotypes of Jatropha curcas in summer

以来源于海南及贵州的两种不同生态型麻风树(Jatropha curcas L.)为试材,利用LI-6400便携式光合作用测量系统及PAM-2100调制叶绿素荧光仪,在夏季对其气体交换特性及叶绿素荧光参数等进行测定。光强-光合速率响应曲线显示两种不同生态型叶片最大净光合速率(Pmax)和光饱和点(LSP)分别为18.9μmol.m-.2s-1、1600μmol.m-2.s-1(贵州型)和20.4μmol.m-.2s-1、1700μmol.m-.2s-1(海南型),而CO2光合速率响应曲线则显示两者的差异不大。两者的净光合速率(Pn)的日变化曲线都呈双峰型,主峰出现在10:00,在14:00左右出现低谷,次峰出现在16:00左右,有明显的光合"午休"现象。海南麻风树的Pmax、LSP、光补偿点(LCP)、表观量子效率(AQY)和暗呼吸速率(Rd)均高于贵州麻风树。两种生态型麻风树PSⅡ最大原初光化学效率(Fv/Fm)日变化无显著差异,而实际光化学效率(ΦPSⅡ)变化趋势与Pn相同。这表明麻风树是一种具有较高的光合速率和强光适应性的木本能源植物,不同生态型麻风树的气体交换特性及叶绿素荧光参数有一定的差异,海南麻风树对强光的适应能力强于贵州麻风树。

Gas exchange and chlorophyll fluorescence parameters in two ecotypes of Jatropha curcas originally growing in Hainan Province and Guizhou Province were determined by a Li-6400 portable photosynthesis analysis system （LI-6400, Li-cor USA） and a chlorophyll fluorometer （PAM 2100, Walz, Germany） in summer. The photosynthetic capacity of Jatropha curcas was high. The light saturation point （LSP） of the Hainan and Guizhou ecotypes was 1700 μmol·m^-2·s^-1 and 1600 μmol·m^-2·s^-1, and the maximum photosynthetic rate （Pmax） was 20.4 μmol m^-2·s^-1 and 18.9 μmol·m^-2·s^-1, respectively. There was no obvious difference in responses of photosynthetic rate to CO2 concentrations between the two ecotypes of Jatropha curcas, Hainan and Guizhou. The diurnal variation of net photosynthetic rate in leaves of the two ecotypes presented a two-peak pattern. The first peak and second peak occurred at about 10：00 am and at 16：00 pm, respectively, an obvious phenomenon of ＂midday depression of photosynthesis＂. The Pmax, LSP, LCP （light compensation point）, AQY （apparent quantum yield） and Rd （dark respiration） of the Hainan ecotype were higher than those of Guizhou ecotype. The daily changes of maximal photochemical efficiency of photosystem Ⅱ （Fv/Fm） exhibited little difference between the Hainan ecotype and the Guizhou ecotype, whereas the daily changes of actual photosystem II efficiency （ΦPSⅡ） were consistent with daily changes of Pn. The Hainan ecotype displayed more tolerance to strong light intensity than Guizhou ecotype. These experimental results indicate that Jatropha curcas is a woody plant with a high photosynthetic capacity and a strong capacity for acclimation to high light intensity and, therefore, a potentially significant bioenergy source.