苔藓植物光合作用荧光光谱和动力学荧光的比较

本文首次比较了光合作用的荧光光谱和荧光动力学在苔藓植物的原始种类和进化种类之间的异同。原始的和进化的苔藓植物具有发射波长相同的室温荧光光谱，其发射高峰位于686-690nm(来自光系统Ⅱ)和736-740nm(来自光系统Ⅰ)。  而它们的低温(77K)荧光光谱有三个发射峰：F687-689和F697-699来自光系统Ⅱ，F723-734来自光系统I。 前两个峰在原始的和进化的种类中基本相同。  按第三个发射峰可把被测的苔藓植物分为两组：发射峰在725nm左右的有细牛毛藓、长肋对齿藓、对齿藓、斜叶芦荟藓、密集匍灯藓和地钱，它们是较原始的藓类和较进化的苔类；发射峰在732nm左右的有细枝羽藓、东亚金灰藓、鼠尾藓、鳞叶藓、粗枝藓和美灰藓等较进化的藓类，也有较原始的钝叶匍灯藓。已知光系统I核心复合物CPI的77K荧光发射峰在722nm，而CPIa(核心复合物与外周天线复合物)和LHC-I(外周天线复合物)的发射峰在730nm。这说明在苔藓植物进化过程中，光系统Ⅱ比较保守；而光系统Ⅰ有所变化，原始的藓类主要含有光系统Ⅰ核心复合物，而较进化的藓类才含有较完善的外周天线复合物。光合作用荧光动力学分析表明，在原始藓类和地钱中具有较低的光系统Ⅱ活性、光系统Ⅱ的原初光能转换效率、光合碳同化和潜在的光合量子转换效率；而较进化的具有较高的活性和效率。 但是，原始的密集匍灯藓也具有较高的活性和效率，而进化的美灰藓却具有较低的活性和效率。这可能表明这两种植物是由原始向进化发展过程中的中间类型。

Comparative Studies on Photosynthetic Fluorescence Spectra and Fluorescence Kinetics of Bryophytes

Bryophytes  are  the  transitional  forms  from  water  habitants  toterrestrials, however, there have been only a few works on their photosynthesis.It was the first time to study on photosynthetic fluorescence spectra  andfluorescence kinetics of primitive and advanced species comparatively. Both theprimitive and  advanced  ones  had  the  same  fluorescence  spectra  at  roomtemperature,  which contained two maximum emissions:  F686-690 from thePhotosystem II and F736-740 from the Photosystem I. And then, there were threemaximum emissions in the fluorescence spectra at 77K :F687-689 and F697-699 fromPhotosystem II, and F723-734 from Photosystem I. The first two maximumemissions were the same for both the primitive and advanced species. Accordingto the third maximum emission the bryophytes under study fell into twocategories: The first one possessing the maximum emission around 725 nm,including   Ditrichum   flexicaule ,   Didymodon   icmadophyllum ,   Didymodonrigidicaulis,  Aloina  obliquifolia,  Plagiomnium  confertidens  and Marchantiapolymorpha,  which were primitive mosses and advanced liverwort. The secondone possessing the maximum emission around  732nm,  including  Thuidiumdelicatulum ,   Pylaisia   brotheri ,   Myuroclada   maximowiczii ,   Taxiphyllumtaxirameum, Gollania neckerella, Eurohypnum leptothallum, which were advancedmosses,  and the primitive one Plagiomnium rostratum.  The characteristics offluorescence spectra implied that the Photosystem  II was conservative  andPhotosystem I was changeable during bryophyte evolution. The primitive mossespossess mainly the PSI core complex (CPI) and then the advanced species containboth CPI and LHC-I.  In analysis of photosynthetic fluorescence kinetics, Fv/(Fc+Fv)  is a measure of the activity of the Photosystem II; Fv/Fm is dependent  on efficiency of primary photoconversion in the Photosystem II; Fm/(Fo+Fv) isrelated to photosynthetic carbon assimilation; and Fd/Fs is a measure of thepotential photosynthetic quantum conversion. The fluorescence kinetics of thebryophyte photosynthesis showed that the Photosystem II activity, the efficieiency ofprimary photoconversion in Photosystem II, the photosynthetic carbon assimila-tion and the efficiency of the potential photosynthetic quantum conversion inprimitive species, such as Ditrichum flexicaule, Didymodon icmadophyllus, D.rigidicaulis, Plagiomnium rostratum  and the liverwort Marchantia polymorpha,were lower than  those in the advanced species,  Myuroclada maximowiczii,Pylaisia  brotheri ,  Gollania  neckerella  Taxiphyllum  taxirameum ,   Thuidiumdelicatulum. However, the primitive Plagiomnium confertidens was of the highactivities and efficiencies and the advanced Eurohypnum leptothallum was of lowones. It seemed that P. confertidens and E. leptothallum were an intermediatefrom the primitive to the advanced.