| Abstract: | Bryophytes are the transitional forms from water habitants to
terrestrials, however, there have been only a few works on their photosynthesis.
It was the first time to study on photosynthetic fluorescence spectra and
fluorescence kinetics of primitive and advanced species comparatively. Both the
primitive and advanced ones had the same fluorescence spectra at room
temperature, which contained two maximum emissions: F686-690 from the
Photosystem II and F736-740 from the Photosystem I. And then, there were three
maximum emissions in the fluorescence spectra at 77K :F687-689 and F697-699 from
Photosystem II, and F723-734 from Photosystem I. The first two maximum
emissions were the same for both the primitive and advanced species. According
to the third maximum emission the bryophytes under study fell into two
categories: The first one possessing the maximum emission around 725 nm,
including Ditrichum flexicaule , Didymodon icmadophyllum , Didymodon
rigidicaulis, Aloina obliquifolia, Plagiomnium confertidens and Marchantia
polymorpha, which were primitive mosses and advanced liverwort. The second
one possessing the maximum emission around 732nm, including Thuidium
delicatulum , Pylaisia brotheri , Myuroclada maximowiczii , Taxiphyllum
taxirameum, Gollania neckerella, Eurohypnum leptothallum, which were advanced
mosses, and the primitive one Plagiomnium rostratum. The characteristics of
fluorescence spectra implied that the Photosystem II was conservative and
Photosystem I was changeable during bryophyte evolution. The primitive mosses
possess mainly the PSI core complex (CPI) and then the advanced species contain
both 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) is
related to photosynthetic carbon assimilation; and Fd/Fs is a measure of the
potential photosynthetic quantum conversion. The fluorescence kinetics of the
bryophyte photosynthesis showed that the Photosystem II activity, the efficieiency of
primary photoconversion in Photosystem II, the photosynthetic carbon assimilation and the efficiency of the potential photosynthetic quantum conversion in
primitive 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 , Thuidium
delicatulum. However, the primitive Plagiomnium confertidens was of the high
activities and efficiencies and the advanced Eurohypnum leptothallum was of low
ones. It seemed that P. confertidens and E. leptothallum were an intermediatefrom the primitive to the advanced. |
