Composition and Characteristic Differences in Photosynthetic Membranes of Two Ecotypes of Reed (Phragmites communis L.) from Different Habitats

Abstract

As compared with the swamp reed (SR) ecotype of Phragmites communis growing in the desert region of northwest China, plants of the dune reed (DR) ecotype from the same region possessed lower chlorophyll (Chl) content in leaves, and less thylakoids and grana stacks in chloroplasts. Tube gel electrophoresis without stain showed that the contents of Chl-protein (Pro) components related to photosystem 2 (PS2) were markedly lower in the DR thylakoid membranes than in the SR thylakoid membranes, while the contents of Chl-Pro components associated with PS1 were almost the same in both types. SDS-PAGE analysis indicated that the content of polypeptides of the light-harvesting Chl a/b complex of PS2 (LHC2) was lower in the DR thylakoids. Besides, the conformation of LHC2 within the DR thylakoid membranes was also altered as indicated by circular dichroism spectra. Hence in the DR, reduced energy harvesting by declining the size of LHC2 might be responsible for the down-regulated PS2 activity. Chl fluorescence parameters. Fv/Fm and quantum efficiency of PS2 (ΦPS2), were lower in the DR leaves than in the SR ones. However, non-photochemical quenching coefficient (qN) was greater in DR than that in SR, implying other energy dissipation way exists in the DR photosynthetic membranes.