Blackwell Publishing Journal Backfiles 1879-2005
Four ecotypes of Phragmites australis from different habitats in northwest China were examined to compare their photosynthetic characteristics. In a swamp ecotype, the Δ13C value of leaf materials was −34.0‰, and bundle sheath cells contained a small amount of organelles and round-shaped chloroplasts, as being similar to typical C3 plants. In a dune ecotype, the Δ13C value was −20.9‰ and bundle sheath cells contained oval-shaped chloroplasts with poorly-developed grana. In light and heavy salt meadow ecotypes, Δ13C values were −30.6‰ and −35.6‰, respectively. The shape of bundle sheath chloroplasts in the light salt meadow ecotype was intermediate between those of the swamp and dune ecotypes. Abundance of bundle sheath organelles in the heavy salt meadow ecotype was intermediate. The swamp ecotype had photosynthetic enzyme activities typical of C3 type plants, whereas the dune ecotype had an increased activity of phosphoenolpyruvate carboxylase (PEPC), a key C4 enzyme, and a decreased ribulose 1,5-bisphosphate carboxylase (Rubisco) activity. The light salt meadow and heavy salt meadow ecotypes had substantial activities of PEPC, which indicates potential for C4 photosynthesis. These data suggest that this species evolved the C3-like ecotype in swamp environments and the C4-like C3-C4 intermediate in dune desert environments, and C3-like C3-C4 intermediates in salt environments.
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