A survey of photosynthetic carbon metabolism in 4 ecotypes of Phragmites australis in northwest China: Leaf anatomy, ultrastructure, and activities of ribulose 1,5-bisphosphate carboxylase, phosphoenolpyruvate carboxylase and glycollate oxidase

Four ecotypes of Phragmites australis from different habitats in northwest China were examined to compare their photosynthetic characteristics. In a s wamp ecotype, the delta(13)C value of leaf materials was -34.0 parts per th ousand, and bundle sheath cells contained a small amount of organelles and round-shaped chloroplasts, as being similar to typical C-3 plants. In a dun e ecotype, the delta(13)C value was -20.9 parts per thousand and bundle she ath cells contained oval-shaped chloroplasts with poorly-developed grana, I n light and heavy salt meadow ecotypes, delta(13)C values were -30.6 parts per thousand and -35.6 parts per thousand, respectively. The shape of bundl e sheath chloroplasts in the light salt meadow ecotype was intermediate bet ween those of the swamp and dune ecotypes, Abundance of bundle sheath organ elles in the heavy salt meadow ecotype was intermediate. The swamp ecotype had photosynthetic enzyme activities typical of C-3 type plants, whereas th e dune ecotype had an increased activity of phosphoenolpyruvate carboxylase (PEPC), a key C-4 enzyme, and a decreased ribulose 1,5-bisphosphate carbox ylase (Rubisco) activity. The light salt meadow and heavy salt meadow ecoty pes had substantial activities of PEPC, which indicates potential for C-4 p hotosynthesis. These data suggest that this species evolved the C-3-like ec otype in swamp environments and the C-4-like C-3-C-4 intermediate in dune d esert environments, and C-3-like C-3-C-4 intermediates in salt environments .