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CO 2 is the main inorganic C species entering photosynthetically active leaf protoplasts of the freshwater macrophyte Ranunculus penicillatus ssp. pseudofluitans
Author(s) -
Newman J. R.,
Raven J. A.
Publication year - 1999
Publication title -
plant, cell and environment
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.646
H-Index - 200
eISSN - 1365-3040
pISSN - 0140-7791
DOI - 10.1046/j.1365-3040.1999.00460.x
Subject(s) - protoplast , macrophyte , photosynthesis , botany , aquatic plant , total inorganic carbon , biology , dissolved organic carbon , carbon fibers , chloroplast , chemistry , carbon dioxide , ecology , biochemistry , materials science , composite number , gene , composite material
Submerged aquatic macrophytes growing in water where free CO 2 is unavailable (above pH 8·2) must use mechanisms to supply external dissolved inorganic carbon in a form available to chloroplasts (CO 2 ). Active transport of HCO 3 – across the plasmalemma has not been proven to be widespread in aquatic macrophytes and catalytic conversion of HCO 3 – to CO 2 is the usual supply mechanism in submerged macrophytes. The interaction of leaf form and function in this respect was investigated in the linear, submerged leaves of Ranunculus penicillatus (Dumort.) Bab ssp. pseudofluitans (Syme) S.Webster. Viable protoplasts were isolated using a mixture of cell wall degrading enzymes optimized for this species. Protoplast viabilities greater than 80% after 5 h of isolation were achieved. Photosynthetic rates of isolated protoplasts were comparable with that of intact plant tissue. Results of carbon isotopic disequilibrium experiments showed that CO 2 was the preferred species of dissolved inorganic carbon for photosynthesis by protoplasts and that HCO 3 – which predominates in the plant’s natural environment mainly contributes by supplying CO 2 outside the cells.