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Environmental regulation of photosynthetic metabolism in the amphibious sedge Eleocharis baldwinii and comparisons with related species
Author(s) -
UENO O.
Publication year - 2004
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 - 10.1111/j.1365-3040.2004.01178.x
Subject(s) - photosynthesis , c4 photosynthesis , rubisco , biology , botany , metabolism , enzyme , vascular bundle , cyperaceae , epidermis (zoology) , poaceae , biochemistry , anatomy
The amphibious leafless sedge, Eleocharis baldwinii, expresses C 4 characteristics in the terrestrial form and intermediate characteristics between C 3 and C 4 photosynthesis in the submerged form. This study examined the immunocytochemical localization of C 3 and C 4 enzymes in culms of the two forms to elucidate the regulatory mechanism of photosynthetic metabolism and compared the activities and amounts of C 3 and C 4 enzymes with those in other Eleocharis species, E. vivipara and E. retroflexa, which show C 4 characteristics on land but C 3 and C 4 characteristics under water. The terrestrial form of E. baldwinii exhibited a C 4 ‐like pattern of enzyme localization. The submerged form exhibited a modified anatomy with well‐developed mesophyll cells and small Kranz cells. The C 4 enzyme levels declined conspicuously in outer mesophyll cells adjacent to the epidermis, whereas Rubisco levels increased throughout the mesophyll in the submerged form. These results suggest that intermediate photosynthesis between C 3 and C 4 photosynthesis in the submerged form results from the predominant operation of the C 3 pathway in the outer mesophyll cells and the C 4 pathway in both the inner mesophyll and Kranz cells. Differences in the degree of C 4 expression in terrestrial forms of Eleocharis species may cause the differences in the expression of photosynthetic modes under water.