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Studies of Elodea nuttallii grown under photorespiratory conditions. III. Quantitative cytological characteristics
Author(s) -
FAGERBERG W. R.,
EIGHMY T. T.,
JAHNKE L. S.
Publication year - 1991
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.1365-3040.1991.tb01333.x
Subject(s) - chloroplast , thylakoid , elodea canadensis , nucleoid , biology , botany , biophysics , chemistry , biochemistry , aquatic plant , ecology , macrophyte , escherichia coli , gene
. Elodea nuttallii was grown in primary effluent from domestic wastewater under conditions in which CO 2 may be limiting. However, high photosynthetic inorganic carbon uptake rates have been reported for Elodea under these conditions. In order to determine if leaf cell structure showed modifications which would support proposed models of a plasma membrane (PM) bicarbonate transport system and observed high photo‐synthetic rates, leaf cell ultrastructure was analysed using quantitative techniques (stereology). A Fold Index (FI) calculated for the PM showed that infolding increased surface area to 2.15 times that of an idealized cell of the same shape and size. Association Indices (Sa) showed a significant association of the mitochondria with the PM. These observations support models for an ATPase‐driven HCO 3 ‐cation cotransport system in Elodea cells. High chloroplast thylakoid surface density values (Sv) were similar to C 4 :monocots and indicated high light‐gathering potential. The granal/stromal (g/s), granal/cristae (g/c), and stromal/cristae (s/c) membrane ratios were similar to those of C 3 plant cells. Thus, Elodea chloroplasts and cells exhibited some structural features similar to both C 3 and C 4 plants. Membrane‐bound inclusion bodies, which occupied 1% of the cell volume, were also observed in the leaf cells. Cell walls and nucleoid regions were absent in these bodies and X‐ray (EDAX) analysis failed to detect any element (above the resolution limit of atomic no. 12) in substantial quantities. Inclusion bodies were observed in both the cytoplasm and the periplast and remain unidentified. A model is proposed for Elodea using an ATPase proton pump in the plasma membrane which extrudes protons into the periplast space between the cell wall and plasma membrane. This proton gradient is coupled to a bicarbonate symport.