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Structural and functional features of the leaves of Ranunculus trichophyllus Chaix., a freshwater submerged macrophophyte
Author(s) -
RASCIO N.,
CUCCATO F.,
DALLA VECCHIA F.,
LA ROCCA N.,
LARCHER W.
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.1365-3040.1999.00394.x
Subject(s) - photosynthesis , carbonic anhydrase , total inorganic carbon , apoplast , chloroplast , tris , bicarbonate , biophysics , cell wall , chemistry , botany , biology , biochemistry , carbon dioxide , organic chemistry , enzyme , gene
AZA, 5‐Acetamido‐1,3,4‐thiadiazole‐2‐sulphonamide
CA, carbonic anhydrase
DIC, dissolved inorganic carbon
Hepes, A‐(2‐hydroxyethyl)‐1 piperazine‐ethane sulfonic acid
IC, inorganic carbon
PAR, photosynthetic active radiation
PATAg, periodic acid‐thiosemicarbazide‐silver proteinate
Tris, tris (hydroxymethyl)‐aminomethane
The structural and physiological strategies developed by the leaves of the freshwater macrophyte Ranunculus trichophyllus to adapt to submersed life were studied. Photosynthesis is carried out mainly by the epidermis cells of the numerous segments into which the leaf is finely dissected. In these cells, containing most of the chloroplasts, a peculiar organization of the wall has been identified by cytochemical tests. A thin compact outer region covers the cell surface and splits up forming large lacunae between adjacent cells. Below it, a thick and loose inner region rich in hydrophilic pectic acids occurs, which grows in along the cell sides giving rise to wide transfer areas. In this latter cell wall region, in which the cell/environment contact and exchanges are amplified, the systems for inorganic carbon supply to photosynthetic cells operate. The leaves of R. trichophyllus can rely on environmental CO 2 and HCO 3 – as sources of inorganic carbon for photosynthesis. A mechanism for bicarbonate utilization seems to involve its conversion to CO 2 by an apoplastic carbonic anhydrase, whose activity gains importance as the availability of environmental CO 2 decreases. Interestingly, it has been demonstrated that in this species CO 2 can also be obtained from HCO 3 – by a photodependent increase in plasmamembrane H + ‐ATPase activity in the transfer areas of the epidermis cells. This is the first time that such a mechanism has been noted in a nonpolar leaf of a submerged macrophyte.