Premium
Carbonate ions appear to neither inhibit nor stimulate use of bicarbonate ions in photosynthesis by Ulva lactuca
Author(s) -
MABERLY S. C.
Publication year - 1992
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.1365-3040.1992.tb01480.x
Subject(s) - photosynthesis , ulva lactuca , bicarbonate , lactuca , total inorganic carbon , carbonate , carbon dioxide , chemistry , chlorophyta , botany , environmental chemistry , biology , algae , organic chemistry
Rates of photosynthesis by the marine macroalga Ulva lactuca were measured in a factorial experiment at five concentrations of HCO 3 − and CO 3 2‐ between 0·20 and 1·26 mol m −3 , but very low concentrations of CO 2 . The results demonstrated that HCO 3 − was available for use, but an analysis of variance showed that CO 3 2‐ had neither an inhibiting nor a stimulating effect on rates of photosynthesis over this concentration range. Over the experiment, pH varied from 8·46 to 10·06 and this also had no significant effect on rates of photosynthesis. The lack of a stimulatory effect of high concentrations of CO 3 2‐ on the rate of photosynthesis at low concentrations of HCO 3 − was taken as circumstantial evidence for direct uptake of HCO 3 − rather than proton extrusion and external production of CO 2 . In the rockpools in which U. lactuca grows, pH values up to 10·35 have been recorded, and for much of the time, CO 3 2‐ was the major form of inorganic carbon available. The apparent lack of an ability to use CO 3 2‐ under these conditions suggests that direct use of CO 3 2‐ as a source of inorganic carbon for photosynthesis is unlikely to be widespread.