Comparison of photosynthetic performance and carboxylation capacity in a range of aquatic macrophytes of different growth forms (original) (raw)
Related papers
Global Change Biology, 2002
Growth rates, photosynthetic responses and the activity, amount and CO 2 affinity of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) were determined for common marine macroalgae grown in seawater (containing 14.5 + 2.1 mM CO 2) or CO 2enriched seawater (averaging 52.8 + 19.2 mM CO 2). The algae were grown in 40 L fiberglass tanks (outdoor) for 4±15 weeks and in a field experimental setup for 5 days. Growth rates of the species studied (representing the three major divisions, i.e. Chlorophyta, Rhodophyta and Phaeophyta) were generally not significantly affected by the increased CO 2 concentrations in the seawater medium. Rubisco characteristics of algae cultivated in CO 2-enriched seawater were similar to those of algae grown in nonenriched seawater. The lack of response of photosynthetic traits in these aquatic plants is likely to be because of the presence of CO 2 concentrating mechanisms (CCMs) which rely on HCO 3 ± utilization, the inorganic carbon (Ci) form that dominates the total Ci pool available in seawater. Significant changes on the productivity of these particular marine algae species would not be anticipated when facing future increasing atmospheric CO 2 levels.
Global Change Biology, 2002
Growth rates, photosynthetic responses and the activity, amount and CO 2 affinity of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) were determined for common marine macroalgae grown in seawater (containing 14.5 + 2.1 mM CO 2) or CO 2enriched seawater (averaging 52.8 + 19.2 mM CO 2). The algae were grown in 40 L fiberglass tanks (outdoor) for 4±15 weeks and in a field experimental setup for 5 days. Growth rates of the species studied (representing the three major divisions, i.e. Chlorophyta, Rhodophyta and Phaeophyta) were generally not significantly affected by the increased CO 2 concentrations in the seawater medium. Rubisco characteristics of algae cultivated in CO 2-enriched seawater were similar to those of algae grown in nonenriched seawater. The lack of response of photosynthetic traits in these aquatic plants is likely to be because of the presence of CO 2 concentrating mechanisms (CCMs) which rely on HCO 3 ± utilization, the inorganic carbon (Ci) form that dominates the total Ci pool available in seawater. Significant changes on the productivity of these particular marine algae species would not be anticipated when facing future increasing atmospheric CO 2 levels.
Canadian Journal of Botany, 1983
1983. Variable photosynthesis/photorespiration ratios in Hydrilla and other submersed aquatic macrophyte species. Can. J. Bot. 61: 229-236. Hydrilla verticillata plants collected from Orange Lake in Florida during the summer exhibited higher net photosynthetic rates and lower photorespiratory and dark respiratory rates than plants collected during the winter when measured at a standard temperature of 25°C. Similar seasonal shifts in the C 0 2 compensation point, ranging from 17 p,L C02/L in summer to 90 in winter, occurred in Hydrilla from three geographically distinct lakes in Florida. Incubation of Hydrilla and five other submersed angiosperms under a high temperature (27°C day) and long photoperiod (14 h) reduced the C 0 2 compensation point to less than 20. A continuously high C 0 2 concentration of 5000 p,L/L (gas phase) prevented the decline in the C 0 2 compensation point, whereas 300 p,L/L induced it. Lake-grown and chamber-grown Hydrilla with low photorespiratory capacity, as determined by low C 0 2 compensation points, showed elevated phosphoenolpyruvate carboxylase activity (239 versus 33 p,mol/mg Chl per hour). Diurnal gas-exchange measurements at 300 and 3000 p,L C 0 2 / L (gas phase) demonstrated that low photorespiration Hydrilla exhibited net C 0 2 fixation in the dark at the higher C 0 2 level, probably via the elevated phosphoenolpyruvate carboxylase activity. Only Hydrilla with low C 0 2 compensation points exhibited net dark fixation and then only during the night period. The excretion of 14C-organic compounds was only 3% of the I4CO2 light fixation rate and thus too low to account for the reduced photorespiration. The potential to alter the photosynthesis/photorespiration ratio appears ubiquitous among submersed freshwater macrophytes. This ratio change to a low photorespiratory capacity, and the induction of a dark fixation capacity, would aid the carbon economy under summer daytime conditions of low inorganic carbon and high 02, where photorespiratory COz loss would otherwise be substantial.
Photosynthesis of marine macroalgae and seagrasses in globally changing CO2 environments
Marine Ecology Progress Series, 1996
Photosynthetic rates of many marine macroalgae are saturated by the present day inorganic carbon (Ci) composition of seawater, while those of seagrasses (or marine angiosperms) are CO1limited. In this study we attempted to simulate the Ci conditions of near-shore seawater during the time that seagrasses colonised the sea (in the Cretaceous), and compare the photosynthetic performance of representatives of the 2 plant groups under those versus present day conditions. The results show that the seagrasses have an affinity for Ci at least as high as the algae under the low pH and high C02/HC03' concentration ratios simulating near-shore areas of the Cretaceous seas, indicating that their photosynthetic capacity then matched that of macroalgae. However, in the high pH and high COz/HCO?-ratlos of today, their a f f~n~t y for Ci is lower than that of the macroalgae, and it is suggested that this deficiency renders them a lower ability for Ci utilisation. This situat~on may possibly be reversed again as global CO2 levels of the atmosphere and, consequently, of near-shore marine habitats increase in the future.
Alternative Methods of Photosynthetic Carbon Assimilation in Marine Macroalgae
PLANT PHYSIOLOGY, 1988
Two green macroalgae, Codium decorticatum and Udotea flabellum, differ photosynthetically. Codium had high O2-sensitive, and Udotea low 02-insensitive, CO2 compensation points; Codium showed a Warburg effect at seawater dissolved inorganic carbon levels and had photorespiratory C02 release, whereas Udotea did not. Seawater dissolved inorganic carbon levels did not saturate photosynthesis. For Codium, but not Udotea, the Warburg effect was increased by ethoxyzolamide, a carbonic anhydrase inhibitor, at high but not low pH. Isolated chloroplasts from both macroalgae showed a Warburg effect that was ethoxyzolamideinsensitive. In both macroalgae, chloroplastic and extrachloroplastic carbonic anhydrase activity was present. P-enolpyruvate carboxykinase (PEPCK) carboxylating activity in Udotea extracts was equivalent to that of ribulose bisphosphate carboxylase, and enzyme activities for C4 acid metabolism and P-enolpyruvate regeneration were sufficient to operate a limited C4-like system. In Udotea, malate and aspartate were earlylabeled photosynthetic products that turned over within 60 seconds. Photorespiratory compounds were much less labeled in Udotea. Low dark fixation rates ruled out Crassulacean acid metabolism. A limited C4-like system, based on PEPCK, is hypothesized to be the mechanism reducing photorespiration in Udotea. Codium showed no evidence of photosynthetic C4 acid metabolism. Marine macroalgae, like terrestrial angiosperms, seem to have diverse photosynthetic modes.
Photosynthetic carbon acquisition in the red algaGracilaria conferta
Marine Biology, 1991
Photosynthetic properties of the common red alga Gracilaria conferta, collected from the eastern Mediterranean Sea were investigated in 1989, in order to begin evaluating its adaptative strategies with regard to the inorganic carbon composition of seawater, and to test whether the alleged C~ photosynthesis of another Gracilaria species is common within the genus. Net photosynthetic rates of G. conferta were, under ambient conditions of inorganic carbon (ca. 10 #M, CO 2 and 2.2 mM HCO~-), not sensitive to 02 over the range 10 to 300 #M, and the CO2 compensation point was low (ca. 0.005 #M), Ribulose-l,5-bisphosphate carboxylase/oxygenase was the major carboxylating enzyme, with a crude extract activity of 175 #tool CO 2 g-1 flesh wt h -1 while phosphoenolpyruvate carboxylase and phosphoenolpyruvate carboxykinase were present at 70 and 20%, respectively, of that activity. No activities of the decarboxylases NADand NADP-malic enzyme could be detected. The 14C pulse-chase incorporation pattern showed that G. conferta fixes inorganic carbon via the photosynthetic carbon reduction cycle only, with no evidence for photosynthetic C 4 acid metabolism. Photosynthesis at the natural seawater pH of 8.2 was, at 25 °C and saturating light, saturated at the ambient inorganic carbon concentration of 2.5 mM. It is proposed that, under ambient inorganic carbon conditions, a CO2 concentrating system other than C 4 metabolism provides an internal CO 2 concentration sufficient to suppress the O 2 effect on ribulose-l,5bisphosphate carboxylase/oxygenase and, thus, on photorespiration, in a medium where the external flee CO 2 concentration is lower than the KIn(CO2) of the carboxylating enzyme. Since inorganic carbon, under natural saturating light conditions, seems not to be a limiting factor for photosynthesis of G. conferta, it likely follows that other nutrients limit the growth of this alga in nature.
Journal of Experimental Marine Biology and Ecology, 2001
This study examines the effect of pH changes on photosynthetic characteristics and the role of dissolved inorganic carbon (DIC) in determining the dominance of three species of macroalgaëC haetomorpha linum (O.F. Muller) Kutzing, Gracilaria verrucosa (Hudson) Papenfuss and Ulva sp. in a Mediterranean coastal lagoon. Fluctuations of pH were measured in the lagoon in summer. 2 Water column CO and HCO concentrations inside the algal mat showed significant diurnal 2 3 fluctuations, from a morning peak to an afternoon low, decreasing 96 and 40%, respectively. The response of photosynthesis to increased pH was examined in laboratory conditions in spring (May) and summer (July). The photosynthetic rate declined rapidly at pH above 8.5 and below 6.5. G. verrucosa responded differently in spring and summer showing acclimation to higher pH in summer than in spring. In Ulva sp. incubations, we observed optimum photosynthesis between pH 6 and 7.5. The decrease in photosynthetic rate below pH 6 was lower (12.30%) than above pH 8 (81.03%). This difference may be related to the origin of the macroalgae, suggesting acclimation to the original pH of the environment. Results from instantaneous photosynthesis measurements indicate that low DIC-availability limits the photosynthetic capacity of G. verrucosa,, C. linum and Ulva sp. in spring and of C. linum at high irradiances in summer. Our results also show that G. verrucosa has a higher efficiency at low CO concentrations than C. linum and Ulva sp. It is 2 suggested that G. verrucosa may be better adapted to maintain higher photosynthetic rates than other macroalgae in conditions of tissue N sufficiency and low water DIC concentrations which are typical of shallow coastal environments in summer.
The Acquisition of Inorganic Carbon in Marine Macrophytes
Israel Journal of Plant Sciences, 1998
The low diffusion rates of solutes in water call for a separation of photosynthetic carbon acquirement in aquatic plants into carbon transport and the subsequent photosynthetic reduction of CO2. This paper will focus on the transport of inorganic carbon from the external medium to the site of fixation in marine macrophytes. In accord with the much higher concentration of HCO3− than of CO2 in seawater, most marine macrophytes can utilize the ionic carbon form for their photosynthetic needs. The two known ways of HCO, utilization are (a) via extracellular, carbonic anhydrase catalyzed dehydration of HCO3− to form CO2, which then diffuses into the photosynthesizing cells, and (b) by direct uptake via a transporter. While the first way may be sufficient to support low rates of photosynthesis in temperate regions, it is viewed as futile under situations where high temperatures and irradiances would cause a high pH to form close to the uptake site of carbon and where, consequently, the CO...
Algal and aquatic plant carbon concentrating mechanisms in relation to environmental change
Photosynthesis Research, 2011
changes in response to the forcing factors. In freshwaters, changes in phytoplankton species composition may alter with environmental change with consequences for frequency of species with or without CCMs. The information available permits less predictive power as to the effect of the forcing factors on CCM expression than for their overall effects on growth. CCMs are currently not part of models as to how global environmental change has altered, and is likely to further alter, algal and aquatic plant primary productivity. Keywords CO 2 concentrating mechanismcombined nitrogeninorganic carbonironmixing depth-photosynthetically active radiationphosphorustemperature-UVA-UVB Abbreviations CCM CO 2 concentrating mechanism DOC Dissolved organic carbon PAR Photosynthetically active radiation (400-700 nm) Rubisco Ribulose bisphosphate carboxylase-oxygenase UVA Ultraviolet A radiation (320-400 nm) UVB Ultraviolet B radiation (280-320 nm)