THE ACQUISITION OF INORGANIC CARBON IN MARINE MACROPHYTES

1998 ◽  
Vol 46 (2) ◽  
pp. 83-87 ◽  
Author(s):  
Sven Beer
Keyword(s):  
Carbonic Anhydrase ◽  
Aquatic Plants ◽  
Inorganic Carbon ◽  
External Medium ◽  
Uptake Mechanism ◽  
Tropical Regions ◽  
Marine Macrophytes ◽  
Photosynthetic Carbon ◽  
Diffusion Rates ◽  
Carbon Transport

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 CO2/HCO3− ratio would be very low. Therefore, it may well be that the direct HCO3− uptake mechanism described for Ulva from more tropical regions confers an adaptational advantage under conditions conducive to higher photosynthetic rates.

Impacts of UV radiation on growth and photosynthetic carbon acquisition in Gracilaria lemaneiformis (Rhodophyta) under phosphorus-limited and replete conditions

2009 ◽  
Vol 36 (12) ◽  
pp. 1057 ◽  
Author(s):  
Zhiguang Xu ◽  
Kunshan Gao
Keyword(s):  
Growth Rate ◽  
Carbonic Anhydrase ◽  
Photosynthetic Efficiency ◽  
Inorganic Carbon ◽  
Inorganic Phosphorus ◽  
Gracilaria Lemaneiformis ◽  
Solar Ultraviolet Radiation ◽  
Relative Growth ◽  
Photosynthetic Carbon ◽  
Solar Ultraviolet

Solar ultraviolet radiation (UVR, 280–400 nm) is known to negatively affect macroalgal growth and photosynthesis, while phosphorus availability may affect their sensitivity to UVR. Here, we show that UV-A enhanced the growth rate of the red macroalga, Gracilaria lemaneiformis Bory de Saint-Vincent under inorganic phosphorus (Pi)-replete but reduced it under Pi-limited conditions. Maximal net photosynthetic rates were significantly reduced by both UV-A and UV-B, but the apparent photosynthetic efficiency was enhanced in the presence of UV-A. The UV-induced inhibition was exacerbated under Pi-limited conditions. The activity of total carbonic anhydrase was enhanced and the photosynthetic affinity for exogenous inorganic carbon (Ci) was raised for thalli grown in the presence of UVR under both Pi-replete and Pi-limited conditions. The relative growth rate was closely related to Ci acquisition capability (Vmax/KDIC), which was enhanced by UVR exposure under Pi-replete but not significantly affected under Pi-limited conditions.

CO2 syndrome in Chlorella

1991 ◽  
Vol 69 (5) ◽  
pp. 1003-1007 ◽  
Author(s):  
Mikio Tsuzuki ◽  
Shigetoh Miyachi
Keyword(s):  
Fatty Acids ◽  
Carbonic Anhydrase ◽  
Key Words ◽  
Inorganic Carbon ◽  
The Other ◽  
Fatty Acids Composition ◽  
High Affinity ◽  
Main Factors ◽  
Inorganic Carbon Transport ◽  
Carbon Transport

Effects of CO2 concentration on microalgae, especially on Chlorella, are discussed from the aspect of the high affinity of microalgae for inorganic carbon (Ci) in photosynthesis. Accumulation of Ci and carbonic anhydrase are the two main factors underlying the high affinity for Ci. The other factors such as development of carboxysomes and pyrenoids under low CO2 conditions may also be important. Contribution of each factor to the high affinity for Ci in photosynthesis seems to differ from species to species. Key words: Chlorella, inorganic carbon transport, carbonic anhydrase, fatty acids composition, CO2.

Inorganic carbon transport in some marine microalgal species

1991 ◽  
Vol 69 (5) ◽  
pp. 1032-1039 ◽  
Author(s):  
M. J. Merrett
Keyword(s):  
Carbonic Anhydrase ◽  
Inorganic Carbon ◽  
Silicone Oil ◽  
Ph Regulation ◽  
Carbonic Anhydrase Activity ◽  
Carbon Accumulation ◽  
Bicarbonate Transport ◽  
High Affinity ◽  
Inorganic Carbon Transport ◽  
Carbon Transport

Inorganic carbon transport was investigated in a range of marine microalgae. A small-celled strain of Stichococcus bacillaris, containing appreciable carbonic anhydrase activity, showed a high affinity for CO2, while measurement of the internal inorganic carbon pool by the silicone oil layer centrifugal filtering technique showed cells concentrated inorganic carbon up to 20-fold in relation to the external medium at pH 5.0 but not pH 8.3. The addition of 14CO2 or H14CO3− to cells in short-term kinetic experiments at pH 8.3 confirmed that only CO2 provides the exogenous substrate for substantial inorganic carbon accumulation within the cell. High-affinity HCO3− transport in Phaeodactylum tricornutum and Porphyridium purpureum is dependent on sodium ions, while intracellular carbonic anhydrase increased the steady-state flux of CO2 from inside the plasmalemma to Rubisco. In the presence of HCO3− the intracellular pH in cells of P. purpureum is 7.1 but on carbon starvation the pH falls to 6.0. Ethoxyzolamide blocks bicarbonate-dependent alkalinization of the cytosol, confirming a central role for carbonic anhydrase–bicarbonate in cytosolic pH regulation. Carbonic anhydrase activity is pH dependent in P. purpureum so synergistic interaction between CO2 uptake and bicarbonate transport may occur.

Evidence for bicarbonate accumulation by Anacystis nidulans

1984 ◽  
Vol 62 (7) ◽  
pp. 1398-1403 ◽  
Author(s):  
Barry J. Shelp ◽  
David T. Canvin
Keyword(s):  
Inorganic Carbon ◽  
Carbon Fixation ◽  
External Medium ◽  
Anacystis Nidulans ◽  
Carbon Pool ◽  
Carbon Accumulation ◽  
Total Carbon ◽  
Apparent Affinity ◽  
Photosynthetic Carbon Fixation ◽  
Photosynthetic Carbon

Kinetic studies of photosynthetic O2 evolution as a function of pH were conducted to investigate the nature of the inorganic carbon used during photosynthesis by Anacystis nidulans. At pH 5, the apparent affinity for carbon during photosynthesis was similar in air-grown and high CO2 grown cells, but at alkaline pH, the apparent affinity was much greater in air-grown cells. The substrate concentration for half-maximum rates of photosynthesis in air-grown cells remained constant as a function of pH when the substrate was expressed as total carbon, suggesting that these cells were capable of using varying proportions of CO2 and [Formula: see text]. Photosynthesis in high CO2 grown algae appeared to be more dependent on CO2 over the pH range, indicating that CO2 was the predominant carbon species used, but [Formula: see text] uptake was also indicated. Internal inorganic carbon and photosynthetic carbon fixation in air-grown cells were determined at pH 8.5, using silicone oil centrifugation. Anacystis accumulated inorganic carbon in large excess of that in the external medium by a mechanism which is sensitive to inhibitors of energy metabolism and independent of concurrent carbon fixation; light was required to accumulate and maintain the internal carbon pool. The degree of accumulation was a function of the carbon concentration in the external medium; at 12 μM external carbon, the accumulation ratio was in excess of 100-fold, whereas at 4.76 mM, the ratio was only 5-fold. The rates of carbon transport were always sufficient to maintain photosynthesis. Carbon efflux rates approaching 40% of the influx rate were found at equilibrium internal carbon concentrations. Kinetic parameters of photosynthesis are discussed with reference to the known properties of algal ribulose bisphosphate (RuBP) carboxylase–oxygenase. It is concluded that the internal inorganic carbon pool serves as an intermediate for photosynthetic carbon fixation and that, if CO2 and [Formula: see text] are in equilibrium, the carbon accumulation at ambient CO2 and O2 is sufficient to suppress RuBP oxygenase activity.

Sources and mechanisms of inorganic carbon transport for coral calcification and photosynthesis

2000 ◽  
Vol 203 (22) ◽  
pp. 3445-3457 ◽  
Author(s):  
P. Furla ◽  
I. Galgani ◽  
I. Durand ◽  
D. Allemand
Keyword(s):  
Inorganic Carbon ◽  
Sea Water ◽  
External Medium ◽  
Dissolved Inorganic Carbon ◽  
Double Labelling ◽  
Stylophora Pistillata ◽  
Coral Calcification ◽  
Lighting Conditions ◽  
Inorganic Carbon Transport ◽  
Carbon Transport

The sources and mechanisms of inorganic carbon transport for scleractinian coral calcification and photosynthesis were studied using a double labelling technique with H(14)CO(3) and (45)Ca. Clones of Stylophora pistillata that had developed into microcolonies were examined. Compartmental and pharmacological analyses of the distribution of(45)Ca and H(14)CO(3) in the coelenteron, tissues and skeleton were performed in dark or light conditions or in the presence of various seawater HCO(3)(−) concentrations. For calcification, irrespective of the lighting conditions, the major source of dissolved inorganic carbon (DIC) is metabolic CO(2) (70–75% of total CaCO(3) deposition), while only 25–30% originates from the external medium (seawater carbon pool). These results are in agreement with the observation that metabolic CO(2) production in the light is at least six times greater than is required for calcification. This source is dependent on carbonic anhydrase activity because it is sensitive to ethoxyzolamide. Seawater DIC is transferred from the external medium to the coral skeleton by two different pathways: from sea water to the coelenteron, the passive paracellular pathway is largely sufficient, while a DIDS-sensitive transcellular pathway appears to mediate the flux across calicoblastic cells. Irrespective of the source, an anion exchanger performs the secretion of DIC at the site of calcification. Furthermore, a fourfold light-enhanced calcification of Stylophora pistillata microcolonies was measured. This stimulation was only effective after a lag of 10 min. These results are discussed in the context of light-enhanced calcification. Characterisation of the DIC supply for symbiotic dinoflagellate photosynthesis demonstrated the presence of a DIC pool within the tissues. The size of this pool was dependent on the lighting conditions, since it increased 39-fold after 3 h of illumination. Passive DIC equilibration through oral tissues between sea water and the coelenteric cavity is insufficient to supply this DIC pool, suggesting that there is an active transepithelial absorption of inorganic carbon sensitive to DIDS, ethoxyzolamide and iodide. These results confirm the presence of CO(2)-concentrating mechanisms in coral cells. The tissue pool is not, however, used as a source for calcification since no significant lag phase in the incorporation of external seawater DIC was measured.

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