Long-term responses of the green-algal lichen Parmelia caperata to natural CO2 enrichment

Acclimation to elevated CO₂ was investigated in Parmelia caperata originating from the vicinity of a natural CO₂ spring, where the average daytime CO₂ concentration was 729 ± 39 μmol mol⁻¹ dry air. Thalli showed no evidence of a down-regulation in photosynthetic capacity following long-term exposure to CO₂ enrichment in the field; carboxylation efficiency, total Ribulose bisphosphate carboxylase/oxygenase (Rubisco) content, apparent quantum yield of CO₂ assimilation, and the light-saturated rate of CO₂ assimilation (measured under ambient and saturating CO₂ concentrations) were similar in thalli from the naturally CO₂ enriched site and an adjacent control site where the average long-term CO₂ concentration was about 355 μmol mol⁻¹. Thalli from both CO₂ environments exhibited low CO₂ compensation points and early saturation of CO₂ uptake kinetics in response to increasing external CO₂ concentrations, suggesting the presence of an active carbon-concentrating mechanism. Consistent with the lack of significant effects on photosynthetic metabolism, no changes were found in the nitrogen content of thalli following prolonged exposure to elevated CO₂. Detailed intrathalline analysis revealed a decreased investment of nitrogen in Rubisco in the pyrenoid of algae located in the elongation zone of thalli originating from elevated CO₂, an effect associated with a reduction in the percentage of the cell volume occupied by lipid bodies and starch grains. Although these differences did not affect the photosynthetic capacity of thalli, there was evidence of enhanced limitations to CO₂ assimilation in lichens originating from the CO₂-enriched site. The light-saturated rate of CO₂ assimilation measured at the average growth CO₂ concentration was found to be significantly lower in thalli originating from a CO₂-enriched atmosphere compared with that of thalli originating and measured at ambient CO₂. At lower photosynthetic photon flux densities, the light compensation point of net CO₂ assimilation was significantly higher in thalli originating from elevated CO₂, and this effect was associated with higher usnic acid content. Received: 8 May 1998 / Accepted: 22 January 1999     

The spatial structure of lichen Hypogymnia physodes (L.) Nyl

Structure analysis based on regular morphological variability at organism level is applied to study the shape and spatial construction of lichen Hypogymnia phyzodes (L.) Nyl. Some structural were determined at juvenile stage of development with the use of this approach. Five of them are dominant. Besides, five the most frequent encounter types of thallus branching were described. It is shown that thallus structure at adult stage is usually built from two main elements forming axial dichotomy. Analysis of thallus shape indicates that transformation of dichotomy elements into trichotomy ones may also take place during growth and development of thallus.     

Functional characteristics of a fruticose type of lichen, Stereocaulon foliolosum Nyl. in response to light and water stress

Stereocaulon foliolosum a fruticose type of lichen under its natural habitat is subjected to low temperature, high light conditions and frequent moisture stress due its rocky substratum. To understand as to how this lichen copes up with these stresses, we studied the reflectance properties, light utilization capacity and the desiccation tolerance under laboratory conditions. S. foliolosum showed light saturation point for photosynthesis at 390 μmol CO₂ m^?2 s^?1 and the light compensation point for photosynthesis at 64 μmol CO₂ m^?2 s^?1. Our experiments show that S. foliolosum has a low absorptivity (30–35 %) towards the incident light. The maximum rates of net photosynthesis and apparent electron transport observed were 1.9 μmol CO₂ m^?2 s^?1 and 45 μmol e^? m^?2 s^?1, respectively. The lichen recovers immediately after photoinhibition under low light conditions. S. foliolosum on subjecting to desiccation results in the decrease of light absorptivity and the reflectance properties associated with water status of the thalli show a change. During desiccation, a simultaneous decrease in photosynthesis, dark respiration and quenching in the fluorescence properties was observed. However, all the observed changes show a rapid recovery on rewetting the lichen. Our study shows that desiccation does not have a severe or long-term impact on S. foliolosum and the lichen is also well adapted to confront high light intensities.     

Trait variability in ontogenesis of epiphytic lichen Hypogymnia physodes (L.) Nyl.

Ontogenesis of the foliose lichen Hypogymnia physodes has been described on the basis of the material obtained from natural populations. Ontogenetic dynamics (diameter of thallus and the number of lobes) and the features of reproductive structures (the number and diameter of labelloid and galeated sorales) were studied in ecologically different pine forests. We reasonably rejected the use of the variance analysis and nonparametric criteria for the result processing. It was shown that the median dynamics and trait variance may be either similar or different throughout the ontogenesis. The trait variances in ecologically different ecotopes were shown to be different.     

The influence of temperature on the water exchange in amphibian eggs and embryos

The water exchange has been measured in oocytes of siredon mexicanum and rana temporaria, and in unfertilized eggs and early gastrulae of the former species, by recording the D₂O? H₂O exchange with the cartesian diver balance. In oocytes, where no diffusion barrier to water is demonstrable, the temperature coefficient Q₁₀ for the exchange of water is about 1.3–1.4, corresponding to that of free diffusion. in unfertilized eggs, and in early gastrulae the exchange is considerably slowed down, indicating that a surface membrane to some extent limits the rate of exchange. at the same time the Q₁₀ value is increased, lying in the range 2.3–3.8. since it is most likely that the exchange even in this case occurs by diffusion, but through membrane pores, it is concluded that the area available for diffusion (pore size or number, or both) increases with temperature.     

Effect of water alkalinity on gill CO2 exchange and internal PCO2 in aquatic animals

In addition to metabolic CO2 production and gill ventilatory flow rate, expired water PCO2 is very dependent on water acid-base balance in a complex way. This is particularly true in carbonated waters at low ambient PCO2 and high pH, where CO2 excreted in the gill water may be buffered by carbonate ions, leading to an increased CO2 capacitance coefficient. The higher the carbonate alkalinity (CA) and the lower the inspired PCO2 (i.e., the higher the inspired water pH), the stronger the carbonate buffering and the smaller the increase of PCO2 in the gill water during respiratory CO2 exchanges. As a consequence, as shown by a number of reported data, increasing the CA leads to blood hypocapnia and respiratory alkalosis at constant low, but not at high, inspired PCO2. In the low range of inspired PCO2, internal PCO2 becomes very sensitive to even small changes of water PCO2, which may explain at least in part the large variability of reported blood PCO2 values in gill breathers. Water CA also influences the amplitude of respiratory acid-base disturbances caused by changes of the gill ventilatory flow rate. Carbonate buffering of excreted CO2 and thus dependence of blood PCO2 on water alkalinity requires catalysis of CO2 hydration by carbonic anhydrase, that must be available from the water side of the gill epithelium.     

Symbiosis extended: exchange of photosynthetic O2 and fungal-respired CO2 mutually power metabolism of lichen symbionts

Photosynthesis Research - Lichens are a symbiosis between a fungus and one or more photosynthetic microorganisms that enables the symbionts to thrive in places and conditions they could not compete...     

The effect of different night conditions on the CO2 fixation in a lichen Xanthoria parietina

CO₂ fixation was studied in a lichen, Xanthoria parietina, kept in continuous light, and with cyclic changes in light intensity, dark period or temperature. The diurnal and seasonal courses of CO₂ exchange were followed. The rate of net photosynthesis was observed to fall from morning to evening, and this decline was more pronounced in winter than in summer. The maximal net photosynthetic rate, 223 ng CO₂g^-1dws^-1, occured in winter and the minimum, 94 ng CO₂g^-1dws^-1, late in spring. The light compensation point in summer was four times as high as in winter. In continuous light (180 or 90 mol photons m^-2s^-1, 15°C) net photosynthesis decreased noticeably during one week, falling below the level maintained in a 12 h light: 12 h dark cycle. Photosynthetic activity did not decrease, however, in lichens held in continuous light (90 mol photons m^-2s^-1) with cyclic changes of temperature (12 h 20 °C: 12 h 5 °C). Active photosynthesis was also maintained in light of cyclically changing intensity (12 h: 12 h, 15 °C) when night-time light was at least 75% lower than illumination by day. A dark period of 4 hours in a 24-h light:dark cycle was sufficient to keep CO₂ fixation at the control level. It seems that plants need an unproductive period during the day to survive and this can be induced by fluctuations in light and/or temperature.     

Antimicrobial activity of extracts of the lichen Parmelia sulcata and its salazinic acid constituent

The antimicrobial activity of the acetone, chloroform, diethyl ether, methanol, and petroleum ether extracts of the lichen Parmelia sulcata and its salazinic acid constituent have been screened against twenty eight food-borne bacteria and fungi. All of the extracts with the exception of the petroleum ether extract showed antimicrobial activity against Aeromonas hydrophila, Bacillus cereus, Bacillus subtilis, Listeria monocytogenes, Proteus vulgaris, Yersinia enterocolitica, Staphylococcus aureus, Streptococcus faecalis, Candida albicans, Candida glabrata, Aspergillus niger, Aspergillus fumigatus, and Penicillium notatum. Salazinic acid did not show antimicrobial activity against L. monocytogenes, P. vulgaris, Y. enterocolitica, and S. faecalis but showed activity against Pseudomonas aeruginosa and Salmonella typhimurium as well. The MIC values of the extracts and the acid for the bacteria and fungi have also been determined.     

The influence of ammoniates on 14CO2 assimilation in flax

A 1 μM solution of ammoniates [ZnCu(NH₃)_n]²⁺(CO₃)²⁻ was inserted into a cut shoot of flax with the transpiration stream of water. Analysis of the ¹⁴C content after ¹⁴CO₂ assimilation by the shoot showed that ammoniates increased radioactive label contents in the tissues (especially in the young leaves and stem). In the leaves the higher sucrose to hexoses ratio, an increased radioactivity of glycerate and malate and decreased incorporation of ¹⁴C into oligosaccharides and pigments were observed. These effects were more pronounced in the young leaves. Spraying of plants with 20 mM solution resulted in an increase of plant height and leaf number.     

An assessment of the relationship between chlorophyll a fluorescence and CO2 gas exchange from field measurements on a moss and lichen

The relationship between CO₂ exchange and relative electron-transport rate through photosystem II (ETR, measured using chlorophyll a fluorescence) was determined for a moss and a green algal lichen, photobiont probably Trebouxia sp., in the field in Antarctica. Net photosynthesis (NP) and dark respiration (DR) were measured over temperatures from zero to 25 °C and gross photosynthesis (GP) calculated (GP = NP + DR). The strong response of DR to temperature in these organisms resulted in substantial changes in CO₂ exchange rates. The moss Bryum argenteum Hedw. showed a strong, linear relationship between GP and ETR. This was an unexpected result since mosses are C₃ plants and, in higher plants, this group normally has a curvilinear GP versus ETR relationship. It is suggested that suppression of DR in the light might be involved. The lichen, Umbilicaria aprina Nyl., had nonlinear relationships between ETR and GP that were different at each measurement temperature. In some cases the lowest ETR was at the higher CO₂ exchange rates. It is suggested that these relationships are the result of strong quenching mechanisms that are inversely proportional to GP. The results support a growing impression that the relationships between ETR and CO₂ exchange are complex in these organisms and different from those found for higher plants. Received: 24 November 1997 / Accepted 2 May 1998     

Aerial release of CO2 and respiratory exchange ratio in intertidal fishes out of water

Synopsis Many fishes in the marine intertidal zone have the ability to exchange respiratory gases in air during brief periods out of water. Previous studies on marine amphibious fishes such as mudskippers and rockskippers have shown that they release CO₂ in air at a rate consistent with its release in aquatic respiration. Respiratory Exchange Ratios (RER, CO₂ released per O₂ consumed) are between 0.7 and 1.0, similar to Respiratory Quotients (CO₂ produced metabolically per O₂ consumed). However, previous studies of temperate intertidal fishes emerged only at low tides have been less consistent, with two species reported similar in ability to the amphibious skipper fishes, and two others reported with much lower RERs in air. This study examines 12 species of fishes, from six families (Batrachoididae, Cottidae, Gobiesocidae, Kyphosidae, Pholididae, and Stichaeidae), present in the intertidal zone of California. All 12 species exchanged O₂ and CO₂ in air. Like the amphibious skipper fishes of marine tropical waters, many intertidal fishes of the temperate zone release CO₂ during low tide emergence in quantities sufficient to match its metabolic production. These results indicate that CO₂ release is not hampered by the change in respiratory medium from water to air.     

Seasonal acclimation in the epiphytic lichen Parmelia sulcata is influenced by change in photobiont population density

CO₂ gas exchange, radial growth, chlorophyll (Chl) content and photobiont density of an epiphytic population of Parmelia sulcata were monitored every 2 months during 1 year in a temperate deciduous forest of Central Italy, to verify possible seasonal variations. Light response curves of south-exposed thalli, built up in the laboratory at 6 and 27°C at optimal thallus hydration, showed that CO₂ gas exchange changed significantly during the year, with a maximum for gross photosynthesis in December at both temperatures. Photoinhibition phenomena occurred in early spring, immediately before tree leaves sprouted. The principal component analysis of CO₂ gas exchange parameters clearly separated the months with from the months without tree canopy cover. Radial growth, measured on marginal lobes of north- and south-exposed thalli, was the highest in December, and the lowest in April. Photobiont density, measured in lobes of south- and north-exposed thalli with a sedimentation chamber, also changed during the year: the number of photobionts was highest in June and December, and lowest in April, although no significant change in cell size and Chl content per cell was evident throughout the year. South-exposed thalli had slightly, but constantly higher photobiont density both on a weight and an area basis. The acclimation of lichen photosynthesis and Chl content to seasonal temperature and light changes should partially be re-visited on the basis of the significant variation in photobiont population density. This phenomenon still awaits, however, a satisfactory explanation, although it is probably related to the seasonal change in nutrient availability.     

CO2 gas exchange of the understory plantAsarum europaeum L. in November

The CO₂ gas exchange rates of the Central European perennial understory plantAsarum europaeum L. were measured in late autumn (October 30 to November 30) in its natural habitat day and night.During these measurements the temperature ranged from 0 to 15°C and the absolute air humidity from 3 to 10 mg H₂O·1^–1. Temperature and absolute air humidity over these ranges did not affect CO₂ net assimilation which was determined almost entirely by quantum flux density.CO₂ net assimilation was light saturated at about 100 M·m^–2·s^–1 quantum flux density. The uptake rate at this point was 4.3 mg·dm^–2·h^–1. The compensation point occurred at approximately 1 M·m^–2·s^–1.     

Seasonal patterns of CO2 and water vapor exchange of three salt marsh succulents

Summary Diurnal carbon dioxide exchange patterns of three salt marsh succulents, Borrichia frutescens, Batis maritima and Salicornia virginica, were determined on a seasonal basis in the marsh at Sapelo Island, Georgia. Year-round photosynthetic activity was observed in these species though winter rates of CO₂ exchange were reduced. Net primary productivity, estimated using gas exchange techniques, agreed with previously reported harvest data. The role of light and temperature in the control of seasonal photosynthetic changes was investigated. A similar variation in light utilization with season was found in all three species, while seasonal temperature acclimation was species dependent. Less than 20% of fixed CO₂ was lost through dark respiration in any of the species.Water use in the salt marsh succulents was found to be relatively inefficient. High rates of transpiration were observed both summer and winter in the succulents.The succulents were judged to be C₃ plants on the basis of several criteria.Contribution No. 391 from the University of Georgia Marine Institute     

CO2 and bicarbonate exchange in the rat liver

Several forms of carbonic anhydrase (CA) have been detected in hepatocytes. The distribution of these enzymes appears to be heterogeneous in the hepatic lobule, and the specific isoenzyme that predominates is influenced by sex steroid levels in the animal. In the present study, experiments were conducted in isolated male rat livers perfused with erythrocyte-free solutions, which were devoid of CA to see if there were sufficient tissue CA activity accessible to the plasma to ensure equilibration between labeled HCO3- and CO2 during a single passage from the portal vein to the hepatic vein. After injection of H14CO3- into the portal vein, emergence of the 14C label from the hepatic vein was slightly more rapid than after injections of 14CO2. After infusion of 5-250 microM of acetazolamide, an inhibitor of CA, H14CO3- was virtually confined to the extracellular space during a single transit through the organ, whereas the outflow of 14CO2 was very prolonged, suggesting that some of the 14C had been "trapped" within the hepatic cells as H14CO3-. Inhibition of CA activity in the intact organ with low doses of acetazolamide suggests the presence of a readily inhibitable isoenzyme of CA on the surface of the hepatocytes, which is directly accessible to both HCO3- and acetazolamide. The outflow patterns of 14CO2 and H14CO3- became the same after infusion of erythrocyte CA into the portal vein. On the basis of the pH of the perfusate and the cellular distribution of 14CO2 and H14CO3- in the presence of CA, an intracellular pH value of 7.26 was calculated.(ABSTRACT TRUNCATED AT 250 WORDS)     

The influence of chironomus plumosus larvae on the exchange of dissolved substances between sediment and water

4th instar Chironomus plumosus larvae (about 1000·m^–2) were added to tubes containing sediment and overlying water. At a temperature of 20°C the larvae greatly increased the trasnport of silica, phosphorus and iron from the sediment to the water. Oxygen concentrations did not influence the exchange of silica. For two non-calcareous sediments the exchange of phosphorus and iron was much higher under anaerobic than under aerobic conditions while the difference was small for sediment from a hardwater lake. Exchange of inorganic nitrogen was little influenced by added chironomid larvae.