Inorganic carbon acquisition systems in cyanobacteria

This minireview focuses on the mechanism of inorganic carbon uptake in cyanobacteria and in particular the two CO₂-uptake systems and two bicarbonate transporters recently identified in Synechocycstis PCC 6803, and their presence in other cyanobacterial strains. This revised version was published online in August 2006 with corrections to the Cover Date.     

The influence of selected water quality parameters on the decay rate and exoenzymatic activity of detritus of Nymphaea alba L. floating leaf blades in laboratory experiments

Summary A chemostat study was conducted to investigate the influence of water quality parameters related to acidification processes on the decomposition of floating leaves of Nymphaea alba L. HCO _inf3 ^sup– and total Al concentration and pH influenced the decay rate. The activity of four cell-wall decaying exoenzymes was measured in the detritus. The activity of two types of pectic enzyme and xylanase was low under acid conditions. Cellulase activity was little affected. The exoenzyme activity seemed to be influenced by the pH of the water within the detritus. Inhibition of pectic enzymes under acid conditions may be an important factor causing the slow decay of macrophyte remains in acid waters.     

Characterisation of carbon dioxide and bicarbonate transport during steady-state photosynthesis in the marine cyanobacterium Synechococcus strain PCC7002

Net O₂ evolution, gross CO₂ uptake and net HCO _inf3 ^su– uptake during steady-state photosynthesis were investigated by a recently developed mass-spectrometric technique for disequilibrium flux analysis with cells of the marine cyanobacterium Synechococcus PCC7002 grown at different CO₂ concentrations. Regardless of the CO₂ concentration during growth, all cells had the capacity to transport both CO₂ and HCO _inf3 ^su– ; however, the activity of HCO _inf3 ^su– transport was more than twofold higher than CO₂ transport even in cyanobacteria grown at high concentration of inorganic carbon (C_i = CO₂ + HCO _inf3 ^su– ). In low-C_i cells, the affinities of CO₂ and HCO _inf3 ^su– transport for their substrates were about 5 (CO₂ uptake) and 10 (HCO _inf3 ^su– uptake) times higher than in high-C_i cells, while air-grown cells formed an intermediate state. For the same cells, the intracellular accumulated C_i pool reached 18, 32 and 55 mM in high-C_i, air-grown and low-C_i cells, respectively, when measured at 1 mM external C_i. Photosynthetic O₂ evolution, maximal CO₂ and HCO _inf3 ^su– transport activities, and consequently their relative contribution to photosynthesis, were largely unaffected by the CO₂ provided during growth. When the cells were adapted to freshwater medium, results similar to those for artificial seawater were obtained for all CO₂ concentrations. Transport studies with high-C_i cells revealed that CO₂ and HCO _inf3 ^su– uptake were equally inhibited when CO₂ fixation was reduced by the addition of glycolaldehyde. In contrast, in low-C_i cells steady-state CO₂ transport was preferably reduced by the same inhibitor. The inhibitor of carbonic anhydrase ethoxyzolamide inhibited both CO₂ and HCO _inf3 ^su– uptake as well as O₂ evolution in both cell types. In high-C_i cells, the degree of inhibition was similar for HCO _inf3 ^su– transport and O₂ evolution with 50% inhibition occurring at around 1 mM ethoxyzolamide. However, the uptake of CO₂ was much more sensitive to the inhibitor than HCO _inf3 ^su– transport, with an apparent I₅₀ value of around 250 M ethoxyzolamide for CO₂ uptake. The implications of our results are discussed with respect to C_i utilisation in the marine Synechococcus strain.Abbreviations Chl chlorophyll - C_i inorganic carbon (CO₂ + HCO _inf3 ^su– ) - CA carbonic anhydrase - CCM CO₂-concentrating mechanism - EZA ethoxyzolamide - GA glycolaldehyde - K_1/2 concentration required for half-maximal response - Rubisco ribulose-1,5,-bisphosphate carboxylase-oxygenase D.S. is a recipient of a research fellowship from the Deutsche Forschungsgemeinschaft (D.F.G.). In addition, we are grateful to Donald A. Bryant, Department of Molecular and Cell Biology and Center of Biomolecular Structure Function, Pennsylvania State University, USA, for sending us the wild-type strain of Synechococcus PCC7002.     

Photosynthesis and apparent affinity for dissolved inorganic carbon by cells and chloroplasts of Chlamydomonas reinhardtii grown at high and low CO2 concentrations

Chloroplasts with high rates of photosynthetic O₂ evolution (up to 120 mol O₂· (mg Chl)^-1·h^-1 compared with 130 mol O₂· (mg Chl)^-1·h^-1 of whole cells) were isolated from Chlamydomonas reinhardtii cells grown in high and low CO₂ concentrations using autolysine-digitonin treatment. At 25° C and pH=7.8, no O₂ uptake could be observed in the dark by high- and low-CO₂ adapted chloroplasts. Light saturation of photosynthetic net oxygen evolution was reached at 800 mol photons·m^-2·s^-1 for high- and low-CO₂ adapted chloroplasts, a value which was almost identical to that observed for whole cells. Dissolved inorganic carbon (DIC) saturation of photosynthesis was reached between 200–300 M for low-CO₂ adapted chloroplasts, whereas high-CO₂ adapted chloroplasts were not saturated even at 700 M DIC. The concentrations of DIC required to reach half-saturated rates of net O₂ evolution (K_m(DIC)) was 31.1 and 156 M DIC for low- and high-CO₂ adapted chloroplasts, respectively. These results demonstrate that the CO₂ concentration provided during growth influenced the photosynthetic characteristics at the whole cell as well as at the chloroplast level.Abbreviations Chl chlorophyll - DIC dissolved inorganic carbon - K_m(DIC) coneentration of dissolved inorganic carbon required for the rate of half maximal net O₂ evolution - PFR photon fluence rate - SPGM silicasol-PVP-gradient medium     

Mechanism of acquisition of exogenous bicarbonate by internodal cells of Chara corallina

Electrophysiological measurements on internodal cells of the alga, Chara corallina Klein ex Willd., em. R.D.W., showed that the potential across the plasmalemma was sensitive to the level of exogenous HCO ₃ ^- . In alkaline solutions (pH 8) the membrane potential depolarized by 50–75 mV when exogenous HCO ₃ ^- was removed from the bathing medium. In the presence of exogenous HCO ₃ ^- , the membrane potential rapidly hyperpolarized when the cell was given a brief dark treatment; in the light the potential was approx.-240 mV; after the cell had been in the dark for 3–6 min the potential was -330 to -350 mV. In the absence of exogenous HCO ₃ ^- the potential only hyperpolarized slowly and to a much smaller extent when cells were placed in the dark. Upon re-illuminating the cell, the potential further hyperpolarized, transiently, and then rapidly depolarized back towards the light-adapted value. (These responses were only obtained when cells were not perturbed by microelectrode insertion into the vacuole.) Analysis of membrane potential and experiments with the extracellular vibrating electrode indicated a high level of correlation between the light- and dark-induced changes in membrane potential and extracellular currents. However, when experiments were conducted in HCO ₃ ^- -free media that contained 1.0 mM phosphate buffer, pH 8, it was found that the dark-induced hyperpolarization of the membrane potential and the light-dependent extracellular currents could be maintained in the absence of exogenous HCO ₃ ^- . These results are interpreted in terms of two basic models by which internodal cells of C. corallina may acquire exogenous HCO ₃ ^- for photosynthesis. They are consistent with HCO ₃ ^- being transported across the plasmalemma via an electrically neutral HCO ₃ ^- –H⁺ cotransport system. The hyperpolarizing response is thought to be the consequence of the operation of an electrogenic H⁺-translocating ATPase that has a transport stoichiometry of 1 H⁺ per ATP hydrolyzed.Abbreviation CPW/B artificial Chara pond water containing exogenous bicarbonate     

The effect of dynamic light regimes on Chlorella

The patterns of diurnal variations in pigmentation and optical cross-section were compared for two cyclostat cultures of Chlorella pyrenoidosa, where the dynamics of the photoperiod differed. Populations were light-limited, nutrient rich and growing on an 8:16 light-dark (LD) cycle. One light regime was an 8 h sine function of the light period (sinusoidal culture), while the second had an 1 h sine function super-imposed on the 8 hour sine function (oscillating sinusoidal culture). Hourly samples were taken throughout a 12 h period including the light period. Determinations were made of chlorophyll (Chl) a and b abundance, in vivo absorption spectra, cell number and volume and used to derive both cell-specific (cell) and optical chlorophyll specific (chl) cross sections, as well as the absorption efficiency, Q, of the cells. The results indicate that C. pyrenoidosa is capable of adapting to dynamics in light intensity within an 8 h photoperiod. The sinusoidal culture showed a constant decrease in the Chl a/b ratio of 28% while the total Chl content per cell increased slightly and chl and Q remained constant, suggesting coordinated changes in reaction centers and light harvesting complexes. Over the oscillating photoperiod, however, the second culture displayed a diurnal variation in Chl a/b ratio, a 20% increase in chl and an apparent oscillation in Q. These observations suggest that an oscillating photoperiod promoted the capability of Chl molecules to collect light and that the fractional area of all Chl molecules exposed to the photon flux is inversely related to the photon flux.     

Physiological responses of carbon-sequestering microalgae to elevated carbon regimes

In order to identify a high carbon-sequestering microalgal strain, the physiological effect of different concentrations of carbon sources on microalgae growth was investigated. Five indigenous strains (I-1, I-2, I-3, I-4 and I-5) and a reference strain (I-0: Coccolithus pelagicus 913/3) were subjected to CO₂ concentrations of 0.03–15% and NaHCO₃ of 0.05–2 g CO₂ l^–1. The logistic model was applied for data fitting, as well as for estimation of the maximum growth rate (μ_max) and the biomass carrying capacity (B_max). Amongst the five indigenous strains, I-3 was similar to the reference strain with regards to biomass production values. The B_max of I-3 significantly increased from 214 to 828 mg l^–1 when CO₂ concentration was increased from 0.03 to 15% (r = 0.955, P = 0.012). Additionally, the B_max of I-3 increased with increasing NaHCO₃ (r = 0.885, P = 0.046) and was recorded at 153 mg l^–1 (at 0.05 g CO₂ l^–1) and 774 mg l^–1 at (2 g CO₂ l^–1). Relative electron transport rate (rETR) and maximum quantum yield (F_v/F_m) were also applied to assess the impact of elevated carbon sources on the microalgal cells at the physiological level. Isolate I-3 displayed the highest rETR confirming its tolerance to higher quantities of carbon. Additionally, the decline in F_v/F_m with increasing carbon was similar for strains I-3 and the reference strain. Based on partial 28s ribosomal RNA gene sequencing, strain I-3 was homologous to the ribosomal genes of Chlorella sp.     

Secretion of HCO 3 − /OH− in cortical distal tubule of the rat

Secretion of bicarbonate has been described for distal nephron epithelium and attributed to apical Cl^–/HCO ₃ ^– exchange in beta-intercalated cells. We investigated the presence of this mechanism in cortical distal tubules by perfusing these segments with acid (pH 6) 10 mm phosphate Ringer. The kinetics of luminal alkalinization was studied in stationary microperfusion experiments by double-barreled pH (ion-exchange resin)/1 m KCl reference microelectrodes. Luminal alkalinization may be due to influx (into the lumen) of HCO ₃ ^– or OH^–, or efflux of H⁺. The magnitude of the Cl^–/ HCO ₃ ^– exchange component was measured by perfusing the lumen with solutions with or without chloride, which was substituted by gluconate. This component was not different from zero in control and alkalotic (chronic plus acute) Wistar rats. Homozygous Brattleboro rats (BRB), genetically devoid of antidiuretic hormone, were used since this hormone has been shown to stimulate H⁺ secretion, which could mask bicarbonate secretion. In these rats, no evidence for Cl^–/HCO ₃ ^– exchange was found in control BRB and in early distal segments of alkalotic animals, but in late distal tubule a significant component of 0.14±0.033 nmol/cm² · sec was observed, which, however, is small when compared to the reabsorptive flow found in control Wistar rats, of 0.95±0.10 nmol/cm² · sec. In addition, 5×10^–4 m SITS had no effect on distal bicarbonate reabsorption in controls as well as on secretion in alkalotic Wistar and Brattleboro rats, which is compatible with the absence of effect of this drug on the apical Cl^–/HCO ₃ ^– exchange in other tissues. It is concluded that most distal alkalinization is not Cl^– dependent, and that Cl^–/HCO ₃ ^– exchange may be found in cortical distal tubule, but its magnitude is, even in alkalosis, markedly smaller than the reabsorptive flux, which predominates in the rats studied in this paper, keeping luminal pH lower than that of blood.     

Potassium channel in rabbit corneal endothelium activated by external anions

Summary The apical membrane of the rabbit corneal endothelium contains a potassium-selective ionic channel. In patch-clamp recordings, the probability of finding the channel in the open state (P _o) depends on the presence of either HCO ₃ ^– or Cl^– in the bathing medium. In a methane sulfonate-containing bath,P _o is <0.05 at all physiologically relevant transmembrane voltages. With 0mm [HCO ₃ ^– ] _o at +60 mV,P _o was 0.085 and increased to 0.40 when [HCO ₃ ^– ] _o was 15mm. With 4mm [Cl^–] _o at +60 mV,P _o was 0.083 and with 150mm Cl^–,P _o increased to 0.36. LowP _o's are also found when propionate, sulphate, bromide, and nitrate are the primary bath anions. The mechanism of action of the anion-stimulated K⁺ channel gating is not yet known, but a direct action of pH seems unlikely. The alkalinization of cytoplasm associated with the addition of 10mm (NH₄)₂SO₄ to the bath and the acidification accompanying its removal do not result in channel activation nor does the use of Nigericin to equilibrate intracellular pH with that of the bath over the pH range of 6.8 to 7.8. Channel gating also is not affected by bathing the internal surface of the patch with cAMP, cGMP, GTP--s, Mg²⁺ or ATP. Blockers of Na/H⁺ exchange, Na⁺–HCO ₃ ^– cotransport, Na⁺–K⁺ ATPase and carbonic anhydrase do not block the HCO ₃ ^– stimulation ofP _o. Several of the properties of the channel could explain some of the previously reported voltage changes that occur in corneal endothelial cells stimulated by extracellular anions.     

Toxicity of nitrapyrin to sunflower under different N nutrition regimes

Summary The purpose of this study was to investigate the phytotoxicity of nitrapyrin 2-chloro-6-(trichloromethyl)pyridine to sunflower (Helianthus annuus L.) under different N regimes and to see if N forms affect the phytotoxicity of nitrapyrin. Sunflower was grown in pot culture for 21 days and was fertilized with (NH₄)₂SO₄, NH₄NO₃ and NaNO₃ to provide 0, 100 and 200 ppm N and with nitrapyrin application of 0 and 20 ppm. All N-treated sunflower plants in all N regimes and regardless of titrapyrin treatment produced more root and shoot dry weights and contained a significantly higher N than untreated check. Nitrapyrin toxicity appeared as a curling of leaf margin and a tendril type of stem growth, the visible toxicity symptoms decreased in the order: (NH₄)₂SO₄>NH₄NO₃>NaNO₃. Furthermore nitrapyrin addition suppressed sunflower growth in each N regime, the suppressing effect being greater with (NH₄)₂SO₄ and NH₄NO₃ than as with NaNO₃. Although, shoot growth from plants receiving nitrapyrin was not significantly affected by any N regime, root growth of nitrapyrin-treated plants was somewhat restricted by NH₄ ⁺−N nutrition relative to NO₃ ⁻−N nutrition.     

Effect of calcium restriction on cardenolide accumulation in two cell lines of Digitalis thapsi grown under different light regimes

The effect of calcium-deprivation on growth and the production of cardenolides in two undifferentiated cell lines of Digitalis thapsi maintained under three different light regimes (16 h photoperiod, darkness, or continuous light) was investigated. Growth was stimulated by continuous light in both cell lines cultured in complete medium. The light regime did not affect cardenolide accumulation in the cells of the hypocotyl-derived line; by contrast, continuous light or darkness increased the production in the leaf-derived line. The elimination of calcium favoured cardenolide production independently of the origin of the suspensions and the light regime, this beneficial effect being predominantly manifested under continuous light.     

Mechanisms of Cl− uptake through brush border membranes isolated from the posterior intestine of the freshwater trout,Oncorhynchus mykiss,R.

Summary This paper presents a study of the mechanisms of Cl^– transport through the brush border membranes of the posterior part of the intestine in the freshwater trout, Oncorhynchus mykiss. The mechanisms for Cl^– transport in the posterior intestine are distinct from those in the middle intestine; an inwardly directed pH gradient stimulates Cl^– uptake by bursh border membrane vesicles, indicating a Cl^–/OH^– exchange. A pH-regulated Cl^– conductance is present, which is not activated at normal intracellular pH. Cl^– uptake is stimulated by an outwardly directed HCO ₃ ^– gradient revealing the presence of a Cl^–/HCO ₃ ^– exchange but, conversely, Cl^– is not exchanged against SO ₄ ^2- . In addition, carbonic anhydrase activities have been detected in both the intracellular and extracellular leaflets of the bursh border membranes which favour the establishment of a bicarbonate gradient. A model of Cl^– transport mechanisms through the brush-border membranes of the posterior intestine of the freshwater trout is proposed.Abbreviations BBM brush border membrane - CA carbonic anhydrase - EGTA ethylene-bis(oxyethylenenitrilo)tetra-acetic acid - FW fresh water - Hepes N-2-hydroxy-ethyl-piperazine-N'-2-ethanesulphonic acid - Mes 2-(N-morpholino)ethane sulphonic acid - SITS 4-acetamido-4-isothiocyanostilbene-2,2-disulphonic acid - TEA triethanolamine - TMA tetramethylammonium - TRIS tris(hydroxymethyl)aminomethane     

Nitrogen nutrition of rice plants under salinity

Two rice (Oryza sativa L.) cultivars, Koshihikari and Pokkali, were grown in solution culture at three concentrations of NaCl or Na₂SO₄ [0 (S0), 50 (S1), and 100 (S2) mmol dm^–3] and three N contents [0.7 (N1), 7 (N2) and 14 (N3) mmol dm^–3]. Salinity significantly decreased dry matter of both cultivars. Pokkali had better growth than Koshihikari under both saline and non-saline conditions. Applications of N enhanced development of shoot dry mass under S0 and S1 treatments up to N2. Under S2, N application had no effect on shoot dry mass of both cultivars. Root dry mass of both cultivars decreased with increasing N application at S1 and S2. Shoot and root NO₃-N content in both rice cultivars increased with increasing N concentration in the nutrient solutions. The absorption of NO₃-N was less in Koshihikari than Pokkali plants, and also was much less in Cl^– than SO₄ ^2– salinity suggesting the antagonism between Cl^– and NO₃ ^–. In addition a significant negative correlation between concentrations of NO₃-N and Cl^– in the shoots or roots was observed in both cultivars     

Fixation of 14CO2 in tissue cultured red raspberry prior to and after transfer to soil

The ¹⁴CO₂ uptake of an aseptically cultured red raspberry clone (Rubus ideaus L.) was examined prior to and after transfer to soil. Individual leaves of transplants, both persistent from culture and new ones, were tested 5 weeks after transplant for ¹⁴CO₂ uptake capability. Transplant leaves of successive weekly age classes took up ¹⁴CO₂ at increasing rates per unit area, displaying a spectrum of photosynthetic competence from low levels close to that of leaves from culture, to that of control plants. This is illustrative of acclimatization to the soil environment and was related to transplant light intensity.     

Evidence for an anion exchanger in the mouse lacrimal gland acinar cell membrane

Summary Anion exchange transport in the mouse lacrimal gland acinar cell membrane was studied by measuring the intracellular H⁺ (pH_i) and Cl^– (aCl_i) activities with double-barreled ion-selective microelectrodes. In a HCO ₃ ^– -free solution of pH 7.4 (HEPES/Tris buffered), pH_i was 7.25 andaCl_i was 33mm. By an exposure to a HCO ₃ ^– (25mm HCO ₃ ^– /5% CO₂, pH 7.4) solution for 15 min,aCl_i was decreased to 25mm and pH_i was transiently decreased to about 7.05 within 1 min, then slowly relaxed to 7.18 in 15 min. Intracellular HCO ₃ ^– concentration [HCO ₃ ^– ]_i, calculated by the Henderson-Hasselbalch's equation, was 11mm at 1 min after the exposure and then slowly increased to 15mm. Readmission of the HCO ₃ ^– -free solution reversed the changes inaCl_i and pH_i. The intracellular buffering power was about 40mm/pH. An addition of DIDS (0.2mm) significantly inhibited the rates of change inaCl_i, pH_i, and [HCO ₃ ^– ]_i caused by admission/withdrawal of the HCO ₃ ^– , solution and decreased the buffer value. Replacement of all Cl^– with gluconate in the HCO ₃ ^– solution increased pH_i, and readmission of Cl^– decreased pH_i. The rates of these changes in pH_i were reduced by DIDS by 32–45% but not by amiloride (0.3mm). In the HCO ₃ ^– solution, a stimulation of intracellular HCO ₃ ^– production by exposing the tissue to 25mm NH ₄ ⁺ increasedaCl_i significantly. While in the HCO ₃ ^– -free solution or in the HCO ₃ ^– , solution containing DIDS, exposure to NH ₄ ⁺ had little effect onaCl_i. All of these findings were consistent with the presence of a reversible, disulfonic stilbene-sensitive Cl^–/HCO ₃ ^– exchanger in the basolateral membrane of the acinar cells. The possibility of anion antiport different from one-for-one Cl^–/HCO ₃ ^– exchange is discussed.     

Losses of inorganic carbon and nitrous oxide from a temperate freshwater wetland in relation to nitrate loading

We studied the export of inorganic carbon and nitrous oxide (N₂O) from a Danish freshwater wetland. The wetland is situated in an agricultural catchment area and is recharged by groundwater enriched with nitrate (NO₃ ^–) (1000 M). NO₃ ^– in recharging groundwater was reduced (57.5 mol NO₃ ^– m^–2 yr^–) within a narrow zone of the wetland. Congruently, the annual efflux of carbon dioxide (CO₂) from the sediment was 19.1 mol C m^–2 when estimated from monthly in situ measurements. In comparison the CO₂ efflux was 4.8 mol C m^–2 yr^–1 further out in the wetland, where no NO₃ ^– reduction occurred. Annual exports of inorganic carbon in groundwater and surface water was 78.4 mol C m^–2 and 6.1 mol C m^–2 at the two sites, respectively. N₂O efflux from the sedimenst was detectable on five out of twelve sampling dates and was significantly (P < 0.0001) higher in the NO₃ ^– reduction zone (0.35–9.40 mol m^–2 h^–1, range of monthly means) than in the zone without NO₃ ^– reduction (0.21–0.41 mol m^–2 h^–1). No loss of dissolved N₂O could be measured. Total annual export of N₂O was not estimated. The reduction of oxygen (O₂) in groundwater was minor throughout the wetland and did not exceed 0.2 mol 0₂ m^–2yr^–1. Sulfate (SO₄ ^––) was reduced in groundwater (2.1 mol SO₄ ^–– m^–2 yr^–1) in the zone without NO₃ ^– reduction. Although the NO₃ ^– in our wetland can be reduced along several pathways our results strongly suggest that NO₃ ^– loading of freshwater wetlands disturb the carbon balance of such areas, resulting in an accelerated loss of inorganic carbon in gaseous and dissolved forms.     

The role of ion antiporters in the maintenance of intracellular pH in rat vascular smooth muscle cells

Vascular smooth muscle intracellular pH is maintained by the Na⁺/H⁺ and Cl^–/HCO ₃ ^– antiporters. The Na⁺/H⁺ exchanger is a major route of H⁺ extrusion in most eukaryotic cells and is present in vascular smooth muscle cells in a similar capacity. It extrudes H^– into the extracellular space in exchange for Na⁺. The Cl^–/HCO ₃ ^– exchanger plays an analogous role to lower the pH of vascular smooth muscle cells when increases in intracellular pH occur. Its activity has also been demonstrated in A7r5 and A10 vascular smooth muscle cells. The Na⁺/H⁺ exchanger is regulated by a number of agents which act through inositol trisphosphate/diacylglycerol, to stimulate the antiporter. Calcium-calmodulin dependent protein kinase may also activate the antiporter in vivo. Phosphorylation of the Cl^–/HCO ₃ ^– exchanger has also been observed but its physiological role is not known. Both these antiporters exist in the plasma membrane as integral proteins with free acidic cytoplasmic termini. These regions may be important in sensing changes in intracellular pH, to which these antiporters respond.Abbreviations CaM Calmodulin - DCCD Dicylohexyl-Carbodiimide - DG Diacylglycerol - DIDS-4 4-Diisthiocyanostilbene-2,2-Disulfonic Acid - IP₃ Inositol Trisphosphate - PKC protein Kinase C - SITS-4 4-Acetamido-4-Isothiocyanstilbene-2,2-Disulfonate - VSMC Vascular Smooth Muscle Cell     

Loblolly pine grown under elevated CO2 affects early instar pine sawfly performance

Seedlings of loblolly pine Pinus taeda (L.), were grown in open-topped field chambers under three CO₂ regimes: ambient, 150 l l^–1 CO₂ above ambient, and 300 l l^–1 CO₂ above ambient. A fourth, non-chambered ambient treatment was included to assess chamber effects. Needles were used in 96 h feeding trials to determine the performance of young, second instar larvae of loblolly pine's principal leaf herbivore, red-headed pine sawfly, Neodiprion lecontei (Fitch). The relative consumption rate of larvae significantly increased on plants grown under elevated CO₂, and needles grown in the highest CO₂ regime were consumed 21% more rapidly than needles grown in ambient CO₂. Both the significant decline in leaf nitrogen content and the substantial increase in leaf starch content contributed to a significant increase in the starch:nitrogen ratio in plants grown in elevated CO₂. Insect consumption rate was negatively related to leaf nitrogen content and positively related to the starch:nitrogen ratio. Of the four volatile leaf monoterpenes measured, only -pinene exhibited a significant CO₂ effect and declined in plants grown in elevated CO₂. Although consumption changed, the relative growth rates of larvae were not different among CO₂ treatments. Despite lower nitrogen consumption rates by larvae feeding on the plants grown in elevated CO₂, nitrogen accumulation rates were the same for all treatments due to a significant increase in nitrogen utilization efficiency. The ability of this insect to respond at an early, potentially susceptible larval stage to poorer food quality and declining levels of a leaf monoterpene suggest that changes in needle quality within pines in future elevated-CO₂ atmospheres may not especially affect young insects and that tree-feeding sawflies may respond in a manner similar to herb-feeding lepidopterans.     

Response of CO2 uptake, chlorophyll content, and some productional features of forest herb Smyrnium perfoliatum L. (Apiaceae) to different light conditions

Smyrnium perfoliatum L. (Apiaceae), an endangered summer forest herb grown in the understory of dominant oak-hornbeam stands in Devinska Kobyla, Little Carpathians region in SW Slovakia, is considered to form at least five leaf types of different physiological and anatomical quality. These observation are based upon the estimated differences of photosynthetic carbon dioxide uptake, chlorophyll content, leaf anatomy, and several quantitative parameters of growth analysis. There is a further attempt to establish, to what extent the daily changing environment, especially the excess of light of fast-moving sun-flecks by the photosynthetic apparatus within any leaf type, according to its dominant shade adaptation could be effectively used.