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1.
Chemoautotrophic symbioses, in which endosymbiotic bacteria are the major source of organic carbon for the host, are found in marine habitats where sulfide and oxygen coexist. The purpose of this study was to determine the influence of pH, alternate sulfur sources, and electron acceptors on carbon fixation and to investigate which form(s) of inorganic carbon is taken up and fixed by the gamma-proteobacterial endosymbionts of the protobranch bivalve Solemya velum. Symbiont-enriched suspensions were generated by homogenization of S. velum gills, followed by velocity centrifugation to pellet the symbiont cells. Carbon fixation was measured by incubating the cells with (14)C-labeled dissolved inorganic carbon. When oxygen was present, both sulfide and thiosulfate stimulated carbon fixation; however, elevated levels of either sulfide (>0.5 mM) or oxygen (1 mM) were inhibitory. In the absence of oxygen, nitrate did not enhance carbon fixation rates when sulfide was present. Symbionts fixed carbon most rapidly between pH 7.5 and 8.5. Under optimal pH, sulfide, and oxygen conditions, symbiont carbon fixation rates correlated with the concentrations of extracellular CO(2) and not with HCO(3)(-) concentrations. The half-saturation constant for carbon fixation with respect to extracellular dissolved CO(2) was 28 +/- 3 microM, and the average maximal velocity was 50.8 +/- 7.1 micromol min(-1) g of protein(-1). The reliance of S. velum symbionts on extracellular CO(2) is consistent with their intracellular lifestyle, since HCO(3)(-) utilization would require protein-mediated transport across the bacteriocyte membrane, perisymbiont vacuole membrane, and symbiont outer and inner membranes. The use of CO(2) may be a general trait shared with many symbioses with an intracellular chemoautotrophic partner. 相似文献
2.
1. To compare biochemical differences between bivalves with and without endosymbiotic chemoautotrophic bacteria, specimens of Solemya velum, a bivalve species known to contain bacterial endosymbionts, and the symbiont-free soft-shelled clam Mya arenaria, were collected from the same subtidal reducing sediments during October and November 1988. 2. Total and free amino acid compositions were determined for both species. Protein-bound amino acids were calculated as the difference between total and free amino acids. In addition, stable isotope ratios of the total and free amino acids of each species were measured to determine potential sources for these molecules. 3. Both species had similar total hydrolyzable- and protein-bound amino acid compositions; approximately 50% of the protein-bound amino acids were essential amino acids. In S. velum, the small size of the digestive system suggests that these amino acids are probably synthesized by the endosymbiotic bacteria and translocated to the animal tissue. The delta 13C and delta 15N ratios of the amino acids are very similar to the isotope ratios previously found in both the endosymbionts and whole tissues of S. velum. The relative and absolute amounts of free amino acids are very different in the two species. In S. velum, the absolute concentrations of taurine, a sulfur-containing amino acid, were greater than the total free amino acid concentrations found in other bivalves. 4. The delta 34S ratios of the free amino acids of S. velum, which were predominantly composed of taurine, were extremely negative (-17.2/1000) suggesting that taurine is synthesized using sulfur originally derived from external reduced sulfur sources, such as pore water sulfides. The possible roles for taurine in this animal-bacteria symbiosis are discussed. 相似文献
3.
The effects of elevated CO 2 (750 ppm vs. 390 ppm) were evaluated on nitrogen (N) acquisition and assimilation by three Medicago truncatula genotypes, including two N-fixing-deficient mutants ( dnf1-1 and dnf1-2) and their wild-type (Jemalong). The proportion of N acquisition from atmosphere and soil were quantified by 15N stable isotope, and N transportation and assimilation-related genes and enzymes were determined by qPCR and biochemical analysis. Elevated CO 2 decreased nitrate uptake from soil in all three plant genotypes by down-regulating nitrate reductase ( NR), nitrate transporter NRT1.1 and NR activity. Jemalong plant, however, produced more nodules, up-regulated N-fixation-related genes and enhanced percentage of N derived from fixation (%Ndf) to increase foliar N concentration and N content in whole plant (Ntotal Yield) to satisfy the requirement of larger biomass under elevated CO 2. In contrast, both dnf1 mutants deficient in N fixation consequently decreased activity of glutamine synthetase/glutamate synthase (GS/GOGAT) and N concentration under elevated CO 2. Our results suggest that elevated CO 2 is likely to modify N acquisition of M. truncatula by simultaneously increasing N fixation and reducing nitrate uptake from soil. We propose that elevated CO 2 causes legumes to rely more on N fixation than on N uptake from soil to satisfy N requirements. 相似文献
4.
空气中CO2浓度升高所导致的温室效应已成为重大的环境问题,受到人们普遍关注.概述了高效固定CO2微藻藻种的筛选和培养方法,分析了微藻固定CO2的无机碳利用形式和浓缩机制,讨论了高效光生物反应器设计和运行目标,简要介绍了微藻(酶)-膜生物反应器集成新技术.并认为今后的研究方向主要是在进一步探索微藻固定CO2有关机理的基础上,构建高效固定CO2的转基因微藻,开发高效膜生物反应集成系统. 相似文献
5.
The aquatic filamentous cyanobacteria Anabaena oscillarioides and Trichodesmium sp. reveal specific cellular regions of tetrazolium salt reduction. The effects of localized reduction of five tetrazolium salts on N 2 fixation (acetylene reduction), 14CO 2 fixation, and 3H 2 utilization were examined. During short-term (within 30 min) exposures in A. oscillarioides, salt reduction in heterocysts occurred simultaneously with inhibition of acetylene reduction. Conversely, when salts failed to either penetrate or be reduced in heterocysts, no inhibition of acetylene reduction occurred. When salts were rapidly reduced in vegetative cells, 14CO 2 fixation and 3H 2 utilization rates decreased, whereas salts exclusively reduced in heterocysts were not linked to blockage of these processes. In the nonheterocystous genus Trichodesmium, the deposition of reduced 2,3,5-triphenyl-2-tetrazolium chloride (TTC) in the internal cores of trichomes occurs simultaneously with a lowering of acetylene reduction rates. Since TTC deposition in heterocysts of A. oscillarioides occurs contemporaneously with inhibition of acetylene reduction, we conclude that the cellular reduction of this salt is of use in locating potential N 2-fixing sites in cyanobacteria. The possible applications and problems associated with interpreting localized reduction of tetrazolium salts in cyanobacteria are presented. 相似文献
6.
Carbon fixation at temperatures above 73°C, the upper limit for photosynthesis, is carried out by chemosynthetic thermophiles. Yellowstone National Park (YNP), Wyoming possesses many thermal features that, while too hot for photosynthesis, presumably support chemosynthetic-based carbon fixation. To our knowledge, in situ rates of chemosynthetic reactions at these high temperatures in YNP or other high-temperature terrestrial geothermal springs have not yet been reported. A microbial community attached to precipitated elemental sulfur (S o floc) at the source of Dragon Spring (73°C, pH 3.1) in Norris Geyser Basin, YNP, exhibited a maximum rate of CO 2 uptake of 21.3 ± 11.9 μg of C 10 7 cells −1 h −1. When extrapolated over the estimated total quantity of S o floc at the spring''s source, the S o floc-associated microbial community accounted for the uptake of 121 mg of C h −1 at this site. On a per-cell basis, the rate was higher than that calculated for a photosynthetic mat microbial community dominated by Synechococcus spp. in alkaline springs at comparable temperatures. A portion of the carbon taken up as CO 2 by the S o floc-associated biomass was recovered in the cellular nucleic acid pool, demonstrating that uptake was coupled to fixation. The most abundant sequences in a 16S rRNA clone library of the S o floc-associated community were related to chemolithoautotrophic Hydrogenobaculum strains previously isolated from springs in the Norris Geyser Basin. These microorganisms likely contributed to the uptake and fixation of CO 2 in this geothermal habitat.The upper temperature limit for primary production via photosynthesis is ∼73°C ( 7, 8, 11). At this temperature, photosynthesis is restricted to cyanobacteria of the genus Synechococcus, which generally inhabit alkaline environments ( 11). In acidic environments (pH < 4.0), the upper temperature limit for photosynthetic-based primary production is ∼56°C. Under these conditions, phototrophic activity is restricted to the unicellular eukaryotic red algae Cyanidium, Galdieria, and Cyanidioschyzon, collectively referred to as “cyanidia” ( 6, 12, 31, 48). Primary production above this temperature in acidic environments occurs through chemoautotrophy, a metabolism restricted to prokaryotes.Yellowstone National Park (YNP), WY, possesses numerous high-temperature (73 to 93°C) geothermal environments that are thought to support communities of microorganisms through chemoautotrophic-based primary production. Evidence for chemosynthesis in these environments is based on the recovery of 16S rRNA gene sequences that are affiliated with cultivated representatives of the phyla Aquificae and Crenarchaeota, many of which are capable of CO 2 fixation via the oxidation of hydrogen (H 2) and/or sulfide (HS −) ( 15, 17, 21, 24, 26, 28, 41, 46). Surprisingly, CO 2 fixation has yet to be demonstrated in situ in YNP hot spring environments (acidic or alkaline) where temperatures exceed the limits of photosynthesis and where primary production is thought to be driven by chemoautotrophic metabolism ( 14, 15, 28, 29).Dragon Spring, an acid-sulfate-chloride (ASC) spring located in the Norris Geyser Basin of YNP, is a likely habitat for chemoautotrophic primary production. The pH of the water is ∼3.1, and the temperature of the water at the source fluctuates from 65 to 78°C, which is well above the upper temperature limit for photosynthesis under acidic conditions. Potential electron donors for chemolithoautotrophic growth in the source water include hydrogen (H 2) and sulfide (S 2−) at concentrations of 13 nM and 65 μM, respectively ( 15). In addition, submerged substrata at the spring''s source are blanketed by precipitates of elemental sulfur (S°), hereafter referred to as S o floc ( 23). Inventories of bacterial and archaeal 16S rRNA genes recovered from S o floc collected from the source of Dragon Spring indicate the presence of Crenarchaeota and Aquificae ( 4, 15). The latter are related to chemolithoautotrophic Hydrogenobaculum spp., representatives of which have recently been isolated from the spring ( 15). In the present study, we demonstrate uptake and fixation of CO 2 at a temperature of 73°C by a Hydrogenobaculum-dominated microbial community associated with S o floc collected from the source of Dragon Spring. This is the first direct evidence of CO 2 uptake in situ by a thermoacidophilic microbial community at a temperature that precludes photosynthesis in terrestrial geothermal springs. 相似文献
8.
Mass spectrometry has been used to investigate the transportof CO 2 in the freshwater diatom Navicula pelliculosa. The timecourseof CO 2 formation in the dark after addition of 100 mmol m 3dissolved inorganic carbon (DIC) to cell suspensions showedthat no external carbonic anhydrase (CA) was present in thesecells. Upon illumination, cells pre-incubated at pH 75 with100 mmol m 3 DIC, removed almost all free CO 2 from themedium at an initial rate of 285 µmol CO 2 mg 1Chl h 1. Equilibrium between HCO 3 and CO 2 in themedium occurred rapidly upon addition of bovine CA, showingthat CO 2 depletion resulted from a selective uptake of CO 2 ratherthan an uptake of all inorganic carbon species. However, photosyntheticO 2 evolution rate remained constant after CO 2 had been depletedfrom the medium indicating that photosynthesis is sustainedprimarily by active HCO 3 uptake. Treatment of cells with2-iodoacetamide (83 mol m 3) completely inhibited CO 2fixation but had little effect on CO 2 transport since initialrates of CO 2 depletion were about 81% that of untreated cells.Transfer of iodoacetamide-treated cells to the dark caused arapid increase in the CO 2 concentration in the medium largelydue to the efflux of the unfixed intracellular DIC pool whichwas found to be about 194 times the concentration of that inthe external medium. These results indicate that Navicula pelliculosaactively takes up molecular CO 2 against a concentration gradientby a process distinct from HCO 3 transport. Key words: Dissolved inorganic carbon, carbonic anhydrase, bicarbonate transport, CO 2 transport, mass spectrometry 相似文献
9.
Many nutritive symbioses between chemoautotrophic bacteria and invertebrates, such as Solemya velum, have delta(13)C values of approximately -30 to -35%, considerably more depleted than phytoplankton. Most of the chemoautotrophic symbionts fix carbon with a form IA ribulose 1,5-bisphosphate carboxylase (RubisCO). We hypothesized that this form of RubisCO discriminates against (13)CO(2) to a greater extent than other forms. Solemya velum symbiont RubisCO was cloned and expressed in Escherichia coli, purified and characterized. Enzyme from this recombinant system fixed carbon most rapidly at pH 7.5 and 20-25 degrees C. Surprisingly, this RubisCO had an epsilon-value (proportional to the degree to which the enzyme discriminates against (13)CO(2)) of 24.4 per thousand, similar to form IB RubisCOs, and higher than form II RubisCOs. Samples of interstitial water from S. velum's habitat were collected to determine whether the dissolved inorganic carbon (DIC) could contribute to the negative delta(13)C values. Solemya velum habitat DIC was present at high concentrations (up to approximately 5 mM) and isotopically depleted, with delta(13)C values as low as approximately -6%. Thus environmental DIC, coupled with a high degree of isotopic fractionation by symbiont RubisCO likely contribute to the isotopically depleted delta(13)C values of S. velum biomass, highlighting the necessity of considering factors at all levels (from environmental to enzymatic) in interpreting stable isotope ratios. 相似文献
10.
The water fluxes and the CO 2 exchange of three leaf succulents, Othonna opima, Cotyledon orbiculata and Senecio medley-woodii, with different leaf anatomy, growth form and CO 2 fixation pathways (C 3, CAM) were monitored with a gas exchange cuvette which was combined with a potometric system to quantify water uptake. Measurements, which are primarily valid for plants with a sufficient water supply, were made during 6 to 10 consecutive days under constant experimental conditions. Water uptake for 24 h exceeded water loss by transpiration only for a S, medley-woodii plant with 10 expanding but only 7 mature leaves. In this case the gained water evidently is put into leaf expansion. All other plants showed balanced transpiration and water uptake rates. O. opima and C. orbiculata have a similar life form, similar water storage volumes and the same natural habitat but their diurnal water uptake patterns differ significantly. In the C 3 plant O. opima water uptake increased when the transpiration increased or transpiration rates were higher than uptake rates and vice versa. On the contrary the CAM plant C. orbiculata transpired during the dark period at constant or decreasing rates but showed steadily increasing uptake rates. Senecio medley-woodii- and C. orbiculata are CAM plants with similar diurnal water uptake patterns with its maximum in uptake during or towards the end of the CO 2 dark fixation period. Water uptake of C. orbiculata was at its minimum at the end of the light period despite transpiration being maximal. The results were discussed considering the different CO 2 fixation pathways. In the investigated CAM succulents, C. orbiculata and S. medley-woodii, the CAM influenced water uptake throughout the whole day and not only during the CO 2 dark fixation period. 相似文献
11.
The aquatic filamentous cyanobacteria Anabaena oscillarioides and Trichodesmium sp. reveal specific cellular regions of tetrazolium salt reduction. The effects of localized reduction of five tetrazolium salts on N(2) fixation (acetylene reduction), CO(2) fixation, and H(2) utilization were examined. During short-term (within 30 min) exposures in A. oscillarioides, salt reduction in heterocysts occurred simultaneously with inhibition of acetylene reduction. Conversely, when salts failed to either penetrate or be reduced in heterocysts, no inhibition of acetylene reduction occurred. When salts were rapidly reduced in vegetative cells, CO(2) fixation and H(2) utilization rates decreased, whereas salts exclusively reduced in heterocysts were not linked to blockage of these processes. In the nonheterocystous genus Trichodesmium, the deposition of reduced 2,3,5-triphenyl-2-tetrazolium chloride (TTC) in the internal cores of trichomes occurs simultaneously with a lowering of acetylene reduction rates. Since TTC deposition in heterocysts of A. oscillarioides occurs contemporaneously with inhibition of acetylene reduction, we conclude that the cellular reduction of this salt is of use in locating potential N(2)-fixing sites in cyanobacteria. The possible applications and problems associated with interpreting localized reduction of tetrazolium salts in cyanobacteria are presented. 相似文献
12.
The occurrence of heterotrophic CO 2 fixation by soil microorganisms was tested in several mineral soils differing in pH and two artificial soils (a mixture of silica sand, alfalfa powder, and nutrient medium inoculated with a soil suspension). Soils were incubated at ambient (∼0.05 vol%) and elevated (∼5 vol%) CO 2 concentrations under aerobic conditions for up to 21 days. CO 2 fixation was detected using either a technique for determining the natural abundance of 13C or by measuring the distribution of labeled 14C-CO 2 in soil and bacteria. The effects of elevated CO 2 on microbial biomass (direct counts, chloroform fumigation extraction method), composition of microbial community (phospholipid fatty acids), microbial activity (respiration, dehydrogenase activity), and turnover rate were also measured. Heterotrophic CO 2 fixation was proven in all soils under study, being higher in neutral soils. The main portion of the fixed CO 2 (98–99%) was found in extracellular metabolites while only ∼1% CO 2 was incorporated into microbial cells. High CO 2 concentration always induced an increase in microbial activity, changes in the composition of the microbial community, and a decrease in microbial turnover. The results suggest that heterotrophic CO 2 fixation could be a widespread process in soils. 相似文献
13.
Shells of the bivalve Arctica islandica are used to reconstruct paleo-environmental conditions (e.g. temperature) via biogeochemical proxies, i.e. biogenic components that are related closely to environmental parameters at the time of shell formation. Several studies have shown that proxies like element and isotope-ratios can be affected by shell growth and microstructure. Thus it is essential to evaluate the impact of changing environmental parameters such as high pCO 2 and consequent changes in carbonate chemistry on shell properties to validate these biogeochemical proxies for a wider range of environmental conditions. Growth experiments with Arctica islandica from the Western Baltic Sea kept under different pCO 2 levels (from 380 to 1120 µatm) indicate no affect of elevated pCO 2 on shell growth or crystal microstructure, indicating that A. islandica shows an adaptation to a wider range of pCO 2 levels than reported for other species. Accordingly, proxy information derived from A. islandica shells of this region contains no pCO 2 related bias. 相似文献
14.
AbstractWe know of three routes that organisms have evolved to synthesize complex organic molecules from CO 2: the Calvin cycle. the reverse tricarboxylic acid cycle, and the reductive acetyl-CoA pathway. This review describes the enzymatic steps involved in the acetyl-CoA pathway, also called the Wood pathway, which is the major mechanism of CO 2 fixation under anaerobic conditions. The acetyl-CoA pathway is also able to form acetyl-CoA from carbon monoxide.There are two parts to the acetyl-CoA pathway: (1) reduction of CO 2 to methyltetrahydrofolate (methyl-H 4folate) and (2) synthesis of acetyl-CoA from methyl-H, folate, a carboxyl donor such as CO or CO 2, and CoA. This pathway is unique in that the major intermediates are enzyme-bound and are often organometallic complexes. Our current understanding of the pathway is based on radioactive and stable isotope tracer studies, purification of the component enzymes (some extremely oxygen sensitive), and identification of the enzyme-bound intcrmediates by chromatographic, spectroscopic. and electrochemical techniques. This review describes the remarkable series of enzymatic steps involved in acetyl-CoA formation by this pathway that is a key component of the global carbon cycle. 相似文献
15.
Cratoneuron filicinum, a drought-sensitive moss, and Tortularuralis, a drought-tolerant moss, fix CO 2 non-autotrophicallyat a rate of about 1.2 and 2.2 µmol h 1 g 1dry wt. respectively. During drying, T. ruralis fixes CO 2 atan undiminished rate until the tissue loses about 60% of theinitial fresh weight. Thereafter, CO 2 fixation rapidly declinesto zero. Dark CO 2 fixation by C.filicinum declines steadilyduring the dehydration period. On rehydration, dark CO 2 fixationis resumed immediately in T. ruralis but not in C.filicinum.When dried T. ruralis is equilibrated with an atmosphere ofnearly 100% relative humidity, its weight increases to about40% of the original fresh weight and dark CO 2 fixation resumesat a rate about 60% of the fresh moss. In C.filicinum thereis only a small increase in weight and little CO 2 fixation inthe dark. The non-autotrophically fixed carbon, in both mossesstudied, is incorporated into amino acids (more than 60% ofthe total, mainly into aspartate, alanine and glutamate) andorganic acids (less than 40% of the total, mainly into malate).It is suggested that on rehydration immediate availability ofNADPH, known to be produced by transhydrogenation from NADHduring dark CO 2 fixation, may be an important factor in therepair of drought-induced cellular damage by reductive biosynthesisof membrane components and other cellular constituents. Key words: Mosses, Dehydration, Rehydration, Dark CO 2 fixation, Amino acids, Organic acids, NADPH, Drought tolerance. 相似文献
16.
Suspensions of dark-adapted guard cell protoplasts of Vicia faba L. alkalinized their medium in response to irradiation with red light. The alkalinization peaked within about 50 minutes and reached steady state shortly thereafter. Simultaneous measurements of O 2 concentrations and medium pH showed that oxygen evolved in parallel with the red light-induced alkalinization. When the protoplasts were returned to darkness, they acidified their medium and consumed oxygen. Both oxygen evolution and medium alkalinization were inhibited by 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU). In photosynthetically competent preparations, light-dependent medium alkalinization is diagnostic for photosynthetic carbon fixation, indicating that guard cell chloroplasts have that capacity. The striking contrast between the responses of guard cell protoplasts to red light, which induces alkalinization, and that to blue light, which activates proton extrusion, suggests that proton pumping and photosynthesis in guard cells are regulated by light quality. 相似文献
17.
A system has been developed for the study of photosynthetic CO 2 fixation by isolated spinach chloroplasts at air levels of CO 2. Rates of CO 2 fixation were typically 20 to 60 micromoles/milligrams chlorophyll per hour. The rate of fixation was linear for 10 minutes but then declined to less than 10% of the initial value by 40 minutes. Ribulose 1,5-bisphosphate (RuBP) levels remained unchanged during this period, indicating that they were not the cause for the decline. The initial activity of the RuBP carboxylase in the chloroplast was high for 8 to 10 minutes and then declined similar to the rate of CO 2 fixation, suggesting that the decline in CO 2 fixation may have been caused by deactivation of the enzyme. 相似文献
18.
Nonautotrophic CO 2 metabolism in Opuntia echinocarpa roots was studied with techniques of manometry and radiometry. The roots were grown in a one-quarter strength nutrient solution for several days; the distal 2 cm was used for physiological studies. The roots assimilated significant quantities of 14CO 2 and appeared to show a crassulacean-type acid metabolism with respect to quality and quantity. Most of the 14C activity was associated with the distal portion of the elongating root indicating correlation with metabolic activity. The 14CO 2 assimilation was comparable to a crassulacean leaf succulent, but 3 times greater than that found for stem tissue of the same Opuntia species. The rates of O2 and CO2 exchange and estimated CO2 fixation were 180, 123, and 57 μl/g per hour. A respiratory quotient of 0.66 was found. The products of 14CO2 fixation were similar in most respects to reported experiments with leaf succulents. Equilibration of the predominant malic acid with isocitric, succinic, and fumaric acids was not evident. The latter observation was interpreted as metabolic isolation of the fixation products rather than poor citric acid cycle activity. A rapid turnover of the fixed 14CO2 was measured by following decarboxlyation kinetics and by product analysis after a postincubation period. The first order rate constant for the steady state release was 4.4 × 10−3 min−1 with a half-time of 157.5 minutes. Amino acids decayed at a more rapid rate than organic acids. 相似文献
19.
Lehnherr, B. M?chler, F. and N?sberger, J. 1985. Effect of CO 2concentration during growth on a CO 2 concentrating mechanismin white clover as predicted from differential 14CO 2/ 12CO 2 uptake.-J. exp. Bot. 36: 1835-1841. White clover was grown at 20 and100 Pa p(CO 2). The CO 2 response of net photosynthesis and differentialuptake of 14CO 2 and 12CO 2 by leaves were measured at varioustemperatures and at various O 2 and CO 2 partial pressures andcompared with predictions from ribulose bisphosphate carboxylase/oxygenasekinetics. Discrepancies between the observed gas exchange characteristicsfor the leaves and those predicted from the enzyme kineticswere interpreted as being due to a CO 2 concentrating mechanism.Plants grown at 20 Pa p(CO 2) showed a higher affinity for CO 2than plants grown at 100 Pa p(CO 2) when measured at 10 ?C. Nodifference in affinity was found at 30 ?C. The postulated CO 2concentrating effect was greater in plants grown at low CO 2than in plants grown at high CO 2 concentration and occurredonly at low temperature and low CO 2 partial pressure. It issuggested that plants grown at the lower CO 2 partial pressurehave a higher affinity for CO 2 due to a more efficient CO 2 concentratingsystem than plants grown at the higher CO 2 partial pressure. Key words: Photosynthesis, CO 2, concentration, RuBP carboxylase/oxygenase 相似文献
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