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This paper reports on seasonal cycles of physical and chemical factors, over a period of two years, which were expected to affect the size and seasonal variation of phytoplankton production in the eutrophic, dimictic Lake Esrom, Denmark. Insolation, transparency, temperature, oxygen, total carbon dioxide, free carbon dioxide, pH, alkalinity, silicate, nitrate, ammonia, orthophosphate and total phosphate, were measured to describe the lake hydrography. They are presented as isopleths. After the spring maximum of phytoplankton, nitrogen and silica rapidly declined to insignificant and limiting concentrations while phosphate- phosphorus declined to 50% (150 μg litre-1) of the winter value. Light can limit phytoplankton production at all seasons. A phosphorus balance showed that there was about 80 t of phosphorus in the lake. Phoshorus recycled in the lake ecosystem was 20 t, 10 t from tributaries and 10 t annually being added to the sediment. The evidence for enrichment includes a discussion on the history of the lake, coring, ground water analyses, changes in hypolimnetic dissolved oxygen, and changes in transparency. The possible influence of pollution from sewage is discussed in relation to the estimated nutrient budget of nitrogen and phosphorus. Increase in nutrients failed to increase phytoplankton production during 17 years. [ABSTRACT FROM AUTHOR]

The after-effect of wind on photosynthesis and transpiration of Festuca arundinacea Schreb., was determined. Following a period of exposure in a controlled environment wind tunnel the wind-treated plants showed reduced rates of photo-synthesis when compared with the controls under standard conditions. Evaporation from paper model tillers was measured and the boundary layer resistance was shown to be low in all but very low wind speeds. Analysis of CO2 and H2O diffusion pathways indicated that mesophyll resistance in wind-treated plants was higher whilst leaf surface resistance was lower than in the controls. The high mesophyll resistance in the wind-treated plants was attributed to reduced water content. [ABSTRACT FROM AUTHOR]

When 8-day seedlings were exposed to 14CO2 in light, approximately 2 hours were required for 14C to reach the apices of the roots. One method used to detect the progress of 14C down the root was to scan the root with a radiochromatogram strip scanner. At this stage most in aqueous ethanol extracts of roots was present as sucrose, equally labelled in glucose and fructose. This was converted only slowly to other components of the soluble fraction so that after 12 hours almost 50% of 14C was still retained in sucrose. 14C exuded from intact roots into surrounding solutions was present in both volatile and non-volatile compounds. In the non-volatile fraction glutamine, glutamic and aspartic acids were the main 14C-amino acids. Exudation of 14C was not affected by changing the inorganic composition of the collecting solution. A change in pH of collecting solution from 6.4 to 5.9 increased exudation. Exudation also increased markedly when 2,4-dinitrophenol or potassium cyanide was present in the collecting solution. [ABSTRACT FROM AUTHOR]

The labeling of intermediate compounds and photosynthetic cofactors during photosynthesis and periods of darkness by Chlorella pyrenoidosa in the presence of 32P-labeled phosphate and 14CO2 have been investigated. Algae adapted to photo- synthesis in air were used, and the level of carbon dioxide was maintained at approximately 0.04% and at constant specific radioactivity during the course of the experiments. The transient changes which occur in the levels of labeled fructose-1,6-diphosphate and in sedoheptulose-1,7-diphosphate, and in the corresponding monophosphates when the light is turned off suggest a light activation of the diphosphatase enzymes which decays after about 2 minutes of darkness. It is suggested that a light-dark switch in enzymic activities permits photosynthesis and glycotysis to occur in light and dark respectively with the same enzymic apparatus. The greatly diminished rate of disappearance ot the carboxylation substrate, ribulose-1,5-diphosphate, after about 2 minutes suggests that there is also a light activation of the carboxylation reaction in vivo. Large transient changes in the level of pyrophosphate between light and dark indicate that there may be an unstable co-factor which decomposes to give pyrophosphate during or after killing of the algal cells. The possibility that this cofactor is involved in an activation of carbon dioxide for the carboxylation reaction in vivo is suggested. Light-dark transient changes in labeling of other compounds of the photosynthetic carbon reduction cycle and related compounds were determined, and possible significance of these changes is discussed. [ABSTRACT FROM AUTHOR]

Cellular constituents(chloroplasts,sap and mitochondrial), separated from spinach leaves, were allowed to photosynthesize in the presence of radio active bicarbonate. The radiocarbon fixed by the chloroplasts was distributed mainly in the phosphate ester while the radiocarbon fixed by the sap was located mostly in the amino acids. the mitochondrial fraction fixed very little radioactive carbon dioxide. the rate of carbon dioxide fixation by the recombined mixture of sap and chloroplasts was greater than the sum of the separate components. the distribution pattern of the fixed radiocarbon of the recombined mixture, however, was qualitatively similar to a combination of the radiocarbon distribution of the separated chloroplasts and sap. The results of experiments carried out with these cellular constituents in the dark and in the presence of other substrates, labelled and unlabelled, are discussed. [ABSTRACT FROM AUTHOR]

1. The impression is conveyed through the literature that studies of the root respiration of intact plants usually constitute a minor and necessary part of more comprehensive works. This fact naturally influences the methods used, and it must be stated that these do not fulfil satisfactorily the conditions that can be reasonably expected for methods intended to elucidate the problem of the course of respiration in intact plants. 2. The method described in this paper (The Tonometer Method) allows frequent and simultaneous determinations of oxygen and carbon dioxide during measurements of root respiration in plants which have their roots in a closed system surrounded by circulating nutrient solution. 3. The tonometer method provides wide possibilities for carrying out arbitrary and rapid changes of the environmental factors of the roots as well as those of other parts of the plant, and for studying the influence of such changes on root respiration. 4. Carbon dioxide and oxygen determinations may be carried out with mean errors of 3.5 and 1.9 per cent, respectively. [ABSTRACT FROM AUTHOR]

The rapid assimilation of small quantities of ammonium, nitrite and nitrate-N by nitrogen-starved cells of Chlorella vulgaris is accompanied by high rates of gas exchange. When all the added nitrogen has been assimilated the rates of gas exchange return to the control values. The total volume of oxygen taken up during the period of nitrogen assimilation is about the same whichever nitrogen source is added but the rate is highest with ammonium-N and lowest with nitrate-N. On the other hand, the rate of carbon dioxide production is much the same whichever salt is added but the total volume of carbon dioxide produced is greatest when nitrate-N is added and least with ammonium-N. The quantities of oxygen absorbed and carbon dioxide produced agree with those expected if ammonium, nitrite and nitrate-N are all assimilated to the same final products and if carbohydrate is the carbon source in the cells. A high respiration rate also follows the addition of hydroxylamine but the gas exchange differs markedly from that expected if hydroxylamine were assimilated to the same products as the other nitrogen sources. [ABSTRACT FROM AUTHOR]

This article studies the evidence for the participation of cytochrome oxidase in photosynthetic fixation of carbon dioxide. A researcher measured the utilization of carbon dioxide by cut leaves with a continous recording method, and found that if leaves were exposed to carbon dioxide mixed with pure nitrogen, the rate of photosytithetic assimilation of carbon dioxide was slowed down after short pt-riods of darkness under these anaerobic conditions. The inhibition was not reversed by exposure to light in the carbon dioxide-nitrogen mixture, but it was reversed by a short exposure to air in darkness.

1. The oxygen uptake and carbon dioxide production of intact and dissected buds has been measured, and the effect of oxygen percentage and seasonal changes on these determined. 2. Oxygen partial pressure curves show the oxygen uptake of intact buds to be normally limited by the rate of oxygen diffusion to the respiring cells. 3. The oxygen uptake of dissected bud parts has been found to be limited at much lower oxygen percentages than in the case of intact buds. 4. Although lowering the temperature lowers the rate of oxygen uptake at any given oxygen percentage, it does not greatly change the overall shape of the oxygen partial pressure curve. 5. Observations on seasonal changes in the respiratory behavior of intact buds show that the oxygen limitation is most severe during late summer, is lessened during the autumn when the respiratory capacity of the buds is depressed, and then is largely removed in late winter and early spring as the respiratory capacity of the buds increases.. (6). Dissected bud parts show a strong »Pasteur» effect; theN2>Qco2/Qo2 air ratio for the bud scales is near 1.0, and for the growing region near 1.4. 7. The limitation of oxygen uptake is reflected by a high aerobic carbon dioxide production resulting in a respiratory quotient greater than unity. 8. The high respiratory quotients have been observed during the months of August and September when the limitation of oxygen uptake is most severe; the H.Q. differs very little from unity when the limitation is not so severe. 9. Lowering the temperature lowers aerobic carbon dioxide production more rapidly than oxygen uptake. 10. These observations are discussed with reference to a growth inhibitor in buds, and a working hypothesis of the nature of rest in these structures is presented. [ABSTRACT FROM AUTHOR]

This article presents a quantitative investigation regarding the composition of wet-heath vegetation in relation to aeration of the ground water and soil in certain communities on the north Hampshire-Berkshire border. The study shows that the cover of several species was closely related to the concentrations of carbon dioxide and hydrogen sulphide in the ground water, particularly Molinia coerulea, that cover decreased as the concentrations of these gases increased. Furthermore, it was concluded that their intercellular space system provided a free path for the oxygen diffusion from shoot to root.

Young plants of the wilty tomato mutant, flacea, in which the stomata resist closure, were sprayed with abscisic acid eight times over a period of 24 hours in light and darkness. The hormone induced closure of stomata similarly in leaves treated either in light or in darkness. Abscisic add does not appear to induce stomatal closure in darkness by increasing the internal CO2 concentration in the leaf, since this concentration should already be very high in darkness. A considerable and rapid decrease of CO2 assimilation and increase of CO2 evolution were demonstrated in mutant as well as in normal plants transferred from light to darkness. [ABSTRACT FROM AUTHOR]

The state of knowledge of the transition of sapwood into heartwood in trees is reviewed, and attention is drawn to the composition of the gas mixture available to such cells as remain alive in wood. The probable effect of such a mixture is postulated and experiments indicate that the high concentrations of carbon dioxide known to exist inside wood are conducive to formation of compounds known to be typical of the heartwood of Acacia mearnsii. [ABSTRACT FROM AUTHOR]

Examination of the effect of CO2-concentration and time of day on the content of malic acid, citric acid, aconitic acid, isocitric acid, succinic acid and fumaric acid in tomato leaves, revealed that the total content of these acids will rise with the CO2-concentration up to 0.10 vol% Co2. In the morning up to 0.22 vol% CO2 was needed for optimal effect. Samples of leaves picked at 1 a.m. showed the lowest content of these acids. At 9 a.m. the content had increased, and at 4 p.m. the increase was considerable. The content of malic and citric acid constituted 36 and 34% of the total acid content. In the afternoon and the night the aconitic acid represented 14% and in the morning 20% of the total acid content. Isocitric acid, fumaric acid and succinic acid occurred only in relatively small concentrations. [ABSTRACT FROM AUTHOR]

The development and use of an improved automatic system for the accurate measurement of dissolved organic carbon (D.O.C.) in fresh waters is described. The method, which covers the range 0–25 mg l-1 D.O.C., is based on the oxidation of organic carbon to carbon dioxide by U.V. radiation. The carbon dioxide produced is measured by a non dispersive infra-red gas analyser (I.R.G.A.). The I.R.G.A. is also used in the semi-automatic measurement of particulate organic carbon (P.O.C.) by a combustion method which allows very low concentrations to be measured using samples of 200 ml or less. Results of surveys of two river systems indicate that D.O.C. concentrations of less than 2.0 mg l-1 are typical in unpolluted chalk streams. D.O.C. concentrations of streams draining acid heathland were found to be significantly higher (3–5.5 mg l-1). D.O.C. concentration was found to increase rapidly during a spate, in a river draining areas of mixed underlying geology. The throughput of D.O.C. during the twenty-five to fifty spates which occur annually in the river could amount to 20–30% of the annual flux of D.O.C. P.O.C. concentration in chalk spring waters (0.03–0.04 mg l-1) were found to be higher than expected from preliminary estimates using membrane filtration techniques. The relevance of the measurement of D.O.C. and P.O.C. flux to estimates of the energy budgets of stream ecosystems is discussed and published methods for the automatic measurement of D.O.C. are reviewed. [ABSTRACT FROM AUTHOR]

Four mosses, Bryum argenteum, Grimmia pulvinata, Hypnum cupressiforme and Tortula muralis were exposed to sulphite, and their uptake of radioactive bicarbonate measured. About 50% reduction in 14C uptake was caused by 0.01-0.1 mM suiphite. The effect of pH indicated that SO2 (or H2SO3') was the active molecular species. Fluoride had little effect on 14C uptake. [ABSTRACT FROM AUTHOR]

Uninfected plantlets of Goodyera repens and plantlets infected with the endophyte Rhizoctonia goodyerae-repentis were fed with 14CO2. Quantities of 14C fixed varied greatly between individuals, but there was a consistent pattern of distribution of label which remained unaltered over four weeks. Very little 14C moved to the rhizomes. The endophytic fungus readily grew from infected plantlets on to Pfeffer agar and small amounts of radioactivity were found in the mycelium growing from previously fed plantlets. 14C leakage from uninfected plantlets was negligible, although low levels of radiactivity occurred in serial washings from them. When the tops alone of infected plants were fed with 14CO2, no radioactivity could be detected in the emerging fungal mycelium. Where rhizomes alone were exposed, small quantities of 14C were detected in the growing mycelium. The fungus readily translocated 14C from the remains of dead protocorms. It appears that R. goodyerae-repentis does not freely utilize recent photosynthate from its host under the conditions of these experiments. [ABSTRACT FROM AUTHOR]

The limitations of present methods for describing the relative importance of different processes in controlling rates of photosynthesis are discussed, and a new method proposed. It is suggested that 'photosynthetic limitations', instead of resistances, should be used to describe the relative importance of different component processes at normal ambient carbon dioxide concentrations. The limitation approach is particularly relevant if the photosynthetic rate is not limited entirely by the supply of carbon dioxide. [ABSTRACT FROM AUTHOR]

A system is described for measuring in situ CO2 evolution rates from forest soil. The apparatus incorporates an infrared gas analyzer with open air flow through 10 chambers which sequentially lower over the forest floor during measurements and raise after measurements are complete. Unlike methods using stationary chambers, this system allows litter and soil horizons to undergo a natural drying cycle. Litter moisture under stationary chambers was 76% of dry weight at the end of a 3-day sample period as compared to 40% under moving chambers and 39% in control plots. Carbon dioxide evolution rates from plots enclosed by stationary chambers ranged from 54 to 90% higher than those from moving chamber plots. Effects of such discrepancies in calculating the carbon balance of forest ecosystems are discussed. Application of the moving chamber apparatus in monitoring gaseous losses from biodegradable waste such as by-products of petroleum is also discussed. [ABSTRACT FROM AUTHOR]

Daily patterns of incorporation of carbon dioxide and inorganic phosphate were measured in phytoplankton from Lake George, New York, in January and February 1972. Rates of photosynthesis oscillated in phase for the entire assemblage and for individual cells of the diatoms Asterionella, Tabellaria, and Fragilaria. The photosynthetic capacity was maximal in the early afternoon. Daily patterns of phosphate uptake were also rhythmic. At ambient concentrations the assemblage takes up phosphate maximally in the morning while individual cells of the large diatom take it up maximally in the evening. A kinetic analysis of phosphate uptake indicated 2 velocities of uptake for cells of Tabellaria and Fragilaria: a hyperbolic function at small and an apparently linear relationship at relatively large concentrations. The large diatoms, in contrast to the total assemblage, functioned maximally at 2 separate times of the day: in the evening at ambient levels and in the morning at 0.4 μm and larger concentrations. Temporal stratification of the nutrient niche may be achieved by several uptake mechanisms in the algal cell that function at different times of the day or with a variable uptake velocity. [ABSTRACT FROM AUTHOR]

The excretion of glycolic acid by the marine diatom Chaetoceros socialis through time was studied. Excreation in axenic cultures was linear for the time intervals used, but for nonaxenic cultures an equilibrium was created, suggesting bacterial uptake of glycolic acid. In studies with an inhibitor of glycolate dehydrogenase, the level of glycolic acid in the medium jumped 15-fold. This shows the presence of the entire set of enzymes which convert glycolic acid to serine and release carbon dioxide. In both axenic and nonaxenic cultures a steady state was reached. All of the data suggest that at high cell densities glycolic acid is liberated from the cell by a passive mechanism. The effect of such an excretion in natural waters is discussed. [ABSTRACT FROM AUTHOR]

Metabolism of radioactive lipids in kernels from peanut plants subjected to 14CO2 under field conditions was studied during dehydration (curing) of the seeds at 22°C or 50°C. Synthesis of lipid was predominant during the first 6 to 12 hours of dehydration whereas degradation dominated between 12 to 24 hours of curing. These changes were related to the moisture content of the dehydrating kernels; a moisture range of 42 to 47 % was found to be an important factor influencing the observed pattern of lipid metabolism. The results from the present study also indicate compartmentalization of lipid metabolism in dehydrating peanut kernels. [ABSTRACT FROM AUTHOR]

Maximum growth of suspension cultures of Paul's Scarlet rose required a low pH (5.2 to 5.4) during the division phase (day 0 to 7) and a higher pH (5.8 to 6.0) during the expansion phase (day 7 to 14). The fresh weight increase was reduced by approximately 22%, but the dry weight was not influenced when cells were grown for 14 days in a CO2 deficient environment. Kinetic studies showed that the first five days of growth was the critical period of nonautotrophic CO2 fixation when cells were grown in medium buffered at pH 5.4. The phosphoenolpyruvate carboxylase activity was highest (0.50 × 106 fresh weight) during the period, when nonautotrophic CO2 fixation appeared to be critical for growth. [ABSTRACT FROM AUTHOR]

Several transpiration suppressants, (phenyl mercuric acetate, Tag 16 (polyethylen emulsion) R14-poly (ethylene adipate) 4-4 Diphenylemethan diisocyanate), which are known to either close stomata or form thin films on leaves, were known to either close stomata of form thin films on leaves, were sprayed on citrus and grapevine seedlings. Water vapor and carbon dioxide exchange of single leaves were measured by means of infra red gas analyzer and LiCl hygrosensors. The effects of the chemicals were evaluated by analyzing net photosynthesis, transpiration, mesophyll resistance to CO2 compensation concentration and respiration. All the chemicals tested increased either mesophyll resistance or CO2 compensation point to various degrees. It is concluded that none of the chemicals tested acted soley on epidermal resistance. All chemical reduced photosynthesis, but the ratio of photosynthesis to transpiration increased in most cases in grapevine but not in citrus. Different chemicals acted differently on citrus and grapevine. The method of analysis used enabled us to evaluate separately the relative effect of a chemical on mesophyll resistance and respiration. [ABSTRACT FROM AUTHOR]

Studies of the marine green flagellate Dunaliella tertiolecta have confirmed and extended previous observations of Steemann Nielsen and his colleagues. Algae, grown at 12°C, assimilated carbon dioxide under light-saturated conditions more rapidly than did those grown at 20°C; for both, the assimilation rate being higher at 20°C than at 12°C. Cells grown at the lower temperature contained higher concentrations of soluble protein, higher activities of ribulose diphosphate carboxylase and showed an enhanced relative rate of protein synthesis during the photosynthetic assimilation of carbon dioxide. This appears to represent true adaptation since it allowed the growth rate at 12°C to be almost the same as that at 20°C. Studies of the marine diatom Phaeodactylum tricornutum have not revealed the same picture of temperature adaptation. Cultures grown at 5°C had significantly higher rates of photosynthesis than did those grown at 10°C, but the same was not true when algae grown at 10°C were compared with those grown at 20°C. In this organism, growth at the lower temperatures reduced its ability to photosynthesize at 20°C. Cells grown at the lower temperatures contained more protein than did those grown at 20°C; this was particularly marked in cells growing at 5°C, a temperature which reduced the growth rate. The relative rate of protein synthesis was higher in Phaeodactylum grown at lower temperatures; but this difference was most marked when the measurements were made at 20°C. [ABSTRACT FROM AUTHOR]

Four aquatic fungi - Apodachlya brachynema and A. minima (Leptomitales), Aphanomyces laevis (Saprolegniales), and Pythium ultimum (Peronosporales) - were tested for growth in synthetic media containing one of a variety of carbon sources. Apodachlya brachynema readily utilized five amino acids - alanine, glutamate, aspartate, proline and leucine - as well as glucose and acetate. Growth on sucrose as a carbon source was slight. Apodachlya minima differed from A. brachynema in that it could not utilize proline and leucine. Aphanomyces laevis grew well on only three of the substrates tested - glucose, alanine and glutamate. Pythium ultimum utilized glucose, sucrose, maltose, cellobiose, alanine, glutamate, aspartate, proline asparagine, ornithine, and serine, but not eight other amino acids. All of these fungi hydrolyzed gelatin. Radioactively labeled carbon dioxide was released during incubation of Aphanomyces laevis in media containing labeled leucine, proline, or phenylalanine. These data provide evidence of some catabolism of the three substrates although none of these substrates can support the growth of Aphanomyces laevis as a sole source of carbon and nitrogen. [ABSTRACT FROM AUTHOR]

Sugarcane leaves respired in full light and the CO2 evolved could be detected in sorghum or maize photosynthesizing in the same closed system. A combination of radiometric and infra-red gas analysis techniques allowed the estimation of photorespiration (total CO2 evolution in light) and photosynthesis at increasing light intensities and of dark respiration. Rates of CO2 evolution approaching those of temperate zone plants occurred at lower light intensities but rapidly decreased with higher light. Smaller but significantly quantities of 14CO2 were released even at intensities approximating full sunlight in leaves of maize, sorghum and sugarcane. Highly efficient CO2 capture may explain the low rates of photorespiration at high light intensities. [ABSTRACT FROM AUTHOR]

A series of experiments were conducted to investigate the effects of moving, normal and carbon dioxide-free air on the stomata within porometer cups attached to the illuminated leaves of Datura stramonium, Pelargonium zonale, Duranta plumieri and Clerodendron inerme. A marked opening stomatal response was obtained in Datura and Pelargonium on changing to carbon dioxide-free air. In general no such response was established in Duranta and Clerodendron. Indications of even an opposite closing effect were shown in the case of Duranta. The present results seem to disprove the reduction of carbon dioxide by photosynthesis as the major factor controlling the wide stomatal opening within a porometer cup. The possibility of a humidity effect is also suggested. [ABSTRACT FROM AUTHOR]

Ethylene increased the peroxidase activity of nine out of ten varieties of sweet potato (Ipomoea batatas (L.) Lam.) root disks tested. The increase which was observed four hours after ethylene treatment was partially overcome by carbon dioxide. The increase was inhibited by actinomycin D and cycloheximide, indicating de novo protein synthesis. Electrophoretic separation on polyacrylamide gets indicated the appearance of two new peroxidase bands. Peroxidase activity in bean petiole explants was localized around the separation layer. Ethylene caused a small increase in peroxidase activity in the petiolar portion of the explant. Phenolic substances bad no effect on abscission consistent with their proposed roles as cofactors for auxin-oxidase, indicating that auxin-oxidase does not play a role in abscission of Coleus blumei Benth, abscission zone explants. [ABSTRACT FROM AUTHOR]

Evidence is presented that the growth of cultured wheat roots is entranced in closed culture systems not only by carbon dioxide but by a further and apparently very volatile product of root metabolism. The formation of this second growth-stimulating substance is not considered to depend upon a reduction of oxygen tension in the culture system. Unlike ethanol the activity of the volatile promoter does not depend upon illumination of the cultures. The volatile promoter cannot be effectively absorbed by a number of gas absorbents. Attempts to demonstrate ethylene production by the roots have been unsuccessful. [ABSTRACT FROM AUTHOR]

In vitro experiments showed that concentrations of CO2 above 6 per cent inhibited succinate oxidation: 30-10 per cent of succinate oxidation may be blocked in the presence of 12 per cent CO2. Storage of rhizome cores in CO2 increased the levels of all the main acids except malic. The amino acids, aspartate, glutamate and alanine, also increased in amounts under these conditions. Cores fix CO2 probably iva the reaction phosphoenolpyruvate to oxaloacetate. Raised CO2 levels increased the rate of diminution of carbohydratem but carbon itself was conserved due to a reduction in CO2 output. [ABSTRACT FROM AUTHOR]

Barley roots contain a CO2 sensitive respiratory fraction which is inhibited in 50 per cent CO2 and is partially restored upon subsequent exposure to air. The residual O2 consumption occurring at CO2 concentrations between 50 per cent and 95 per cent amounts to about 40 per cent of the O2 uptake in air and can support K+ uptake for a limited time at a rate equal to or higher than occurs in air. Above 95 per cent CO2, both O2 and K+ uptakes decrease rapidly. 2,4-dinitrophenol (DNP), in the range of 10-6 to 10-5 M, stimulates O2 uptake by the roots in air. The stimulation is absent when roots are treated with DNP in 80 per cent CO2, presumably because of the reduced demand for inorganic phosphate and phosphate acceptor at the lower respiratory level in high CO2. In either air or CO2, K+ uptake is strongly inhibited by DNP. A comparison of the respiratory and K+ uptake data indicates that O2 consumption is a necessary requirement for the uptake process in high CO2. Protoplasmic streaming in the root cells is rapidly stopped by high CO2 although K+ uptake and O2 consumption continue. The cation uptake mechanism in high CO2 appears to be limited to the stationary cytoplasm. It is also possible that a similar mechanism may be involved in cation uptake in air. [ABSTRACT FROM AUTHOR]

The postharvest respiratory drifts for six stages of development of pineapple fruit (Ananas comosus cv. Cayenne) ranging from dry flower to senescence are presented. Based upon these data, pineapple is a non-climacteric fruit. Pineapple does produce ethylene gas but when levels ranging from 0.01 to 1000 μl/l were applied to stage 4 fruits (fruit just at the start of ripening) no respiration or chemical changes were induced which could be interpreted as affecting the ripening processes. A decrease in the oxygen concentration (to 2.5 per cent) resulted in a decrease in the respiration rate. An increased carbon dioxide concentration (up to 10 per cent) had not detectable effect on the respiration rate. [ABSTRACT FROM AUTHOR]

The incorporation of sulphur from external sulphate into different fractions was studied in cells with a P content of 0.6 to 1 mg/g fresh weight as against 3 to 5 mg/g fresh weight in normal cells. — There is a flat and broad optimum for the action of pH in the region between 5.7 and 7. — In most cases, citrate inhibits the uptake of sulphur. — Five per cent CO2 in the air enhances the incorporation of S. It is suggested that the effects of CO2 may well be exerted by way of the carboxylation and decarboxylation mechanisms in the cells. — Selenate inhibits the formation of DNA-S and protein S more than that of lipid S, but the main effect in both cases seems to be in an early step of the assimilation of sulphate. In the absence of external phosphate, the inhibition is counteracted by CO2, especially in darkness. Phosphate enhances the action of selenate on the organic S fractions, and in its presence CO2 and darkness make the inhibition more pronounced. — Without P in the medium, the effects of selenate on uptake into the inorganic sulphate fraction are smaller than when the organic fractions are concerned. In the presence of CO2 even stimulations due to selenate have been observed. External phosphate brings the inhibition of uptake into cellular SO42- to the same level as found in the case of organic S. More than one pathway for the uptake as SO42- seem possible. — Anaerobiosis and menadione affect the organic S fractions more than the sulphate; 2,4-dinitrophenol has a more uniform action all over the field. [ABSTRACT FROM AUTHOR]

Detached soybean cotyledons fixed CO2 both in the light and dark. Carbon dioxide fixed by the light and dark reactions replaced only a small portion of CO2 lost by respiration up to the 10th day. In the dark most of the 14C label was found in the acidic fraction, while in the light 65 per cent of the activity was found in the neutral and basic fractions. [ABSTRACT FROM AUTHOR]

The atmosphere in which seeds germinate can profoundly affect the level of germination and dormancy. Seeds were germinated in atmospheres containing various concentrations of carbon dioxide and oxygen. At the same time the effect of light on these systems was examined. The germination of partially dormant populations of with oat seed is inhibited by white light. This response to light is most apparent when the caryopsis is enclosed in the pales. Investigations into the effect of the ambient atmosphere on germination have indicated Unit, while oxygen is a necessary factor in the germination of this species, carbon dioxide also has an effect. A luck of carbon dioxide increases the degree of light inhibition of germination; 3 per cent carbon dioxide (by volume) allows germination in light; 20 per cent carbon dioxide inhibits germination in light and darkness at all tested oxygen concentrations. [ABSTRACT FROM AUTHOR]

The experiments showed that incorporation of S from the sulphate in the medium into normal cells of Scenedesmus was enhanced by light, relatively most in the case of lipid S and least in the inorganic sulphate fraction. The effects of light were, generally, increased by the presence of CO2 and nitrogen salts. CO2 did not significantly alter the proportions between the fractions, but the presence of nitrogen increased the formation of protein S more than the synthesis of S-containing lipids. - It is suggested that lipid S is formed as a "sink", when a step between sulphite and -SH becomes increasingly rate-limiting in the overall reduction of sulphate. Furthermore, incorporation as SO42- and as lipid S may be regulated by more or less independent processes. [ABSTRACT FROM AUTHOR]

The rate of carbon dioxide exchange in both light and darkness by detached tobacco leaves placed at various oxygen concentrations was measured by an Infra-Red CO2 Analyzer and a Clark oxygen electrode. It was observed that during illumination oxygen had two different effects. One was to stimulate carbon dioxide evolution and the other to inhibit carbon dioxide absorption. Concentration of carbon dioxide at compensation point was found to be a linear function of oxygen concentration and this has been explained as due mainly to an increased evolution of carbon dioxide. Such an evolution during illumination has been called photorespiration. Increased concentrations of oxygen also had a stimulating effect on the magnitude of the initial post-illumination burst of carbon dioxide in darkness, but no effect on the subsequent steady rates. These data have been explained as due to the suspension of regular respiration in darkness and its replacement by a different process, tentatively called photorespiration. A second effect of oxygen was to reduce the efficiency (called "carboxylation efficiency") with which a leaf was able to remove carbon dioxide from the atmosphere. [ABSTRACT FROM AUTHOR]

In the transverse sections of fresh Avena coleoptile certain intercellular spaces are transparent, others are dark. The transparent spaces represent the result of water-logging of the originally water-lined air passages. The dark spaces are lined with a plastic lipid-containing membrane which can be impregnated with melted paraffin. In the living tissue this membrane can be cut transversely and the cut sections presumably seal off the gas inside thus causing the dark interfacial refraction. Because of the high permeability of lipids to carbon dioxide and the virtual impermeability to oxygen and nitrogen, there is a reason to believe that the lipid-lined spaces are filled with gas rich in carbon dioxide, and the lipid membrane may function as a regulator of the diffusion pressure of this gas. [ABSTRACT FROM AUTHOR]

Cell-free preparations of Chlamydomonas reinhardtii incorporated 14CO2 into amino acids and organic acids. The addition of phosphoenolpyruvate but not of pyruvate greatly enhanced this incorporation. It is suggested that phosphoenolpyruvate carboxylase is a quantitatively important reaction in CO2 fixation and serves to replenish Krebs cycle intermediates when the Krebs cycle is used in a synthetic capacity. [ABSTRACT FROM AUTHOR]

The factors limiting light-saturated net photosynthesis al natural carbon dioxide concentrations were examined in seven woody or herbaceous species possessing a wide range of maximum photosynthetic rates. In most cases the rate of photosynthesis was linearly related to the ambient carbon dioxide concentration up to 300 ppm, but in some leaves with a low light-saturated rate of net photosynthesis, the rates of chemical processes also seemed to be limiting. When photosynthesis was limited only by the rate of transfer of carbon dioxide from the ambient air to the reaction sites in the chloroplasts, the resistances to carbon dioxide transfer could be calculated. The differences among the species in net photosynthetic rates were caused by differences in both stomatal and mesophyll resistance but the variation in the stomatal resistance was considerably larger than the variation in the mesophyll resistance. Within the species the variation in the minimum stomatal resistance was rather large in some cases whereas the variation in the mesophyll resistance was generally small. Uptake of carbondioxide in light through the adaxial cuticle of hypostomatous leaves was negligible or undetectable. Cuticular transpiration, on the other hand, varied appreciably both among and, in some cases, within species. The cuticular resistance to water vapour transfer was increased by intense light and reduced by increasing the leaf temperature from 17 to 22°C. [ABSTRACT FROM AUTHOR]

The extension of Avena coleoptiles grown in the dark in aerobic atmospheres containing Co2 concentrations ranging from zero to 90%, and in an anaerobic atmosphere consisting of 100% CO2 have been compared with extension in air and in an anaerobic atmosphere of pure nitrogen. In concentrations between 0.5 % and 10 % CO2 growth rates were higher and final lengths greater than those in air. No differences were detected in the growth of coleoptiles in air and in air from which CO2 had been removed. In 15 % CO2, and in higher CO2 concentrations, rates of growth and final lengths were less than those in air. In general the depression of growth was more marked with increasing concentration. In 100 % nitrogen extension growth appeared to be completely inhibited, in contrast to 100 % CO2 where small increases in length were observed. The presence of oxygen coupled with a very high CO2 concentration appeared to be more toxic than 100 % CO2 alone. Extension growth in 100 % oxygen was greater than that in air. [ABSTRACT FROM AUTHOR]

Incorporation of sulphate S from the medium into the cell fractions of sulphate (excluding the apparent free space), soluble reduced S, lipid S, DNA-S, and protein S was studied with - P cells of Scenedesmus, containing 0.2–0.3 mg P/g fresh weight as compared with 3–5 mg/g for normal cells. In the early stages, uptake of sulphate to all fractions is inhibited by the presence of inorganic phosphate in the medium. Later on phosphate increases incorporation into DNA-S, and protein S; total uptake is, however, decreased during the whole experimental period. Absorption of sulphate is higher in the presence of 5 per cent CO2 in the aeration stream than in air free from CO2, in darkness as well as in light. Illumination gives variable effects, depending upon the way in which CO2 and phosphate are combined, and upon the fraction considered. Production and excretion of sulphite or hydrogen sulphide into the medium did not occur under the conditions used. The data collected are primarily concerned with the influx and incorporation processes. The metabolic chains leading to different sulphur fractions do not seem to compete strongly for any early intermediate(s) of sulphate incorporation. pH is also excluded as the cause of phosphate effects. Four different models are proposed as possible explanations for the inhibiting effects of phosphate on sulphate uptake: (A) permeability effects; (B) competition effects; (C) effects mediated via the anion respiration as envisaged by Lundegärdh; (D) effects on the PAPS producing system. These systems do not exclude each other and may well act together. [ABSTRACT FROM AUTHOR]

Symptoms of P deficiency develop comparatively slowly in cultures of Scenedesmus. The ‘mean cell’ becomes larger than in normal cultures, and the per cent dry matter rises. The reversal from - P to normal cells is also a slow process, during which cell divisions are somewhat disturbed, so that the ‘mean cell’ may still be rather large although per cent dry mailer has reverted to its normal value. Normal cells contain 3–5 mg P per g fresh weight. When phosphate is again given to - P cells their P level increases to twice the normal within a few hours and to at least 4–5 times the normal within a day. The rate of the P uptake then reverts to the normal. In short time experiments phosphate uptake is increased by light and inhibited by carbon dioxide. [ABSTRACT FROM AUTHOR]

A new type of electrode for continuous measurement of pCO2 in solution and tissues has been employed for the determination of the carbon dioxide concentration of root tissues. The carbon dioxide concentration of the intact wheat roots changes with the distance from the foot tip. It was possible lo find some correlation between the carbon dioxide production in respiration per unit nitrogen and the gas accumulation. Carbon dioxide accumulation in excised chlorophyllous wheat roots in darkness exceeds 10 per cent by volume. The diffusion of carbon dioxide from the inner parts of the roots outwards through the epidermal layer was about 70 per cent of that through cut surfaces. The epidermis offers a measurable resistance to carbon dioxide diffusion. The carbon dioxide concentration of the excised roots was twice that recorded in the intact roots. The factors governing the accumulation of carbon dioxide have been discussed. [ABSTRACT FROM AUTHOR]

A pronounced increase in the gas exchange, both the consumption of oxygen and the production of carbon dioxide, was found after addition of malonate (0.01 M) to Cryptococcus terriccolus cells respiring endogenously. The value of the R.Q. changed from 0.73 for the endogenous respiration to 1.54 in the fourth hour after the malonate addition. By using acetone powders of the organism. The presence of a decarboxylase, active on malonate, was proven. Only 25 per cent of the malonate was decarboxylated by the preparations employed. The decarboxylation by whole cells was blocked completely by the addition of 2,4-dinitrophenol. The total oxygen uptake and carbon dioxide output during the complete malonate decomposition exceeded the theoretical values calculated. The differences were shown to be due to a weak, normal endogenous respiration going on. The growth of glucose-grown cells of C. terricolus on malonate exceeded that on acetate after two days. However, on repeated transfers to malonate media, the growth was the same as with acetate. The possible relation between the malonate decarboxylase and the enzyme system activating fatty acid synthesis in C. terricolus, is discussed. [ABSTRACT FROM AUTHOR]

The effect of temperature on the opening movements of the stomatal cells has been determined in leaves which, before the experiments, were saturated with water and kept in darkness for 12-14 hours. Opening was elicited by light, as well as by CO2-free air. The rate was measured at 5, 10, 15. 25. 30. 35. 40. and 45°C, and compared with that at 20°C, determined concurrently in each experiment. Arrangements were made to ensure that the initially water-saturated object did not suffer any net loss of water during the experimental period. This prevented the occurrence of passive opening movements and hydroactive closing movements. The experiments at 40 and 45 °C were an exception, since they involved a minor water loss. It is found that in Vida Faba, stomatal opening is inappreciable at 5°C, both in light and in CO2-free medium in darkness. The rate increases with rising temperature, and at 35°C reaches a value 60-70 per cent higher than that at 20°C. At 40°C the values are highly variable, and al 45° a decrease takes place which is greatest in the experiments made in light. The experimental period is limited to 2-3 hours, i.e., the time during which the first opening phase occurs. It is pointed out that if a longer period or the maximal opening width that can be reached k chosen, no definite relation is apparent between the course of opening and the temperature. In some other species studied (e.g. Rumex ucetosu, Callha palustris, Lysimachia ihyrsillora, and Avena sativa) at 20° and 30°C, no effect of temperature could be established. The probable explanation is that the high turgor of the leaves — which was a prerequisite for the experiments — hampered the opening movements of the stomata, so that the pressure of the epidermal cells on the guard cells, rather than the temperature, was decisive for opening. [ABSTRACT FROM AUTHOR]

A study has been made of those opening movements of the stomatal cells elicited by removal of carbon dioxide -- denoted here as the CO2-sensitive opening movements -- and of the dependence of these movements on the hydratur of the object. The experimental objects were Vicia Faba and Ranunculus ficaria. It is found that in cases where transpiration and water uptake are so balanced that only a slight water deficit appears (2--5 per cent in the plants in question), the CO2-sensitive movements can proceed for several hours, and reach high values. Opening is, on the contrary, interrupted and is succeeded by hydroactive closure when the deficit has exceeded a certain critical value -- the threshold value -- and has a certain minimum duration -- the reaction time. The hydroactive effect increases in strength with the size and duration of the deficit. It no deficit forms, or if the turgor pressure is raised instead, the opening movement may fail to occur, or is replaced by a decrease in with of the guard cells, despite removal of CO2. When the deficit starts to occur, a passive opening effect is sometimes added to the CO2 effect. The CO2-induced mode of reaction is in conformity with the mode of reaction of the guard cells to tight. This conformity substantiates the view that the CO2 effect contributes to stomatal opening. The assumption that it is the sole cause of opening is not compatible with the fact that it arises concurrently with, and as a result of, photosynthesis in the guard cells, associated with production of an osmotically active substance in them. Consequently, the CO2-sensitive effect and the current photosynthetic production are simultaneously active in photoactive opening. Like other hitherto known kinds of stomatal movements, the CO2-sensitive effect is dependent on the hydratur of the object. The chief factor decisive for the state and movements of the stomata is neither light nor CO2, but the water deficit of the organ or, more exactly, the hydroactive closing reaction. This is because the strength of this reaction is determined by the size and duration of the water deficit. [ABSTRACT FROM AUTHOR]

A study has been made of the occurrence of the three types of induction curves (CO2-time curves), i.e., the primary-peak curve, the light-gush curve, and the half-arch curve, in 8 species of red algae, 5 species of brown algae and 6 species of green algae. The results are reviewed in Table 1. The primary-peak type of curve dominates among the red algae as well as among the cormophytes. Both primary-peak curves and light-gush curves are found among the brown and the green algae: the light-gush type occurs most frequently. A small number of half-arch curves are found within all of the taxonomic groups studied. In the case of Chlorella the light-gush curves appear only when the cells are grown in a medium enriched in carbon dioxide (air containing 3 to 5 % CO2 is bubbled through the nutrient solution) and when the determinations of the carbon dioxide exchange are made in air rich in carbon dioxide. Other species of green algae show light-gush curves when grown in media in equilibrium with the carbon dioxide content of ordinary atmospheric air, as do some of the species of brown algae included in the present study. The CO2-acceptor systems responsible for the formation of the various types of induction curves are discussed. [ABSTRACT FROM AUTHOR]

Root respiration in intact tomato roots was studied by simultaneous determinations of carbon dioxide release and oxygen consumption. When the root remained in undisturbed nutrient solution for a short time preceeding the determinations (20 minutes), the rate of carbon dioxide release was higher during the initial experimental period (20-30 minutes) than during the subsequent period. The oxygen uptake proceeded at a constant rate throughout the experiment. The hypothesis is advanced that the "extra" carbon dioxide release during the initial experimental period is due to a delayed release of carbon dioxide produced and accumulated in the root tissue prior to the experiment. It is concluded that determination of oxygen consumption is the most reliable method of measuring root respiration in short time experiments. [ABSTRACT FROM AUTHOR]