Extracellular products of phytoplankton photosynthesis

1965 ◽  
Vol 162 (989) ◽  
pp. 517-534 ◽  
Keyword(s):  
Organic Matter ◽  
Total Carbon ◽  
Trophic Relationships ◽  
Low Light ◽  
Light Intensities ◽  
Wide Range ◽  
Different Types ◽  
Extracellular Products ◽  
Total Primary Productivity

Following exposure in situ for periods of 3 to 24 h of samples of lake or sea waters to which 14 C-bicarbonate had been added, radioactivity was found in dissolved organic matter in the water as well as in the cells of phytoplankton. The amount in the water was between 7 and 50% of the total carbon fixed in the photic zone of the water column. This production of extracellular 14 C-labelled organic matter was found under a wide variety of conditions and with many different types of phytoplankton community. It thus seems likely that the widely used method, in which fixation of 14 C in particulate matter only is determined, under­estimates total primary productivity. The labelled organic substances in the water are probably liberated by intact photosynthesizing cells rather than by breakage of cells during filtration. Glycollic acid is likely to be one of the principal substances concerned. Over a wide range of light intensities liberation of extracellular products by a given phytoplankton population was proportional to the amount of carbon fixed in the cells, except that it tended to be relatively greater at low light intensities (< 1 kilolux) and at light intensities high enough to inhibit photosynthesis ( > 50 kilolux), when as much as 95% of the total organic 14 C might be extracellular. Population density, period of exposure to 14 C-bicarbonate and species differences also affect the extent of excretion. The implications of extensive liberation by phytoplankton of extracellular products of photosynthesis for our understanding of the trophic relationships in aquatic habitats seem to be considerable.

scholarly journals First in situ estimations of small phytoplankton carbon and nitrogen uptake rates in the Kara, Laptev, and East Siberian seas

2018 ◽  
Author(s):  
Bhavya P. Sadanandan ◽  
Jang Han Lee ◽  
Ho Won Lee ◽  
Jae Joong Kaang ◽  
Jae Hyung Lee ◽  
...  
Keyword(s):  
Sea Ice ◽  
Nitrogen Uptake ◽  
N Uptake ◽  
Total Carbon ◽  
The Arctic ◽  
Carbon And Nitrogen ◽  
Uptake Rates ◽  
Wide Range ◽  
Small Phytoplankton

Abstract. Carbon and nitrogen uptake rates by small phytoplankton (0.7–5 μm) in the Kara, Laptev, and East Siberian seas in the Arctic Ocean were quantified using in situ isotope labelling experiments for the first time as part of the NABOS (Nansen and Amundsen Basins Observational System) program during August 21 to September 22, 2013. The depth integrated C, NO3−, and NH4+ uptake rates by small phytoplankton showed a wide range from 0.54 to 15.96 mg C m−2 h−1, 0.05 to 1.02 and 0.11 to 3.73 mg N m−2 h−1, respectively. The contributions of small phytoplankton towards the total C, NO3−, and NH4+ was varied from 24 to 89 %, 32 to 89 %, and 28 to 89 %, respectively. The turnover times for NO3− and NH4+ by small phytoplankton during the present study point towards the longer residence times (years) of the nutrients in the deeper waters, particularly for NO3−. Relatively, higher C and N uptake rates by small phytoplankton obtained during the present study at locations with less sea ice concentrations points towards the possibility of small phytoplankton thrive under sea ice retreat under warming conditions. The high contributions of small phytoplankton towards the total carbon and nitrogen uptake rates suggest capability of small size autotrophs to withstand in the adverse hydrographic conditions introduced by climate change.

Respiration in the light measured by 12CO 2 emission in 13CO 2 atmosphere in maize leaves

2001 ◽  
Vol 28 (11) ◽  
pp. 1103 ◽  
Author(s):  
Francesco Loreto ◽  
Violeta Velikova ◽  
Giorgio Di Marco
Keyword(s):  
Gas Exchange ◽  
Mitochondrial Respiration ◽  
Bundle Sheath ◽  
Gas Exchange Parameters ◽  
Low Light ◽  
Light Intensities ◽  
Wide Range ◽  
Bundle Sheath Cells ◽  
Maize Leaves ◽  
Exchange Parameters

The mitochondrial respiration during photosynthesis is difficult to measure and is indirectly estimated mainly in C 3 plants. Loreto et al. [(1999) Australian Journal of Plant Physiology 26, 733–736] have shown that the emission of 12 CO 2 from illuminated leaves exposed to air containing 13 CO 2 measures photorespiration and mitochondrial respiration in C 3 leaves. This method was used to measure the mitochondrial respiration in illuminated maize leaves. The 12 CO 2 emission was steady after 30 s, a time sufficient to label the CO 2 leakage from bundle sheath cells with 13 CO 2 , but not the mitochondrial respiration in the light. The emission was low (0.1–0.4 ppm or 0.2–0.4 µmol m –2 s –1 ) in a wide range of leaf temperatures and light intensities, but increased at light intensities below 200 µmol m –2 s –1 and at temperatures above 42°C. At 120 s after labelling, the leaf was darkened and the emission rapidly matched the mitochondrial respiration measured by gas exchange. The emission of 12 CO 2 in the light was inversely correlated with photosynthesis. This suggested that most of the respiratory CO 2 was refixed by photosynthesis. The amount of refixed intercellular 12 CO 2 was calculated from gas-exchange parameters. It was 60 to 90% of the tota l12 CO 2 in leaves illuminated and exposed to temperatures below 42°C. In leaves with reduced photosynthesis because of exposure to higher temperatures or low light, the 12 CO 2 refixation decreased. The sum of refixed and emitted 12 CO 2 was close to the mitochondrial respiration in the dark. This suggested that in these leaves the mitochondrial respiration was not inhibited in the light. In salt- and water-stressed leaves, however, the sum of refixed and emitted 12 CO 2 was lower than mitochondrial respiration in the dark, suggesting that the mitochondrial respiration may be inhibited in the light.

Studies in situ of the primary production of an area of inshore antarctic sea

1969 ◽  
Vol 49 (2) ◽  
pp. 393-405 ◽  
Author(s):  
A. J. Horne ◽  
G. E. Fogg ◽  
D. J. Eagle
Keyword(s):  
Primary Production ◽  
Primary Productivity ◽  
High Light ◽  
Total Carbon ◽  
The South ◽  
Orkney Islands ◽  
In Situ Techniques ◽  
Light Intensities ◽  
South Orkney Islands

The primary productivity of an area of inshore sea in the South Orkney Islands was measured using in situ techniques in two consecutive seasons. Liberation of extracellular products of photosynthesis occurred, accounting for about 1 % of the total carbon fixed at the depth of maximum photosynthesis but rising to 38 % or more when photosynthesis was inhibited at high light intensities.

Growth kinetics of Marquis wheat. II. Carbon dioxide dependence

1972 ◽  
Vol 50 (4) ◽  
pp. 883-889 ◽  
Author(s):  
F. D. H. Macdowall
Keyword(s):  
Carbon Dioxide ◽  
Light Intensity ◽  
Carbon Dioxide Concentration ◽  
Dry Weight ◽  
Maximum Growth ◽  
Carbon Dioxide Enrichment ◽  
Low Light ◽  
Growth Coefficient ◽  
Light Intensities ◽  
Wide Range

Marquis wheat was grown in growth rooms with four different concentrations of carbon dioxide and four to seven different intensities of light in a 16-h photoperiod at 25 °C. Growth was expressed quantitatively as the pseudo-first-order rate coefficient. Carbon dioxide stimulated growth, but the effect was greater the lower the light intensity in opposition to the known effect on photosynthesis. Carbon dioxide and light, in effect, did not influence the "rate" of growth of wheat additively but, rather, mutually compensated over a wide range. The growth coefficient of the roots was a little less than that of the shoots at all carbon dioxide concentrations and light intensities, probably owing to the cost of translocation. However, root growth benefited most from carbon dioxide enrichment at low light intensities. At intermediate light intensity there appeared to be a carbon dioxide concentration optimal for shoot growth. Carbon dioxide enrichment did not influence the maximum growth coefficient of Marquis wheat with respect to light intensity. The light-using efficiency of growth, calculated for vanishingly low light intensity at which it is maximal, was maximal for shoots at 1300 ppm CO2 but that for laminal area and root dry weight increased with CO2 to 2200 ppm at which the value for "leaves" was nearly fourfold that for roots. Unlike photosynthesis, the stimulation of growth by raised CO2 concentration was accomplished by increased efficiency of, and not capacity for, the net photosynthetic use of light.

Studies on the Factors Affecting the Release of Organic Matter By Skeletonema Costatum (Greville) Cleve in Culture

1973 ◽  
Vol 53 (4) ◽  
pp. 937-956 ◽  
Author(s):  
L. Ignatiades ◽  
G. E. Fogg
Keyword(s):  
Organic Matter ◽  
Skeletonema Costatum ◽  
Physiological Activity ◽  
Marine Phytoplankton ◽  
Low Light ◽  
Factors Affecting ◽  
Light Intensities

A few studies on the excretion of organic matter by marine phytoplankton in culture have been reported (Guillard & Wangersky, 1958; Wangersky & Guillard, 1960; Stewart, 1963; Hellebust, 1965). Eppley & Sloan (1965) reported extensive excretion in Skeletonema costatum (Greville) Cleve cultures as they approached senescence and emphasized that excretion is inversely proportional to the physiological activity of cells. Hellebust (1965) demonstrated the release of high amounts (up to 38% of the carbon assimilated) of organic matter by Sk. costatum cells exposed to low light intensities. It is apparent that more knowledge is needed in order to define the intra- and extracellular factors affecting the excretion.

Carbon Isotopic Characteristics of Different Genetic Type Condensates in China

2011 ◽  
Vol 29 (6) ◽  
pp. 699-710 ◽  
Author(s):  
Shipeng Huang ◽  
Zecheng Wang ◽  
Xiaoqi Wu ◽  
Fengrong Liao ◽  
Jinxing Dai
Keyword(s):  
Organic Matter ◽  
Isotopic Composition ◽  
Carbon Isotopes ◽  
Organic Matters ◽  
Total Hydrocarbon ◽  
Carbon Isotopic ◽  
Wide Range ◽  
Different Types ◽  
Organic Matter Type ◽  
Petroliferous Basin

Condensate pools with reservoir ages of Ordovician, Permian, Triassic, Jurassic, Cretaceous, Eogene, and Neogene were found in every giant petroliferous Basin in China. Condensates generated by sapropelic organic matters (sapropelic condensates) are of high- to over-mature stages, while the maturities of those generated by humic organic matters (humic condensates) cover a wide range, from early mature to over-mature. Carbon isotopes of 143 condensate samples were analyzed in this work, and we found that both the organic matter type and the maturity significantly influenced the isotopic composition of the condensates. The total hydrocarbon isotopic values of the humic condensates range from −29.9% to −21.7%, with an average of −26.0% (94 samples), while those sapropelic condensates are lighter generally, covering a range of −33.9% to −26.0% with an average of −29.5% (40 samples). δ13Caromatics value is strongly inheritable to the organic matter type and it combined with the δ13Csaturates value can be used to distinguish condensates of different types. δ13Caromatics value of sapropelic condensate is less than −27.5%, while the δ13Caromatics and the δ13Csaturates values of humic condensate are larger than −27.5% and −29.5%, respectively.

Soil properties influencing compactability of forest soils in British Columbia

2004 ◽  
Vol 84 (2) ◽  
pp. 219-226 ◽  
Author(s):  
M. Krzic ◽  
C. E. Bulmer ◽  
F. Teste ◽  
L. Dampier ◽  
S. Rahman
Keyword(s):  
British Columbia ◽  
Organic Matter ◽  
Water Content ◽  
Bulk Density ◽  
Forest Soils ◽  
Tree Planting ◽  
Total Carbon ◽  
Regression Equations ◽  
Wide Range ◽  
Proctor Test

The widespread use of heavy machinery during harvesting and site preparation in timber plantations in British Columbia (BC) has led to concerns that compaction causes a reduction in long-term soil productivity. Impacts of properties such as total C, water content, and texture on compactability of forest soils in BC were assessed. Two compactability indices were used: maximum bulk density (MBD) and susceptibility to compaction (SC) determined by the standard Proctor test. Soil samples were collected from 16 sites throughout BC covering a wide range of biogeoclimatic zones. Soils varied in texture (12 to 87% sand, 9 to 76% silt, and 2 to 53% clay) and organic matter content (18 to 76 g kg-1 total C). A strong negative correlation was observed between MBD and gravimetric water content at which MBD was achieved (WMBD) and between MBD and total C. Similarly, WMBD and total C had strong effects on SC. The estimation of either MBD or SC values was not substantially improved by including texture parameters to the regression equations in addition to the total C. The implication of the relationships observed in this study is that increases in soil organic matter reduce the risk of compactability, which is particularly important for forest soils where compaction is generally not corrected by implements after tree planting. The information is also useful for assessing the extent of compaction on soils affected by machine traffic. Key words: Soil compaction, Susceptibility to compaction, maximum bulk density, Proctor test, total carbon

scholarly journals Compartments of organic matter in an Oxisol under different types of no-tillage systems

2018 ◽  
Vol 39 (2) ◽  
pp. 533
Author(s):  
Roni Fernandes Guareschi ◽  
Marcos Gervasio Pereira ◽  
Paula Fernanda Chaves Soares ◽  
Fabiana Da Costa Barros ◽  
Adriano Perin ◽  
...  
Keyword(s):  
Organic Matter ◽  
Climatic Conditions ◽  
Total Carbon ◽  
Control Treatment ◽  
No Tillage ◽  
Tillage Systems ◽  
Total Carbon Content ◽  
Soil C ◽  
Different Types ◽  
Tillage System

The objective of this study was to evaluate the changes in soil carbon (C) as well as its fractions of physical (particulate organic carbon associated with minerals), chemical (fulvic and humic acids and humins), and oxidizable (F1, F2, F3, and F4) forms of an Oxisol under no-tillage systems (SPD) under different successions and crop rotations in the Cerrado area. In order to do this, the areas of consolidated SPD (10 to 20 years) under the same soil and climatic conditions were selected in Montividiu (GO), with soybean-corn succession (SSM), soybean-millet succession (SSMt), soybean-millet-bean-cotton rotation (RSMFA), crop-livestock integration (ILP), and a native cerrado (CE) area used as a control treatment In each area, samples were collected at depths of 0.0-0.05, 0.05-0.10, 0.10-0.20, and 0.20-0.40 m, respectively. The no-tillage system with crop rotation, followed by no-tillage system with crop-livestock integration, were the ones that presented the greatest potential to increase total carbon content in soil, presenting higher C contents of the granulometric, humic, and oxidizable fractions of the soil organic matter (SOM), compared with the other areas of no-tillage systems with succession of the respective evaluated crops. The no-tillage areas with corn and soybean/millet succession systems showed a similar pattern in soil C accumulation, as well as in the compartments of SOM evaluated.

Taphonomy of plant fossils from the Viséan of East Kirkton, West Lothian, Scotland

1993 ◽  
Vol 84 (3-4) ◽  
pp. 267-274 ◽  
Author(s):  
R. E. Brown ◽  
A. C. Scott ◽  
T. P. Jones
Keyword(s):  
Organic Matter ◽  
Plant Fossils ◽  
Wide Range ◽  
Show Evidence ◽  
Mineral Replacement

ABSTRACTThe Viséan sequence at East Kirkton contains abundant plant fossils which show a wide range of preservation states. Most of the plant fragments are allochthonous, but stigmarian rootlets are found in situ at the top of the sequence and form mats near the base, where they are preserved in cherts. Axes have commonly been reworked within tuffs at the base. The majority of the plants are preserved as fragmentary compressions, although mineral replacement of the organic matter has occurred in some places. A number of woody axes which have been permineralised by phases of calcite and silica are found in the limestone and tuffs of the sequence. These axes often show complex mineralisation patterns and can occur at the centre of stromatolitic nodules. Some are well preserved and appear to have been permineralised rapidly whereas others show evidence of decay prior to calcite growth or degradation after stromatolite developed. Fusain (fossil charcoal) is abundant in the sequence, in addition to fusain transition fossils caused by partial charring, which suggests the occurrence of palaeowildfires in the area. The plant fossils have been assigned to a number of categories (some of which are new), based on their varied preservation states.

In-situ electrical-resistivity measurements in the high-voltage electron microscope

1978 ◽  
Vol 36 (1) ◽  
pp. 68-69
Author(s):  
W. E. King
Keyword(s):  
Electrical Resistivity ◽  
Electron Microscope ◽  
High Voltage ◽  
Resistivity Measurements ◽  
Voltage Electron ◽  
High Voltage Electron Microscope ◽  
High Voltage Electron ◽  
Wide Range ◽  
Helium Gas

A side-entry type, helium-temperature specimen stage that has the capability of in-situ electrical-resistivity measurements has been designed and developed for use in the AEI-EM7 1200-kV electron microscope at Argonne National Laboratory. The electrical-resistivity measurements complement the high-voltage electron microscope (HVEM) to yield a unique opportunity to investigate defect production in metals by electron irradiation over a wide range of defect concentrations.A flow cryostat that uses helium gas as a coolant is employed to attain and maintain any specified temperature between 10 and 300 K. The helium gas coolant eliminates the vibrations that arise from boiling liquid helium and the temperature instabilities due to alternating heat-transfer mechanisms in the two-phase temperature regime (4.215 K). Figure 1 shows a schematic view of the liquid/gaseous helium transfer system. A liquid-gas mixture can be used for fast cooldown. The cold tip of the transfer tube is inserted coincident with the tilt axis of the specimen stage, and the end of the coolant flow tube is positioned without contact within the heat exchanger of the copper specimen block (Fig. 2).

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