CO2 Exchange at Low PPFD and Low CO2 Levels: Measurement and Simulation

Survival of Campylobacter jejuni, inoculated into turkey roll slices and stored under seven different atmospheric mixtures, was determined. Turkey roll samples were stored at 4°C for 18 d and at 21°C for 48 h. The effects of various atmospheric mixtures on aerobic, psychrotrophic, and lactic acid bacterial populations were also determined throughout storage. Campylobacter jejuni was inactivated under all atmospheric gas mixtures tested throughout storage. Increasing CO2 concentration inside the package from 0% to 100% CO2 resulted in a lower rate of inactivation of C. jejuni at both storage temperatures. Increases in CO2 concentrations provided greater inhibition of aerobic and psychrotrophic populations as compared to low CO2 levels. The effect of CO2 on survival of C. jejuni and growth rate of aerobic, psychrotrophic, and lactic acid bacteria was more pronounced at 4°C. Campylobacters were isolated from inoculated turkey roll held under all atmospheres by enrichment procedures on the 18th day and 48th hour of storage at 4 and 21°C, respectively, with an initial population of log 6.0 Campylobacter s/g. However, no Campylobacters were isolated by 18 d of storage at 4°C by direct plating.

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Predicting Pleistocene climate from vegetation in North America

Climate of the Past ◽

10.5194/cp-3-109-2007 ◽

2007 ◽

Vol 3 (1) ◽

pp. 109-118 ◽

Cited By ~ 32

Author(s):

C. Loehle

Keyword(s):

North America ◽

Ice Age ◽

Temperate Species ◽

Eastern North America ◽

Biogeographic Patterns ◽

Free Zone ◽

Low Co2 ◽

Pleistocene Climate ◽

Co2 Levels ◽

Climate Indicator

Abstract. Climates at the Last Glacial Maximum have been inferred from fossil pollen assemblages, but these inferred climates are colder for eastern North America than those produced by climate simulations. It has been suggested that low CO2 levels could account for this discrepancy. In this study biogeographic evidence is used to test the CO2 effect model. The recolonization of glaciated zones in eastern North America following the last ice age produced distinct biogeographic patterns. It has been assumed that a wide zone south of the ice was tundra or boreal parkland (Boreal-Parkland Zone or BPZ), which would have been recolonized from southern refugia as the ice melted, but the patterns in this zone differ from those in the glaciated zone, which creates a major biogeographic anomaly. In the glacial zone, there are few endemics but in the BPZ there are many across multiple taxa. In the glacial zone, there are the expected gradients of genetic diversity with distance from the ice-free zone, but no evidence of this is found in the BPZ. Many races and related species exist in the BPZ which would have merged or hybridized if confined to the same refugia. Evidence for distinct southern refugia for most temperate species is lacking. Extinctions of temperate flora were rare. The interpretation of spruce as a boreal climate indicator may be mistaken over much of the region if the spruce was actually an extinct temperate species. All of these anomalies call into question the concept that climates in the zone south of the ice were extremely cold or that temperate species had to migrate far to the south. An alternate hypothesis is that low CO2 levels gave an advantage to pine and spruce, which are the dominant trees in the BPZ, and to herbaceous species over trees, which also fits the observed pattern. Thus climate reconstruction from pollen data is probably biased and needs to incorporate CO2 effects. Most temperate species could have survived across their current ranges at lower abundance by retreating to moist microsites. These would be microrefugia not easily detected by pollen records, especially if most species became rare. These results mean that climate reconstructions based on terrestrial plant indicators will not be valid for periods with markedly different CO2 levels.

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Activation Energy Analysis and Limiting Factors in Photosynthesis

Australian Journal of Biological Sciences ◽

10.1071/bi9720419 ◽

1972 ◽

Vol 25 (2) ◽

pp. 419 ◽

Cited By ~ 3

Author(s):

RM Gifford ◽

RB Musgrave

Keyword(s):

Activation Energy ◽

Temperature Response ◽

Co2 Concentration ◽

Co2 Exchange ◽

Photochemical Reactions ◽

High Light ◽

Limiting Factors ◽

Grass Species ◽

Low Co2 ◽

Rate Limiting

It has been proposed that activation energies of CO2 exchange obtained from Arrhenius plots of the temperature response of leaf CO2 exchange rates (or the equivalent QIO analysis) should elucidate the rate-limiting processes. Chmora and Oya (1967), for example, suggest that a QlO (15-25�0) of about 1 for maize photo-synthesis at low light and low CO2 concentration implies photochemical reactions are limiting, at high light and high CO2 a QIO of 1 �6 implies enzyme reactions are limiting, whilst at high light and low CO2 a QlO of 1� 25 suggests diffusion is limiting. Bjorkman, Nobs, and Hiesey (1969) surmise that for Mimulus sp. at 0�07% CO2 the coincidence of QIO (15-30�0) for both CO2 exchange (at 1'5% oxygen and saturating light) and extracted carboxydismutase (QlO = 2�7-3�3) could reflect a causal relationship. Charles-Edwards and Charles-Edwards (1970) find that for clones of three grass species there is a clustering of the determinations of activation energy around certain values. It is suggested that each such value may be characteristic of a certain rate-limiting process.

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Propranolol-vagal-alveolar CO2 interactions on collateral gas flow in dog lungs

Journal of Applied Physiology ◽

10.1152/jappl.1982.52.6.1426 ◽

1982 ◽

Vol 52 (6) ◽

pp. 1426-1431 ◽

Cited By ~ 2

Author(s):

L. E. Olson ◽

N. E. Robinson

Keyword(s):

Gas Flow ◽

Vagal Stimulation ◽

High Co2 ◽

Low Co2 ◽

Co2 Levels ◽

Lung Segment ◽

Airway Opening ◽

Residual Capacity ◽

Propranolol Treatment ◽

End Tidal

The mechanical properties of a collaterally ventilating lung segment were studied in 18 anesthetized paralyzed mongrel dogs artificially ventilated with room air end-tidal CO2 fraction = 5%. Nine dogs were pretreated with propranolol, and nine dogs were not. With 0, 5, or 12% CO2 in O2 flowing into the segment, steady-state resistance of segmental airways (Rss) and time for 90% pressure equilibration (T90) between the segment and airway opening after flow was discontinued were determined at functional residual capacity with the vagus nerve ipsilateral to the segment intact, sectioned, or electrically stimulated. Vagal stimulation increased Rss and T90 at all CO2 levels, whereas unilateral vagotomy had no effect. Propranolol treatment enhanced the increase in Rss caused by vagal stimulation at low but not at high CO2 levels, suggesting that high CO2 mimics the effect of propranolol on Rss. High levels of CO2 did not have the same effect as propranolol on T90, propranolol treatment reducing the increase in T90 caused by vagal stimulation at high but not at low CO2 levels. These results demonstrate that local changes in alveolar CO2 tensions modify but do not abolish the effect of vagal stimulation on collateral ventilation.

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Predicting Pleistocene climate from vegetation

Climate of the Past Discussions ◽

10.5194/cpd-2-979-2006 ◽

2006 ◽

Vol 2 (5) ◽

pp. 979-1000

Author(s):

C. Loehle

Keyword(s):

Ice Age ◽

Temperate Species ◽

Tropical Mountains ◽

Biogeographic Patterns ◽

Free Zone ◽

Low Co2 ◽

Pleistocene Climate ◽

Climate Simulations ◽

Co2 Levels ◽

Climate Indicator

Abstract. Climates at the Last Glacial Maximum have been inferred from fossil pollen assemblages, but these inferred climates are colder than those produced by climate simulations. Biogeographic evidence also argues against these inferred cold climates. The recolonization of glaciated zones in eastern North America following the last ice age produced distinct biogeographic patterns. It has been assumed that a wide zone south of the ice was tundra or boreal parkland (Boreal-Parkland Zone or BPZ), which would have been recolonized from southern refugia as the ice melted, but the patterns in this zone differ from those in the glaciated zone, which creates a major biogeographic anomaly. In the glacial zone, there are few endemics but in the BPZ there are many across multiple taxa. In the glacial zone, there are the expected gradients of genetic diversity with distance from the ice-free zone, but no evidence of this is found in the BPZ. Many races and related species exist in the BPZ which would have merged or hybridized if confined to the same refugia. Evidence for distinct southern refugia for most temperate species is lacking. Extinctions of temperate flora were rare. The interpretation of spruce as a boreal climate indicator may be mistaken over much of the region if the spruce was actually an extinct temperate species. All of these anomalies call into question the concept that climates in the zone south of the ice were very cold or that temperate species had to migrate far to the south. Similar anomalies exist in Europe and on tropical mountains. An alternate hypothesis is that low CO2 levels gave an advantage to pine and spruce, which are the dominant trees in the BPZ, and to herbaceous species over trees, which also fits the observed pattern. Most temperate species could have survived across their current ranges at lower abundance by retreating to moist microsites. These would be microrefugia not easily detected by pollen records, especially if most species became rare. These results mean that climate reconstruction based on terrestrial plant indicators will not be valid for periods with markedly different CO2 levels.

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Assimilate Movement in Lolium and Sorghum Leaves. Iii. Carbon Dioxide Concentration Effects on the Metabolism and Translocation of Photosynthate.

Functional Plant Biology ◽

10.1071/pp9820705 ◽

1982 ◽

Vol 9 (6) ◽

pp. 705 ◽

Cited By ~ 5

Author(s):

IF Wardlaw

Keyword(s):

Water Stress ◽

Stomatal Closure ◽

Carbon Dioxide Concentration ◽

Co2 Concentration ◽

Co2 Exchange ◽

Co2 Uptake ◽

Concentration Effects ◽

Low Light ◽

Low Co2 ◽

Before And After

Raising the CO2 concentration of air to 720 �l I-� increased the rate of net CO2 uptake by the leaf of Lolium temulentum, a C*3 species, more than in Sorghum sudanense, a C*4 species. In Lolium, but not in Sorghum, high CO2 over a 6 h period resulted in relatively more of the additional leaf photosynthate being partitioned into storage rather than to translocation. Removing CO2 from the air passing over a 5 cm length of leaf before and after a pulse application of 14CO2 resulted in a reduced labelling of sucrose and a slower rate of export of 14C-labelled photosynthate in both species. With the fall in net CO2 exchange by the leaf section deprived of CO2 there was a compensating increase within this section in retention of photosynthate derived from the distal part of the leaf. Evidence provided by 14CO2 pulse chase experiments and CO2 exchange studies confirmed the relative enhancement of photorespiration under low CO2 concentrations in Lolium, but not in Sorghum. The CO2 depletion experiments provide a useful base for comparison with the effect of low light and water stress on photosynthate metabolism and translocation in that both these conditions reduce CO2 uptake. There is support for the suggestion that the change in photosynthate metabolism under water stress in C*3 species may result from reduced CO2 entry into the leaf due to stomatal closure.

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Photoprotection is regulated by light-independent CO2 availability

10.1101/2021.10.23.465040 ◽

2021 ◽

Author(s):

M. Águila Ruiz-Sola ◽

Serena Flori ◽

Yizhong Yuan ◽

Gaelle Villain ◽

Emanuel Sanz-Luque ◽

...

Keyword(s):

Chlamydomonas Reinhardtii ◽

Green Alga ◽

Total Darkness ◽

Transcript Accumulation ◽

High Co2 ◽

Co2 Concentrating Mechanism ◽

Low Co2 ◽

Co2 Levels ◽

Excess Light ◽

The Impact

Photosynthetic algae cope with suboptimal levels of light and CO2. In low CO2 and excess light, the green alga Chlamydomonas reinhardtii activates a CO2 Concentrating Mechanism (CCM) and photoprotection; the latter is mediated by LHCSR1/3 and PSBS. How light and CO2 signals converge to regulate photoprotective responses remains unclear. Here we show that excess light activates expression of photoprotective and CCM-related genes and that depletion of CO2 drives these responses, even in total darkness. High CO2 levels, derived from respiration or impaired photosynthetic fixation, repress LHCSR3 and CCM genes while stabilizing the LHCSR1 protein. We also show that CIA5, which controls CCM genes, is a major regulator of photoprotection, elevating LHCSR3 and PSBS transcript accumulation while inhibiting LHCSR1 accumulation. Our work emphasizes the importance of CO2 in regulating photoprotection and the CCM, demonstrating that the impact of light on photoprotection is often indirect and reflects intracellular CO2 levels.

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Relationship between the inhibition of leaf respiration by light and enhancement of leaf dark respiration following light treatment

Functional Plant Biology ◽

10.1071/pp97159 ◽

1998 ◽

Vol 25 (4) ◽

pp. 437 ◽

Cited By ~ 115

Author(s):

Owen K. Atkin ◽

John R. Evans ◽

Katharina Siebke

Keyword(s):

Dark Respiration ◽

Intercellular Co2 Concentration ◽

Co2 Concentration ◽

Fast Response ◽

Co2 Exchange ◽

Common Mechanism ◽

Low Co2 ◽

Leaf Dark Respiration ◽

Co2 Release ◽

Intercellular Co2

Respiration (R, non-photorespiratory mitochondrial CO2 release) in leaves is inhibited by light. However, exposure to darkness after a period of illumination can also result in R being temporarily stimulated (termed ‘light enhanced dark respiration’, LEDR). We used a fast-response CO2 exchange system to investigate these observations in tobacco leaves. After switching off the light, there were two peaks of CO2 release, the first at 15–20 s (the photorespiratory post-illumination burst) and the second at 180–250 s (LEDR). LEDR occurred in all post-illumination experiments, independent of O2 or CO2 concentration. However, LEDR increased with increasing irradiance during the pre-dark period, suggesting some dependency on prior photosynthesis. We investigated the inhibition of R by light at low CO2 concentrations (?*): ?* is the intercellular CO2 concentration at which net CO2 release represents R in the light. The inhibition of R in the light took about 50 s and was even evident at 3 mmol photons m-2 s-1, regardless of the light quality (red, blue or white). The inhibition of R by light showed similar dependency on irradiance as LEDR, such that the degree of inhibition was positively correlated with the level of LEDR. In the light, switching from 350 ppm to a low CO2 concentration that resulted in the intercellular CO2 concentration being at ?*, resulted in R initially increasing and then stabilising. Maintaining the leaf at ?* did not, therefore, lead to an underestimation of R. Our data suggest that a common mechanism may be responsible for both the inhibition of R by light and LEDR.

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