Post-illumination CO2 Exchange and Light-induced CO2 Bursts during C4 Photosynthesis

1997 ◽  
Vol 24 (4) ◽  
pp. 517 ◽  
Author(s):  
Agu Laisk ◽  
Gerald E. Edwards
Keyword(s):  
Malic Enzyme ◽  
Co2 Exchange ◽  
Co2 Uptake ◽  
Low Light ◽  
Co2 Response ◽  
Amaranthus Cruentus ◽  
Dark Light ◽  
Gas System ◽  
Detailed Kinetics ◽  
Kinetics Of

Detailed kinetics of the post-illumination CO2 exchange, and darklight transients following post-illumination exchange, were measured in leaves of Sorghum bicolor, a NADP-malic enzyme (NADP-ME), and Amaranthus cruentus, a NAD-malic enzyme (NAD-ME) type C4 plant using a gas system that has a full-response time of 3.5 s. The amount of CO2 fixed in the dark (assimilatory charge, AC) was up to 200 µmol m-2 for A. cruentus and 350-450 µmol m-2 for S. bicolor. AC was at its maximum value at CO2 concentrations close to the inflection of the CO2 response curve, and decreased when photosynthesis was limited by low light intensity. The kinetics of post-illumination CO2 fixation indicate that the rate of carboxylation in the C4 cycle is limited by the supply of phosphoenolpyruvate. In A. cruentus, under saturating CO2 the post-illumination CO2 uptake was replaced by a burst (68 µmol m-2). In S. bicolor, the dark-light induction commenced with a rapid CO2 burst (less than 5 s) of 46 µmol m-2, followed by a gulp. The observed CO2 transients show imbalances in the C4 and C3 cycles. In S. bicolor the lack of a post-illumination burst, and the presence of the light- induced CO2 burst is taken as evidence for strict coupling of malate decarboxylation to PGA reduction in NADP-ME species; the opposite response in A. cruentus indicates the lack of strict coupling between the C4 and C3 cycle in NAD-ME species.

scholarly journals Corrigendum to: Does the C4 plant Trianthema portulacastrum (Aizoaceae) exhibit weakly expressed crassulacean acid metabolism (CAM)?

2021 ◽  
Vol 48 (12) ◽  
pp. 1315
Author(s):  
Klaus Winter ◽  
Milton Garcia ◽  
Aurelio Virgo ◽  
Jorge Ceballos ◽  
Joseph A. M. Holtum
Keyword(s):  
Crassulacean Acid Metabolism ◽  
Acid Metabolism ◽  
Co2 Exchange ◽  
Co2 Uptake ◽  
C4 Plant ◽  
Low Level ◽  
Kranz Anatomy ◽  
Trianthema Portulacastrum ◽  
Annual Herb ◽  
Kinetics Of

We examined whether crassulacean acid metabolism (CAM) is present in Trianthema portulacastrum L. (Aizoaceae), a pantropical, salt-tolerant C4 annual herb with atriplicoid-type Kranz anatomy in leaves but not in stems. The leaves of T. portulacastrum are slightly succulent and the stems are fleshy, similar to some species of Portulaca, the only genus known in which C4 and CAM co-occur. Low- level nocturnal acidification typical of weakly expressed, predominantly constitutive CAM was measured in plants grown for their entire life-cycle in an outdoor raised garden box. Acidification was greater in stems than in leaves. Plants showed net CO2 uptake only during the light irrespective of soil water availability. However, nocturnal traces of CO2 exchange exhibited curved kinetics of reduced CO2 loss during the middle of the night consistent with low-level CAM. Trianthema becomes the second genus of vascular land plants in which C4 and features of CAM have been demonstrated to co-occur in the same plant and the first C4 plant with CAM-type acidification described for the Aizoaceae. Traditionally the stems of herbs are not sampled in screening studies. Small herbs with mildly succulent leaves and fleshy stems might be a numerically significant component of CAM biodiversity.

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

1982 ◽  
Vol 9 (6) ◽  
pp. 705 ◽  
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.

CO2 and Temperature-dependent Induction in C4 Photosynthesis: an Approach to the Hierarchy of Rate-limiting Processes

1997 ◽  
Vol 24 (4) ◽  
pp. 505 ◽  
Author(s):  
Agu Laisk ◽  
Gerald E. Edwards
Keyword(s):  
C4 Photosynthesis ◽  
Co2 Concentration ◽  
Temperature Dependent ◽  
Co2 Response ◽  
Amaranthus Cruentus ◽  
Low Co2 ◽  
Phosphoglyceric Acid ◽  
Rate Of Photosynthesis ◽  
Rate Limiting ◽  
Kinetics Of

Rate-limiting processes for C4 photosynthesis were examined in Sorghum bicolor, an NADP-ME type species, and Amaranthus cruentus, an NAD-ME type C4 species, by studying the kinetics of transient changes in photosynthetic rates following rapid changes in CO2 or temperature. Primary responses (faster than 15 s) to increasing CO2 or temperature are considered direct effects on the turnover rate of the C4 cycle, whereas medium transient changes (2–3 min) are considered due to build-up of C4 cycle intermediates, and the slowest transient changes (20–30 min) are thought to be related to end product synthesis. Reciprocal plot of carboxylation rates versus cell wall (dissolved) CO2 concentration (Cw) gives an apparent Km (CO2) of 8 µM and a Vm of 200 µmol m-2 s-1 for PEP carboxylase, which is about 4 times higher than the maximum rate of photosynthesis. Under strictly limiting CO2, the rate of PEP carboxylation in C4 photosynthesis is independent of temperature (20–35°C), suggesting a physical rather than a biochemical limitation. It is suggested that the rates of C3 and C4 cycles are coordinated through the pool sizes of the C4 cycle, which are in equilibrium with the pool of 3-phosphoglyceric acid. At low CO2, the C4 pools decrease and are slowly regenerated at elevated CO2, restricting the CO2 response of C4 photosynthesis.

Photoinhibition of natural phytoplankton assemblages in Lake Erie exposed to solar ultraviolet radiation

2000 ◽  
Vol 57 (2) ◽  
pp. 371-379 ◽  
Author(s):  
Christopher A Marwood ◽  
Ralph EH Smith ◽  
John A Furgal ◽  
Murray N Charlton ◽  
Keith R Solomon ◽  
...  
Keyword(s):  
Lake Erie ◽  
Pulse Amplitude ◽  
Ultraviolet B ◽  
Surface Radiation ◽  
Low Light ◽  
Solar Ultraviolet Radiation ◽  
Phytoplankton Assemblages ◽  
Photosystem Ii Efficiency ◽  
Kinetics Of ◽  
Modulated Chlorophyll Fluorescence

Photoinhibition was examined in natural assemblages of phytoplankton from Lake Erie exposed to ambient solar radiation. The impacts on photosynthesis of photosynthetically active radiation (400-700 nm) (PAR), ultraviolet-A radiation (320-400 nm) (UVA), and ultraviolet-B radiation (295-320 nm) (UVB) were assessed at three sites on the lake using pulse amplitude modulated chlorophyll fluorescence. Short exposures (<= 30 min) to sunlight containing UVB (1.8-4.4 mmol·m-2) resulted in the rapid loss of up to 60% of photosystem II efficiency (in the dark-adapted state) (Fv/Fm) and quantum yield (in the light-adapted state) (ΔF/F'm). Exposure to UVA (46-105 mmol·m-2) generally diminished Fv/Fm and, to a lesser extent, ΔF/F'm. Short exposures to PAR (733-1588 mmol·m-2) had no significant effects on electron transport. Recovery from UVA- or UVB-induced photoinhibition was complete for Fv/Fm and 90% complete for ΔF/F'm after 2 h in low light. The results indicate that exposures of phytoplankton to surface radiation need only be short in duration to cause substantial UV inhibition of photosynthesis. However, depending on the kinetics of mixing of the water column, recovery of photosynthesis is possible if there is sufficient time for repair of UV damage. Future elevated levels of solar UVB due to ozone depletion could significantly inhibit primary production in mesotrophic lakes such as Lake Erie.

Detailed Kinetics and Thermochemistry of C2H5+ O2:  Reaction Kinetics of the Chemically-Activated and Stabilized CH3CH2OO•Adduct

2002 ◽  
Vol 106 (32) ◽  
pp. 7276-7293 ◽  
Author(s):  
Chad Y. Sheng ◽  
Joseph W. Bozzelli ◽  
Anthony M. Dean ◽  
Albert Y. Chang
Keyword(s):  
Reaction Kinetics ◽  
Detailed Kinetics ◽  
Kinetics Of

scholarly journals Greenhouse gas flux measurements in a forestry-drained peatland indicate a large carbon sink

2011 ◽  
Vol 8 (11) ◽  
pp. 3203-3218 ◽  
Author(s):  
A. Lohila ◽  
K. Minkkinen ◽  
M. Aurela ◽  
J.-P. Tuovinen ◽  
T. Penttilä ◽  
...  
Keyword(s):  
Carbon Sink ◽  
Accumulation Rate ◽  
Peat Soil ◽  
Net Ecosystem Exchange ◽  
Flux Measurement ◽  
Co2 Exchange ◽  
Co2 Uptake ◽  
Flux Measurements ◽  
Ch4 And N2o ◽  
Carbon Dioxide Co2

Abstract. Drainage for forestry purposes increases the depth of the oxic peat layer and leads to increased growth of shrubs and trees. Concurrently, the production and uptake of the greenhouse gases carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) change: due to the accelerated decomposition of peat in the presence of oxygen, drained peatlands are generally considered to lose peat carbon (C). We measured CO2 exchange with the eddy covariance (EC) method above a drained nutrient-poor peatland forest in southern Finland for 16 months in 2004–2005. The site, classified as a dwarf-shrub pine bog, had been ditched about 35 years earlier. CH4 and N2O fluxes were measured at 2–5-week intervals with the chamber technique. Drainage had resulted in a relatively little change in the water table level, being on average 40 cm below the ground in 2005. The annual net ecosystem exchange was −870 ± 100 g CO2 m−2 yr−1 in the calendar year 2005, indicating net CO2 uptake from the atmosphere. The site was a small sink of CH4 (−0.12 g CH4 m−2 yr−1) and a small source of N2O (0.10 g N2O m−2 yr−1). Photosynthesis was detected throughout the year when the air temperature exceeded −3 °C. As the annual accumulation of C in the above and below ground tree biomass (175 ± 35 g C m−2) was significantly lower than the accumulation observed by the flux measurement (240 ± 30 g C m−2), about 65 g C m−2 yr−1 was likely to have accumulated as organic matter into the peat soil. This is a higher average accumulation rate than previously reported for natural northern peatlands, and the first time C accumulation has been shown by EC measurements to occur in a forestry-drained peatland. Our results suggest that forestry-drainage may significantly increase the CO2 uptake rate of nutrient-poor peatland ecosystems.

scholarly journals Short-term Effects of Grazing Exclusion on Net Ecosystem CO2 Exchange and Net Primary Production in a Pannonian Sandy Grassland

2012 ◽  
Vol 40 (2) ◽  
pp. 67 ◽  
Author(s):  
Szilard CZOBEL ◽  
Orsolya SZIRMAI ◽  
Zoltan NEMETH ◽  
Csaba GYURICZA ◽  
Judit GAZI ◽  
...  
Keyword(s):  
Carbon Sequestration ◽  
Primary Production ◽  
Net Primary Production ◽  
Plant Productivity ◽  
Co2 Exchange ◽  
Co2 Uptake ◽  
Aboveground Phytomass ◽  
Grazing Exclusion ◽  
Sequestration Potential ◽  
Sandy Grassland

Using portable, non-destructive own developed chambers (d=60 cm) and infrared gas analyses, the in situ field investigation was performed to study the seasonal and inter-annual dynamics of the stand level CO2-flux and production of sandy grassland that has been extensively grazed for decades. Furthermore, NEE measurements and biomass samples were used to identify the initial effects of grazing exclusion on CO2 exchange, aboveground phytomass and potential plant productivity in years of significantly different precipitation levels. A considerable inter-annual variation in all of the studied parameters was found both in the non-grazed and grazed stands. As a result of the grazing exclusion the CO2 uptake potential of the non-grazed stand increased by 13% compared to the grazed stand. It was more significant in the extreme dry year (220%), however, in wet year slightly lower average carbon sequestration was detected at the non-grazed stand (-13%), than that of the grazed area. Significant carbon sequestration potential was only detected during wet periods in both stands. The rate of CO2 uptake was found to be nearly six times higher in the non-grazed stand in the wet year than in the previous extremely dry year. The drought in 2003 significantly reduced the CO2 uptake of both stands, leading to lower annual net primary production and potential plant productivity. The annual net primary production dropped by almost 40% in the extremely dry year but then it rose by nearly two and a half times in the subsequent year with adequate rainfall.

Reaction Kinetics of Poly-Si Etching in TMAH Solution

2021 ◽  
Vol 314 ◽  
pp. 60-65
Author(s):  
Taegun Park ◽  
Sangwoo Lim
Keyword(s):  
Reaction Kinetics ◽  
Alkaline Solution ◽  
Etching Rate ◽  
Tetramethylammonium Hydroxide ◽  
Dissolved Gas ◽  
Metal Free ◽  
Effect Of Water ◽  
Detailed Kinetics ◽  
Kinetics Of ◽  
Tmah Solution

Tetramethylammonium hydroxide (TMAH) is a metal-free strong alkaline solution which can etch poly-Si. The concentration of dissolved gas as well as the concentration of TMAH affects etching rate of poly-Si. The detailed kinetics of poly-Si etching in TMAH solution is investigated in this study. The effect of water and TMAH concentration on the etching kinetics of poly-Si was investigated by using various concentrations of TMAH solution. It is found that H2O in TMAH solution plays an important role in etching poly-Si. Presence of dissolved CO2 and O2 in TMAH solution tends to inhibit etching of poly-Si. The concentration of dissolved CO2 and O2 in TMAH were reduced by Ar bubbling, thereby the poly-Si etching rate increased.

scholarly journals Spatiotemporal pH Heterogeneity as a Promoter of Cancer Progression and Therapeutic Resistance

Cancers ◽  
2019 ◽  
Vol 11 (7) ◽  
pp. 1026 ◽  
Author(s):  
David E. Korenchan ◽  
Robert R. Flavell
Keyword(s):  
Cancer Cells ◽  
Cancer Progression ◽  
Co2 Exchange ◽  
Therapeutic Resistance ◽  
Slow Time ◽  
Phenotypic Changes ◽  
Ph Buffering ◽  
Available Technology ◽  
Kinetics Of

Dysregulation of pH in solid tumors is a hallmark of cancer. In recent years, the role of altered pH heterogeneity in space, between benign and aggressive tissues, between individual cancer cells, and between subcellular compartments, has been steadily elucidated. Changes in temporal pH-related processes on both fast and slow time scales, including altered kinetics of bicarbonate-CO2 exchange and its effects on pH buffering and gradual, progressive changes driven by changes in metabolism, are further implicated in phenotypic changes observed in cancers. These discoveries have been driven by advances in imaging technologies. This review provides an overview of intra- and extracellular pH alterations in time and space reflected in cancer cells, as well as the available technology to study pH spatiotemporal heterogeneity.

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