A simple dynamic model of photosynthesis in oak leaves: coupling leaf conductance and photosynthetic carbon fixation by a variable intracellular CO2 pool

2004 ◽  
Vol 31 (12) ◽  
pp. 1195 ◽  
Author(s):  
Steffen M. Noe ◽  
Christoph Giersch
Keyword(s):  
Carbon Fixation ◽  
Calvin Cycle ◽  
Target Function ◽  
Vapour Pressure Deficit ◽  
Co2 Assimilation ◽  
Leaf Conductance ◽  
Co2 Partial Pressure ◽  
Sink Term ◽  
Essential Components ◽  
Oak Leaves

Modelling the diurnal course of photosynthesis in oak leaves (Quercus robur L.) requires appropriate description of the dynamics of leaf photosynthesis of which diurnal variations in leaf conductance and in CO2 assimilation are essential components. We propose and analyse a simple photosynthesis model with three variables: leaf conductance (gs), the CO2 partial pressure inside the leaf (pi), and a pool of Calvin cycle intermediates (aps). The environmental factors light (I) and vapour pressure deficit (VPD) are used to formulate a target function G(I, VPD) from which the actual leaf conductance is calculated. Using this gs value and a CO2 consumption term representing CO2 fixation, a differential equation for pi is derived. Carboxylation corresponds to the sink term of the pi pool and is assumed to be feedback-inhibited by aps. This simple model is shown to produce reasonable to excellent fits to data on the diurnal time courses of photosythesis, pi and gs sampled for oak leaves.

scholarly journals Whole-Genome Transcriptional Profiling of Bradyrhizobium japonicum during Chemoautotrophic Growth

2008 ◽  
Vol 190 (20) ◽  
pp. 6697-6705 ◽  
Author(s):  
William L. Franck ◽  
Woo-Suk Chang ◽  
Jing Qiu ◽  
Masayuki Sugawara ◽  
Michael J. Sadowsky ◽  
...  
Keyword(s):  
Bradyrhizobium Japonicum ◽  
Carbon Fixation ◽  
Cultured Cells ◽  
Isocitrate Lyase ◽  
Nitrogenase Activity ◽  
Glyoxylate Cycle ◽  
Transcriptional Profiling ◽  
Pentose Phosphate ◽  
Hydrogen Gas ◽  
Essential Components

ABSTRACT Bradyrhizobium japonicum is a facultative chemoautotroph capable of utilizing hydrogen gas as an electron donor in a respiratory chain terminated by oxygen to provide energy for cellular processes and carbon dioxide assimilation via a reductive pentose phosphate pathway. A transcriptomic analysis of B. japonicum cultured chemoautotrophically identified 1,485 transcripts, representing 17.5% of the genome, as differentially expressed when compared to heterotrophic cultures. Genetic determinants required for hydrogen utilization and carbon fixation, including the uptake hydrogenase system and components of the Calvin-Benson-Bassham cycle, were strongly induced in chemoautotrophically cultured cells. A putative isocitrate lyase (aceA; blr2455) was among the most strongly upregulated genes, suggesting a role for the glyoxylate cycle during chemoautotrophic growth. Addition of arabinose to chemoautotrophic cultures of B. japonicum did not significantly alter transcript profiles. Furthermore, a subset of nitrogen fixation genes was moderately induced during chemoautotrophic growth. In order to specifically address the role of isocitrate lyase and nitrogenase in chemoautotrophic growth, we cultured aceA, nifD, and nifH mutants under chemoautotrophic conditions. Growth of each mutant was similar to that of the wild type, indicating that the glyoxylate bypass and nitrogenase activity are not essential components of chemoautotrophy in B. japonicum.

scholarly journals Design and in vitro realization of carbon-conserving photorespiration

2018 ◽  
Vol 115 (49) ◽  
pp. E11455-E11464 ◽  
Author(s):  
Devin L. Trudeau ◽  
Christian Edlich-Muth ◽  
Jan Zarzycki ◽  
Marieke Scheffen ◽  
Moshe Goldsmith ◽  
...  
Keyword(s):  
Carbon Fixation ◽  
Calvin Cycle ◽  
Computational Design ◽  
Carbon Loss ◽  
Fixation Rate ◽  
Bisphosphate Carboxylase ◽  
Stoichiometric Model ◽  
Synthetic Routes ◽  
Coa Reductase

Photorespiration recycles ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) oxygenation product, 2-phosphoglycolate, back into the Calvin Cycle. Natural photorespiration, however, limits agricultural productivity by dissipating energy and releasing CO2. Several photorespiration bypasses have been previously suggested but were limited to existing enzymes and pathways that release CO2. Here, we harness the power of enzyme and metabolic engineering to establish synthetic routes that bypass photorespiration without CO2 release. By defining specific reaction rules, we systematically identified promising routes that assimilate 2-phosphoglycolate into the Calvin Cycle without carbon loss. We further developed a kinetic–stoichiometric model that indicates that the identified synthetic shunts could potentially enhance carbon fixation rate across the physiological range of irradiation and CO2, even if most of their enzymes operate at a tenth of Rubisco’s maximal carboxylation activity. Glycolate reduction to glycolaldehyde is essential for several of the synthetic shunts but is not known to occur naturally. We, therefore, used computational design and directed evolution to establish this activity in two sequential reactions. An acetyl-CoA synthetase was engineered for higher stability and glycolyl-CoA synthesis. A propionyl-CoA reductase was engineered for higher selectivity for glycolyl-CoA and for use of NADPH over NAD+, thereby favoring reduction over oxidation. The engineered glycolate reduction module was then combined with downstream condensation and assimilation of glycolaldehyde to ribulose 1,5-bisphosphate, thus providing proof of principle for a carbon-conserving photorespiration pathway.

An intrinsically disordered protein, CP12: jack of all trades and master of the Calvin cycle

2012 ◽  
Vol 40 (5) ◽  
pp. 995-999 ◽  
Author(s):  
Brigitte Gontero ◽  
Stephen C. Maberly
Keyword(s):  
Amino Acids ◽  
Stress Responses ◽  
Intrinsically Disordered Proteins ◽  
Calvin Cycle ◽  
Intrinsically Disordered Protein ◽  
Disulfide Bridge ◽  
Co2 Assimilation ◽  
Disordered Proteins ◽  
Dimensional Structure ◽  
Intrinsically Disordered

Many proteins contain disordered regions under physiological conditions and lack specific three-dimensional structure. These are referred to as IDPs (intrinsically disordered proteins). CP12 is a chloroplast protein of approximately 80 amino acids and has a molecular mass of approximately 8.2–8.5 kDa. It is enriched in charged amino acids and has a small number of hydrophobic residues. It has a high proportion of disorder-promoting residues, but has at least two (often four) cysteine residues forming one (or two) disulfide bridge(s) under oxidizing conditions that confers some order. However, CP12 behaves like an IDP. It appears to be universally distributed in oxygenic photosynthetic organisms and has recently been detected in a cyanophage. The best studied role of CP12 is its regulation of the Calvin cycle responsible for CO2 assimilation. Oxidized CP12 forms a supramolecular complex with two key Calvin cycle enzymes, GAPDH (glyceraldehyde-3-phosphate dehydrogenase) and PRK (phosphoribulokinase), down-regulating their activity. Association–dissociation of this complex, induced by the redox state of CP12, allows the Calvin cycle to be inactive in the dark and active in the light. CP12 is promiscuous and interacts with other enzymes such as aldolase and malate dehydrogenase. It also plays other roles in plant metabolism such as protecting GAPDH from inactivation and scavenging metal ions such as copper and nickel, and it is also linked to stress responses. Thus CP12 seems to be involved in many functions in photosynthetic cells and behaves like a jack of all trades as well as being a master of the Calvin cycle.

Inhibition of CO2 Assimilation by Supraoptimal CO2: Effect of Light and Temperature

1983 ◽  
Vol 10 (1) ◽  
pp. 75 ◽  
Author(s):  
KC Woo ◽  
SC Wong
Keyword(s):  
Partial Pressure ◽  
Co2 Concentration ◽  
Co2 Assimilation ◽  
Quantum Yields ◽  
Co2 Partial Pressure ◽  
Low Co2 ◽  
O2 Partial Pressure ◽  
Partial Pressures ◽  
High Partial Pressure ◽  
Partial Pressure Of Co2

In cotton the rate of CO2 assimilation, at O2 partial pressures up to 200 mbar, increased to a maximum and then declined as the intercellular partial pressure of CO2 was increased. The specific intercellular partial pressure of CO2 at which rate of assimilation began to decline depended on the environmental conditions. At 19 mbar partial pressure of O2 the decline occurred at CO2 partial pressure >390 �bar. At 200 mbar partial pressure of O2 it occurred at CO2 partial pressure > 534 �bar. O2 increased the CO2 partial pressure required for inhibition but it did not appear to affect the steepness of the decline of rate of assimilation with further increase in partial pressure of CO2 once the decline became apparent. The decline was more readily observed at low temperature and low O2 partial pressure, and in plants grown at low light and NO3- levels. It was also observed in cowpea and sunflower. Changes in quantum efficiency in cotton at high and low CO2 concentrations were observed. At ambient CO2 concentration (300 �bar), the quantum yields measured at 19 and 200 mbar partial pressure of O2 were 0.072 � 0.0003 and 0.053 � 0.0060 mol CO2 per mol absorbed quanta, respectively. In contrast, at 900 �bar CO2 partial pressure the respective values were 0.050 � 0.0023 and 0.070 � 0.0006 mol CO2 per mol absorbed quanta. The nature of the inhibition of CO2 assimilation by high partial pressure of CO2 is discussed.

Soil drying and its effect on leaf conductance and CO2 assimilation of Vigna unguiculata (L.) Walp

Oecologia ◽  
1988 ◽  
Vol 75 (1) ◽  
pp. 99-104 ◽  
Author(s):  
B. I. L. Küppers ◽  
M. Küppers ◽  
E. -D. Schulze
Keyword(s):  
Vigna Unguiculata ◽  
Co2 Assimilation ◽  
Leaf Conductance ◽  
Soil Drying

Quantitative trait locus mapping of the transpiration ratio related to preflowering drought tolerance in sorghum (Sorghum bicolor)

2014 ◽  
Vol 41 (11) ◽  
pp. 1049 ◽  
Author(s):  
Mohankumar H. Kapanigowda ◽  
William A. Payne ◽  
William L. Rooney ◽  
John E. Mullet ◽  
Maria Balota
Keyword(s):  
Sorghum Bicolor ◽  
Quantitative Trait ◽  
Agronomic Traits ◽  
Stomatal Density ◽  
Recombinant Inbred Lines ◽  
Vapour Pressure Deficit ◽  
Field Capacity ◽  
Co2 Assimilation ◽  
Mean Values ◽  
Trait Locus

To meet future food needs, grain production must increase despite reduced water availability, so waterproductivity must rise. One way to do this is to raise the ratio of biomass produced to water transpired, which is controlled by the ratio of CO2 assimilation (A) to transpiration (E) (i.e. the transpiration ratio, A : E divided by vapour pressure deficit) or anything affecting stomatal movement.. We describe the genetic variation and basis of A, E and A : E among 70 recombinant inbred lines (RILs) of sorghum (Sorghum bicolor (L.) Moench), using greenhouse experiments. Experiment 1 used 40% and 80% of field capacity (FC) as water regimes; Experiment 2 used 80% FC. Genotype had a significant effect on A, E and A : E. In Experiment 1, mean values for A : E were 1.2–4.4 mmol CO2 mol–1 H2O kPa–1 and 1.6–3.1 mmol CO2 mol–1 H2O kPa–1 under 40% and 80% FC, respectively. In Experiment 2, values were 5.6–9.8 mmol CO2 mol–1 H2O kPa–1. Pooled data for A : E and A : E VPD–1 from Experiment 1 indicate that A : E fell quickly at temperatures >32.3°C. A : E distributions were skewed. Mean heritabilities for A : E were 0.9 (40% FC) and 0.8 (80% FC). Three significant quantitative trait loci (QTLs) associated with A:E, two on SBI-09 and one on SBI-10, accounted for 17–21% of the phenotypic variation. Subsequent experiments identified 38 QTLs controlling variation in height, flowering, biomass, leaf area, greenness and stomatal density. Colocalisation of A : E QTLs with agronomic traits indicated that these QTLs can be used for improving sorghum performance through marker assisted selection (MAS) under preflowering drought stress.

scholarly journals Leaf Conductance in Relation to Rate of CO2 Assimilation

1985 ◽  
Vol 78 (4) ◽  
pp. 830-834 ◽  
Author(s):  
Suan-Chin Wong ◽  
Ian R. Cowan ◽  
Graham D. Farquhar
Keyword(s):  
Co2 Assimilation ◽  
Leaf Conductance

Diurnal and Developmental Changes in Canopy Gas Exchange in Relation to Growth in Transplanted and Direct-Seeded Flooded Rice

1990 ◽  
Vol 17 (2) ◽  
pp. 119 ◽  
Author(s):  
M Dingkuhn ◽  
HF Schnier ◽  
SKD Datta ◽  
E Wijangco ◽  
K Dorffling
Keyword(s):  
Vapour Pressure Deficit ◽  
Co2 Assimilation ◽  
Tiller Number ◽  
Planting Density ◽  
Dry Matter Accumulation ◽  
Light Saturation ◽  
Area Index ◽  
Flooded Rice ◽  
Transplanted Rice ◽  
Direct Seeded

Transplanted and direct-seeded flooded rice were compared in a field experiment using identical planting density and geometry. Leaf area index (LAI), plant dry weight, and tiller number were determined at 7-14 d intervals from seeding to maturity. Canopy CO2 and H2O exchange were measured using a mobile depletion-chamber system which requires 1-1.5 minutes per measurement. The canopy CO2 assimilation rates confirmed the plant dry matter accumulation observed. Diurnal measurements of net CO2 assimilation and night respiration indicated a mild midday/afternoon depression that depended on the atmospheric vapour pressure deficit (VPD). Light response of canopy CO2 assimilation exhibited light saturation at full daylight when LAI was lower than 1. No light saturation was observed at higher LAI. Transplanting shock in transplanted rice reduced net assimilation rates and delayed foliage expansion and tillering by 15 days. Crop development was retarded by 7 days. Uninhibited growth of direct-seeded rice during the vegetative stage led to superior biological yield and tiller number at maturity while grain yield was equal to that of transplanted rice. Potential yield increase in direct-seeded flooded rice is discussed on the basis of growth kinetics and assimilate source/sink relationships.

Carbon Dioxide Assimilation by Pineapple Plants, Ananas comosus (L.) Merr. II. Effects of Variation of the Day/Night Temperature Regime

1980 ◽  
Vol 7 (4) ◽  
pp. 375 ◽  
Author(s):  
TF Neales ◽  
PJM Sale ◽  
CP Meyer
Keyword(s):  
Temperature Regime ◽  
Co2 Assimilation ◽  
Leaf Conductance ◽  
Ananas Comosus ◽  
Co2 Efflux ◽  
Night Temperature ◽  
Cam Plants ◽  
Ambient Temperatures ◽  
Single Leaf ◽  
Enclosure Methods

The effects of variation of day/night temperature regime on the diurnal patterns of CO2 assimilation of pineapple plants were examined using single leaf and field enclosure methods. At day temperatures of 30°C, increasing night temperatures from 20 to 35°C reduced the total assimilation of CO2 per daily light/dark cycle from 6.5 to 1.3 g CO2 m-2 (leaf area) day-1, and also reduced the proportion of total CO2 assimilation that occurred at night from c. 90% to c. 40%. Decreasing day temperatures (30 to 10°C) had little effect on total daily CO2 assimilation in warm (25°C) nights, but reduced it in cooler (15°C) nights. At day temperatures of <152C, CO2 assimilation took place predominantly (60-100%) in the photoperiod. In cool (10°C) days, the normal inverted stomatal rhythm of CAM plants was reversed; leaf conductance was high (c. 1.0 mm s-1) throughout the photoperiod and a large CO2 efflux was observed, lasting c. 2 h, at the beginning of the dark period. Leaf conductance of pineapples, by day and by night, is strongly influenced by ambient temperatures, with cool conditions favouring stomatal opening.

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