Pathways of CO2 Fixation in the CAM Plant Kalanchoe daigremontiana. I Patterns of 14CO2 Fixation in the Light

1974 ◽  
Vol 1 (4) ◽  
pp. 503 ◽  
Author(s):  
CB Osmond ◽  
WG Allaway
Keyword(s):  
Steady State ◽  
Co2 Fixation ◽  
Growth Conditions ◽  
Light Period ◽  
C3 Plant ◽  
Initial Burst ◽  
14Co2 Fixation ◽  
C4 Species ◽  
Dark Fixation ◽  
Night Period

Leaves of K. daigremontiana from plants grown under controlled conditions were exposed to 14CO2 in the light for 15 s followed by a chase in 12CO2. During steady-state photosynthesis in the late light period the pulsechase labelling of photosynthetic intermediates was very similar to that observed in the C3 plant Atriplex patula subsp. hastata. Labelling of C4 acids and the distribution of 14C within [14C]malate isolated from leaves of K. daigremontiana in these experiments suggest that these acids arise by a secondary carboxylation of labelled phosphoenolpyruvate. During the initial burst of photosynthesis following the night period, pulse-chase labelling of photosynthetic intermediates was quite similar to that observed in A. spongiosa, a C4 species. Degradation of labelled malate suggests that the C4 acids are formed largely by the primary carboxylation of phosphoenolpyruvate during the initial burst of photosynthesis and that these intermediates mix with the pool of malate formed in previous dark fixation. Growth conditions which substantially alter the proportion of CO2 fixed during the clay and night did not alter the pulse-chase behaviour of photosynthetic intermediates.

Light-Enhanced Dark 14CO2 Fixation by Leaves in Relation to the C4 Dicarboxylic Acid Pathway of Photosynthesis

1977 ◽  
Vol 4 (5) ◽  
pp. 833 ◽  
Author(s):  
AS Raghavendra ◽  
VSR Das
Keyword(s):  
Carbon Fixation ◽  
C4 Plants ◽  
C3 Plant ◽  
14Co2 Fixation ◽  
Detached Leaves ◽  
Dark Fixation ◽  
Primary Acceptor ◽  
Sugar Phosphates ◽  
Amaranthus Paniculatus ◽  
Acid Pathway

The technique of light-enhanced dark carbon dioxide fixation has been employed to critically examine the primary route of CO2 incorporation in leaves of two C4 plants (Setaria italica and Amaranthus paniculatus) in comparison with that of a C3 plant (Rumex vesicarius). Prior illumination of detached leaves enhanced their dark 14CO2 fixation five- to tenfold over that of unilluminated leaves. No variation was observed among C3 and C4 plants, in the conditions required for their light-enhanced dark fixation. Fifty to sixty percent of initially incorporated radioactivity by the leaves of R. vesicarius was in 3-phosphoglycerate. The leaves of S. italica and A. paniculatus fixed most of the radioactivity into the C4 acids malate and aspartate. Sugar phosphates, including 3-phosphoglycerate, were not labelled at all. Our data confirm that, in C4 plants, CO2 is initially fixed through phosphoenolpyruvate carboxylation and thus disprove earlier claims that ribulose bisphosphate can be the primary acceptor of CO2 in a C4 plant. The observations further suggested that aspartate formation during carbon fixation might be favoured by illumination.

Effect of Oxygen and carbon Diozide Concentrations on Gross Dark CO2 Fixation and Dark Respiration in Bryophyllim diagremontiaum

1977 ◽  
Vol 4 (5) ◽  
pp. 745
Author(s):  
A Kaplan ◽  
J Gale ◽  
A Poljakoff-Mayber
Keyword(s):  
Time Course ◽  
Co2 Fixation ◽  
Dark Period ◽  
Dark Respiration ◽  
Principal Component ◽  
Light Period ◽  
Co2 Uptake ◽  
Dark Fixation ◽  
Effect Of Oxygen ◽  
Dark Co2 Fixation

Effects of O2 and CO2 concentrations on the rates of net and gross dark CO2 fixation in B. daigremontianum were examined. Raising [CO2]i from 60 to 420 �ll-� resulted in a decrease in the rate of dark respiration, increase in the rate of gross dark fixation (GDF) and shortened the time taken to reach maximum rate of GDF. However, cumulative GDF was relatively unaffected by [CO2]i at that range. At 14�C, lowering [O2] from 21 to 1.5 % had little effect on the rates and time course of dark respiration and GDF. However, at 24�C, this caused a drop in the rate of dark respiration, changed the time dependence of GDF and slightly increased cumulative GDF. Consequently, at 24�C cumulative net CO2 uptake was 3 .3 times higher at 1 .5 % versus 21% O2. These data are discussed in view of the suggested hypothesis that the amount of available substrate, at the end of the light period, is a principal component of the regulation of the amount of gross dark fixation and dark respiration in the following dark period.

Endogenous Tachykinin Release Contributes to the Locomotor Activity in Lamprey

2007 ◽  
Vol 97 (5) ◽  
pp. 3331-3339 ◽  
Author(s):  
Carolina Thörn Pérez ◽  
Russell H. Hill ◽  
Sten Grillner
Keyword(s):  
Spinal Cord ◽  
Steady State ◽  
Locomotor Activity ◽  
Initial Period ◽  
Burst Frequency ◽  
Ongoing Activity ◽  
Initial Burst ◽  
Tachykinin Receptor ◽  
Spinal Network ◽  
Endogenous Release

Tachykinins are present in lamprey spinal cord. The goal of this study was to investigate whether an endogenous release of tachykinins contributes to the activity of the spinal network generating locomotor activity. The locomotor network of the isolated lamprey spinal cord was activated by bath-applied N-methyl-d-aspartate (NMDA) and the efferent activity recorded from the ventral roots. When spantide II, a tachykinin receptor antagonist, was bath-applied after reaching a steady-state burst frequency (>2 h), it significantly lowered the burst rate compared with control pieces from the same animal. In addition, the time to reach the steady-state burst frequency (>2 h) was lengthened in spantide II. These data indicate that an endogenous tachykinin release contributes to the ongoing activity of the locomotor network by modulating the glutamate–glycine neuronal network responsible for the locomotor pattern. We also explored the effects of a 10-min exogenous application of substance P (1 μM), a tachykinin, and showed that its effect on the burst rate depended on the initial NMDA induced burst frequency. At low initial burst rates (∼0.5 Hz), tachykinins caused a marked further slowing to 0.1 Hz, whereas at higher initial burst rates, it instead caused an enhanced burst rate as previously reported, and in addition, a slower modulation (0.1 Hz) of the amplitude of the motor activity. These effects occurred during an initial period of ∼1 h, whereas a modest long-lasting increase of the burst rate remained after >2 h.

Effects of preillumination with light of different wavelengths on subsequent dark CO2-fixation in Chlorella cells

1970 ◽  
Vol 48 (6) ◽  
pp. 1203-1207 ◽  
Author(s):  
Shigetoh Miyachi ◽  
Daisuke Hogetsu
Keyword(s):  
Blue Light ◽  
Co2 Fixation ◽  
Red Light ◽  
Anaerobic Conditions ◽  
Nitrogen Gas ◽  
Pep Carboxylase ◽  
Radioactive Carbon ◽  
Initial Fixation ◽  
Dark Fixation ◽  
Dark Co2 Fixation

The effects of preillumination with monochromatic red or blue light on the subsequent dark 14CO2-fixation in Chlorella cells were studied under aerobic as well as anaerobic conditions. When the cell suspension was made aerobic by bubbling air (CO2-free) throughout the periods of preillumination and the following dark 14CO2-fixation, the initial fixation product was mainly PGA. The radioactive carbon first incorporated in PGA was transferred mostly to aspartate during the later periods of dark 14CO2-fixation. The rate of 14C-incorporation into aspartate after preillumination with blue light was 2 to 3 times as high as that observed after red-light pretreatment. The observations support our previous inference that the activity of PEP carboxylase in Chlorella cells is stimulated by preillumination with blue light. When nitrogen gas was used during preillumination and the subsequent dark fixation, the radioactivity of 14C incorporated during the initial enhanced 14CO2-fixation was eventually transferred to alanine and lactate. The increase in radioactivity of alanine and lactate was more pronounced during dark fixation after preillumination with red light than after preillumination with blue light.

scholarly journals Quantifying the propagation of parametric uncertainty on flux balance analysis

2021 ◽  
Author(s):  
Hoang V Dinh ◽  
Debolina Sarkar ◽  
Costas D Maranas
Keyword(s):  
Steady State ◽  
Flux Balance Analysis ◽  
Parametric Uncertainty ◽  
Growth Conditions ◽  
Flux Balance ◽  
First Case ◽  
Genetic Perturbations ◽  
Balance Analysis ◽  
Cellular Phenotypes ◽  
The Impact

Flux balance analysis (FBA) and associated techniques operating on stoichiometric genome-scale metabolic models play a central role in quantifying metabolic flows and constraining feasible phenotypes. At the heart of these methods lie two important assumptions: (i) the biomass precursors and energy requirements neither change in response to growth conditions nor environmental/genetic perturbations, and (ii) metabolite production and consumption rates are equal at all times (i.e., steady-state). Despite the stringency of these two assumptions, FBA has been shown to be surprisingly robust at predicting cellular phenotypes. In this paper, we formally assess the impact of these two assumptions on FBA results by quantifying how uncertainty in biomass reaction coefficients, and departures from steady-state due to temporal fluctuations could propagate to FBA results. In the first case, conditional sampling of parameter space is required to re-weigh the biomass reaction so as the molecular weight remains equal to 1 g/mmol, and in the second case, metabolite (and elemental) pool conservation must be imposed under temporally varying conditions. Results confirm the importance of enforcing the aforementioned constraints and explain the robustness of FBA biomass yield predictions.

scholarly journals Characterization of the Bradyrhizobium japonicum ftsH Gene and Its Product

1999 ◽  
Vol 181 (23) ◽  
pp. 7394-7397 ◽  
Author(s):  
Franz Narberhaus ◽  
Carmen Urech ◽  
Hauke Hennecke
Keyword(s):  
Escherichia Coli ◽  
Steady State ◽  
Western Blot ◽  
Bradyrhizobium Japonicum ◽  
State Level ◽  
Growth Conditions ◽  
Cellular Function ◽  
Steady State Level

ABSTRACT The Bradyrhizobium japonicum ftsH gene was cloned by using a set of widely applicable degenerated oligonucleotides. Western blot experiments indicated that the FtsH protein was produced under standard growth conditions and that it was not heat inducible. Attempts to delete the ftsH gene in B. japonicum failed, suggesting a pivotal cellular function of this gene. The expression ofB. japonicum ftsH in an ftsH-negativeEscherichia coli strain significantly enhanced the fitness of this mutant and reduced the steady-state level of ς32.

Observations on the Hydrolysis of p-Nitrophenyl Acylates by Purified Bovine Thrombin

1973 ◽  
Vol 30 (02) ◽  
pp. 248-254 ◽  
Author(s):  
Roger L. Lundblad
Keyword(s):  
Steady State ◽  
Time Course ◽  
Phenylmethylsulfonyl Fluoride ◽  
Bovine Thrombin ◽  
Initial Burst ◽  
Reaction Proceeds ◽  
Hydrolysis Of ◽  
Enzyme Intermediate ◽  
Acetate Derivative

SummaryThe ability of purified bovine thrombin to catalyze the hydrolysis of p-nitrophenyl acetate and p-nitrophenyl butyrate has been studied. The butyrate derivative appears to be hydrolyzed more rapidly than the acetate derivative. An examination of the time course of hydrolysis of these compounds by thrombin shows an initial ‘‘burst” reaction followed by a slower ‘‘steady-state” reaction. The hydrolysis of p-nitrophenyl acylates by thrombin is inhibited by the presence of benzamidine as well as by prior reaction of thrombin with phenylmethylsulfonyl fluoride. It is suggested that bovine thrombin catalyzes the hydrolysis of p-nitrophenyl acylates and that the reaction proceeds via the formation of an acyl-enzyme intermediate.

scholarly journals Variations through the day of hepatic and muscular cathepsin A (carboxypeptidase A; EC 3.4.12.2), C (dipeptidyl peptidase; EC 3.4.14.1) and D (endopeptidase D; EC 3.4.23.5) activities and fee amino acids of blood in rats: influence of feeding schedule

1980 ◽  
Vol 44 (1) ◽  
pp. 61-69 ◽  
Author(s):  
Christiane Obled M. Arnal ◽  
C. Valin
Keyword(s):  
Amino Acids ◽  
Essential Amino Acids ◽  
Dipeptidyl Peptidase ◽  
Maximum Activity ◽  
Light Period ◽  
Feeding Schedule ◽  
Carboxypeptidase A ◽  
Growing Rats ◽  
Meal Feeding ◽  
Night Period

1. Growing rats were fed either ad lib. or with six (equal) meals offered every 4 h (form 10.00 hours). Rats of each group were killed at intervals of 4 h begining at 11.00 hours. Activities of cathepsin A (carboxy-peptidase A; EC 3.4. 12. 2), C (dipeptidyl peptidase; EC 3.4.14.1) and D (endopeptidase D EC 3.4.23.5) were measured in liver and muscle homogenates and free amino acids in blood were determined.2. In the rats fed ad lib. activities of carboxypeptidase A and endopeptidase D in liber and muscle showed significant variation, with maximum activity in the light period. In general, meal-feeding only caused minor differences in cathepsin activities; although significant differences occurred for carboxypeptidase A. For the latter enzyme a peak in activity occurred in the dark as well as in the light period.3. Irrespective of the feeding schedule, the lower concentration of free essential amino acids of blood occurred generally during the night period. With the controlled-feeding schedule there is an increase of essential amino acids and a slight decrease of non-essential amino acids of blood.

Photosynthetic Mechanisms of Weeds in Taiwan

1993 ◽  
Vol 20 (6) ◽  
pp. 757 ◽  
Author(s):  
CH Lin ◽  
YS Tai ◽  
DJ Liu ◽  
MSB Ku
Keyword(s):  
Malic Enzyme ◽  
Co2 Fixation ◽  
C4 Photosynthesis ◽  
C3 Plants ◽  
C4 Species ◽  
On This Island ◽  
High Precipitation ◽  
Biochemical Analyses ◽  
Pep Carboxykinase ◽  
First Time

One hundred and one species (in 36 families) of weeds on cultivated land in Taiwan were investigated for the occurrence of Kranz leaf anatomy and activities of key enzymes of C4 photosynthesis to determine their photosynthetic mechanisms. Based on the anatomical and biochemical analyses, 75 species were found to possess the C3 and 26 species the C4 pathway of photosynthetic CO2 fixation. Among the 26 C4 species, 15 species are in Gramineae, 6 in Cyperaceae, 2 each in Euphorbiaceae and Amaranthaceae, and 1 in Portulacaceae. Two C4 species in the Gramineae, namely Digitaria radicosa (Presl) Miq. and Sporobolus fertilis (Steud.) Clayton, were recorded as C4 plants for the first time. The biochemical subdivisions of these C4 weeds were also determined. As in the natural C4 populations, the NADP-malic enzyme subtype of C4 photosynthesis dominates the list of C4 weeds on this island (62%), while the PEP carboxykinase subtype is relatively rare (12%). NAD-malic enzyme subtype has an intermediate representation (26%). The high proportion of weeds in Taiwan being C3 plants is noteworthy, and it may be accounted for by the high precipitation in this subtropical island.

Optimal structure and development of uneven-aged Norway spruce forests

2011 ◽  
Vol 41 (12) ◽  
pp. 2389-2402 ◽  
Author(s):  
Olli Tahvonen
Keyword(s):  
Steady State ◽  
Interest Rate ◽  
Norway Spruce ◽  
Large Scale ◽  
Size Structure ◽  
Basal Area ◽  
Growth Conditions ◽  
Optimal Harvesting ◽  
Tree Model ◽  
Individual Tree

Optimal harvesting of Norway spruce ( Picea abies (L.) Karst.) forests is studied applying an individual-tree model for uneven-aged management. Optimization is carried out by gradient-based, large-scale interior point methods. Assuming volume maximization and natural regeneration, it is optimal to apply uneven-aged management. Under artificial regeneration, the result is the reverse. Economically optimal solutions with a 20-year harvesting interval produce an annual sawn timber output of 4.4–2.4 m3·ha–1 depending on thermal zone and interest rate. Before harvest basal area varies between 18 and 12 m2·ha–1 and the diameter of harvested trees between 15 and 33 cm. In contrast with the classic inverted J-structure, optimal steady-state size structure resembles a serrate form. Profitability of even- and uneven-aged management is compared assuming that the initial stand state represents an optimal uneven-aged steady state. A switch to even-aged management is optimal given the most favorable growth conditions and interest rate below 1%–2%. In other cases, it is economically optimal to continue uneven-aged management although volume output remains lower than under even-aged management.

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