scholarly journals Decreased-activity mutants of phosphoglucose isomerase in the cytosol and chloroplast of Clarkia xantiana. Impact on mass-action ratios and fluxes to sucrose and starch, and estimation of Flux Control Coefficients and Elasticity Coefficients

1989 ◽  
Vol 261 (2) ◽  
pp. 457-467 ◽  
Author(s):  
A L Kruckeberg ◽  
H E Neuhaus ◽  
R Feil ◽  
L D Gottlieb ◽  
M Stitt
Keyword(s):  
Light Intensity ◽  
Starch Synthesis ◽  
Phosphoglucose Isomerase ◽  
Wild Type ◽  
Low Light ◽  
Subcellular Compartment ◽  
Flux Control Coefficients ◽  
Substrate Ratio ◽  
Control Coefficients ◽  
Clarkia Xantiana

1. Subcellular-compartment-specific decreased-activity mutants of phosphoglucose isomerase in Clarkia xantiana were used to analyse the control of sucrose and starch synthesis during photosynthesis. Mutants were available in which the plastid phosphoglucose isomerase complement is decreased to 75% or 50% of the wild-type level, and the cytosol complement to 64%, 36% or 18% of the wild-type level. 2. The effects on the [product]/[substrate] ratio and on fluxes to sucrose or starch and the rate of photosynthesis were studied with the use of saturating or limiting light intensity to impose a high or low flux through these pathways. 3. Removal of a small fraction of either phosphoglucose isomerase leads to a significant shift of the [product]/[substrate] ratio away, from equilibrium. We conclude that there is no ‘excess’ of enzyme over that needed to maintain its reactants reasonably close to equilibrium. 4. Decreased phosphoglucose isomerase activity can also alter the fluxes to starch or sucrose. However, the effect on flux does not correlate with the extent of disequilibrium, and also varies depending on the subcellular compartment and on the conditions. 5. The results were used to estimate Flux Control Coefficients for the chloroplast and cytosolic phosphoglucose isomerases. The chloroplast isoenzyme exerts control on the rate of starch synthesis and on photosynthesis in saturating light intensity and CO2, but not at low light intensity. The cytosolic enzyme only exerts significant control when its complement is decreased 3-5-fold, and differs from the plastid isoenzyme in exerting more control in low light intensity. It has a positive Control Coefficient for sucrose synthesis, and a negative Control Coefficient for starch synthesis. 6. The Elasticity Coefficients in vivo of the cytosolic phosphoglucose isomerase were estimated to lie between 5 and 8 in the wild-type. They decrease in mutants with a lowered complement of cytosolic phosphoglucose isomerase. 7. The implications of these results for regulation and for evolution are discussed.

The Kok Effect and Its Relationship to Photorespiration in Tobacco

1981 ◽  
Vol 36 (5-6) ◽  
pp. 450-454
Author(s):  
Ryuichi Ishii ◽  
Georg H. Schmid
Keyword(s):  
Mass Spectrometry ◽  
Structural Change ◽  
Light Intensity ◽  
Dark Respiration ◽  
Hill Reaction ◽  
Wild Type ◽  
Intensity Curve ◽  
Low Light ◽  
In The Wild ◽  
The Hill

Abstract The Kok effect of photosynthesis was investigated in different tobacco mutants. It was found that the breaks in the light intensity curve were always at or around 1000 lux in all plants tested regardless of the unit sizes which differed by a factor of 10. It was concluded that the photo­ receptor responsible for the effect must be present in the wild type and the chlorophyll deficient mutants in the same amount and is probably not chlorophyll. Due to the fact that the light dependency of the Hill reaction in isolated tobacco chloroplasts also shows a break at or around the “Kok intensity” it was concluded that probably a structural change of the photochemical apparatus around 1000 lux contributes to the effect. Measurement of 180 2-uptake by mass spectrometry at low light intensity shows at low CO2-concentration an enhancement of 180 2-uptake again at/around 1000 lux indicating that photorespiration starts to function at the “Kok intensity”. Due to the fact that 180 2-uptake remains constant at high CO2-concentrations the break in the photosynthetic light intensity curve cannot be due to an inhibition of “dark respiration” at low light intensities.

Response of chlorina barley mutants to heat stress under low and high light

2003 ◽  
Vol 30 (5) ◽  
pp. 515 ◽  
Author(s):  
Katya Georgieva ◽  
Ivanka Fedina ◽  
Liliana Maslenkova ◽  
Violeta Peeva
Keyword(s):  
Heat Stress ◽  
Light Intensity ◽  
Photosynthetic Activity ◽  
High Light Intensity ◽  
High Light ◽  
O2 Evolution ◽  
Wild Type ◽  
Hordeum Vulgare L ◽  
Low Light ◽  
Low Light Intensity

Barley plants (Hordeum vulgare L.) of wild type and two chlorina mutants, chlorina 126 and chlorina f2, were subjected to 42°C for 5 h at light intensities of 100 and 1000 μmol photons m–2 s–1. The exposure of plants to heat stress at a light intensity of 100 μmol m–2 s–1 induced enormous proline accumulation, indicating that the effect of heat stress was stronger when it was combined with low light intensity. The functional activity of PSII, O2�evolution and flash-induced thermoluminescence B-band amplitude were strongly reduced when plants were exposed to heat at low light intensity. The results clearly showed that high light intensity had a protective effect on photosynthetic activity when barley plants were treated with high temperature. Comparison of the thermosensitivity of wild type plants and chlorina mutants revealed that O2 evolution in chlorina 126 and, especially, in chlorina f2 was more sensitive to heat than in wild type.

scholarly journals ACHT4-driven oxidation of APS1 attenuates starch synthesis under low light intensity in Arabidopsis plants

2015 ◽  
Vol 112 (41) ◽  
pp. 12876-12881 ◽  
Author(s):  
Erez Eliyahu ◽  
Ido Rog ◽  
Dangoor Inbal ◽  
Avihai Danon
Keyword(s):  
Light Intensity ◽  
Starch Content ◽  
Starch Synthesis ◽  
Feedback Regulation ◽  
Small Subunit ◽  
Control Mechanisms ◽  
In Planta ◽  
Low Light ◽  
Disulfide Exchange ◽  
C Terminus

The regulatory mechanisms that use signals of low levels of reactive oxygen species (ROS) could be obscured by ROS produced under stress and thus are better investigated under homeostatic conditions. Previous studies showed that the chloroplastic atypical thioredoxin ACHT1 is oxidized by 2-Cys peroxiredoxin (2-Cys Prx) in Arabidopsis plants illuminated with growth light and in turn transmits a disulfide-based signal via yet unknown target proteins in a feedback regulation of photosynthesis. Here, we studied the role of a second chloroplastic paralog, ACHT4, in plants subjected to low light conditions. Likewise, ACHT4 reacted in planta with 2-Cys Prx, indicating that it is oxidized by a similar disulfide exchange reaction. ACHT4 further reacted uniquely with the small subunit (APS1) of ADP-glucose pyrophosphorylase (AGPase), the first committed enzyme of the starch synthesis pathway, suggesting that it transfers the disulfides it receives from 2-Cys Prx to APS1 and turns off AGPase. In accordance, ACHT4 participated in an oxidative signal that quenched AGPase activity during the diurnal transition from day to night, and also in an attenuating oxidative signal of AGPase in a dynamic response to small fluctuations in light intensity during the day. Increasing the level of expressed ACHT4 or of ACHT4ΔC, a C terminus-deleted form that does not react with APS1, correspondingly decreased or increased the level of reduced APS1 and decreased or increased transitory starch content. These findings imply that oxidative control mechanisms act in concert with reductive signals to fine tune starch synthesis during daily homeostatic conditions.

Pendugaan Parameter Genetik Kedelai Generasi F4 pada Intensitas Cahaya Rendah

Agrotek ◽  
2018 ◽  
Vol 2 (3) ◽  
Author(s):  
Yohanis Amos Mustamu ◽  
Trikoesoemaningtyas Trikoesoemaningtyas ◽  
Desta Wirnas ◽  
Didy Sopandie ◽  
Darman M. Arsyad
Keyword(s):  
Light Intensity ◽  
Genetic Parameter ◽  
Design Experiment ◽  
Low Light ◽  
Experimental Field ◽  
High Heritability ◽  
Intensity Condition ◽  
Augmented Design ◽  
Genetic Coefficient ◽  
The University

The objective of this study was to collect information on genetic parameter and agronomy character of soybean F4 generation in the low light intensity condition. The parameter was tested to 130 lines F4 which are produced by Balai Besar Pengkajian dan Pengembangan Teknologi Pertanian (BBP2TP) Boor and the genotype of Sibayak, Tegal, Tanggamus, and Argomulyo were used as controls. The experiment was conducted in the university�s experimental field in Cikabayan, from September to December 2007. A total of 130 advance (F4) soybean lines were evaluated under shading in an augmented design experiment. The result of this study showed that all character has low genetic coefficient. The weight character of 25 grains has a considerably high heritability number in low li

scholarly journals Growth of Haematococcus pluvialis on a Small-Scale Angled Porous Substrate Photobioreactor for Green Stage Biomass

2021 ◽  
Vol 11 (4) ◽  
pp. 1788
Author(s):  
Thanh-Tri Do ◽  
Binh-Nguyen Ong ◽  
Tuan-Loc Le ◽  
Thanh-Cong Nguyen ◽  
Bich-Huy Tran-Thi ◽  
...  
Keyword(s):  
Light Intensity ◽  
Algal Biomass ◽  
Haematococcus Pluvialis ◽  
Biomass Productivity ◽  
Pilot Scale ◽  
Small Scale ◽  
Porous Substrate ◽  
Low Light ◽  
Green Algal ◽  
Green Stage

In the production of astaxanthin from Haematococcus pluvialis, the process of growing algal biomass in the vegetative green stage is an indispensable step in both suspended and immobilized cultivations. The green algal biomass is usually cultured in a suspension under a low light intensity. However, for astaxanthin accumulation, the microalgae need to be centrifuged and transferred to a new medium or culture system, a significant difficulty when upscaling astaxanthin production. In this research, a small-scale angled twin-layer porous substrate photobioreactor (TL-PSBR) was used to cultivate green stage biomass of H. pluvialis. Under low light intensities of 20–80 µmol photons m−2·s−1, algae in the biofilm consisted exclusively of non-motile vegetative cells (green palmella cells) after ten days of culturing. The optimal initial biomass density was 6.5 g·m−2, and the dry biomass productivity at a light intensity of 80 µmol photons m−2·s−1 was 6.5 g·m−2·d−1. The green stage biomass of H. pluvialis created in this small-scale angled TL-PSBR can be easily harvested and directly used as the source of material for the inoculation of a pilot-scale TL-PSBR for the production of astaxanthin.

Transfer of photosynthetically fixed carbon between the prokaryotic green alga Prochloron and its ascidian host

1983 ◽  
Vol 34 (3) ◽  
pp. 431 ◽  
Author(s):  
DJ Griffiths ◽  
L Thinh
Keyword(s):  
Light Intensity ◽  
Green Alga ◽  
Host Tissue ◽  
Total Carbon ◽  
Symbiotic Association ◽  
Fixed Carbon ◽  
Low Light ◽  
Ascidian Species ◽  
Dark Fixation ◽  
Efficient Transfer

In the symbiotic association between the prokaryotic green alga Prochloron and three didemnid host species (Diplosoma similis, Lissoclinum bistratum, Trididemnum cyclops), between 6 and 51 % of the total carbon fixed during exposure for 1 h to H14CO3- in the light (150 �E m-2 s-1) becomes associated with the host tissue. Dark fixation of 14CO2 in these ascidian species and in Lissoclinum punctatum never exceeds 6% of photosynthetic fixation at saturating light intensity. The corresponding values for dark fixation of 14CO2 in isolated Prochloron cells fall within the same range. There is very little excretion of photosynthate from whole colonies of the above ascidian species nor from Didemnum molle, Lissoclinum voeltzkowi and Trididemnum miniatum (usually less than 1 % of total photosynthate at saturation light intensity), suggesting an efficient transfer mechanism from Prochloron to host. Evidence from pulse-chase experiments suggests that transfer probably involves the early products of photosynthesis. The extent of transfer of photosynthate between Prochloron and T. cyclops varies with the rate of photosynthetic 14CO2 fixation into the whole colony but there is some transfer even at low light intensities, which strongly limit photosynthesis.

scholarly journals Response of Photosynthesis and Chlorophyll Fluorescence Parameters of Castanopsis kawakamii Seedlings to Forest Gaps

Forests ◽  
2019 ◽  
Vol 11 (1) ◽  
pp. 21
Author(s):  
Zhong-sheng He ◽  
Rong Tang ◽  
Meng-jia Li ◽  
Meng-ran Jin ◽  
Cong Xin ◽  
...  
Keyword(s):  
Chlorophyll Fluorescence ◽  
Light Intensity ◽  
Seedling Growth ◽  
Group Treatment ◽  
Control Group ◽  
Low Light ◽  
Chlorophyll Fluorescence Parameters ◽  
Forest Gaps ◽  
Low Light Intensity ◽  
Weak Light

Light is a major environmental factor limiting the growth and survival of plants. The heterogeneity of the light environment after gap formation in forest influences the leaf chlorophyll contents, net photosynthetic rate (Pn), and chlorophyll fluorescence, thus influencing the growth and regeneration of Castanopsis kawakamii seedlings. The aim of this study was to explore the effects of weak light on the photosynthetic physiology of C. kawakamii seedlings in forest gaps and non-gaps. The results showed that (1) the contents of chlorophyll a (Chl-a), chlorophyll b (Chl-b), and total chlorophyll (Chl-T) in forest gaps were lower than in non-gaps. Seedlings tended to increase chlorophyll content to absorb light energy to adapt to low light intensity in non-gap environments. (2) The Pn values of C. kawakamii seedlings in forest gaps were significantly higher than in non-gaps, and forest gaps could improve the seedlings’ photosynthetic capacity. (3) The C. kawakamii seedlings in forest gaps were more sensitive to weak light and control group treatment, especially the tall seedlings, indicating that seedlings require more light to satisfy their growth needs in the winter. The seedlings in non-gaps demonstrated better adaptability to low light intensity. The light intensity was not adequate in weak light conditions and limited seedling growth. We suggest that partial forest selection cutting could improve light intensity in non-gaps, thus promoting seedling growth and regeneration of C. kawakamii more effectively in this forest.

A laboratory study of vertical migration

1955 ◽  
Vol 144 (916) ◽  
pp. 329-354 ◽  
Keyword(s):  
Light Intensity ◽  
Vertical Migration ◽  
Time Course ◽  
Tap Water ◽  
Low Light ◽  
Overhead Light ◽  
Light Intensities ◽  
Orientation Response ◽  
Reduced Light ◽  
Characteristic Maximum

In a tank filled with a suspension of indian ink in tap water, a population of Daphnia magna will undergo a complete cycle of vertical migration when an overhead light source is cycli­cally varied in intensity. A ‘dawn rise’ to the surface at low intensity is followed by the descent of the animals to a characteristic maximum depth. The animals rise to the surface again as the light decreases, and finally show a typical midnight sinking. The light intensities at the level of the animals in this experiment are of the same order as those which have been reported in field observations; the time course of the movement also repeats the natural conditions in the field. The process is independent of the duration of the cycle and is related only to the variation in overhead light intensity. At low light intensity the movement of the animal is determined solely by positive photo-kinesis; the dawn rise is a manifestation of this, and is independent of the direction of the light. At high light intensities there is an orientation response which is superimposed upon an alternating positive (photokinetic) phase and a negative phase during which movement is inhibited. The fully oriented animal shows a special type of positive and negative phototaxis, moving towards the light at reduced light intensities and away from it when the light intensity is increased. In this condition it follows a zone of optimum light intensity with some exactness. Experiments show that an animal in this fully oriented condition will respond to the slow changes of intensity characteristic of the diurnal cycle, while being little affected by tran­sient changes of considerable magnitude.

Extracellular carbohydrate liberation in the flagellates Isochrysis galbana and Prymnesium parvum

1965 ◽  
Vol 45 (3) ◽  
pp. 755-772 ◽  
Author(s):  
A. F. H. Marker
Keyword(s):  
Organic Matter ◽  
Light Intensity ◽  
Nitrogen Starvation ◽  
Axenic Culture ◽  
Isochrysis Galbana ◽  
Prymnesium Parvum ◽  
Extracellular Production ◽  
Low Light ◽  
Passive Release ◽  
Dying Cells

The production of extracellular carbohydrate has been studied in Isochrysis galbana and Prymnesium parvum in axenic culture. Increased extracellular production of carbohydrate occurred at reduced and increased salinity, low light intensity and under conditions of nitrogen starvation in Isochrysis, and in some cases appeared to be associated with the sedimentation of the cells from stagnant culture. Extracellular carbohydrate production was found to be greatest during the early and later stages in growth and dropped to a minimum during the mid-growth phase. Experiments indicated that the cells were not being damaged during harvesting of the cultures. A close similarity was found between the monosaccharide components of the intra- and extracellular carbohydrate after acid hydrolysis; both contained glucose, galactose, arabinose, xylose and ribose. It is suggested that the production of most of the extracellular carbohydrate is due to the passive release of organic matter from dead or dying cells.

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