scholarly journals Cytochrome c is reduced mainly by plastoquinol and not by superoxide in thylakoid membranes at low and medium light intensities: its specific interaction with thylakoid membrane lipids

2003 ◽  
Vol 375 (1) ◽  
pp. 215-220 ◽  
Author(s):  
Jerzy KRUK ◽  
Małgorzata JEMIOŁA-RZEMIŃSKA ◽  
Kazimierz STRZAŁKA
Keyword(s):  
Superoxide Dismutase ◽  
Cytochrome C ◽  
Light Intensity ◽  
Thylakoid Membrane ◽  
Membrane Lipids ◽  
Specific Interaction ◽  
Thylakoid Membranes ◽  
Superoxide Production ◽  
Low Light ◽  
Cyt C

We have found that, at low light intensity (5–10 μmol photons·m−2·s−1), photoreduction of cyt (cytochrome) c by isolated thylakoids was not inhibited by dinitrophenylether of iodonitrothymol, an inhibitor of the cyt b6–f complex, and the inhibition was only partial at medium light intensity (50–200 μmol photons·m−2·s−1). The photoreduction was not significantly influenced by superoxide dismutase. The conclusion that cyt c could be reduced directly by the plastoquinone pool was confirmed by the observation that plastoquinol-9 reduced cyt c efficiently when it was incorporated into liposome membranes prepared from thylakoid membrane lipids. It was shown that the cyt is specifically bound to thylakoid lipid liposomes owing to the presence of negatively charged lipids, phosphatidylglycerol and sulphoquinovosyldiacylglycerol, and the reduction was stimulated by the presence of monogalactosyldiacylglycerol, an inverted micelles-forming lipid, in the membranes, where the cyt c reduction by plastoquinol probably takes place. The results obtained are also discussed in terms of reliability of the method of cyt c photoreduction for determining superoxide production by illuminated thylakoids.

Superoxide, Xanthine Oxidase and Platelet Reactions: Further Studies on Mechanisms by which Oxidants Influence Platelets

1981 ◽  
Vol 45 (03) ◽  
pp. 290-293 ◽  
Author(s):  
Peter H Levine ◽  
Danielle G Sladdin ◽  
Norman I Krinsky
Keyword(s):  
Superoxide Dismutase ◽  
Cytochrome C ◽  
Xanthine Oxidase ◽  
Direct Effect ◽  
Platelet Function ◽  
Experimental Conditions ◽  
Release Reaction

SummaryIn the course of studying the effects on platelets of the oxidant species superoxide (O- 2), Of was generated by the interaction of xanthine oxidase plus xanthine. Surprisingly, gel-filtered platelets, when exposed to xanthine oxidase in the absence of xanthine substrate, were found to generate superoxide (O- 2), as determined by the reduction of added cytochrome c and by the inhibition of this reduction in the presence of superoxide dismutase.In addition to generating Of, the xanthine oxidase-treated platelets display both aggregation and evidence of the release reaction. This xanthine oxidase induced aggreagtion is not inhibited by the addition of either superoxide dismutase or cytochrome c, suggesting that it is due to either a further metabolite of O- 2, or that O- 2 itself exerts no important direct effect on platelet function under these experimental conditions. The ability of Of to modulate platelet reactions in vivo or in vitro remains in doubt, and xanthine oxidase is an unsuitable source of O- 2 in platelet studies because of its own effects on platelets.

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 The transit sequence mediates the specific interaction of the precursor of ferredoxin with chloroplast envelope membrane lipids.

1993 ◽  
Vol 268 (6) ◽  
pp. 4037-4042
Author(s):  
R. van't Hof ◽  
W. van Klompenburg ◽  
M. Pilon ◽  
A. Kozubek ◽  
G. de Korte-Kool ◽  
...  
Keyword(s):  
Membrane Lipids ◽  
Specific Interaction ◽  
Chloroplast Envelope ◽  
Envelope Membrane ◽  
Chloroplast Envelope Membrane

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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