Model systems for photosynthesis. VII. Chlorophyll a photosensitized reduction of methyl viologen by hydroquinones

1980 ◽  
Vol 373 (1753) ◽  
pp. 179-187 ◽  
Keyword(s):  
Ascorbic Acid ◽  
Chlorophyll A ◽  
Photosystem I ◽  
Methyl Viologen ◽  
Empirical Relation ◽  
Electron Donors ◽  
Model Systems ◽  
Cyclic Process ◽  
Subsequent Reaction ◽  
Permanent Storage

The use of hydroquinones as electron donors for in vitro models of Photosystem I has been investigated. Excited chlorophyll a (Chi*) was first reacted with methyl viologen (MV 2+ ) to give ChI + and MV t . The subsequent reaction of ChI t with hydroquinones was slower than the comparable reaction with alternative electron donors such as cysteine or ascorbic acid, and an empirical relation was observed between the redox potential of the hydroquinone and the rate constant for its reaction with ChI t . This sequence of reactions stores 40 % of the energy available in the chlorophyll a triplet state, but no permanent storage of energy was achieved since MV t back-reacts with quinone to give a cyclic process.

Identification of a single-copy gene encoding a Type I chlorophyll a/b-binding polypeptide of photosystem I in Arabidopsis thaliana

1992 ◽  
Vol 84 (4) ◽  
pp. 561-567 ◽  
Author(s):  
Poul E. Jensen ◽  
Michael Kristensen ◽  
Tine Hoff ◽  
Jan Lehmbeck ◽  
Bjarne M. Stummann ◽  
...  
Keyword(s):  
Arabidopsis Thaliana ◽  
Chlorophyll A ◽  
Photosystem I ◽  
Single Copy ◽  
Type I ◽  
Single Copy Gene ◽  
Gene Encoding ◽  
Copy Gene

ChemInform Abstract: PHOTOPROCESSES IN PHOTOSYSTEM I MODEL SYSTEMS

1984 ◽  
Vol 15 (31) ◽  
Author(s):  
J. E. HUNT ◽  
J. J. KATZ ◽  
A. SVIRMICKAS ◽  
J. C. HINDMAN
Keyword(s):  
Photosystem I ◽  
Model Systems

Solubility of Iron in Model Systems Containing Organic Acids and Lignin

1992 ◽  
Vol 55 (11) ◽  
pp. 893-898 ◽  
Author(s):  
TAKESHI SUZUKI ◽  
FERGUS M. CLYDESDALE ◽  
TIRA PANDOLF
Keyword(s):  
Ascorbic Acid ◽  
Organic Acids ◽  
Model Systems ◽  
Molar Ratio ◽  
Soluble Form ◽  
Enhancing Effect ◽  
Gastrointestinal Ph ◽  
Soluble Iron ◽  
Ph Values ◽  
Ph Conditions

The effect of six organic acids, ascorbic, citric, fumaric, lactic, malic, and succinic, alone and in combination, at a 1:1.9 molar ratio (Fe+2:ligand) on the solubility of iron was evaluated in the presence of lignin under simulated gastrointestinal pH conditions. The enhancing effect, evaluated under two systems of preparation at two pH values, was in the following order: citric>malic>ascorbic>lactic,fumaric>succinic. Citric acid solubilized 80 and 81% of iron under both pH conditions. When ascorbic acid was mixed with fumaric, lactic, and succinic acids, a higher percentage of soluble iron was retained than with these three acids alone. In the case of citric and malic acids, the addition of ascorbic acid reduced the soluble iron. The percentage of soluble iron obtained when prepared at the endogenous pH (2.5–3.1) was higher than that at pH 5.5. These results indicated that ascorbate bound less iron in a soluble form than citrate or malate but more than fumarate, lactate, or succinate. Also, combinations of citric with malic acid did not demonstrate a synergistic effect.

scholarly journals Radish (Raphanus sativus L.) morphophysiology under salinity stress and ascorbic acid treatments

2018 ◽  
Vol 36 (3) ◽  
pp. 257-265
Author(s):  
Ana Gabriela de Sousa Basílio ◽  
Leonardo Vieira De Sousa ◽  
Toshik Iarley Da Silva ◽  
Joana Gomes De Moura ◽  
Anderson Carlos de Melo Gonçalves ◽  
...  
Keyword(s):  
Ascorbic Acid ◽  
Chlorophyll A ◽  
Irrigation Water ◽  
Raphanus Sativus ◽  
Saline Water ◽  
Block Design ◽  
Total Content ◽  
Shoot Height ◽  
Fluorescence Maximum ◽  
Raphanus Sativus L

The use of saline or low-quality water in agriculture is an alternative to increasing water demand, especially in arid or semi-arid regions. However, the use of water with high levels of salts causes disturbances in plants, which can lead to their death; thus, alternatives to mitigate these effects are relevant in current agriculture. Currently, antioxidants are used to mitigate the effects of salts in plants, and among them ascorbic acid has been frequently mentioned. Therefore, the aim of this study was to evaluate the effect of irrigation with saline water combined with applications of ascorbic acid on the development and photosynthetic activity of radish (Raphanus sativus L.) plants. This experiment was carried out in a greenhouse with a randomized block design, with the treatments distributed in a 5.5 incomplete factorial scheme, composed of five electrical conductivities of the irrigation water (ECw): 0.50, 1.30, 3.25, 5.20 and 6.00 dS m-1, and five ascorbic acid (AA) doses: 0.00, 0.29, 1.00, 1.71, and 2.00 mM. The evaluated variables were: shoot height, leaf number, tuberous root diameter, chlorophyll a, b and total content, chlorophyll a/b ratio, initial fluorescence, maximum fluorescence, variable fluorescence and quantum yield of photosystem II. The saline water influenced the analyzed variables in the radish crop regardless of the ascorbic acid application. The ascorbic acid was not efficient in attenuating the deleterious effect of salinity in the irrigation water on the development and fluorescence of the radish. However, it was observed that the concentration of 1.00 mM of ascorbic acid promoted an increase in chlorophyll a, b and total in the saltstressed radish plants.

Paths of deactivation of excitation of chlorophyll a in various model systems

1994 ◽  
Author(s):  
Danuta Frackowiak ◽  
Bogumil Zelent ◽  
Henryk M. Malak ◽  
Roman Cegielski ◽  
Alfons Planner ◽  
...  
Keyword(s):  
Chlorophyll A ◽  
Model Systems
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