Search results for "photorespiration"
showing 10 items of 17 documents
The Water to Water Cycles in Microalgae.
2016
In oxygenic photosynthesis, light produces ATP plus NADPH via linear electron transfer, i.e. the in-series activity of the two photosystems: PSI and PSII. This process, however, is thought not to be sufficient to provide enough ATP per NADPH for carbon assimilation in the Calvin-Benson-Bassham cycle. Thus, it is assumed that additional ATP can be generated by alternative electron pathways. These circuits produce an electrochemical proton gradient without NADPH synthesis, and, although they often represent a small proportion of the linear electron flow, they could have a huge importance in optimizing CO2 assimilation. In Viridiplantae, there is a consensus that alternative electron flow comp…
The phosphorylated pathway of serine biosynthesis links plant growth with nitrogen metabolism
2021
Abstract Because it is the precursor for various essential cellular components, the amino acid serine is indispensable for every living organism. In plants, serine is synthesized by two major pathways: photorespiration and the phosphorylated pathway of serine biosynthesis (PPSB). However, the importance of these pathways in providing serine for plant development is not fully understood. In this study, we examine the relative contributions of photorespiration and PPSB to providing serine for growth and metabolism in the C3 model plant Arabidopsis thaliana. Our analyses of cell proliferation and elongation reveal that PPSB-derived serine is indispensable for plant growth and its loss cannot b…
Studying the Function of the Phosphorylated Pathway of Serine Biosynthesis in Arabidopsis thaliana
2017
Photorespiration is an essential pathway in photosynthetic organisms and is particularly important to detoxify and recycle 2-phosphoglycolate (2-PG), a by-product of oxygenic photosynthesis. The enzymes that catalyze the reactions in the photorespiratory core cycle and closely associated pathways have been identified; however, open questions remain concerning the metabolic network in which photorespiration is embedded. The amino acid serine represents one of the major intermediates in the photorespiratory pathway and photorespiration is thought to be the major source of serine in plants. The restriction of photorespiration to autotrophic cells raises questions concerning the source of serin…
The Glycerate and Phosphorylated Pathways of Serine Synthesis in Plants : The Branches of Plant Glycolysis Linking Carbon and Nitrogen Metabolism
2018
Serine metabolism in plants has been studied mostly in relation to photorespiration where serine is formed from two molecules of glycine. However, two other pathways of serine formation operate in plants and represent the branches of glycolysis diverging at the level of 3-phosphoglyceric acid. One branch (the glycerate – serine pathway) is initiated in the cytosol and involves glycerate formation from 3-phosphoglycerate, while the other (the phosphorylated serine pathway) operates in plastids and forms phosphohydroxypyruvate as an intermediate. Serine formed in these pathways becomes a precursor of glycine, formate and glycolate accumulating in stress conditions. The pathways can be linked …
Effect of Phosphinothricin (Glufosinate) on Photosynthesis and Photorespiration
1990
Phosphinothricin (PPT) causes a rapid inhibition of photosynthesis under atmospheric conditions (400 ppm CO2, 21% O2). However, under conditions (1000 ppm CO2, 2% O2) under which photorespiration cannot occur, there is no or only a very low rate of photosynthesis inhibition by phosphinothricin. Under both conditions, a strong NH4 +-accumulation is apparent caused through the inhibition of glutamine synthetase by phosphinothricin. This indicates, that NH4 +-accumulation cannot be the primary cause for photosynthesis inhibition by phosphinothricin, but a process in connexion with photorespiration plays a central role. Through the lack of amino donors, the transamination of glyoxylate to glyci…
Photosynthesis and transpiration of healthy and diseased spruce trees in the course of three vegetation periods
1988
CO2- and H2O-gas exchange of 20- to 25-year-old spruce trees from a plantation in the Hunsruck mountains were investigated over a period of 3 years. All measurements were made as pair comparisons, i.e., in each case the gas exchange of a damaged tree and of a relatively healthy tree in its immediate vicinity was measured simultaneously. A second plantation in the Westerwald mountains consisted of 18-year-old apparently healthy spruce trees. Pair comparison at this location meant comparison of two healthylooking trees. The investigations at both locations included diurnal course measurements of photosynthesis and transpiration, and light saturation curves and CO2-saturation curves of photosy…
The Effect of Phosphinothricin (Glufosinate) on Photosynthesis II. The Causes of Inhibition of Photosynthesis
1987
It was shown in the previous study that phosphinothricin (glufosinate) causes an accumulation of ammonia and inhibition of photosynthesis. The extent to which there is a connection between these two processes is now investigated in the present study. First of all. the role of NH3 per se in the impairment of photosynthesis was to be clarified. For this purpose, the inhibition of photosynthesis was investigated in relation to exogenously applied ammonia in chloroplasts, protoplasts and entire leaves. The comparison with the experimental results in leaves in which the ammonia was formed endogenously (by action of phosphinothricin) shows that the ammonia toxicity at least cannot be solely resp…
Effect of phosphinothricin (glufosinate) on photosynthesis and photorespiration of C3 and C 4 plants.
1990
Phosphinothricin (glufosinate), an irreversible inhibitor of glutamine synthetase, causes an inhibition of photosynthesis in C3 (Sinapis alba) and C4 (Zea mays) plants under atmospheric conditions (400 ppm CO2, 21% O2). This photosynthesis inhibition is proceeding slower in C4 leaves. Under non-photorespiratory conditions (1000 ppm CO2, 2% O2) there is no inhibition of photosynthesis. The inhibition of glutamine synthetase by phosphinothricin results in an accumulation of NH4 (+). The NH4 (+)-accumulation is lower in C4 plants than in C3 plants. The inhibition of glutamine synthetase through phosphinothricin in mustard leaves results in a decrease in glutamine, glutamate, aspartate, asparag…
Serine biosynthesis by photorespiratory and nonphotorespiratory pathways: and interesting interplay with unknown regulatory networks
2013
[EN] Photorespiration is a primary metabolic pathway, which, given its energy costs, has often been viewed as a wasteful process. Despite having reached the consensus that one important function of photorespiration is the removal of toxic metabolite intermediates, other possible functions have emerged, and others could well emerge in the future. As a primary metabolic pathway, photorespiration interacts with other routes; however the nature of these interactions is not well known. One of these interacting pathways could be the biosynthesis of serine, since this amino acid is synthesised through photorespiratory and non-photorespiratory routes. At present, the exact contribution of each rout…
Die Wirkung unterschiedlicher Lichtintensitäten während der Anzucht auf die CO2-Kompensationslage, die Glykolsäure-Oxidase- und Ribulosebiphosphat-Ca…
1978
Summary Sinapis alba (white mustard) plants were grown under conditions of strong (100 W · m -2 ) and weak (3 W · m -2 ) light and the effect of the light intensity during growth on the CO 2 -compensation point and the activities of glycolic acid oxidase and ribulose bisphosphate carboxylase were studied. The CO 2 -compensation concentration was determined according to two methods: firstly in a closed system with an infrared CO 2 -analyzer, and secondly according to the curve of net photosynthesis as a function of C0 2 -concentration over the range of 400 vpm CO 2 to the CO 2 -compensation point (Fig. 4). The intensity of light during growth was observed to exert an unmistakable effect on t…