COMT1 Silencing Aggravates Heat Stress-Induced Reduction in Photosynthesis by Decreasing Chlorophyll Content, Photosystem II Activity, and Electron Transport Efficiency in Tomato

Photosystem II particles that retain the ability to evolve O2 have been used to examine acceptor and inhibitor sites in the photosynthetic electron transfer chain between Q and plastoquinone. Employing the water to dichlorobenzoquinone reaction to assay photosystem II activity, we have demonstrated that electron transport in thylakoids and particles is equally sensitive to inhibition by DCMU. dinoseb, metribuzin, HQNO and DBMIB. Based on differential sensitivity to inhibition by DCMU vs. HQNO or DBMIB, we suggest that when synthetic quinones, e.g. 2,6-dichlorobenzoquinone operate as Hill reagents in particles they are reduced primarily by the plastoquinone pool. When synthetic quinones, e.g. 5,6-methylenedioxy-2,3-dimethyl benzoquinone act as autoxidizable acceptors they accept electron from the Q/B complex at a point that is located between the DCMU and HQNO (DBMIB) inhibition sites.

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Photoautotrophic Chenopodium rubrum Cell Suspension Cultures Resistant against Photosynthesis-Inhibiting Herbicides II. Physiological and Biochemical Properties

Zeitschrift für Naturforschung C ◽

10.1515/znc-1994-11-1215 ◽

1994 ◽

Vol 49 (11-12) ◽

pp. 791-801 ◽

Cited By ~ 2

Author(s):

Jutta Thiemann ◽

Wolfgang Barz

Keyword(s):

Electron Transport ◽

Photosystem Ii ◽

Chlorophyll Content ◽

Photosynthetic Capacity ◽

Growth Parameters ◽

Cell Suspension Cultures ◽

Photosynthetic Electron Transport ◽

Cell Number ◽

Biochemical Properties ◽

Chenopodium Rubrum

Eight photoautotrophic cell cultures of Chenopodium rubrum, which are resistant against the photosystem II inhibitor metribuzin, were characterized for their growth parameters, chlorophyll content and photosynthetic capacity. Herbicide resistance of the eight lines results from different mutations in the D 1 protein of photosystem II, which is the target for different photosystem II inhibitors. In the presence of 10-5 ᴍ metribuzin the eight lines showed substantial growth reduction depending on the degree of resistance, and this effect is explained by a reduced electron transport in photosystem II. The impaired photosynthetic capacity of the green cells in the presence of high metribuzin concentrations, leads to compensation effects similar to shade accommodation of plants. Adaptation includes an increase of the chlorophyll content, a decrease of the chlorophyll a/b ratios as well as an increase of thylakoid stacking and cell number per unit fresh weight. In the absence of the herbicide photosynthetic electron transport is not impaired, as indicated by measurements of electron transfer rates in photosystem II and flash-induced reduction kinetics of P-700+. In summary the alterations of the D 1 protein of the eight cell lines do not result in a reduced electron transport in photosystem II.

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Studies of Components of the Thylakoid Membrane of Undamaged and Damaged Spruce Trees at Different Mountain Sites

Zeitschrift für Naturforschung C ◽

10.1515/znc-1993-11-1215 ◽

1993 ◽

Vol 48 (11-12) ◽

pp. 911-922 ◽

Cited By ~ 4

Author(s):

Aloysius Wild ◽

Petra Strobel ◽

Ute Flammersfeld

Keyword(s):

Electron Transport ◽

Photosystem Ii ◽

Chlorophyll Content ◽

Thylakoid Membrane ◽

Electron Transport Rate ◽

D1 Protein ◽

Cytochrome F ◽

West Germany ◽

Transport Rate ◽

Photosynthetic Membranes

During a five-year period, components of the thylakoid membrane in needles of the second generation of undamaged and damaged trees of Norway spruce were studied at three different mountain sites in West Germany. Visible signs of damage at these sites are a yellowing of the light-exposed sides of the needles as well as the loss of needles. The goal of this study was to determine damage-induced alterations in composition and physiological reactions of the thylakoid membranes in spruce needles. In order to meet this purpose, contents of chlorophyll a and b, electron transport rate of photosystem II, contents of the D 1 protein, cytochrome f, as well as P-700 were measured. The chlorophyll content in the needles of the damaged spruce trees was significantly lower than in the needles of the undamaged trees. In addition to this, the typical annual course of chlorophyll content was exclusively observed in the needles of the undamaged spruce trees. If related to dry weight, a drastic reduction of the electron transport rate and of the redox components of the thylakoid membrane was observed due to damage, indicating a degeneration of the photosynthetic membranes. The contents of D1 protein and the photosynthetic electron transport rates were also markedly reduced in the needles of the damaged trees, when related to chlorophyll content of thylakoids, suggesting an early and particular impairment of photosystem II. The comparison of spruce trees showing different signs of damage demonstrates that certain biochemical parameters concerning the photosynthetic membranes (chlorophyll, cytochrome f, ratio photosystem II/I) reflect the extent of damage and are suitable for an early indication of a beginning, but still invisible damage of spruce trees.

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Photosystem I-dependent cyclic electron transport is important in controlling Photosystem II activity in leaves under conditions of water stress

Photosynthesis Research ◽

10.1007/bf00029818 ◽

1992 ◽

Vol 34 (3) ◽

pp. 449-464 ◽

Cited By ~ 42

Author(s):

Eva Katona ◽

Spidola Neimanis ◽

Gerald Sch�nknecht ◽

Ulrich Heber

Keyword(s):

Water Stress ◽

Electron Transport ◽

Photosystem Ii ◽

Photosystem I ◽

Cyclic Electron Transport ◽

Photosystem Ii Activity

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Effects of heat stress on gas exchange and photosystem II (PSII) photochemical activity of Phillyrea angustifolia exposed to elevated CO2 and subsaturating irradiance

Botany ◽

10.1139/b07-132 ◽

2008 ◽

Vol 86 (4) ◽

pp. 435-441 ◽

Cited By ~ 4

Author(s):

Luca Vitale ◽

Carmen Arena ◽

Amalia Virzo De Santo ◽

Nicola D’Ambrosio

Keyword(s):

Heat Stress ◽

Electron Transport ◽

Gas Exchange ◽

Photosystem Ii ◽

Photochemical Efficiency ◽

Calvin Cycle ◽

Fluorescence Measurements ◽

Significant Difference ◽

Psii Photochemical Efficiency ◽

Phillyrea Angustifolia

Gas exchange and chlorophyll a fluorescence measurements were performed simultaneously on leaves of Phillyrea angustifolia L. to assess the effects of heat stress (30 min at 40 °C) on photosynthesis and photosystem II (PSII) photochemical efficiency of plants grown at ambient CO2 and exposed to an elevated CO2 concentration (800 µmol·mol–1) and 300 µmol photons·m–2·s–1. No significant difference was found in the heat-induced decreases of net photosynthesis (PN), quantum yield of PSII electron transport (ΦPSII), and maximum PSII photochemical efficiency (Fv/Fm) between plants exposed to ambient and elevated CO2 concentrations, showing that elevated CO2 was not able to reduce the potential for photoinhibition at high temperatures under moderate light conditions. The heat-induced decrease of PN was higher than that of ΦPSII indicating that reductive power was more utilized in non-assimilatory processes than in CO2 fixation at both CO2 treatments. This result suggested that impairment of the Calvin cycle rather than electron transport inhibition was the main cause of the limitation in CO2 fixation.

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Herbicides which Inhibit Electron Transport or Produce Chlorosis and Their Effect on Chloroplast Development in Radish Seedlings I. Chlorophyll a Fluorescence Transients and Photosystem II Activity

Zeitschrift für Naturforschung C ◽

10.1515/znc-1982-3-420 ◽

1982 ◽

Vol 37 (3-4) ◽

pp. 268-275 ◽

Cited By ~ 1

Author(s):

K. H. Grumbach

Keyword(s):

Electron Transport ◽

Photosystem Ii ◽

Chlorophyll A ◽

Oxygen Evolution ◽

Chlorophyll A Fluorescence ◽

Photosynthetic Electron Transport ◽

Photosystem Ii Activity ◽

Chlorophyll A Fluorescence Transients ◽

Radish Seedlings ◽

Fluorescence Transients

Abstract Diuron and bentazon are very strong inhibitors of the photosynthetic electron transport in isolated radish chloroplasts. The chlorosis producing herbicide SAN 6706 also inhibited the photosystem II dependent oxygen evolution. Aminotriazole had no effect. The inhibitor concentration for 50% inhibition of photosystem II activity was 10-7 m for diuron and 10-4 m for bentazon and SAN 6706 respectively.Diuron and bentazon quenched the chlorophyll a fluorescence transients in isolated radish chloroplasts drastically, while aminotriazole was not effective. It was of particular interest that the bleaching herbicide SAN 6706 inhibited photosystem II dependent oxygen evolution in a similar concentration as bentazon but had no effect on the chlorophyll a-fluorescence transients suggesting that SAN 6706 is not binding to the same site of the electron transport chain as diuron and bentazon.Apart from their direct influence on electron transport in isolated photosynthetically active chloroplasts the photosystem II and bleaching herbicides assayed also strongly affected photosynthesis in radish seedlings that were grown in the presence of the herbicides for a long time. As already obtained using isolated chloroplasts, photosystem II dependent oxygen evolution like the chlorophyll a fluorescence transients were strongly inhibited by the photosystem II herbicides diuron and bentazon. A reduction but no inhibition of photosystem II activity was observed in plants that were grown in the presence of aminotriazole. The pyridazinone SAN 6706 was behaving contradictory. In partly green plants photosystem II activity was still maintained and even higher than in untreated plants while in albinistic plants no photosynthetic activity was detected.

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