Regulation of electron transport in maize mesophyll chloroplasts: The relationship between chlorophyll a fluorescence quenching and O2 evolution

Simultaneous measurements were made of O2 exchange, inorganic carbon (Ci) accumulation and assimilation, and chlorophyll a fluorescence of the cyanobacterium Synechococcus UTEX 625. The addition of Ci to cells at the CO2 compensation point resulted in quenching of chlorophyll a fluorescence in the presence or absence of the CO2 fixation inhibitor, iodoacetamide. The magnitude of quenching was related to electron flow to terminal electron acceptors such as CO2 and O2. When photosynthetic CO2 fixation was allowed, the rate of electron transport, as expressed by (F*m – F)/F*m, was highly correlated with the onset of photosynthesis. When CO2 fixation was inhibited by the addition of iodoacetamide, the observed fluorescence quenching was consistent with the enhanced rate of O2 photoreduction that occurred when Ci was added. There was a close correlation (r = 0.98) between the magnitude of O2-dependent fluorescence quenching and the amount of O2 photoreduction. The degree of stimulation of electron flow to O2 photoreduction was dependent on the inorganic carbon concentration. The K1/2 (Ci) for extracellular Ci was 1.36 ± 0.13 μM (mean ± SD, n = 3) and K1/2 (Ci) for the intracellular Ci pool was 1.4 ± 0.18 mM (mean ± SD, n = 3). The reduction of N,N-dimethyl-p-nitrosoaniline was also stimulated by the addition of Ci, whereas the addition of Ci had no effect on the reduction of 2,6-dimethylbenzoquinone and ferricyanide. The results suggest that Ci stimulates electron flow in photosystem I. Key words: cyanobacteria, O2 photoreduction, fluorescence, Ci concentrating mechanism, inorganic carbon pool, linear electron transport, kinetic study.

Download Full-text

Electron Transport-Dependent Chlorophyll-a Fluorescence Quenching by O2 in Various Algae and Higher Plants

PLANT PHYSIOLOGY ◽

10.1104/pp.73.4.886 ◽

1983 ◽

Vol 73 (4) ◽

pp. 886-888 ◽

Cited By ~ 11

Author(s):

Doug Bruce ◽

William Vidaver ◽

Konrad Colbow ◽

Radovan Popovic

Keyword(s):

Electron Transport ◽

Fluorescence Quenching ◽

Chlorophyll A ◽

Chlorophyll A Fluorescence ◽

Higher Plants

Download Full-text

Effects of Different Planting Densities on Photosynthesis in Maize Determined via Prompt Fluorescence, Delayed Fluorescence and P700 Signals

Plants ◽

10.3390/plants10020276 ◽

2021 ◽

Vol 10 (2) ◽

pp. 276

Author(s):

Wanying Chen ◽

Bo Jia ◽

Junyu Chen ◽

Yujiao Feng ◽

Yue Li ◽

...

Keyword(s):

Electron Transport ◽

Chlorophyll A ◽

Chlorophyll A Fluorescence ◽

Electron Transport Chain ◽

Plant Density ◽

Photosynthetic Electron Transport ◽

Planting Density ◽

Strong Impact ◽

Photosynthetic Electron Transport Chain ◽

Transport Chain

The mutual shading among individual field-grown maize plants resulting from high planting density inevitably reduces leaf photosynthesis, while regulating the photosynthetic transport chain has a strong impact on photosynthesis. However, the effect of high planting density on the photosynthetic electron transport chain in maize currently remains unclear. In this study, we simultaneously measured prompt chlorophyll a fluorescence (PF), modulated 820 nm reflection (MR) and delayed chlorophyll a fluorescence (DF) in order to investigate the effect of high planting density on the photosynthetic electron transport chain in two maize hybrids widely grown in China. PF transients demonstrated a gradual reduction in their signal amplitude with increasing planting density. In addition, high planting density induced positive J-step and G-bands of the PF transients, reduced the values of PF parameters PIABS, RC/CSO, TRO/ABS, ETO/TRO and REO/ETO, and enhanced ABS/RC and N. MR kinetics showed an increase of their lowest point with increasing high planting density, and thus the values of MR parameters VPSI and VPSII-PSI were reduced. The shapes of DF induction and decay curves were changed by high planting density. In addition, high planting density reduced the values of DF parameters I1, I2, L1 and L2, and enhanced I2/I1. These results suggested that high planting density caused harm on multiple components of maize photosynthetic electron transport chain, including an inactivation of PSII RCs, a blocked electron transfer between QA and QB, a reduction in PSI oxidation and re-reduction activities, and an impaired PSI acceptor side. Moreover, a comparison between PSII and PSI activities demonstrated the greater effect of plant density on the former.

Download Full-text

Relationship between action spectra for chlorophyll a fluorescence and photosynthetic O2 evolution in algae

Journal of Plankton Research ◽

10.1093/plankt/8.3.537 ◽

1986 ◽

Vol 8 (3) ◽

pp. 537-548 ◽

Cited By ~ 21

Author(s):

A. Neori ◽

M. Vernet ◽

O. Holm-Hansen ◽

F.T. Haxo

Keyword(s):

Chlorophyll A ◽

Chlorophyll A Fluorescence ◽

O2 Evolution ◽

Action Spectra ◽

Photosynthetic O2 Evolution

Download Full-text

The polyphasic chlorophyll a fluorescence rise measured under high intensity of exciting light

Functional Plant Biology ◽

10.1071/fp05095 ◽

2006 ◽

Vol 33 (1) ◽

pp. 9 ◽

Cited By ~ 217

Author(s):

Dušan Lazár

Keyword(s):

Electron Transport ◽

Chlorophyll A ◽

Chlorophyll A Fluorescence ◽

High Intensity ◽

High Temperature Stress ◽

Electron Acceptors ◽

Exciting Light ◽

Electric Voltage ◽

Light Gradient ◽

Fluorescence Rise

Chlorophyll a fluorescence rise caused by illumination of photosynthetic samples by high intensity of exciting light, the O–J–I–P (O–I1–I2–P) transient, is reviewed here. First, basic information about chlorophyll a fluorescence is given, followed by a description of instrumental set-ups, nomenclature of the transient, and samples used for the measurements. The review mainly focuses on the explanation of particular steps of the transient based on experimental and theoretical results, published since a last review on chlorophyll a fluorescence induction [Lazár D (1999) Biochimica et Biophysica Acta 1412, 1–28]. In addition to ‘old’ concepts (e.g. changes in redox states of electron acceptors of photosystem II (PSII), effect of the donor side of PSII, fluorescence quenching by oxidised plastoquinone pool), ‘new’ approaches (e.g. electric voltage across thylakoid membranes, electron transport through the inactive branch in PSII, recombinations between PSII electron acceptors and donors, electron transport reactions after PSII, light gradient within the sample) are reviewed. The K-step, usually detected after a high-temperature stress, and other steps appearing in the transient (the H and G steps) are also discussed. Finally, some applications of the transient are also mentioned.

Download Full-text

Seasonality and Small Spatial-Scale Variation of Chlorophyll a Fluorescence in Bryophyte Syntrichia ruralis [Hedw.] in Semi-Arid Sandy Grassland, Hungary

Plants ◽

10.3390/plants9010092 ◽

2020 ◽

Vol 9 (1) ◽

pp. 92 ◽

Cited By ~ 1

Author(s):

Ruchika ◽

Zsolt Csintalan ◽

Evelin Ramóna Péli

Keyword(s):

Quantum Yield ◽

Fluorescence Quenching ◽

Spatial Scale ◽

Chlorophyll A ◽

Chlorophyll A Fluorescence ◽

Small Spatial Scale ◽

Variation Trend ◽

Fluorescence Parameters ◽

Semi Arid ◽

Sandy Grassland

Bryophytes face challenges due to global climate change which is leading to in-depth research in monitoring and studying their photosynthetic activity. The aim of this preliminary experiment was to study the seasonal variation trend in the chlorophyll a fluorescence parameters, Fv/Fm (ratio of variable to maximum fluorescence), photochemical fluorescence quenching (qP), photochemical quantum yield of photosystem II (ΦPS II), fluorescence quenching (qN), and non-photochemical quenching (NPQ), in the moss cushions of Syntrichia ruralis [Hedw.] collected from semi-arid sandy dunes for two slopes i.e., north-east (NE) and south-west (SW) direction. Our results showed a seasonal and small-spatial scale variation trend in all chlorophyll fluorescence parameters. These variations are due to different seasonal conditions referring to different degrees of environmental stress. ΦPS II and qP values were maximum in winter and in spring seasons while Fv/Fm, NPQ and qN were maximum in summer. Based on the different exposition of dunes, the SW slope showed increased values of the effective quantum yield of PS II and qP in comparison to the NE slope due to the optimal microclimate conditions for their expansion. These results may refer to the future changing in diversification and coverage of the Syntrichia species in semi-arid sandy grassland due to more effective metabolism in the beneficial microclimatic conditions.

Download Full-text