On the Relationship Between Electron Transport Rate and Photosynthesis in Leaves of the C4 Plant Sorghum bicolor Exposed to Water Stress, Temperature Changes and Carbon Metabolism Inhibition

1995 ◽  
Vol 22 (6) ◽  
pp. 885 ◽  
Author(s):  
F Loreto ◽  
D Tricoli ◽  
GD Marco
Keyword(s):  
Water Stress ◽  
Electron Transport ◽  
Sorghum Bicolor ◽  
Carbon Metabolism ◽  
Sweet Sorghum ◽  
Co2 Assimilation ◽  
Linear Electron ◽  
Reaction Centres ◽  
Metabolism Inhibition ◽  
The Relationship

We examined the effect of carbon metabolism inhibition, temperature, and water stress on the relationship between the linear electron transport and photosynthetic CO2 assimilation in sweet sorghum, Sorghum bicolor (L.) Moench. Carbon metabolism was inhibited either by removing CO2 from the air or by feeding glyceraldehyde to the leaves. Irrespective of the method used, the linear electron transport and photosynthesis were coordinately inhibited. However, when photosynthesis was totally inhibited, a residual electron transport between 20 and 35 μmol m-2 s-1 could be measured. The residual electron transport increased with increasing leaf temperature up to 38�C and was higher in water-stressed leaves than in control leaves. Temperature affected photosynthesis in intact leaves. The optimal temperature for photosynthesis in control leaves was between 30 and 35�C. The ratio between linear electron transport and photosynthesis showed a temperature dependency similar to that of photosynthesis. As a consequence, the electrons required to fix one mole of CO2 were 5.5 at suboptimal temperatures but were 6.5 at 30�C. Our results indicate that the relationship between linear electron transport and photosynthesis is not perfectly steady in nature but is subject to transient changes. The observed changes in the linear electron transport were mostly related to changes in the efficiency of light trapping by open photosystem II (PSII) reaction centres, while the fractions of open PSII reaction centres were relatively constant during the experiment. Water stress severely reduced the photosynthetic CO2 assimilation of sweet sorghum leaves. The greater the water stress, the lower the temperature at which optimal photosynthesis was reached. The linear electron transport was coordinately inhibited by water stress but a residual electron transport was again found when photosynthesis was extremely reduced by water stress. Under water-stress conditions the fraction of PSII reaction centres in an open state was very low but constant, and the temperature dependent reduction of linear electron transport was caused by the reduction of the efficiency of energy capture of PSII reaction centres.

Oxygen-sensitive Differences in the Relationship between Photosynthetic Electron Transport and CO2 Assimilation in C3 and C4 Plants during State Transitions

1997 ◽  
Vol 24 (4) ◽  
pp. 495 ◽  
Author(s):  
James R. Andrews ◽  
Neil R. Baker
Keyword(s):  
Electron Transport ◽  
Quantum Efficiency ◽  
Photosynthetic Electron Transport ◽  
Co2 Assimilation ◽  
State Transitions ◽  
Large Decrease ◽  
Maize Leaves ◽  
Significant Change ◽  
The Relationship ◽  
State 1

Wheat (C3) and maize (C4) leaves were exposed to light treatments that were limiting for CO2 assimilation and which excite preferentially photosystem I (PSI) or photosystem II (PSII) and induce State 1 or State 2, respectively. In order to examine the relationships between linear electron transport and CO2 in leaves during State transitions, simultaneous measurements of CO2 assimilation, chlorophyll fluorescence and absorbance at 820 nm were used to estimate the quantum efficiencies of CO2 assimilation and PSII and PSI photochemistry. In wheat leaves with photorespiratory activity, no significant change in quantum efficiency of CO2assimilation was observed during State transitions. This was not the case when photorespiration was inhibited with either 2% O2 or 1000 ppm CO2 and transition from State 2 to State 1 was accompanied by a large decrease (c. 20%) in the quantum efficiency of CO2 assimilation which was not associated with a decrease in the quantum efficiency of electron transport through PSII. Photorespiration appears to buffer the quantum efficiency of CO2 assimilation from changes associated with decreases in the rate of CO2 fixation resulting from imbalances in PPFD absorption by PSI and PSII. When maize leaves were subjected to similar State transitions, no significant change in the quantum efficiency of CO2 assimilation was observed on transition from State 2 to State 1, but on switching back to State 2 a very large decrease (c. 40%) was observed. This decrease could be prevented if leaves were maintained in either 2% O2 or 593 ppm CO2. The possible occurrence of photorespiration in maize leaves on transition from State 1 to State 2, which could result from an inhibition of the CO2 concentrating mechanism, cannot account for the decrease in the quantum efficiency of CO2 assimilation since the relationship between PSII electron transport and CO2 assimilation remained similar throughout the State transitions. Also changes in the phosphorylation status of the light-harvesting chlorophyll a/b protein associated with PSII cannot be implicated in this phenomenon.

Quantitative Mapping of Leaf Photosynthesis Using Chlorophyll Fluorescence Imaging

1995 ◽  
Vol 22 (2) ◽  
pp. 277 ◽  
Author(s):  
B Genty ◽  
S Meyer
Keyword(s):  
Chlorophyll Fluorescence ◽  
Electron Transport ◽  
Quantum Yield ◽  
Co2 Assimilation ◽  
Linear Electron ◽  
Leaf Photosynthesis ◽  
Heterogeneous Distribution ◽  
Fluorescence Measurements ◽  
Wide Range ◽  
Photochemical Yield

A method has been developed for routine, non-invasive monitoring of the topography of leaf photochemistry. The method uses video images of leaf chlorophyll fluorescence, taken during steady-state photosynthesis and during a transitory saturation of photochemistry, to construct, pixel by pixel, an image of the photochemical yield of photosystem II (PSII). The photochemical yield of PSII was estimated according to Genty et al. (1989) (Biochimica et Biophysica Acta 990, 87-92). The effectiveness of the method was shown by mapping the heterogeneous distribution of photosynthetic activity after treatment with either a herbicide (DCMU), abscisic acid, or during the course of the induction of photosynthesis. Leaf CO2 assimilation was simultaneously monitored under non- photorespiratory conditions to estimate the average quantum yield of linear electron transport. A unique proportional relationship was found between the mean photochemical yield of PSII calculated from images of the photochemical yield of PSII, and the average quantum yield of linear electron transport in three plant species exposed to a wide range of treatments or conditions. This new ability to quantitatively visualise leaf photochemistry provides a powerful tool to probe the spatial distribution of leaf photosynthesis. Possible errors in estimating the photochemical yield of PSII from mean fluorescence measurements are discussed.

scholarly journals The relationship between plant height and sugar accumulation in the stems of sweet sorghum (Sorghum bicolor (L.) Moench)

2017 ◽  
Vol 203 ◽  
pp. 181-191 ◽  
Author(s):  
Sanyukta Shukla ◽  
Terry J. Felderhoff ◽  
Ana Saballos ◽  
Wilfred Vermerris
Keyword(s):  
Sorghum Bicolor ◽  
Plant Height ◽  
Sweet Sorghum ◽  
Sugar Accumulation ◽  
The Relationship ◽  
Sorghum Bicolor L

scholarly journals Photosynthetic linear electron flow drives CO2 assimilation in maize leaves

2021 ◽  
Author(s):  
Ginga Shimakawa ◽  
Chikahiro Miyake
Keyword(s):  
Electron Transport ◽  
Electron Flow ◽  
Photosynthetic Electron Transport ◽  
Co2 Assimilation ◽  
C4 Plants ◽  
C3 Plants ◽  
Reaction Centre ◽  
Linear Electron ◽  
C3 And C4 Plants ◽  
Intact Leaves

Abstract Photosynthetic organisms commonly develop the strategy to keep the reaction centre chlorophyll of photosystem I, P700, oxidised for preventing the generation of reactive oxygen species in excess light conditions. In photosynthesis of C4 plants, CO2 concentration is kept at higher levels around ribulose 1,5-bisphosphate carboxylase/oxygenase (Rubisco) by the cooperation of the mesophyll and bundle sheath cells, which enables them to assimilate CO2 at higher rates and to survive under drought stress. However, the regulatory mechanism of photosynthetic electron transport for P700 oxidation is still poorly understood in C4 plants. Here we assessed gas exchange, chlorophyll fluorescence, electrochromic shift, and near infrared absorbance in the intact leaves of NADP-malic enzyme subtype of C4 plants maize in a comparison with the C3 plant field mustard. Instead of the alternative electron sink due to photorespiration, photosynthetic linear electron flow was strongly limited between photosystems I and II dependent on the proton gradient across the thylakoid membrane (ΔpH) in response to the suppression of CO2 assimilation in maize. The increase of ΔpH for P700 oxidation was caused by the regulation of proton conductance of chloroplast ATP synthase but not by promoting cyclic electron flow, which was supported by linear relationships among CO2 assimilation rate, linear electron flow, P700 oxidation, ΔpH, and the oxidation rate of ferredoxin. At the scale of intact leaves, the ratio of PSI to PSII was estimated almost 1:1 in both C3 and C4 plants. Overall, the photosynthetic electron transport was regulated for P700 oxidation in maize through the same strategies as in C3 plants only except for the capacity of photorespiration despite the structural and metabolic differences in photosynthesis between C3 and C4 plants.

Environmental Effects on the Relationship Between the Quantum Yields of Carbon Assimilation and in vivo PsII Electron Transport in Maize

1991 ◽  
Vol 18 (3) ◽  
pp. 267 ◽  
Author(s):  
JP Krall ◽  
GE Edwards
Keyword(s):  
Electron Transport ◽  
Energy Dissipation ◽  
Quantum Yield ◽  
High Energy ◽  
Co2 Assimilation ◽  
Quantum Yields ◽  
Photon Flux ◽  
Ps Ii ◽  
C4 Species ◽  
The Relationship

The partitioning of light energy absorbed by photosystem (PS) II in the C4 species maize was investigated under various photosynthetic photon flux densities (PPFD), temperatures, and intercellular CO2 concentrations. The relationship between the quantum yield of PSII electron transport (�e) and the quantum yield of CO2 assimilation (ΦCO2) was generally found to be linear, with similar slopes. This indicates that PSII electron transport is tightly coupled to CO2 assimilation such that measurements of �e may be used to estimate photosynthetic rates in maize. Coefficients of quenching of PSII chlorophyll fluorescence indicated that, under excessive PPFD or when CO2 assimilation was decreased due to suboptimal or supraoptimal temperature or low Ci, the energy in excess of that needed to drive the reduced rate of PSII electron transport was dissipated via a mechanism known to be correlated to the trans-thylakoid proton gradient (high energy quenching, qE) and a mechanism believed to arise in the PSII antenna chlorophyll (qN(slow)). At suboptimal temperature the energy dissipation was principally at the antenna level and qE was low, while at supraoptimal temperature the reverse was true. The results are discussed relative to coupling of PSII activity to CO2 fixation and mechanisms of energy dissipation in this C4 species.

The relationship between CO2 assimilation and electron transport in leaves

1990 ◽  
Vol 25 (3) ◽  
pp. 213-224 ◽  
Author(s):  
Jeremy Harbinson ◽  
Bernard Genty ◽  
Neil R. Baker
Keyword(s):  
Electron Transport ◽  
Co2 Assimilation ◽  
The Relationship

Increased capacity for photosynthesis in wheat grown at elevated CO2: the relationship between electron transport and carbon metabolism

Planta ◽  
1995 ◽  
Vol 197 (3) ◽  
Author(s):  
DimahZ. Habash ◽  
MatthewJ. Paul ◽  
MartinA.J. Parry ◽  
AlfredJ. Keys ◽  
DavidW. Lawlor
Keyword(s):  
Electron Transport ◽  
Elevated Co2 ◽  
Carbon Metabolism ◽  
The Relationship

Studies on the Relationship between Photosynthetic Electron Transport and Carbon Metabolism

1995 ◽  
pp. 1809-1812
Author(s):  
D. Z. Habash ◽  
M. A. J. Parry ◽  
M. J. Paul ◽  
S. Parmar ◽  
S. Driscoll ◽  
...  
Keyword(s):  
Electron Transport ◽  
Carbon Metabolism ◽  
Photosynthetic Electron Transport ◽  
The Relationship

Effects of water stress on photosynthesis, chlorophyll fluorescence and photoinhibition in wheat plants

1998 ◽  
Vol 25 (8) ◽  
pp. 883 ◽  
Author(s):  
Congming Lu ◽  
Jianhua Zhang
Keyword(s):  
Water Stress ◽  
Co2 Assimilation ◽  
Photochemical Quenching ◽  
Reaction Centre ◽  
Ps Ii ◽  
Energy Capture ◽  
Stress Effects ◽  
Reaction Centres ◽  
Net Co2 Assimilation ◽  
Non Photochemical Quenching

Effects of water stress on photosynthesis, PS II photochemistry and photoinhibition were investigated in wheat plants (Tritium aestivum L.). To separate water stress effects from photoinhibition, water stress was imposed at low irradiance (180 µmol m-2 s-1). When water stress developed gradually, net CO2 assimilation rate and leaf stomatal conductance decreased significantly. However, water stress had no effects on the PS II photochemistry in dark-adapted leaves. There were no significant changes in the maximal efficiency of PS II photochemistry and no apparent damages in PS II reaction centre, its oxidising and acceptor sides, or its antennae system. However, PS II photochemistry in light-adapted leaves was modified in water-stressed plants. This was shown by the decrease in the efficiency of excitation energy capture by open PS II reaction centres and the quantum yield of PS II electron transport and a significant increase in non-photochemical quenching. In addition, water stress increased the susceptibility to photoinhibition. The extent of photoinhibition became more pronounced as water stress increased. It was found that water-stressed plants exhibited a much greater accumulation of the QB-non-reducing PS II reaction centres and a smaller increase in non- photochemical quenching during photoinhibition. Such changes might be responsible for the increased susceptibility to photoinhibition.

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