CO2 assimilation, ribulose-1,5-bisphosphate carboxylase/oxygenase, carbohydrates and photosynthetic electron transport probed by the JIP-test, of tea leaves in response to phosphorus supply

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.

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P-E2-14 Photosynthetic electron transport, CO2 assimilation and wheat productivity

Progress in Biophysics and Molecular Biology ◽

10.1016/s0079-6107(97)80539-1 ◽

1996 ◽

Vol 65 ◽

pp. 154

Keyword(s):

Electron Transport ◽

Photosynthetic Electron Transport ◽

Co2 Assimilation

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Relationship between CO2 Assimilation, Photosynthetic Electron Transport, and Active O2 Metabolism in Leaves of Maize in the Field during Periods of Low Temperature

PLANT PHYSIOLOGY ◽

10.1104/pp.116.2.571 ◽

1998 ◽

Vol 116 (2) ◽

pp. 571-580 ◽

Cited By ~ 270

Author(s):

Michael J. Fryer ◽

James R. Andrews ◽

Kevin Oxborough ◽

David A. Blowers ◽

Neil R. Baker

Keyword(s):

Electron Transport ◽

Low Temperature ◽

Photosynthetic Electron Transport ◽

Co2 Assimilation

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Interactive effects of CO2 enrichment and brassinosteroid on CO2 assimilation and photosynthetic electron transport in Cucumis sativus

Environmental and Experimental Botany ◽

10.1016/j.envexpbot.2011.09.002 ◽

2012 ◽

Vol 75 ◽

pp. 98-106 ◽

Cited By ~ 36

Author(s):

Yu-Ping Jiang ◽

Fei Cheng ◽

Yan-Hong Zhou ◽

Xiao-Jian Xia ◽

Kai Shi ◽

...

Keyword(s):

Electron Transport ◽

Cucumis Sativus ◽

Co2 Enrichment ◽

Photosynthetic Electron Transport ◽

Co2 Assimilation ◽

Interactive Effects

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Down-Regulation of Photosynthetic Electron Transport and Decline in CO2 Assimilation under Low Frequencies of Pulsed Lights

Plants ◽

10.3390/plants10102033 ◽

2021 ◽

Vol 10 (10) ◽

pp. 2033

Author(s):

Marguerite Cinq-Mars ◽

Guy Samson

Keyword(s):

Electron Transport ◽

Electron Flow ◽

Net Photosynthesis ◽

Photosynthetic Electron Transport ◽

Co2 Assimilation ◽

Primary Electron ◽

Duty Ratio ◽

Low Frequencies ◽

Light Pulses ◽

Kinetics Of

The decline in CO2 assimilation in leaves exposed to decreasing frequencies of pulsed light is well characterized, in contrast to the regulation of photosynthetic electron transport under these conditions. Thus, we exposed sunflower leaves to pulsed lights of different frequencies but with the same duty ratio (25%) and averaged light intensity (575 μmoles photons m−2 s−1). The rates of net photosynthesis Pn were constant from 125 to 10 Hz, and declined by 70% from 10 to 0.1 Hz. This decline coincided with (1) a marked increase in nonphotochemical quenching (NPQ), and (2) the completion after 25 ms of illumination of the first phase of P700 photooxidation, the primary electron donor of PSI. Under longer light pulses (<5 Hz), there was a slower and larger P700 photooxidation phase that could be attributed to the larger NPQ and to a resistance of electron flow on the PSI donor side indicated by 44% slower kinetics of a P700+ dark reduction. In addition, at low frequencies, the decrease in quantum yield of photochemistry was 2.3-times larger for PSII than for PSI. Globally, our results indicate that the decline in CO2 assimilation at 10 Hz and lower frequencies coincide with the formation of NPQ and a restriction of electron flows toward PSI, favoring the accumulation of harmless P700+.

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Photosynthetic linear electron flow drives CO2 assimilation in maize leaves

10.21203/rs.3.rs-222497/v1 ◽

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.

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