Photosystem II quantum yields, off-line measured P/I parameters and carbohydrate dynamics inChlorella vulgaris grown under a fluctuating light regime and its application for optimizing mass cultures

Several biochemical models of photosynthesis exist that consider the effects of the dynamic adjustment of enzymatic and stomatal processes on carbon assimilation under fluctuating light. However, the rate of electron transport through the light reactions is commonly modelled by means of an empirical equation, parameterised with data obtained at the steady state. A steady-state approach cannot capture the dynamic nature of the adjustment of the light reactions under fluctuating light. Here we present a dynamic model approach for photosystem II that considers the adjustments in the regulative non-photochemical processes. The model is initially derived to account for changes occurring at the seconds-to-minutes time-scale under field conditions, and is parameterised and tested with chlorophyll fluorescence data. Results derived from this model show good agreement with experimentally obtained photochemical and non-photochemical quantum yields, providing evidence for the effect that the dark reactions exert in the adjustment of the energy flows at the light reactions. Finally, we compare the traditional steady-state approach with our dynamic approach and find that the steady-state approach produces an underestimation of the modelled electron transport rate (ETR) under rapidly fluctuating light (1 s or less), whereas it produces overestimations under slower fluctuations of light (5 s or more).

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A chloroplast thylakoid lumen protein is required for proper photosynthetic acclimation of plants under fluctuating light environments

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1712206114 ◽

2017 ◽

Vol 114 (38) ◽

pp. E8110-E8117 ◽

Cited By ~ 15

Author(s):

Jun Liu ◽

Robert L. Last

Keyword(s):

Photosystem Ii ◽

Light Stress ◽

High Irradiance ◽

Light Conditions ◽

Agricultural Plant ◽

Photosynthetic Organisms ◽

Fluctuating Light ◽

Stress Susceptibility ◽

Efficiency And Productivity ◽

Photosynthetic Adaptation

Despite our increasingly sophisticated understanding of mechanisms ensuring efficient photosynthesis under laboratory-controlled light conditions, less is known about the regulation of photosynthesis under fluctuating light. This is important because—in nature—photosynthetic organisms experience rapid and extreme changes in sunlight, potentially causing deleterious effects on photosynthetic efficiency and productivity. Here we report that the chloroplast thylakoid lumenal protein MAINTENANCE OF PHOTOSYSTEM II UNDER HIGH LIGHT 2 (MPH2; encoded byAt4g02530) is required for growth acclimation ofArabidopsis thalianaplants under controlled photoinhibitory light and fluctuating light environments. Evidence is presented thatmph2mutant light stress susceptibility results from a defect in photosystem II (PSII) repair, and our results are consistent with the hypothesis that MPH2 is involved in disassembling monomeric complexes during regeneration of dimeric functional PSII supercomplexes. Moreover,mph2—and previously characterized PSII repair-defective mutants—exhibited reduced growth under fluctuating light conditions, while PSII photoprotection-impaired mutants did not. These findings suggest that repair is not only required for PSII maintenance under static high-irradiance light conditions but is also a regulatory mechanism facilitating photosynthetic adaptation under fluctuating light environments. This work has implications for improvement of agricultural plant productivity through engineering PSII repair.

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Growth under Fluctuating Light Reveals Large Trait Variation in a Panel of Arabidopsis Accessions

Plants ◽

10.3390/plants9030316 ◽

2020 ◽

Vol 9 (3) ◽

pp. 316 ◽

Cited By ~ 1

Author(s):

Elias Kaiser ◽

Dirk Walther ◽

Ute Armbruster

Keyword(s):

Photosystem Ii ◽

Chemical Potential ◽

Genomic Variation ◽

Operating Efficiency ◽

Photochemical Quenching ◽

Low Light ◽

Trait Variation ◽

Light Regimes ◽

Fluctuating Light ◽

Non Photochemical Quenching

The capacity of photoautotrophs to fix carbon depends on the efficiency of the conversion of light energy into chemical potential by photosynthesis. In nature, light input into photosynthesis can change very rapidly and dramatically. To analyze how genetic variation in Arabidopsis thaliana affects photosynthesis and growth under dynamic light conditions, 36 randomly chosen natural accessions were grown under uniform and fluctuating light intensities. After 14 days of growth under uniform or fluctuating light regimes, maximum photosystem II quantum efficiency (Fv/Fm) was determined, photosystem II operating efficiency (ΦPSII) and non-photochemical quenching (NPQ) were measured in low light, and projected leaf area (PLA) as well as the number of visible leaves were estimated. Our data show that ΦPSII and PLA were decreased and NPQ was increased, while Fv/Fm and number of visible leaves were unaffected, in most accessions grown under fluctuating compared to uniform light. There were large changes between accessions for most of these parameters, which, however, were not correlated with genomic variation. Fast growing accessions under uniform light showed the largest growth reductions under fluctuating light, which correlated strongly with a reduction in ΦPSII, suggesting that, under fluctuating light, photosynthesis controls growth and not vice versa.

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Quantum Yields of Photosystem II Electron Transport and Carbon Dioxide Fixation in C4 Plants

Functional Plant Biology ◽

10.1071/pp9900579 ◽

1990 ◽

Vol 17 (5) ◽

pp. 579 ◽

Cited By ~ 40

Author(s):

JP Krall ◽

GE Edwards

Keyword(s):

Carbon Dioxide ◽

Electron Transport ◽

Quantum Yield ◽

Photosystem Ii ◽

Malic Enzyme ◽

Co2 Fixation ◽

C4 Plants ◽

Quantum Yields ◽

Ps Ii ◽

Co2 Concentrations

The quantum yields of non-cyclic electron transport from photosystem II (determined from chlorophyll a fluorescence) and carbon dioxide assimilation were measured in vivo in representative species of the three subgroups of C4 plants (NADP-malic enzyme, NAD-malic enzyme and PEP-carboxykinase) over a series of intercellular CO2 concentrations (CI) at both 21% and 2% O2. The CO2 assimilation rate was independent of O2 concentration over the entire range of Ci (up to 500 μbar) in all three C4 subgroups. The quantum yield of PS II electron transport was similar, or only slightly greater, in 21% v. 2% O2 at all Ci values. In contrast, in the C3 species wheat there was a large O2 dependent increase in PS II quantum yield at low CO2, which reflects a high level of photorespiration. In the C4 plants, the relationship of the quantum yield of PS II electron transport to the quantum yield of CO2 fixation is linear suggesting that photochemical use of energy absorbed by PS II is tightly linked to CO2 fixation in C4 plants. This relationship is nearly identical in all three subgroups and may allow estimates of photosynthetic rates of C4 plants based on measurements of PS II photochemical efficiency. The results suggest that in C4 plants both the photoreduction of O2 and photorespiration are low, even at very limiting CO2 concentrations.

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Quantum Yield of Photosystem II and Efficiency of CO2 Fixation in Flaveria (Asteraceae) Species under Varying Light and CO2

Functional Plant Biology ◽

10.1071/pp9910369 ◽

1991 ◽

Vol 18 (4) ◽

pp. 369 ◽

Cited By ~ 14

Author(s):

JP Krall ◽

GE Edwards ◽

MSB Ku

Keyword(s):

Quantum Yield ◽

Photosystem Ii ◽

Co2 Fixation ◽

C4 Photosynthesis ◽

Co2 Assimilation ◽

Quantum Yields ◽

Progressive Development ◽

Psii Activity ◽

C3 And C4 Photosynthesis

The quantum yields of electron transport from photosystem II (PSII) (Φe, determined from chlorophyll a fluorescence), and CO2 assimilation (ΦCO2, photosynthetic rate/light intensity) were measured simultaneously in vivo with representative species of Flaveria which show a progression in development between C3 and C4 photosynthesis and in reduction of photorespiration. These were F. pringlei (C3), F. sonorensis (C3-C4, but lacking a C4 cycle), F. floridana (C3-C4, with partially functional C4 cycle), F. brownii (C4-like) and F. bidentis (C4). The level of PSII activity with varying CI under 210 mbar O2 was very similar in all species. However, the progressive development of C4 characteristics among the species produced an increased efficiency in utilisation of PSII derived energy for CO2 assimilation under 210 mbar O2, due to reduced photorespiratory losses at low CO2 levels. In all species, when photorespiration was limited by low O2 (20 mbar), there was a linear or near linear relationship between the quantum yield of PSII v. the quantum yield of CO2 fixation with varying intercellular levels of CO2 (Ci) indicating that CO2 fixation in this case is linked to PSII activity. When switching from 20 to 210 mbar O2 at atmosphere levels of CO2, there was a similar decrease in the efficiency in utilising PSII activity for CO2 assimilation at different light intensities, but the degree of sensitivity to O2 progressively decreased among the species concomitant with the development of C4 photosynthesis. These results may help explain why there is an advantage to evolution of C4 photosynthesis in environments where Ci becomes limiting.

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