Photochemistry, energy dissipation and cold-hardening in Eucalyptus nitens and E. pauciflora

1998 ◽  
Vol 25 (5) ◽  
pp. 581 ◽  
Author(s):  
Mark J. Hovenden ◽  
Charles R. Warren
Keyword(s):  
Electron Transport ◽  
Energy Dissipation ◽  
Low Temperatures ◽  
Heat Dissipation ◽  
Photosynthetic Electron Transport ◽  
Thermal Dissipation ◽  
Photon Flux ◽  
Photon Flux Density ◽  
Eucalyptus Nitens ◽  
Dissipation Processes

The allocation of absorbed photon energy to thermal energy dissipation and photosynthetic electron transport was investigated as a function of photosynthetic photon flux density (PPFD) and temperature in two species of subalpine eucalypt, Eucalyptus nitens (Deane et Maiden) Maiden and E. pauciflora Sieb. ex Spreng. The proportion of absorbed light utilised in photosynthetic electron transport decreased with increasing PPFD, and the decrease was more pronounced the lower the temperature. The proportion diverted into dissipation processes increased with increasing PPFD to a maximum where it reached a plateau. This maximum increased with decreasing temperature. Exposure to a succession of cold (4˚C) nights increased the photochemical quantum yield of photosystem II and decreased the allocation of excitation energy to thermal dissipation processes in conditions of excess light, particularly at low temperatures. Consequently, the photosynthetic electron transport rate (ETR) was higher and heat dissipation rate (HDR) was lower in hardened plants than in non-hardened plants at low temperatures. At 20˚C, ETR was generally higher than HDR in all plants, but as the temperature decreased, HDR became the dominant process. The PPFD at which HDR exceeded ETR decreased with decreasing temperature, and at low temperatures was always lower in non-hardened plants than hardened plants, although quite similar between species.

scholarly journals Photosynthesis Regulation in Response to Fluctuating Light in the Secondary Endosymbiont Alga Nannochloropsis gaditana

2019 ◽  
Vol 61 (1) ◽  
pp. 41-52 ◽  
Author(s):  
Alessandra Bellan ◽  
Francesca Bucci ◽  
Giorgio Perin ◽  
Alessandro Alboresi ◽  
Tomas Morosinotto
Keyword(s):  
Electron Transport ◽  
Electron Flow ◽  
Incident Light ◽  
Photosynthetic Apparatus ◽  
Photosynthetic Electron Transport ◽  
Thermal Dissipation ◽  
Photochemical Quenching ◽  
Nannochloropsis Gaditana ◽  
Fluctuating Light ◽  
Light Fluctuations

Abstract In nature, photosynthetic organisms are exposed to highly dynamic environmental conditions where the excitation energy and electron flow in the photosynthetic apparatus need to be continuously modulated. Fluctuations in incident light are particularly challenging because they drive oversaturation of photosynthesis with consequent oxidative stress and photoinhibition. Plants and algae have evolved several mechanisms to modulate their photosynthetic machinery to cope with light dynamics, such as thermal dissipation of excited chlorophyll states (non-photochemical quenching, NPQ) and regulation of electron transport. The regulatory mechanisms involved in the response to light dynamics have adapted during evolution, and exploring biodiversity is a valuable strategy for expanding our understanding of their biological roles. In this work, we investigated the response to fluctuating light in Nannochloropsis gaditana, a eukaryotic microalga of the phylum Heterokonta originating from a secondary endosymbiotic event. Nannochloropsis gaditana is negatively affected by light fluctuations, leading to large reductions in growth and photosynthetic electron transport. Exposure to light fluctuations specifically damages photosystem I, likely because of the ineffective regulation of electron transport in this species. The role of NPQ, also assessed using a mutant strain specifically depleted of this response, was instead found to be minor, especially in responding to the fastest light fluctuations.

Resistance is useful: diurnal patterns of photosynthesis in C3 and crassulacean acid metabolism epiphytic bromeliads

2002 ◽  
Vol 29 (6) ◽  
pp. 679 ◽  
Author(s):  
Kate Maxwell
Keyword(s):  
Crassulacean Acid Metabolism ◽  
Acid Metabolism ◽  
Photosynthetic Electron Transport ◽  
Co2 Assimilation ◽  
Enzyme Activation ◽  
Photon Flux ◽  
Photon Flux Density ◽  
Cam Plants ◽  
Diurnal Patterns ◽  
Rubisco Activation

This paper originates from a presentation at the IIIrd International Congress on Crassulacean Acid Metabolism, Cape Tribulation, Queensland, Australia, August 2001 Diurnal patterns of photosynthesis in response to environmental variables were investigated in an obligate C3 and a facultative C3-crassulacean acid metabolism (CAM) bromeliad species. A midday depression of photosynthesis occurred in both C3 groups, mediated as a decrease in stomatal conductance in response to increased vapour pressure difference. The response was associated with a reduction in Rubisco activation state during the period of maximum photon flux density. In contrast, the switch to CAM resulted in a strong shift in the pattern of Rubisco carbamylation, with full enzyme activation delayed until the midday period. For the first time it is demonstrated that the pattern of Rubisco activation differs between C3 and CAM plants of the same species under identical conditions. Despite large differences in Rubisco content between C3 and CAM plants, neither the amount of Rubisco or enzyme activity is thought to be limiting for photosynthesis, and it is suggested that Rubisco may function as a nitrogen store. Extreme CO2 diffusion limitation resulted in low rates of atmospheric CO2 assimilation that were associated with high rates of photosynthetic electron transport, and it is likely that photorespiration constitutes a significant electron sink over the entire diurnal course. Leaf morphological and physiological adaptations to drought stress are necessary for the epiphytic lifestyle but limit CO2 assimilation and confound the likelihood of high productivity.

scholarly journals Response of Photosynthetic Performance to Drought Duration and Re-Watering in Maize

Agronomy ◽  
2020 ◽  
Vol 10 (4) ◽  
pp. 533
Author(s):  
Yuying Jia ◽  
Wanxin Xiao ◽  
Yusheng Ye ◽  
Xiaolin Wang ◽  
Xiaoli Liu ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Electron Transport ◽  
Energy Dissipation ◽  
Quantum Yield ◽  
Photosynthetic Electron Transport ◽  
Photosynthetic Performance ◽  
Electron Acceptors ◽  
Drought Duration ◽  
Acceptor Side ◽  
Antioxidase Activity

The drought tolerance and capacity to recover after drought are important for plant growth and yield. In this study, two maize lines with different drought resistance were used to investigate the effects of different drought durations and subsequent re-watering on photosynthetic capacity, electron transfer and energy distribution, and antioxidative defense mechanisms of maize. Under short drought, maize plants decreased stomatal conductance and photosynthetic electron transport rate, and increased NPQ (Non-photochemical quenching) to dissipate excess excitation energy in time and protect the photosynthetic apparatus. With the increased drought duration, NPQ, antioxidase activity, PItotal (total performance index), ∆I/Io, ψEo (quantum yield for electron transport), φEo (efficiency/probability that an electron moves further than QA−), δRo (efficiency/probability with which an electron from the intersystem electron carriers is transferred to reduce end electron acceptors at the PSI acceptor side) and φRo (the quantum yield for the reduction of the end electron acceptors at the PSI acceptor side) were significantly reduced, while Y(NO) (quantum yield of nonregulated energy dissipation) and MDA (malondialdehyde) began to quickly increase. The photosynthetic rate and capacity of photosynthetic electron transport could not recover to the level of the plants subjected to normal water status after re-watering. These findings indicated that long drought damaged the PSI (photosystem I) and PSII (photosystem II) reaction center and decreased the electron transfer efficiency, and this damage could not be recovered by re-watering. Different drought resistance and recovery levels of photosynthetic performance were achieved by different maize lines. Compared with D340, D1798Z had higher NPQ and antioxidase activity, which was able to maintain functionality for longer in response to progressive drought, and it could also recover at more severe drought after re-watering, which indicated its higher tolerance to drought. It was concluded that the capacity of the energy dissipation and antioxidant enzyme system is crucial to mitigate the effects caused by drought, and the capacity to recover after re-watering was dependent on the severity and persistence of drought, adaptability, and recovery differences of the maize lines. The results provide a profound insight to understand the maize functional traits’ responses to drought stresses and re-watering.

Exposure of high-light-grown cultures of Chlorella vulgaris to darkness inhibits the relaxation of excitation pressure: uncoupling of the redox state of the photosynthetic electron transport chain and phenotypic plasticity

Botany ◽  
2017 ◽  
Vol 95 (12) ◽  
pp. 1125-1140 ◽  
Author(s):  
Lauren Hollis ◽  
Norman P.A. Hüner
Keyword(s):  
Electron Transport ◽  
Chlorella Vulgaris ◽  
Electron Transport Chain ◽  
Redox State ◽  
Light Harvesting ◽  
Photosynthetic Electron Transport ◽  
High Light ◽  
Photon Flux ◽  
Photosynthetic Electron Transport Chain ◽  
Transport Chain

Chlorella vulgaris acclimated to high light (HL) conditions exhibited a pale-green phenotype characterized by reduced chlorophyll and light harvesting polypeptide abundance compared with the dark green phenotype of the control, low-light-grown (LL) cultures. We hypothesized that if chloroplast redox status was the sole regulator of phenotype, exposure to darkness should cause reversion of the HL to LL phenotype. Surprisingly, HL cells transferred to darkness or dim light failed to green. Thus, phenotypic reversion is light-dependent with an optimal photon flux density (PFD) of 110 μmol photons·m−2·s−1. HL cells shifted to this PFD exhibited increased chlorophyll and light harvesting polypeptide abundance, which were inhibited by 2,5-dibromo-3-methyl-6-isopropyl-benzoquinone but not by 3-(3′,4′-dichlorophenyl)-1,1-dimethylurea. We conclude that photoacclimation of HL-grown cells to LL is governed by the redox state of the intersystem photosynthetic electron transport chain (PETC) at this PFD. At lower light levels, cells maintained the HL phenotype, despite an oxidized status of the PETC. Because 110 μmol photons·m−2·s−1 was the optimal PFD for protochlorophyllide oxidoreductase accumulation, we suggest that stabilization of light-harvesting polypeptides by chlorophyll binding may also govern photoacclimation in C. vulgaris. The possible role of the metabolic balance between respiration and photosynthesis is also discussed.

Examination of pre-industrial and future [CO2] reveals the temperature-dependent CO2 sensitivity of light energy partitioning at PSII in eucalypts

2010 ◽  
Vol 37 (11) ◽  
pp. 1041 ◽  
Author(s):  
Barry A. Logan ◽  
Carolyn R. Hricko ◽  
James D. Lewis ◽  
Oula Ghannoum ◽  
Nathan G. Phillips ◽  
...  
Keyword(s):  
Electron Transport ◽  
Energy Dissipation ◽  
Fluorescence Emission ◽  
Photosynthetic Electron Transport ◽  
Co2 Assimilation ◽  
Energy Partitioning ◽  
O2 Evolution ◽  
Tree Seedlings ◽  
Temperature Dependent ◽  
Photosynthetic O2 Evolution

We grew faster-growing Eucalyptus saligna Sm. and slower-growing Eucalyptus sideroxylon A. Cunn ex Woolls tree seedlings in sunlit glasshouses at all combinations of 290 µL L–1 (pre-industrial), 400 µL L–1 (modern) or 650 µL L–1 (future) global atmospheric CO2 ([CO2]), and ambient or ambient + 4°C temperature. To assess photosynthetic performance, we simultaneously measured light-saturated CO2 assimilation (Asat) and chlorophyll fluorescence emission along with the capacity for photosynthetic O2 evolution and leaf pigment composition. Photosynthetic response to [CO2] was similar between species. Increasing [CO2] but not temperature increased Asat. The response of photosynthetic electron transport to [CO2] was temperature-dependent and manifested through adjustments in energy partitioning at PSII. Increasing [CO2] resulted in greater PSII operating efficiencies at the elevated temperature. We observed no associated acclimatory adjustments in the capacity for photosynthetic O2 evolution or changes in leaf chlorophyll content. Photoprotective energy dissipation responded to increasing [CO2] and temperature. Across species and treatments, increased energy partitioning to electron transport was always associated with decreased partitioning to energy dissipation. Our results suggest that in response to increasing [CO2] and temperature, E. saligna and E. sideroxylon meet increased demands for the products of electron transport via adjustments in energy partitioning, not through acclimation of the capacity for photosynthetic electron transport or light absorption.

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.

Towards understanding oscillations: a mathematical model of the biochemistry of photosynthesis

1989 ◽  
Vol 323 (1216) ◽  
pp. 369-384 ◽  
Keyword(s):  
Electron Transport ◽  
Carbon Assimilation ◽  
Photon Flux ◽  
Photon Flux Density ◽  
Redox States ◽  
Proton Charge ◽  
Regulatory Systems ◽  
Transport Chain ◽  
High Proton ◽  
Udpglucose Pyrophosphorylase

A general model of electron transport, carbon assimilation, starch and sucrose synthesis was built on the basis of two partial models. Individual reactions were described by their Δ G' 0 , V m and K m values for substrates and products. The system of 33 differential equations was solved on a personal computer programmed in Turbo-PASCAL 3.0. The rate of cytosolic fructose bisphosphatase (FBPase) is modelled to be dependent on the concentration of fructose 2,6-bisphosphate (F2,6BP). The synthesis of the latter is activated by inorganic phosphate and inactivated by triose phosphates. The quantum efficiency of PSII is depressed at high proton charge in thylakoids and at high redox states of the electron transport chain. One of the aims of the model was to check whether these regulatory systems could cause oscillations in photosynthesis. Transients calculated from a low to high photon flux density and from a low to high CO 2 concentration revealed an overshoot but no oscillations. Therefore, it has not been sufficiently proved whether cytosolic FBPase and PSII activity control oscillations in photosynthesis. The phosphate-limited photosynthesis is stable in cases where UDPglucose pyrophosphorylase and ADPglucose pyrophosphorylase have greater affinity for ATP (UTP) than CO 2 assimilation. In a phosphate-limited state high ΔpH is not generated, as electron transport becomes limited by the low concentration of 1,3-diphosphoglycerate.

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