Light use in relation to carbon gain in the mangrove, Avicennia marina, under hypersaline conditions

1999 ◽  
Vol 26 (3) ◽  
pp. 245 ◽  
Author(s):  
M. A. Sobrado ◽  
M. C. Ball
Keyword(s):  
Electron Transport ◽  
Avicennia Marina ◽  
Co2 Assimilation ◽  
Photochemical Quenching ◽  
Carbon Gain ◽  
Co2 Concentrations ◽  
Fluorescence Characteristics ◽  
Electron Transport Rates ◽  
Non Photochemical Quenching ◽  
Intercellular Co2

Photosynthesis was studied in relation to light use in the mangrove, Avicennia marina (Forsk.) Vierh. var. australasica (Walp.) Moldenke, growing under soil salinities equivalent to one and two times seawater (i.e. 35 and 60‰). Midday CO2 assimilation rates averaged 7.6 0.7 and 4.3 0.3 µmol m–2 s–1 at the seawater and hypersaline sites, respectively. Despite this difference, xanthophyll pool sizes per Chl and epoxidation states were similar at both sites. Non-photochemical quenching also indicated comparable energy dissipation from pigment beds. Electron transport rates calculated from fluorescence characteristics were also similar and exceeded the requirements to sustain measured assimilation rates. However, cell wall conductance was low in seawater plants (75 mmol m2 s–1 ) and declined to 40 mmol m–2 s–1 in hypersaline plants. This would cause CO2 concentrations in chloroplasts (Cc ) to be lower than expected from measurements of intercellular CO2 concentrations (Ci ). In seawater plants, Cc was estimated to be 144 µmol mol–1 when Ci was 245 mmol mol–1, while values for Cc and Ci in hypersaline plants were 78 and 212 mmol mol–1, respectively. Reductions in Cc would enhance rates of photorespiration relative to assimilation, with the higher photorespiratory rates being sufficient to account for apparent excess electron transport rates.

Characterisation of Three Components of Non-photochemical Fluorescence Quenching and Their Response to Photoinhibition

1988 ◽  
Vol 15 (2) ◽  
pp. 163 ◽  
Author(s):  
B Demmig ◽  
K Winter
Keyword(s):  
Fluorescence Quenching ◽  
Heat Dissipation ◽  
Photosynthetic Electron Transport ◽  
Co2 Assimilation ◽  
Nerium Oleander ◽  
Photochemical Quenching ◽  
Ps Ii ◽  
Fluorescence Characteristics ◽  
Non Photochemical Quenching ◽  
Three Components

Three components of non-photochemical fluorescence quenching were distinguished according to their response to irradiance and to their relaxation kinetics upon darkening. Two components of quenching were restricted to excessive irradiance and were interpreted to reflect radiationless dissipation. One relaxed rapidly upon darkening, and increased sharply when irradiance became excessive, i.e. as soon as net CO2 assimilation rate was no longer linearly related to irradiance, and attained a maximum value with only small further increases in irradiance. The second component relaxed slowly, increased mark- edly when the rapidly relaxing component had reached its maximum, and continued to increase linearly with increasing irradiance. The third component was already present at low irradiances, relaxed very slowly, and may be related to an altered distribution of excitation energy between PS II and PS I. Following exposure to weak illumination under conditions preventing photosynthetic electron transport (20 mbar O2, zero CO2), the reduction state of Q was initially high and decreased as non- photochemical fluorescence quenching indicative of radiationless dissipation developed. Subsequent to photoinhibitory treatments in high light and 20 mbar O2, zero CO2, an increased reduction state of Q as well as increased non-photochemical quenching of the two types indicative of increased heat dissipation was observed. In sunflower a lasting increase in the reduction state of Q was observed and fluorescence characteristics reflected photoinhibitory damage. In Nerium oleander, increased radiationless dissipation of the slowly relaxing type was the predominant response and the reduction state of Q was increased only transiently.

scholarly journals The JcWRKY tobacco transgenics showed improved photosynthetic efficiency and wax accumulation during salinity

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Prashant More ◽  
Parinita Agarwal ◽  
Priyanka S. Joshi ◽  
Pradeep K. Agarwal
Keyword(s):  
Electron Transport ◽  
Photosynthetic Efficiency ◽  
Crop Productivity ◽  
Major Constituent ◽  
Photochemical Quenching ◽  
Subtle Effect ◽  
Cellular Reactive Oxygen Species ◽  
Photosynthesis Efficiency ◽  
Major Factors ◽  
Non Photochemical Quenching

AbstractSalinity is one of the major factors negatively affecting crop productivity. WRKY transcription factors (TFs) are involved in salicylic acid (SA) mediated cellular reactive oxygen species homeostasis in response to different stresses, including salinity. Therefore, the effect of NaCl, NaCl + SA and SA treatments on different photosynthesis-related parameters and wax metabolites were studied in the Jatropha curcas WRKY (JcWRKY) overexpressing tobacco lines. JcWRKY transgenics showed improved photosynthesis rate, stomatal conductance, intercellular CO2 concentration/ambient CO2 concentration ratio (Ci/Ca ratio), electron transport rate (ETR), photosynthesis efficiency (Fv/Fm), photochemical quenching (qP), non-photochemical quenching (NPQ) and quantum yield of PSII electron transport (ΦPSII) in response to salinity stress, while exogenous SA application had subtle effect on these parameters. Alkane, the major constituent of wax showed maximum accumulation in transgenics exposed to NaCl. Other wax components like fatty alcohol, carboxylic acid and fatty acid were also higher in transgenics with NaCl + SA and SA treatments. Interestingly, the transgenics showed a higher number of open stomata in treated plants as compared to wild type (WT), indicating less perception of stress by the transgenics. Improved salinity tolerance in JcWRKY overexpressing tobacco transgenics is associated with photosynthetic efficiency and wax accumulation, mediated by efficient SA signalling. The transgenics showed differential regulation of genes related to photosynthesis (NtCab40, NtLhcb5 and NtRca1), wax accumulation (NtWIN1) and stomatal regulation (NtMUTE, NtMYB-like, NtNCED3-2 and NtPIF3). The present study indicates that JcWRKY is a potential TF facilitating improved photosynthesis with the wax metabolic co-ordination in transgenics during stress.

scholarly journals The chloroplast NADPH thioredoxin reductase C, NTRC, controls non-photochemical quenching of light energy and photosynthetic electron transport inArabidopsis

2016 ◽  
Vol 39 (4) ◽  
pp. 804-822 ◽  
Author(s):  
Belén Naranjo ◽  
Clara Mignée ◽  
Anja Krieger-Liszkay ◽  
Dámaso Hornero-Méndez ◽  
Lourdes Gallardo-Guerrero ◽  
...  
Keyword(s):  
Electron Transport ◽  
Thioredoxin Reductase ◽  
Photosynthetic Electron Transport ◽  
Light Energy ◽  
Photochemical Quenching ◽  
Non Photochemical Quenching

scholarly journals Physiological and microclimatic consequences of variation in agricultural management of maize

2020 ◽  
Vol 99 (1) ◽  
pp. 132-148
Author(s):  
Rosa Guadalupe Pérez-Hernández ◽  
Manuel Jesus Cach-Pérez ◽  
Rosaura Aparacio-Fabre ◽  
Hans Van der Wal ◽  
Ulises Rodríguez-Robles
Keyword(s):  
Electron Transport ◽  
Soil Temperature ◽  
Electron Transport Rate ◽  
Agricultural Management ◽  
Transport Rate ◽  
Management Systems ◽  
Photochemical Quenching ◽  
Physiological Performance ◽  
Maize Plants ◽  
Non Photochemical Quenching

Background: Maize is cultivated under different agricultural management systems, which influence the ecological dynamics of the crop, and therefore the physiology of the plant. Questions: What is the effect of different agricultural management on the microclimate and the physiology of maize plants? Studied species: Zea mays L. Study site and dates: Nacajuca, Tabasco, Mexico; January to April 2017. Methods: Physiological performance of maize plants and microclimatic variation in the crop area was characterized under three management systems: maize monoculture, maize-bean, and maize-bean-squash intercropping. Each treatment was established in three 100 m2 plots (300 m2 per treatment). Four measurements were taken between days 33 and 99 after maize sowing, to characterize five microclimatic parameters (relative air humidity, air and soil temperature, vapor-pressure deficit and soil volumetric water content) and nine physiological parameters (photosynthesis, transpiration, water use efficiency, stomatal conductance, electron transport rate, quantum efficiency of photosystem II, non-photochemical quenching, foliar water potential and chlorophyll content). Results: Maximum soil temperature was up to 4.4 ºC less in the maize-bean system than in the monoculture at 15:00 h; soil in the maize-bean-squash intercropping retained up to 45 % more water than the monoculture throughout the day. Photosynthesis and electron transport rate in the maize-bean intercropping was up to 32 % higher than in the monoculture. The highest non-photochemical quenching and transpiration rate were observed in the maize-bean-squash system. Conclusions: The maize-bean and maize-bean-squash combination provides maize plants with lower soil temperature and higher water availability, allowing them better physiological performance compared to monoculture.

scholarly journals Providing an additional electron sink by the introduction of cyanobacterial flavodiirons enhances the growth of Arabidopsis thaliana in varying light

2020 ◽  
Author(s):  
Suresh Tula ◽  
Fahimeh Shahinnia ◽  
Michael Melzer ◽  
Twan Rutten ◽  
Rodrigo Gómez ◽  
...  
Keyword(s):  
Arabidopsis Thaliana ◽  
Electron Transport ◽  
Photosystem I ◽  
Photosynthetic Electron Transport ◽  
Photosynthetic Performance ◽  
Growth Potential ◽  
Photochemical Quenching ◽  
Transport Chain ◽  
Non Photochemical Quenching ◽  
Electron Sink

AbstractThe ability of plants to maintain photosynthesis in a dynamically changing environment is of central importance for their growth. As their photosynthetic machinery typically cannot adapt rapidly to fluctuations in the intensity of radiation, the level of photosynthetic efficiency is not always optimal. Cyanobacteria, algae, non-vascular plants (mosses and liverworts) and gymnosperms all produce flavodiirons (Flvs), a class of proteins not represented in the angiosperms; these proteins act to mitigate the photoinhibition of photosystem I. Here, genes specifying two cyanobacterial Flvs have been expressed in the chloroplasts of Arabidopsis thaliana in an attempt to improve the robustness of Photosystem I (PSI). The expression of Flv1 and Flv3 together shown to enhance the efficiency of the utilization of light and to boost the plant’s capacity to accumulate biomass. Based on an assessment of the chlorophyll fluorescence in the transgenic plants, the implication was that photosynthetic activity (including electron transport flow and non-photochemical quenching during a dark-to-light transition) was initiated earlier in the transgenic than in wild type plants. The improved photosynthetic performance of the transgenics was accompanied by an increased production of ATP, an acceleration of carbohydrate metabolism and a more pronounced partitioning of sucrose into starch. The indications are that Flvs are able to establish an efficient electron sink downstream of PSI, thereby ensuring that the photosynthetic electron transport chain remains in a more oxidized state. The expression of Flvs in a plant acts to both protect photosynthesis and to control the ATP/NADPH ratio; together, their presence is beneficial for the plant’s growth potential.

scholarly journals The role of Cytochrome $$\text {b}_{6}\text {f}$$ in the control of steady-state photosynthesis: a conceptual and quantitative model

2021 ◽  
Author(s):  
J. E. Johnson ◽  
J. A. Berry
Keyword(s):  
Steady State ◽  
Electron Transport ◽  
Transport System ◽  
Carbon Metabolism ◽  
Quantitative Model ◽  
Electron Transport System ◽  
Photochemical Quenching ◽  
Photosynthetic Control ◽  
Non Photochemical Quenching

AbstractHere, we present a conceptual and quantitative model to describe the role of the Cytochrome $$\hbox {b}_{6}\hbox {f}$$ b 6 f complex in controlling steady-state electron transport in $$\hbox {C}_{3}$$ C 3 leaves. The model is based on new experimental methods to diagnose the maximum activity of Cyt $$\hbox {b}_{6}\hbox {f}$$ b 6 f in vivo, and to identify conditions under which photosynthetic control of Cyt $$\hbox {b}_{6}\hbox {f}$$ b 6 f is active or relaxed. With these approaches, we demonstrate that Cyt $$\hbox {b}_{6}\hbox {f}$$ b 6 f controls the trade-off between the speed and efficiency of electron transport under limiting light, and functions as a metabolic switch that transfers control to carbon metabolism under saturating light. We also present evidence that the onset of photosynthetic control of Cyt $$\hbox {b}_{6}\hbox {f}$$ b 6 f occurs within milliseconds of exposure to saturating light, much more quickly than the induction of non-photochemical quenching. We propose that photosynthetic control is the primary means of photoprotection and functions to manage excitation pressure, whereas non-photochemical quenching functions to manage excitation balance. We use these findings to extend the Farquhar et al. (Planta 149:78–90, 1980) model of $$\hbox {C}_{3}$$ C 3 photosynthesis to include a mechanistic description of the electron transport system. This framework relates the light captured by PS I and PS II to the energy and mass fluxes linking the photoacts with Cyt $$\hbox {b}_{6}\hbox {f}$$ b 6 f , the ATP synthase, and Rubisco. It enables quantitative interpretation of pulse-amplitude modulated fluorometry and gas-exchange measurements, providing a new basis for analyzing how the electron transport system coordinates the supply of Fd, NADPH, and ATP with the dynamic demands of carbon metabolism, how efficient use of light is achieved under limiting light, and how photoprotection is achieved under saturating light. The model is designed to support forward as well as inverse applications. It can either be used in a stand-alone mode at the leaf-level or coupled to other models that resolve finer-scale or coarser-scale phenomena.

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