scholarly journals Effect of irradiance and nitrate levels on the relationship between gross photosynthesis and electron transport rate in the seagrass Cymodocea nodosa

2015 ◽  
Vol 41 (2) ◽  
pp. 93-105
Author(s):  
Alejandro Cabello-Pasini
Keyword(s):  
Electron Transport ◽  
Electron Transport Rate ◽  
Transport Rate ◽  
Cymodocea Nodosa ◽  
Gross Photosynthesis ◽  
The Relationship

scholarly journals Investigating on relationship between effective quantum efficiency and irradiance

2017 ◽  
Author(s):  
Zi-Piao Ye ◽  
Shuang-Xi Zhou ◽  
Xiao-Long Yang ◽  
Hua-Jing Kang ◽  
Piotr Robakowski
Keyword(s):  
Excited State ◽  
Electron Transport ◽  
Quantum Efficiency ◽  
Cross Section ◽  
Electron Transport Rate ◽  
Photosynthetic Pigment ◽  
Transport Rate ◽  
Absorption Cross ◽  
Ps Ii ◽  
The Relationship

AbstractModels describing the relationship between effective quantum efficiency of PS II (ΦPSII) and irradiance (I) are routinely used to determine how irradiance influences effective quantum efficiency and photosynthetic electron transport rate (ETR). However, with no single model one can accurately describe the relationship between ΦPSII and I, and explain the interdependence between ΦPSII and biophysical properties of photosynthetic pigments, especially in plants growing under low level irradiances. Basing on the mechanistic model of photosynthetic electron transport rate we have developed the model of the relationship between ΦPSII and I. The new model reveals that ΦPSII increases with photochemistry (kP) and heat dissipation (kD). Furthermore, the values of key parameters calculated using the new model were compared with the values calculated with two other empirical models. The new model was perfectly fitted to the light-response curves of ΦPSII. The key calculated photosynthetic parameters: maximum ΦPSII, maximum ETR and their corresponding saturation irradiance were close to the measured values. In addition, our model associates ΦPSII with intrinsic features of photosynthetic pigments. We concluded that ΦPSII decreased with increasing I due to the decrease in the effective absorption cross-section of photosynthetic pigments molecules.HighlightA model of the relationship between effective quantum efficiency of PS II (ΦPSII) and irradiance (I) has been developed. Using this new model it was found that ΦPSII decreased with increasing I due to the decrease in the effective absorption cross-section of photosynthetic pigments molecules.AbbreviationsETRElectron transport rateETRmaxMaximum electron transport rateFSteady-state fluorescenceFm′Maximum fluorescence in the lightFvVariable fluorescence yield of the dark-adapted leafgiDegeneration of energy level of photosynthetic pigment molecules in the ground state igkDegeneration of energy level of photosynthetic pigment molecules in the excited state kIIrradianceNPQNon-photochemical quenchingN0Total light-harvesting pigment moleculesPARsatSaturation irradiance corresponding to ETRmaxkPRate of photochemical reactionkDRate of non-radiative heat dissipationPS IIPhotosystem IIaeInitial slope of light-response curve of electron transport rateα′Fraction of light absorbed by PS IIβ′Leaf absorptanceξ1Probability of photochemistryξ2Probability of non-radiative heat dissipationξ3Probability of fluorescenceσikEigen-absorption cross-section of photosynthetic pigment from ground state i to excited state k due to light illuminationEffective optical absorption cross-section of photosynthetic pigment molecule from ground state i to excited state k due to light illuminationφExciton-use efficiency in PS IIτAverage lifetime of the photosynthetic pigment molecules in the lowest excited stateΣPSIIEffective quantum efficiency of PS II

scholarly journals Updating the steady state model of C4 photosynthesis

2021 ◽  
Author(s):  
Susanne von Caemmerer
Keyword(s):  
Steady State ◽  
Electron Transport ◽  
Electron Transport Rate ◽  
Transport Rate ◽  
Initial Slope ◽  
Carboxylase Activity ◽  
Quantitative Correlation ◽  
Steady State Model ◽  
State Models

AbstractC4 plants play a key role in world agriculture. For example, C4 crops such as maize and sorghum are major contributors to both first and third world food production and the C4 grasses sugarcane; miscanthus and switchgrass are major plant sources of bioenergy. In the challenge to manipulate and enhance C4 photosynthesis, steady state models of leaf photosynthesis provide and important tool for gas exchange analysis and thought experiments that can explore photosynthetic pathway changes. Here the C4 photosynthetic model by von Caemmerer and Furbank (1999) has been updated with new kinetic parameterisation and temperature dependencies added. The parameterisation was derived from experiments on the C4 monocot, Setaria viridis, which for the first time provides a cohesive parametrisation. Mesophyll conductance and its temperature dependence have also been included, as this is an important step in the quantitative correlation between the initial slope of the CO2 response curve of CO2 assimilation and in vitro PEP carboxylase activity. Furthermore, the equations for chloroplast electron transport have been updated to include cyclic electron transport flow and equations have been added to calculate electron transport rate from measured CO2 assimilation rates.HighlightThe C4 photosynthesis model by von Caemmerer and Furbank (1999) has been updated. It now includes temperature dependencies and equations to calculate electron transport rate from measured CO2 assimilation rates.

scholarly journals Mefenpyr-diethyl as a safener for haloxyfop-methyl in bahiagrass

2021 ◽  
Author(s):  
Roque de Carvalho Dias ◽  
Leandro Bianchi ◽  
Vitor Muller Anunciato ◽  
Leandro Tropaldi ◽  
Paulo Vinicius da Silva ◽  
...  
Keyword(s):  
Electron Transport ◽  
Protective Effect ◽  
Plant Height ◽  
Electron Transport Rate ◽  
Transport Rate ◽  
Low Doses ◽  
Protective Response ◽  
Randomized Design ◽  
Dry Biomass ◽  
Completely Randomized Design

Abstract Mefenpyr-diethyl is a foliar-acting safener of the pyrazoline chemical group, and after its absorption, the metabolization and detoxification of herbicides occur in treated plants. Studies have demonstrated the protective effect of this safener for the herbicide fenoxaprop-P-ethyl in grass. Thus, this work aimed to evaluate whether a tank mixture of mefenpyr-diethyl has a protective response to haloxyfop-methyl in non-perennial bahiagrass. The experiment had a completely randomized design and was carried out in a greenhouse, using five replications with a 10x2 factorial scheme and ten doses of haloxyfop-methyl (0.00, 0.24, 0.49, 0.97, 1.95, 3.90, 7.79, 15.59, 31.28, and 62.35 g a.i. ha-1) in the presence or absence of a tank mixture of mefenpyr-diethyl (50 g a.i. ha-1). Phytotoxicity and electron transport rate (ETR) were evaluated at 7, 14, 21, and 28 days after application (DAA), in addition to plant height and dry biomass at 28 DAA. In general, phytotoxicity increased due to the higher levels of the herbicide haloxyfop-methyl. The application of mefenpyr-diethyl, in turn, provided lower levels of phytotoxicity, as well as lower reductions in ETR, height, and dry biomass when compared to untreated plants. These results show the safener action of a tank mixture of mefenpyr-diethyl on low doses of haloxyfop-methyl in non-perennial bahiagrass.

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