scholarly journals Estimation of the steady-state cyclic electron flux around PSI in spinach leaf discs in white light, CO2-enriched air and other varied conditions

2013 ◽  
Vol 40 (10) ◽  
pp. 1018 ◽  
Author(s):  
Jiancun Kou ◽  
Shunichi Takahashi ◽  
Riichi Oguchi ◽  
Da-Yong Fan ◽  
Murray R. Badger ◽  
...  
Keyword(s):  
Steady State ◽  
Electron Flux ◽  
Leaf Tissue ◽  
Linear Electron ◽  
Total Electron ◽  
Leaf Discs ◽  
Relative Water ◽  
Photochemical Yield ◽  
Spinach Leaf ◽  
Upper Estimate

Cyclic electron flux (CEF) around PSI is essential for efficient photosynthesis and aids photoprotection, especially in stressful conditions, but the difficulty in quantifying CEF is non-trivial. The total electron flux through PSI (ETR1) and the linear electron flux (LEFO2) through both photosystems in spinach leaf discs were estimated from the photochemical yield of PSI and the gross oxygen evolution rate, respectively, in CO2-enriched air. ΔFlux = ETR1 – LEFO2 is an upper estimate of CEF. Infiltration of leaf discs with 150 μM antimycin A did not affect LEFO2, but decreased ΔFlux 10-fold. ΔFlux was practically negligible below 350 μmol photons m−2 s−1, but increased linearly above it. The following results were obtained at 980 μmol photons m−2 s−1. ΔFlux increased 3-fold as the temperature increased from 5°C to 40°C. It did not decline at high temperature, even when LEFO2 decreased. ΔFlux increased by 80% as the relative water content of leaf discs decreased from 100 to 40%, when LEFO2 decreased 2-fold. The method of using ΔFlux as a non-intrusive upper estimate of steady-state CEF in leaf tissue appears reasonable when photorespiration is suppressed.

Optimising the linear electron transport rate measured by chlorophyll a fluorescence to empirically match the gross rate of oxygen evolution in white light: towards improved estimation of the cyclic electron flux around photosystem I in leaves

2018 ◽  
Vol 45 (11) ◽  
pp. 1138 ◽  
Author(s):  
Meng-Meng Zhang ◽  
Da-Yong Fan ◽  
Guang-Yu Sun ◽  
Wah Soon Chow
Keyword(s):  
Chlorophyll A ◽  
Oxygen Evolution ◽  
Photosystem I ◽  
Chlorophyll A Fluorescence ◽  
Near Infrared ◽  
Electron Flux ◽  
Linear Electron ◽  
Total Electron ◽  
Gross Rate

The cyclic electron flux (CEF) around photosystem I (PSI) was discovered in isolated chloroplasts more than six decades ago, but its quantification has been hampered by the absence of net formation of a product or net consumption of a substrate. We estimated in vivo CEF in leaves as the difference (ΔFlux) between the total electron flux through PSI (ETR1) measured by a near infrared signal, and the linear electron flux through both photosystems by optimised measurement of chlorophyll a fluorescence (LEFfl). Chlorophyll fluorescence was excited by modulated green light from a light-emitting diode at an optimal average irradiance, and the fluorescence was detected at wavelengths >710 nm. In this way, LEFfl matched the gross rate of oxygen evolution multiplied by 4 (LEFO2) in broad-spectrum white actinic irradiance up to half (spinach, poplar and rice) or one third (cotton) of full sunlight irradiance. This technique of estimating CEF can be applied to leaves attached to a plant.

scholarly journals The enzymology of adenosine triphosphate sulphurylase from spinach leaf tissue. Kinetic studies and a proposed reaction mechanism

1974 ◽  
Vol 139 (1) ◽  
pp. 27-35 ◽  
Author(s):  
W. H. Shaw ◽  
J. W. Anderson
Keyword(s):  
Enzyme Activity ◽  
Steady State ◽  
Exchange Reaction ◽  
Initial Rate ◽  
Leaf Tissue ◽  
Kinetic Studies ◽  
Forward Direction ◽  
Sequential Mechanism ◽  
Spinach Leaf ◽  
Atp Sulphurylase

1. Sulphate-dependent PPi–ATP exchange, catalysed by purified spinach leaf ATP sulphurylase, was correlated with the concentration of MgATP2− and MgP2O72−; ATP sulphurylase activity was not correlated with the concentration of free Mg2+. 2. Sulphate-dependent PPi–ATP exchange was independent of PPi concentration, but dependent on the concentration of ATP and sulphate. The rate of sulphate-dependent PPi–ATP exchange was quantitatively defined by the rate equation applicable to the initial rate of a bireactant sequential mechanism under steady-state conditions. 3. Chlorate, nitrate and ADP inhibited the exchange reaction. The inhibition by chlorate and nitrate was uncompetitive with respect to ATP and competitive with respect to sulphate. The inhibition by ADP was competitive with respect to ATP and non-competitive with respect to sulphate. 4. ATP sulphurylase catalysed the synthesis of [32P]ATP from [32P]PPi and adenosine 5′-sulphatophosphate in the absence of sulphate; some properties of the reaction are described. Enzyme activity was dependent on the concentration of PPi and adenosine 5′-sulphatophosphate. 5. The synthesis of ATP from PPi and adenosine 5′-sulphatophosphate was inhibited by sulphate and ATP. The inhibition by sulphate was non-competitive with respect to PPi and adenosine 5′-sulphatophosphate; the inhibition by ATP was competitive with respect to adenosine 5′-sulphatophosphate and non-competitive with respect to PPi. It was concluded that the reaction catalysed by spinach leaf ATP sulphurylase was ordered; expressing the order in the forward direction, MgATP2− was the first product to react with the enzyme and MgP2O72− was the first product released. 6. The expected exchange reaction between sulphate and adenosine 5′-sulphatophosphate could not be demonstrated.

Metabolic Detoxification of Phenmedipham in Leaf Tissue of Tolerant and Susceptible Species

Weed Science ◽  
1990 ◽  
Vol 38 (3) ◽  
pp. 206-214 ◽  
Author(s):  
H. Maelor Davies ◽  
Alexis Merydith ◽  
Liane Mende-Mueller ◽  
Alpo Aapola
Keyword(s):  
Oxygen Evolution ◽  
Leaf Tissue ◽  
The Other ◽  
Leaf Discs ◽  
Metabolic Detoxification

Phenmedipham metabolism in leaf tissue of sugarbeet (tolerant) and rapeseed (sensitive) was compared. Sugarbeet leaf discs metabolized phenmedipham much more rapidly than rapeseed leaf discs, forming two metabolites of relatively low polarity. The less polar of these (metabolite 21) was a precursor to the other (metabolite 11), and its properties indicate derivation from phenmedipham by a single hydroxylation and monoglycosylation. Synthetic N-hydroxyphenmedipham was converted by both species into a compound that cochromatographs with metabolite 21. Purified metabolite 21 was much less inhibitory to light-driven oxygen evolution by isolated thylakoids of both species than was phenmedipham. Hydroxylation/glycosylation without prior carbamate hydrolysis appears to be a major factor in the tolerance of sugarbeet to phenmedipham.

Study on electron emission by a spherical object: dynamics of trapped particles

2019 ◽  
Vol 85 (2) ◽  
Author(s):  
G. Coppa ◽  
R. Mulas
Keyword(s):  
Steady State ◽  
Electron Emission ◽  
Steady State Solution ◽  
Total Charge ◽  
Electron Charge ◽  
Spherical Object ◽  
Total Electron ◽  
Trapped Particles ◽  
Damped Oscillations ◽  
Spherical Plasma

In this paper, the dynamics of electrons emitted by a spherical object when the total charge of the system is constant is studied in detail. In particular, the condition for which the total electron charge presents damped oscillations is deduced rigorously by considering a perturbation with respect to the steady-state solution. The results obtained can be of utility in simulating the expansion of a spherical plasma by separating the ion and electron time scales.

scholarly journals Phosphoenolpyruvate Carboxylase from Spinach Leaf Tissue

1974 ◽  
Vol 53 (6) ◽  
pp. 829-834 ◽  
Author(s):  
S. K. Mukerji ◽  
S. F. Yang
Keyword(s):  
Phosphoenolpyruvate Carboxylase ◽  
Leaf Tissue ◽  
Spinach Leaf

scholarly journals Measurement of CO2 and H2O Vapor Exchange in Spinach Leaf Discs

1983 ◽  
Vol 71 (1) ◽  
pp. 102-107 ◽  
Author(s):  
Gary C. Harris ◽  
John K. Cheesbrough ◽  
David A. Walker
Keyword(s):  
Leaf Discs ◽  
Spinach Leaf
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