Dynamics of the energy flow through photosystem II under changing light conditions: a model approach

2006 ◽  
Vol 33 (3) ◽  
pp. 229 ◽  
Author(s):  
Albert Porcar-Castell ◽  
Jaana Bäck ◽  
Eija Juurola ◽  
Pertti Hari

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).

1990 ◽  
Vol 17 (5) ◽  
pp. 579 ◽  
Author(s):  
JP Krall ◽  
GE Edwards

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.


2013 ◽  
Vol 50 (3) ◽  
pp. 343-352 ◽  
Author(s):  
E. M. FONSECA JÚNIOR ◽  
J. CAMBRAIA ◽  
C. RIBEIRO ◽  
M. A. OLIVA ◽  
J. A. OLIVEIRA ◽  
...  

SUMMARYWe aimed to evaluate aluminium (Al) effects on the photosynthetic apparatus of two rice cultivars with contrasting tolerances to Al. Nine-days-old seedlings were exposed to 0 or 1 mM Al for 10 days, and then dry mass, Al and chloroplastidic pigment contents and photosynthetic parameters were determined. Al accumulated mainly in the roots of the Al-treated plants. In the leaves, Al increased only in the sensitive cultivar, but there was no difference between the cultivars in Al-treated plants. The root and leaf dry mass, the net carbon assimilation rate, stomatal conductance and internal CO2 concentration were all reduced in response to Al application, but only in the sensitive cultivar. Both the initial fluorescence and potential photochemical efficiency of photosystem II were unresponsive to the Al treatments, regardless of the cultivar. In the Al-sensitive cultivar, Al provoked significant decreases in the photochemical quenching coefficient, quantum yield of photosystem II electron transport and apparent electron transport rate, in parallel to an unaltered non-photochemical quenching coefficient. All of these parameters remained at the control levels in the tolerant cultivar. The chloroplastidic pigment content increased only in the Al-tolerant cultivar, whereas it remained unaltered after Al treatment in the sensitive cultivar. In conclusion, Al induced stomatal and (most likely) photochemical constraints on photosynthesis but with no apparent signs of photoinhibition in the Al-sensitive cultivar. Despite the similar Al levels of the cultivars, unchanging biomass accumulation or photosynthetic performance in the tolerant cultivar challenged with Al highlights its higher intrinsic ability to cope with Al stress.


1993 ◽  
Vol 48 (3-4) ◽  
pp. 163-167
Author(s):  
Koichi Yoneyama ◽  
Yoshihiro Nakajima ◽  
Masaru Ogasawara ◽  
Hitoshi Kuramochi ◽  
Makoto Konnai ◽  
...  

Abstract Through the studies on structure-activity relationships of 5-acyl-3-(1-aminoalkylidene)-4-hydroxy-2 H-pyran-2,6(3 H)-dione derivatives in photosystem II (PS II) inhibition, overall lipophilicity of the molecule was found to be a major determinant for the activity. In the substituted N -benzyl derivatives, not only the lipophilicity but also the electronic and steric characters of the substituents greatly affected the activity. Their mode of PS II inhibition seemed to be similar to that of DCMU , whereas pyran-enamine derivatives needed to be highly lipophilic to block the electron transport in thylakoid membranes, which in turn diminished the permeability through biomembranes.


1984 ◽  
Vol 39 (5) ◽  
pp. 374-377 ◽  
Author(s):  
J. J. S. van Rensen

The reactivation of the Hill reaction in CO2-depleted broken chloroplasts by various concentrations of bicarbonate was measured in the absence and in the presence of photosystem II herbicides. It appears that these herbicides decrease the apparent affinity of the thylakoid membrane for bicarbonate. Different characteristics of bicarbonate binding were observed in chloroplasts of triazine-resistant Amaranthus hybridus compared to the triazine-sensitive biotype. It is concluded that photosystem II herbicides, bicarbonate and formate interact with each other in their binding to the Qв-protein and their interference with photosynthetic electron transport.


1988 ◽  
Vol 43 (11-12) ◽  
pp. 871-876 ◽  
Author(s):  
Imre Vass ◽  
Narendranath Mohanty ◽  
Sándor Demeter

Abstract The effect of photoinhibition on the primary (QA) and secondary (QB) quinone acceptors of photosystem I I was investigated in isolated spinach thylakoids by the methods of thermoluminescence and delayed luminescence. The amplitudes of the Q (at about 2 °C) and B (at about 30 °C) thermoluminescence bands which are associated with the recombination of the S2QA- and S2QB charge pairs, respectively, exhibited parallel decay courses during photoinhibitory treatment. Similarly, the amplitudes of the flash-induced delayed luminescence components ascribed to the recombination of S20A and S2OB charge pairs and having half life-times of about 3 s and 30 s, respectively, declined in parallel with the amplitudes of the corresponding Q and B thermoluminescence bands. The course of inhibition of thermoluminescence and delayed luminescence intensity was parallel with that of the rate of oxygen evolution. The peak positions of the B and Q thermoluminescence bands as well as the half life-times of the corresponding delayed luminescence components were not affected by photoinhibition. These results indicate that in isolated thylakoids neither the amount nor the stability of the reduced OB acceptor is preferentially decreased by photoinhibition. We conclude that either the primary target of photodamage is located before the O b binding site in the reaction center of photosystem II or QA and OB undergo simultaneous damage.


1988 ◽  
Vol 53 (22) ◽  
pp. 2205-2207 ◽  
Author(s):  
K. Sadra ◽  
C. M. Maziar ◽  
B. G. Streetman ◽  
D. S. Tang

2017 ◽  
Vol 19 (6) ◽  
pp. 884-906 ◽  
Author(s):  
Viktoria C. E. Langer ◽  
Wolfgang Maennig ◽  
Felix Richter

The awarding of the Olympic Games to a certain city or the announcement of a city’s Olympic bid may be considered as a news shock that affects agents’ market expectations. A news shock implies potential impacts on the dynamic adjustment process that change not only the volatility but also the long-run steady-state levels of endogenous economic variables. In this study, we contribute to and extend previous researchers’ attempts to empirically test for the Olympic Games as a news shock by implementing full structural models and by matching Olympic hosts and bidders to structurally similar countries.


Biochemistry ◽  
2005 ◽  
Vol 44 (28) ◽  
pp. 9746-9757 ◽  
Author(s):  
Boris K. Semin ◽  
Elena R. Lovyagina ◽  
Kirill N. Timofeev ◽  
Ilya I. Ivanov ◽  
Andrei B. Rubin ◽  
...  

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