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Start Over Creator Heber, U.

1. Oscillations in photosynthesis and reduction of photosystem 1 acceptor side in sunflower leaves. Functional cytochrome b6/f photosystem 1 ferredoxin-NADP reductase supercomplexes

Creator:
Lais, A., Oja, V., Walker, D., and Heber, U.
Format:
print
Type:
model:internalpart and TEXT
Language:
Multiple languages
Description:
CO2 and O2 exchange rates, chlorophyll fluorescence and P700 oxidation (absorption at 830 nm) were recorded in Helianthus amuus L. leaves grown in soil in a growth cabinet. Phase-portraits of CO2 exchange rate plotted against three other parameters were ušed to interpret control of electron transport during photosynthesis oscillations, initiated by transfer from air to the saturating CO2. Plots of the CO2 exchange rate vs. P700 revealed that the P700 part which remained oxidized was almost proportional to CO2 exchange rate during both the ascending and descending phase of oscillations.
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

2. Steady-state and induction kinetics of the photosynthetic electron transport related to donor side oxidation and acceptor side reduction of photosystem 1 in sunflower leaves

Creator:
Laisk, A., Oja, V., and Heber, U.
Format:
print
Type:
model:internalpart and TEXT
Language:
Multiple languages
Description:
The photosynthetic CO2 exchange rate, chlorophyll fluorescence and P700 oxidation (absorption at 830 nm) were recorded in attached leaves of sunflower plants grown in soil by irradiance 460 pmol m'2 s‘i. Ehiring the photosynthesis in 510 cm^ m*3 CO2, 1 % O2, photosystem 1 (PS 1) effíciency was ahnost totally determined by the donor side oxidation under all irradiances. Fluorescence data showed that this control was exercised mostly by ApH-dependent plastoquinol oxidation. At 1.5 pM intracellular [CO2], the PS 1 reduction level on the acceptor side became signifícant and increased as [CO2] -> 0. ApH controlled the electron flow when the rate exceeded the value of 50 pmol(e‘) m'2 s‘i, which was close to the rate supporting photorespiration and CO2 reassimilation at CO2 compensation concentration in 21 % O2. The ApH ability to control the electron transport rate adequately prevented electron carriers reduction at PS 1 acceptor side, with stomata dosed under stress. When the low CO2 oř carbon reduction enzymes inactivation restricted the electron transport downstream of PS 1, open PS 1 centres (oxidised on acceptor sides) percentage declined in proportion to CO2 uptake rate. This makes us doubt the common belief that the rapid electron transport in photosynthesis involves interconnected, mobile electron carrier pools of plastocyanin and ferredoxin (Fd). Rather, the implications are explored in terms of supercomplexes involving cytochrome b(Jf, PC, PS 1, Fd and Fd-NADP reductase.
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

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