The noninvasive monitoring of the redox status of photosynthetic electron transport chains in Hibiscus rosa-sinensis and Tradescantia leaves.

We present an approach to the noninvasive determination of the electron capacity of the intersystem pool of electron carriers in chloroplasts in situ. As apt experimental models, we used the leaves of Hibiscus rosa-sinensis and Tradescantia species. Electron paramagnetic resonance and optical response of P (the primary electron donor in Photosystem I) were applied to measuring electron transport in chloroplasts.

Structural and Functional Aspects of Electron Transport Thermoregulation and ATP Synthesis in Chloroplasts.

The review is focused on analysis of the mechanisms of temperature-dependent regulation of electron transport and ATP synthesis in chloroplasts of higher plants. Importance of photosynthesis thermoregulation is determined by the fact that plants are ectothermic organisms, whose own temperature depends on the ambient temperature. The review discusses the effects of temperature on the following processes in thylakoid membranes: (i) photosystem 2 activity and plastoquinone reduction; (ii) electron transfer from plastoquinol (via the cytochrome bf complex and plastocyanin) to photosystem 1; (iii) transmembrane proton transfer; and (iv) ATP synthesis.

Temperature-dependent regulation of electron transport and ATP synthesis in chloroplasts in vitro and in silico.

The significance of temperature-dependent regulation of photosynthetic apparatus (PSA) is determined by the fact that plant temperature changes with environmental temperature. In this work, we present a brief overview of temperature-dependent regulation of photosynthetic processes in class B chloroplasts (thylakoids) and analyze these processes using a computer model that takes into account the key stages of electron and proton transport coupled to ATP synthesis. The rate constants of partial reactions were parametrized on the basis of experimental temperature dependences of partial photosynthetic processes: (1) photosystem II (PSII) turnover and plastoquinone (PQ) reduction, (2) the plastoquinol (PQH) oxidation by the cytochrome (Cyt) bf complex, (3) the ATP synthase activity, and (4) the proton leak from the thylakoid lumen.

Connectivity between electron transport complexes and modulation of photosystem II activity in chloroplasts.

In chloroplasts, photosynthetic electron transport complexes interact with each other via the mobile electron carriers (plastoquinone and plastocyanin) which are in surplus amounts with respect to photosystem I and photosystem II (PSI and PSII), and the cytochrome b f complex. In this work, we analyze experimental data on the light-induced redox transients of photoreaction center P in chloroplasts within the framework of our mathematical model. This analysis suggests that during the action of a strong actinic light, even significant attenuation of PSII [for instance, in the result of inhibition of a part of PSII complexes by DCMU or due to non-photochemical quenching (NPQ)] will not cause drastic shortage of electron flow through PSI.