Фотоиндуцированная генерация электрических потенциалов в мембранах растительной клетки

Пикуленко, М.М.

Автор: Пикуленко М.М.
Год издания: 2005
Место издания: СТ-ПРИНТ г. Москва
Объём: 22 страниц
Монография
DOI: 10.13140/RG.2.1.4282.5042
Аннотация: The task of assessing biological systems includes monitoring the physiological condition of the organism, cells, and the organelles. In the case of green plants, analysis of chlorophyll fluorescence provides considerable information, including the efficiency of charge separations in photosystem II (PSII), the rate of linear electron transport, and “energy-dependent quenching” related to the pH gradient (pH) at the chloroplast thylakoid membranes. In addition to pH, the transmembrane electric potential of thylakoids is crucial for energy conversion. Unlike the fluorescence parameters, correct measurements of the transmembrane potential can be made with microelectrodes on certain plant species possessing giant chloroplasts; e.g., Anthoceros. The choice of a hornwort Anthoceros as a test object for assessing the quality of water is substantiated by such advantages as the feasibility of simultaneous measurements of the chloroplast membrane potential, the electric potential changes at the cell membrane, and changes in chlorophyll fluorescence parameters occurring upon the absorption of photosynthetically active radiation (PAR). Its thin thallus facilitates the access of substances from the outer medium to the cell surface, which is important for testing the action of physiologically active agents on photopotentials of the chloroplast and cell membranes. In this respect, Anthoceros thalli are beneficial, because the penetration of substances into the leaves of a vast majority of species is hampered by leaf multilayer structure and numerous aerial cavities in intercellular spaces. The use of small-size thalli necessitates the application of sensitive fluorometric devices collecting light emission from the area of 0.01 to 10 mm2. Specialized fluorometers  a Microscopy-PAM (Walz, Germany) based on the saturation pulse method and a plant efficiency analyzer (PEA, Hansatech, United Kingdom) designed for measurements of the fluorescence induction curves with a time resolution of 10 s  fully meet these requirements. The Microscopy-PAM device allows measurements on microscopic parts of a thallus such parameters as the quantum yield of the charge separations in PSII (F/Fm’), coefficient of photochemical quenching related to the redox state of PSII primary acceptor, and the coefficient of nonphotochemical quenching indicative of energy-dependent fluorescence quenching related to pH formation in the thylakoids. A remarkable property of Anthoceros cells is an electrical excitation of the plasma membrane in response to light pulses with a length of few seconds. The action potentials are enhanced upon deenergization of cells with phosphorylation uncouplers and are suppressed upon the excessive energization in the presence of some electron acceptors (methyl viologen). The feasibility of a complex assessment of the cell physiological condition based on meaurements of photoelectric responses of chloroplasts, light-triggered action potential at the plasma membrane, and paremeters of photosynthetic activity implies that the micromethods are promising for cell biomonitoring. By assaying the physiological condition of plant test object researchers may reveal slight changes in phyciochemical parameters of the outer medium.
Добавил в систему: Пикуленко Марина Маиловна

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Фотоиндуцированная генерация электрических потенциалов в мембранах растительной клеткикнига

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