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Physiological implications of action potential in characean cell: Effects on pH bands and spatial pattern of photosynthesisстатья
Информация о цитировании статьи получена из
Web of Science
Дата последнего поиска статьи во внешних источниках: 29 мая 2015 г.
- Авторы: Bulychev A.A., Krupenina N.A.
- Сборник: Action Potential: Biophysical and Cellular Context, Initiation, Phases and Propagation
- Серия: Cell Biology Research Progress
- Год издания: 2010
- Место издания: Nova Science Publishers Incorporated New York
- Первая страница: 65
- Последняя страница: 98
- Аннотация: Most plants generate propagating action potentials (APs) upon injuries or other stimuli. The functional significance of APs is intriguing but still unclear, except for a few cases of insectivorous and sensitive plants. In characean algae, close relatives of higher plants, the membrane excitation exerts marked effects on spatial heterogeneity of chloroplast and plasmalemma functions. The light-dependent “pH bands” in characean internodes are highly sensitive to AP generation. The spatial pattern of apoplastic pH collapses transiently after membrane excitation, indicating temporal inhibition of H+-pump activity in acid zones and of counter-directed passive H+ flows in alkaline areas. The plasmalemma conductance in the alkaline regions decreases several fold during post-excitation period in parallel with the drop of apoplastic pH, while the conductance in acid regions is barely affected. The blockade of high pH channels permeable to H+ (OH–) seems to be the key event in the AP impact on pH pattern and cell electrogenesis. Imaging of chlorophyll fluorescence in resting Chara corallina cells revealed the patterns of photosynthetic activity and non-photochemical quenching, which are finely concerted with the pH bands. Unlike temporal decline of the pH bands after AP propagation, heterogeneity of photosynthesis and fluorescence quenching was temporally enhanced in the post-excitation period. The enhancement might be related to opposite changes in cytosolic pH following the AP-induced cessation of counter-directed H+ fluxes in the alkaline and acid cell regions. Effects of AP on photosynthetic pattern differed strikingly in the absence and presence of the herbicide methyl viologen (MV). Under natural conditions, the spatial heterogeneity of photosynthesis was enhanced after AP owing to stronger inhibition in chloroplasts of alkaline cell regions with minor changes in acid regions. By contrast, the effect of a single AP on photosynthesis in the presence of MV was most pronounced in the acid regions and led to irreversible smoothing of the spatial pattern. These and other results indicate that MV cannot permeate the composite membrane barrier (plasmalemma + chloroplast envelope) under resting conditions but gains access to its interaction sites within the chloroplast during or after AP generation. The gated ion channels might provide a pathway for permeation of physiologically active amounts of MV across the plasmalemma.
- Добавил в систему: Булычев Александр Александрович