Electrophysiological characteristics of the unicellular green alga Micrasterias torreyi |
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Authors: | Päivi Vuorio Juhani Lehtonen |
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Institution: | Dept of Biology, Univ. of Turku, SF-20500 Turku, Finland. |
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Abstract: | The electrophysiological characteristics of the unicellular green alga Micrasterias torreyi Bail. are studied here for the first time using microelectrode techniques. The resting potential of the plasma membrane varied between –39.5 and –42.2 mV for different developmental stages of the dividing cell and was –41.7 mV ( se = 3.2, n = 9) in the interphase cells. The resting potential of the chloroplast envelope was lower, –53.9 mV ( se = 3.6, n = 15). Supraoptimal K+ (20 m M ) had no clear effects on the plasma membrane but caused a depolarization of 10 mV in the chloroplast. Additional external Ca2+ (10 m M ) depolarized the membrane potential quite strongly (by 23 mV). Low external pH did not affect the resting potential of the cell. There is a marked difference in the resting potential values between non-vacuolated cells (about –40 mV), to which Micrasterias belongs, and vacuolated plant cells (–100 to –250 mV). This indicates the participation of the tonoplast in the transport of ions and charged molecules in vacuolated cells. Na+ and Cl?, which play an important role in ion metabolism in most plant cells, are not needed by Micrasterias . |
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Keywords: | Calcium electrophysiology membrane potential Micrasterias torreyi potassium |
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