Sr. Mcculloch et Mj. Beilby, THE ELECTROPHYSIOLOGY OF PLASMOLYSED CELLS OF CHARA-AUSTRALIS, Journal of Experimental Botany, 48(312), 1997, pp. 1383-1392
The electrophysiology of non-turgid cells of Chara australis was inves
tigated. The data fell into two categories. (i) 20% of cells; these we
re relatively unaffected by plasmolysis (with the exception of a small
depolarization) and retained many aspects of normal electrophysiologi
cal behaviour, such as excitation and K+-state I/V characteristics whe
n exposed to 5 mol m(-3) K+. (ii) 80% of cells; these showed electroph
ysiology significantly altered by plasmolysis. These cells exhibited a
large depolarization and became highly conductive after plasmolysis.
The classic current relaxation kinetics upon voltage step changes dimi
nished. The channels constituting this high conductance state appeared
to be weakly anion selective. Application of Ca2+ channel blocker LaC
l3, did not prevent development of the high conductance. Upon exposure
to 5 mol m(-3) K+,the negative conductance regions were much less pro
nounced than those in turgid cells. Excitation was abolished. Cells in
both categories showed a steady increase in conductance with time, Th
e effects of plasmolysis on cell membrane conductance were irreversibl
e. The information gathered from turgorless Chara cells can be extrapo
lated to explain depolarized or positive resting potentials and predom
inance of weakly anion selective channels in some higher plant cell pr
otoplasts.