ELECTROROTATIONAL SPECTRA OF PROTOPLASTS GENERATED FROM THE GIANT MARINE ALGA VALONIA UTRICULARIS

Protoplasts of Valonia utricularis is lacking the large central vacuol e can be generated by cutting multi-nucleated, giant ''mother'' cells into small pieces after short exposure to air. When the protoplasmic c ontent was squeezed out into sea water, irregularly shaped, green colo ured aggregates were formed which changed into spherical protoplasts ( radius of 20-60 mu m) after about 2 h. In these protoplasts the dense internal material (consisting mainly of organelles) was separated from the plasmalemma by a thin transparent layer containing a large number of small lipid vesicles. Cell wall regeneration occurred rapidly afte r protoplast formation. A central vacuole developed after about 10 h. The regenerated cells continued to grow and were viable for several mo nths. Electrorotation studies on 2-3 h old protoplasts at pH 7 in low- and fairly high-conductivity solutions showed one or two anti-field r otation peaks (depending on medium conductivity) between 10 kHz to 1 M Hz as well as one co-field rotation peak between 10 MHz to 100 MHz. Th e rotation spec tra could not be fitted on the basis of the single- (o r multi-) shell model (i.e., by modelling the cells as a homogeneous s phere surrounded by one or more layers). However, fairly good agreemen t between the experimental data and theory could be obtained by assumi ng that the rotational behaviour of the protoplasts depends not only o n passive electrical properties of the plasmalemma but is influenced b y ''mobile charges'' of carrier transport systems and/or the dielectri c behaviour of the aggregated chloroplasts and vesicles.