Chlorolemma-A Continuous Membrane Layer between the Plasmalemma and the Streaming Cytoplasm inNitellopsis obtusaandNitella translucens, which takes part in the Generation of the Resting Potential, in its Light-Induced Changes and in the Generation of the Action Potential

At slow stepwise insertion of the glass micro-electrode into the cell of Nitellopsis obtusa and Nitella translucens four potential jumps were recorded which corresponded to the penetration of the micro-electrode across the cell wall, the plasmalemma, the supposed chlorolemma and the tonoplast, respectively. The photo-electric depolarization appeared after the third jump only, which was supposed to be the penetration of a membrane layer between the plasmalemma and the streaming part of the cytoplasm. The vibration of this chlorolemma, caused probably by the protoplasmic streaming, resulted in large (up to 100 mV) hyperpolarizing and depolarizing potential fluctuations when the micro-electrode tip was near to this membrane. During cell excitation the potential difference (p.d.) had changed also across the chlorolemma. It was shown that the potential changes across the chlorolemma, caused by local illumination on the isolated part of the cell, were measurable also at a considerable distance (more than 1-4 cm) from the illuminated and isolated sequence. The lightand electron microphotographs obtained showed that the chloroplasts might really form a very compact layer with tight connections between the neighbouring chloroplasts and that there existed at least one continuous membrane layer which separated the immobile chloroplasts from the streaming cytoplasm. It was concluded that the p.d. measured between the streaming cytoplasm and the external medium was the sum of the p.d.s across the cell wall, the plasmalemma and the chlorolemma, respectively.