Chlorolemma-A Continuous Membrane Layer between the Plasmalemma and the Streaming Cytoplasm in Nitellopsis obtusa and Nitella 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 intothe cell of Nitellopsis obtusa andNitella translucens four potentialjumps were recorded which corresponded to the penetration ofthe micro-electrode across the cell wall, the plasmalemma, thesupposed chlorolemma and the tonoplast, respectively. The photo-electricdepolarization appeared after the third jump only, which wassupposed to be the penetration of a membrane layer between theplasmalemma and the streaming part of the cytoplasm. The vibrationof this chlorolemma, caused probably by the protoplasmic streaming,resulted in large (up to 100 mV) hyperpolarizing and depolarizingpotential fluctuations when the micro-electrode tip was nearto this membrane. During cell excitation the potential difference(p.d.) had changed also across the chlorolemma- It was shownthat the potential changes across the chlorolemma, caused bylocal illumination on the isolated part of the cell, were measurablealso at a considerable distance (more than 1.4 cm) from theilluminated and isolated sequence. The light- and electron microphotographsobtained showed that the chloroplasts might really form a verycompact layer with tight connections between the neighbouringchloroplasts and that there existed at least one continuousmembrane layer which separated the immobile chloroplasts fromthe streaming cytoplasm. It was concluded that the p.d. measuredbetween the streaming cytoplasm and the external medium wasthe sum of the p.d.s across the cell wall, the plasmalemma andthe chlorolemma, respectively. Key words: Resting potential, Photo-electric responses, Characean algae, Chlorolemma