Some unusual high speed responses to electrical stimulation in Nitella with microscopic observations of...

Nitella flexilis living in Surrey ponds shows an unusual response to external electrical stimulation. This response is shorter (250 milliseconds) than the normal response (5 seconds), nor does it seem to obey the all-or-none law; decreasing the level of stimulus introduces a delay in its appearance. Microelectrode studies suggest that this response though propagated down the length of the cell is a surface phenomenon as compared to the normal response which is generated across the membrane. Normasky interference microscopic observation of the cytoplasm of those cells exhibiting this response shows large vesicles whose contents rotate, as opposed to those cells showing a normal response which do not show these vesicles. This response is associated with local extinction of groups of Nitella flexilis from ponds in Surrey and a temporary reduction in numbers in certain areas of the New Forest. Electrical excitation itself induces vesicle formation and its associated response in Nitella flexilis, and to a far lesser degree in Nitella translucens. In Nitella translucens alternating electromagnetic fields of low strength induce the formation of vesicles whose contents actively rotate in some individual cells. These vesicles are always accompanied by distortions in electrical response to stimulation. In its response to electromagnetic fields, Nitella translucens is very variable. Nitella opaca exhibits the same response as Nitella flexilis including the same fragility of survival. Electrical studies may throw light on the contentious problem as to whether Nitella opaca is in reality a separate species from Nitella flexilis.