Effect of UV-irradiation on protoplasmic streaming, behaviour and structural organization in the slime mould Physarum polycephalum

UV-irradiation (254 nm) affected protoplasmic streaming in Physarum in a variety of ways including increased viscosity of the protoplasm, irregular streaming and an increase in the period of duration. It induced considerable vacuolization of the endoplasm and disruption of the circular invagination system. UV-light induced a negative phototactic response in phaneroplasmodia and reduced or stopped completely their migration. Phase-contrast microscopy of UV-irradiated phaneroplasmodia (10 and 30 min) showed membrane surface blebbing.