Consequences of impeding in mitochondrial function in Physarum polycephalum. II. Influence on "de novo" generation of contractile activities and responses to glucose and blue light.

The "de novo" generation of longitudinal contractile activity in endoplasmic veins is inhibited by 5 mM KCN, whereas 10 mM alpha-ketoglutarate combined with 5 mM AMP abolishes this inhibiting effect in spite of a continued presence of KCN. An analysis of the Young's modulus and studies on the morphogenesis of endoplasmic veins reveal morphological effects of an impediment of cell respiration: (1) an increased fibrillogenesis and changes in the spatial distribution of cytoplasmic actomyosin fibrils, (2) an impediment of the "de novo" generation of the plasmalemma invaginations, and (3) the appearance of a thick cortical layer of ground-plasm. These effects of KCN do not appear in the presence of alpha-ketoglutarate and AMP, and disappear by their subsequent application. Impediment of cell respiration by 5 mM KCN inhibits the tensiometrically registrable responses to glucose and blue light. Both reactions are restored in the presence of KCN by an additional application of 10 mM alpha-ketoglutarate combined with 5 mM AMP. The importance of mitochondrial function with respect to morphogenetic events and to the perception and transduction of external signals as well as to locomotory reactions of Physarum plasmodia is discussed.