Yoshiharu Oda

BLUE AND NEAR ULTRAVIOLET REVERSIBLE PHOTOREACTION IN CONIDIAL DEVELOPMENT OF THE FUNGUS, ALTERNARIA TOMATO

In the sporulation of Alternaria tomato, conidiophores are induced by near ultraviolet irradiation but not by darkness, and the conidia develop only when the irradiation is followed by a period of darkness. Conidial development is suppressed by a short exposure to blue light at a definite time during the dark period following the inductive irradiation. The suppression of conidial development by blue light can be reversed by exposure to near ultraviolet light immediately following the blue light irradiation. This reversion is reversibly suppressed by a further exposure to blue light immediately following near ultraviolet irradiation.

Further studies on the blue and near ultraviolet reversible photoreaction with an intracellular particulate fraction of the fungus, Alternaria tomato

Further studies have been made on the blue and near ultraviolet-reversible photoreaction in a cell-free system of the fungus Alternaria tomato, prepared by two-layer sucrose density gradient centrifugation. A light-minus-dark difference spectrum of the supernatant fraction showed a dip in the near ultraviolet region, mainly at 280 nm, when irradiated with near ultraviolet light which could not be reversed by following the initial irradiation with blue light. The difference spectrum of the dialyzed particulate fraction, located in the 68% sucrose band, showed a peak absorbance in the blue region, mainly at 400 nm, when irradiated with near ultraviolet light, and also could not be reversed by blue light. When the particulate fraction plus the supernatant fraction was irradiated with near ultraviolet light, the increment rate of peak absorbance in the blue region increased compared to that of the particulate fraction lacking the supernatant, and both peak absorbance in the blue region and the dip in the near ultraviolet region were reversed by irradiation with blue light following the application of near ultraviolet light. Thus, it was concluded that two photoresponsive systems are involved in blue and near ultraviolet reversible photoreaction on an intracellular particulate fraction.

EFFECT OF POLYOXIN ON THE MORPHOGENESIS OF THE FUNGUS, ALTERNARIA TOMATO WITH SPECIAL REFERRENCE TO PHOTOSPORULATION

Photosporulation of Alternaria tomato was very little influenced by polyoxin at concentrations below 10 μg/ml, although hyphae and conidia were morphologically affected. The hyphae grown in the presence of polyoxin were easily disrupted.