Abstract
1) The present paper deals with the thermal effect on the germination of the conidia, the growth of the mycelium and the formation of the conidia of Helminthosporium Oryzae, and also the thermal death point.
2) The optimum temperature for the germination of the conidia lies between 20° and 30°C., at which temperature the greatest germination percentage (70 percent or more) of conidia is secured.
3) The minimum temperature for conidia germination is 2°C. The germ tubes produced at this temperature, are spherical or elliptical and pronouncedly swell up, and never linear, as those of normal shape are.
4) The maximum temperature for conidia germination is 41°C., at which the germ tubes are also spherical or elliptical, but smaller than those formed at 2°C.
5) The best growth of the mycelium was secured at a temperature between, 27° and 30°C.
6) The maximum temperature for the formation of the conidia is between 35° and 38°C., and the minimum temperature 5°C.
7) Conidia formed at the optimum temperature, are obclavate and curve to one side; those formed at 5°C. are cylindrical and straight and have a smaller number of the septa; and those at 30°C. are shorter and wider than those formed at 20°C.
8) Conidia formed at lower temperature are dark in color, and become lighter with the rise of temperature.
9) The thermal death point (in 10 minutes exposures) for the conidia is 50-51°C.; and for the germinated conidia on hyphae 48-50°C.
