Phylogenetic Differentiation of the Cultivated Rice Plant. : V. Variation of minimum germination temperature and temperature constant among rice varieties.

Abstract

1. From germination tests at six temperature levels ranging from 30 to 11.7'C, minimum germination temperature and temperature response in germination rate wer.e measured in various varieties of Eastern Asia. The mininium temperature was shown by the lowest temperature at which the germination capacity within 20 days reached 50%. The temperature response was expressed in terms of BELEHRADEK'S temperature constant, since the days of germination and temperature showed, if both were in logarithms, a rectilinear regression line. 2. Varieties of the "Continental" group were generally higher in minimum germination temperature than those of t.he "Inslrlar" group, while within the same group, varieties frcm high latitudinal regions were lower than those from low latitudinal regions. The lowest was 11'C for some Japanese varieties, and the highest was 17'C for some varieties of Indochina. Varieties of the Insular group were generally low in germination rate, and those with relatively high germination rates tended to be low in regard to minimum germination temperature.