Abstract:Germination or dormancy of seeds depends on the content of Pfr and Pfr/(Pr+Pfr) ratio established in photosensitive seeds. The level of Pfr in seeds is affected by multiple factors. The non-photoblastic seeds contain appropriate Pfr level when ripen and the light-favored seed does after being irradiated with white light or red light to some degrees, but light-inhibited seeds can germinate only when they contain low Pfr after long duration in darkness. The seed photosensitivity is not absolute and influenced by the environmental conditions of mother plant, maturation degrees, storing status of seed itself, spectral composition, fluence rate, photoperiod, germination temperature, O2 supplying state and treatments with chemicals.