Photoblasticism is a mechanism of seed dormancy. Photoblastic seeds require light in order to germinate. Once germination starts, the stored nutrients that have accumulated during maturation start to be digested which then supports cell expansion and overall growth. Within light-stimulated germination, Phytochrome B (PHYB) is the photoreceptor that is responsible for the beginning stages of germination. When red light is present, PHYB is converted to its active form and moves from the cytoplasm to the nucleus where it upregulates the degradation of PIF1. PIF1, phytochrome-interaction-factor-1, negatively regulates germination by increasing the expression of proteins that repress the synthesis of gibberellin (GA), a major hormone in the germination process. Another factor that promotes germination is HFR1 which accumulates in light in some way and forms inactive heterodimers with PIF1.