INFLUENCE OF ENVIRONMENT DURING MATERNAL PLANT-GROWTH ON DORMANCY OF SHATTERCANE (SORGHUM-BICOLOR) AND GIANT FOXTAIL (SETARIA-FABERI) SEED

The germination behavior of giant foxtail and shattercane seed was inv estigated to determine whether environment in which maternal plants gr ow and progeny seed develop affects seed dormancy. Giant foxtail and s hattercane seed was collected in 1985, 1991, and 1992. Plants from thi s seed were grown to maturity in the field and the greenhouse in 1993 and 1994. Experiments were conducted using mature progeny seed collect ed from these planes to determine the influence of environment of mate rnal growth on seed germination. Greenhouse-raised giant foxtail seed was more dormant than field-raised seed. progeny of the 1991 giant fox tail collection had the most dormant seed, whereas progeny of the 1992 collection had the least dormant seed. Field-raised shattercane seed was more dormant than greenhouse-raised seed, but this dormancy was ea sily overcome by placing them in fluctuating temperatures. Moist strat ification of giant foxtail seed increased its overall germination and reduced the differences in germination between individual collections and between field- and greenhouse-raised seed lots. Moist stratificati on of shattercane seed resulted in increased variability in germinatio n within and among seed lots. Subjecting shattercane seed to freezing and thawing was most detrimental and caused an 89% reduction in germin ation due to seed death. These data indicate that before overwintering , giant foxtail seed differed in germination percentage, but overwinte ring reduced these differences. Shattercane seed produced in different environments had similar germination percentage. This suggests that s uccessful overwintering depends on its ability to survive freezing and thawing conditions.