Seed Dormancy and Germination Requirements of Torilis scabra (Apiaceae)

Abstract

The timing of seed germination significantly affects the fitness and life cycle of plants. Torilis scabra is a perennial medicinal herb occurring in mixed forests but the increasing use and modification of forestlands in recent decades has led to the degeneration of its natural habitat. Nonetheless, the requirements for germination in T. scabra remain unclear. The present study focused on identifying conditions necessary to break T. scabra seed dormancy and describing its seed dormancy type. By periodically collecting seeds that were sown in the field, germination phenology was studied. The impact of light, temperature, and warm/cold stratification on breaking seed dormancy and promoting germination was also determined through incubating seeds in laboratory conditions. Additionally, the effect of GA3 was explored to more accurately identify the type of dormancy present. The results demonstrated that the seeds of T. scabra possessed small, undeveloped embryos with physiological dormancy at the time of maturity. In the field, embryo growth initiated in early spring and the embryo–seed length ratio increased by ~300% before the radical emerged. In the laboratory, the embryo–seed length ratio increased from 0.24 to 0.82 when seeds were subjected to cold stratification at 4 °C and then transferred to 15/25 °C. Germination was observed across a broad temperature range after cold stratification. GA3 also helped to break dormancy but after-ripening did not. Taken together, the results suggest that seeds of T. scabra have non-deep simple morphophysiological dormancy.