Effect of seed size and fungicide on germination and survival of buried seeds of two grassland species on the Loess Plateau, China

Seed size has important fitness consequences that potentially extend throughout the life cycle of plants. However, the effect of variation in seed size on seed survival in the field is poorly understood. We used two grassland species Setaria viridis (physiological dormancy) and Lespedeza davurica (physical dormancy) to test the effect of within species seed size variation on seed germination, viability and susceptibility to pathogen attack in the soil. Seed bags with different sizes of seeds for each species were treated with fungicide or water (control) and buried for 4 months in the field on the Loess Plateau, China. We found that field germination of large seeds was consistently higher than that of small seeds for both species. Small seeds of S. viridis had higher field mortality than large seeds, but the mortality of seeds of L. davurica was not affected by seed size. More small than large seeds of L. davurica remained viable during field burial, but the viability of buried seeds S. viridis did not differ with size. Our study suggests that within species seed size can influence germination, mortality and viability of buried seeds in the soil, but seeds with different kinds of dormancy shows different patterns in the relationship between seed size and seed survival.