Seed mass affects emergence but not germination in native grassland forage species

Abstract

For ecological restoration of degraded grasslands, species selection and knowledge of the species biology are essential. Seed germination and seedling establishment, as well as seed regenerative traits, can partially determine direct seeding success in this context. The objectives of this study are (1) to characterize the seeds of 29 native forage species of the Pampa Austral grasslands, (2) to evaluate their germination and emergence, and (3) to evaluate the relationship between germination and emergence and seed traits (mass, length, width, and length/width ratio), to test the usefulness of these traits for rapid species selection. We studied the germination percentage of untreated (UG) and treated (TG) seeds under laboratory conditions of 29 native forage species (four legumes, nine cool season, and 16 warm-season grasses) and the percentage of field emergence (FE) for 17 of those species, selected based on their UG. Additionally, all species were characterized, including thousand-seed mass, length, width, and length/width ratio. Average UG was 53.30 3.17% for Poaceae and 25.63 5.73% for Fabaceae. Four cool season and eight warm-season grasses had UG greater than 60%. Mean FE was 35.18 0.66% 2 months after sowing. FE has a direct relationship with seed mass (r2 = 0.69; p < 0.001), while this relationship was not observed for UG under laboratory conditions (r2 = 0.15; p = 0.7174). In Pampa Austral grasslands, seed mass proved to be a relevant trait for species selection given its strong relationship with FE.