Flooding, light, and temperature conditions affect seed germination of herbaceous and shrub species in wet grasslands from the Cerrado

Seed germination is a crucial biological process that influences plant establishment in wetlands, where species must adapt to seasonal water-level fluctuations. In the open wetlands of the Cerrado, germination strategies are still poorly understood. Thus, we aimed to investigate the germination responses of 15 species from wet grasslands to various factors, including light, alternating temperatures, water flotation, submersion, and post-flooding recovery conditions. Seeds were collected from wetland areas and subjected to controlled experiments to assess germination under constant (25 °C) and alternating (20/30°C) temperatures, light versus dark conditions, and different water exposure treatments. Additionally, we calculated a flooding resistance index (FRI) to compare species adaptability to flooding conditions. Our results indicate that most species required light for germination, and alternating temperatures significantly enhanced germination in eight species studied. The effect of water flotation on germination varied among species, with a negative effect in five species. Four species increased germination when seeds floated in water. Submersion generally reduced germination in most species, although some were able to recover after flooding. Four species had increased germination in post-flooding conditions. Seven species exhibited high FRI (≥ 0.62), which may contribute to their successful establishment in wetter terrains. These results indicate that light and temperature fluctuations are key environmental factors regulating seed germination in wet grassland species, while flooding is a selective filter. Understanding these germination traits improves our ability to predict vegetation changes and restore open Cerrado wetlands from seeds.