Broad Seed Germination Niche as an Adaptation to Heterogeneous Aquatic Habit—a Case Study of Four Potamogeton species

Abstract: Aquatic habitats represent an extremely heterogeneous media for the inhabiting its plants, because key environmental factors vary there rapidly at relatively small scales. In this study, we explore the seed germination strategies of four pondweed species (Potamogeton compressus L., P. natans L., P. pectinatus L. and P. vaginatus Turcz.) in relation to the habitats they occupy. We hypothesised that, due to the high heterogeneity of aquatic environments, none of the environmental factors, such as light, temperature fluctuations or oxygen would play the role of a reliable trigger for seed germination of these species. The results of the germination experiments confirm the proposed hypothesis: under almost all conditions – fluctuating and constant temperatures, light and darkness, aerobic, flooded and hypoxia conditions – germination percentages ranged from 88.5 to 100%. An interspecific comparison of germination patterns also evidenced that all the investigated species showed the same response to all the studied environmental factors. We speculate that similar adaptations present in other aquatic macrophytes may point out the broader occurrence of this phenomenon in aquatic plants.