Interactions between sulfide and reproductive phenology of an annual aquatic plant, wild rice (Zizania palustris)

Aquatic plants live in anoxic sediments that favor formation of hydrogen sulfide, a known phytotoxin. We investigated how the phenology of reproductive life stages of wild rice (Zizania palustris Poaceae), an annual aquatic graminoid, is influenced by rooting zone sulfur geochemistry in response to elevated sulfate and sulfide. In addition, we characterized how redox conditions in the rooting zone change throughout reproduction to determine if they are tied to plant life stage. The redox conditions in sediment decreased just prior to flowering, and again just prior to seed production for all plants, allowing sulfide to accumulate at the root surface of sulfate-amended plants. Plants exposed to sulfide initiated seed production later than unamended plants. Sulfide appears to slow plant development in a way that gives the plant less time to allocate nutrients to seeds before senescence. The impact of sulfide in delaying reproductive life stages of wild rice and changing seasonal rooting zone biogeochemistry could extend to other plant species and additional chemical species that change mobility with redox potential, such as phosphate, manganese, mercury, and other metals.