<i>Zizania palustris</i>, more commonly known as wild rice, has become the official grain of the state of Minnesota. It holds a place of great cultural, spiritual and nutritive importance for thousands of people. In Minnesota it thrives in its central and northern parts, especially in shallow lakes of around 1-3 feet water. Wild rice is sensitive to sulfate concentrations; large stands are rarely found in waters with surface water sulfate concentrations above 10 ppm. (Parker & Deanb, 1976). Oxygen diffusion from the roots to the sediment plays an important role in the formation of iron oxides which we believe protects the plant from incoming and toxic iron sulfides (Van der Welle et al., 2007). This experiment intended to test the mechanism of formation of iron oxides on seedlings, and how they differ in high-sulfur environments in contrast with control environments. Four tanks were homogeneously prepared with sediment and water from Rice Portage Lake on the Fond du Lac reservation. Plants were grown in either 15cm high water columns or 40 cm water columns. There were 6 columns per tank each one of them divided into 4 compartments. Two tanks had sulfate added to the surface water and sulfide added to the sediment. Two tanks were left un-amended for control conditions. Concentrations of iron, sulfur were recorded and a saturation index was calculated for FeS. Increased levels of sulfate and sulfide in the water column system promote higher saturation indexes which seem to suggest higher probability of iron sulfide formation in the sediment. Plants in tanks with added sulfur showed less amount of iron in root surfaces than those in the control tanks. The addition of sulfide may have prevented the iron oxides from forming and protecting the roots. In control tanks, there is more iron that stays dissolved and less chance of iron-sulfide formation, which in case of increasing ROL as the seedling develops will result in higher concentrations of iron oxide formation. Taller water columns extended the amount of time it took the plant to reach the surface and develop a highly photosynthetically active leaf, therefore extending the time it took to produce iron oxides. Iron-oxide production will be dependent on the amount of iron available in the system, the levels of sulfate and sulfide and the oxygen available.<br/>

Sulfur and iron geochemistry in the rhizosphere of wild rice (Zizania palustris)

255th National Meeting (2018)

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