Abstract Detail

Biotic and abiotic stress

Tuominen, L.K. [2], Fort, Douglas J. [1], Mathis, Michael B. [1], Walker, Rachel [2], Hansel, Mike [2], Hall, Scott [3], Richards, Robin [3], Grattan, S.R. [4], Anderson, Kurt [5].

Toxicity of Sulfate and Sulfide in Hydroponically-Grown Wild Rice (Zizania palustris) Seedlings.

Wild rice (Zizania palustris) is an emergent aquatic species found in North American lakes, rivers, and streams, particularly in the Great Lakes region of the United States and Canada. This species is sacred to Anishinaabe tribes in the region and is part of the traditional foodways of these people. Wild rice is also important as an agricultural crop and as food for wild waterfowl. Field research prior to 1950 indicated that sulfate concentration may be a determining factor in wild rice habitat. However, the limit of 10 mg/L identified at that time appears to be unusually low, given sulfate’s role as a phytonutrient in aquatic and terrestrial species. We therefore hypothesized that wild rice seedlings experience toxicity due to root zone sulfide rather than sulfate per se, and we tested this hypothesis in two phases.
We first compared seedlings grown in a dose-response series of sulfate concentrations for 21 d under hydroponic conditions with those grown under a series of chloride concentrations of equivalent electrical conductivity (EC). Of ten measures of plant growth and health, four were negatively impacted by 5000 mg/L sulfate relative to the control, while time to 30% seedling emergence was reduced at 2500 mg/L sulfate. Of the negatively impacted measures, root length and phytotoxicity were impacted at lower EC-equivalent doses of chloride, suggesting that osmotic stress was the main reason for sulfate toxicity in these measures. In contrast, shoot length and leaf number were impacted at lower sulfate doses than EC-equivalent chloride doses. These findings support the ideas that (a) sulfate is far less toxic to wild rice seedlings than suggested by field research, and (b) this toxicity is often attributable to osmotic stress rather than sulfate per se.
We next studied the effects of 250 uM sulfide on wild rice seedlings grown for 21 d under two different hypoxic conditions and two different iron concentrations. Sulfide negatively impacted a range of plant growth measures under whole-plant hypoxia, but under root-zone hypoxia fewer measures exhibited toxicity. Furthermore, addition of 10 mg/L iron had a clear mitigating effect on sulfide toxicity. Current trials aim to establish dose-response curves for sulfide toxicity in wild rice at three different iron concentrations. Overall, the findings to date support the idea that, under field conditions, wild rice seedlings are more likely to experience toxicity due to root zone sulfide rather than sulfate per se, and only under low iron concentrations.

1 - Fort Environmental Laboratories, 515 South Duncan, Stillwater, OK, 74074, USA
2 - Barr Engineering Co., 4700 West 77th Street, Minneapolis, MN, 55435, USA
3 - ENVIRON International, 201 Summit View Drive, Suite 300, Brentwood, TN, 37027, USA
4 - University of California, Department of Land, Air, and Water Resources, One Shields Avenue, Davis, CA, 95616, USA
5 - ALLETE, Inc., 30 West Superior Street, Duluth, MN, 55802, USA

Keywords:
Zizania palustris
sulfate
sulfide
chloride
osmotic stress
iron
root zone hypoxia
toxicology.

Presentation Type: Oral Paper:Papers for Topics
Session: 7
Location: Salon 13/14/The Shaw Conference Centre
Date: Monday, July 27th, 2015
Time: 8:45 AM
Number: 7004
Abstract ID:672
Candidate for Awards:None