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Phytotoxicity of Depleted Uranium on Three Grasses Characteristic of Different Successional Stages

Center for Ecological Risk Assessment and Management, Dep. of Fishery and Wildlife Biology, Colorado State Univ., Fort Collins, CO 80523;

Terry McLendon

Dep. of Biological Sciences, Univ. of Texas-El Paso, El Paso, TX 79968.

^* Corresponding author (mmeyer{at}lamer.colostate.edu).

ABSTRACT

In response to a paucity of data on the chemical toxicity of uranium (U) to plants, a factorial experiment employing five U concentrations (0, 50, 500, 5000, 25 000 mg kg^–1) and three moisture regimes (low, medium, and high) was performed using three native grasses. Buchloe dactyloides (buffalograss; mid/late-seral), Schizachyrium scoparium (little bluestem; late-seral), and Aristida purpurea (purple threeawn; early/mid-seral) were grown in monocultures and as a mixture of two species under all combinations of U and moisture levels. This design allowed for the analysis of U effects, as well as possible interactions with moisture stress. Several measures of plant health and viability were made, including: percent emergence, plant survival, shoot biomass, and number and weight of inflorescences. Decreases in plant biomass, fecundity, and long-term survivability were observed only at the highest U level (25 000 mg kg ¹). No significant differences (P < 0.05) between the U treatment levels were observed in terms of seedling emergence and survival. Drought stress also negatively impacted survival and biomass, but acted independently of U stress.