Plant Toxicity and Plant Uptake of Fluorobenzoate and Bromide Water Tracers
- Robert S. Bowman *,
- Jill Schroeder,
- Rao Bulusu,
- Marta Remmenga and
- Rose Heightman
Dep. of Earth and Environmental Science and Geophysical Research Center, New Mexico Inst. of Mining and Technology, Socorro, NM 87801; Dep. of Entomology, Plant Pathology, and Weed Science, New Mexico Inst. of Mining and Technology, Socorro, NM 87801; University Statistics Center, New Mexico State Univ., Las Cruces, NM 88003. Abstract
The plant toxicity and plant uptake of pentafluorobenzoate (PFBA); 2,6-difluorobenzoate (2,6-DFBA); 3,4-difluorobenzoate (3,4-DFBA); and KBr were determined in greenhouse experiments. The germination of 11 different crop species was not inhibited by the fluorobenzoates at concentrations below 250 mg L−1 and KBr at concentrations below 500 mg L−1. Alfalfa (Medicago sativa L.), barley (Hordeum vulgare L.), and canola were planted in sealed pots in which different concentrations of the tracers were maintained in the soil solution. The threshold for plant growth inhibition by the fluorobenzoates was between 50 and 125 mg L−1; KBr did not inhibit growth even at 1000 mg L−1. At the no-growth-effect level of 50 mg L−1, 0.1 to 55% of the added fluorobenzoates or Br was recovered from the tissue of seedling alfalfa, barley, or canola. As much as 65% of the added fluorobenzoates was not recovered; the fluorobenzoates were presumably degraded in the soil or metabolized fallowing plant uptake. All of the added Br was recovered. The greatest mass loss was observed for 3,4-DFBA (the isomer with the highest negative-log acid dissociation constant); otherwise there was no correlation of plant response with fluorobenzoate properties. The results show that fluorobenzoates and Br can be readily taken up by growing plants, and that fluorobenzoate mass losses may occur when plants are present.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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