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Fluorine and white clover: Assessing fluorine's impact on Rhizobium leguminosarum.

Thangavelautham GeretharanParamsothy JeyakumarMichael BrethertonChristopher W N Anderson
Published in: Journal of environmental quality (2020)
The soil fluorine (F) concentration in New Zealand agricultural soils has increased with time as a direct result of the widespread application of phosphate fertilizer to land. Elevated soil F concentrations may potentially harm soil microorganisms, which are important for nutrient cycling and soil formation. Rhizobium leguminosarum is a N2 -fixing soil bacterium that is a fundamental component in New Zealand legume-based pastoral farming. Any impact of F on Rhizobium leguminosarum would have an adverse effect on New Zealand pasture production. In this study, F toxicity to Rhizobium leguminosarum was examined as a first step to develop F guideline values for New Zealand agricultural soils. Bottle-based experiments were conducted to examine the effect of the F- ion on Rhizobium-white clover (Trifolium repens L.) symbiosis by observing nodule morphology and growth. Results indicate that the F- concentration that causes 10% inhibition of Rhizobium respiration (IC10 ) for F- toxicity to Rhizobium leguminosarum was >100 mg F-  L-1 . Significant morphological changes occurred when Rhizobium was exposed to F concentrations of 500 and 1000 mg L-1 . Both light and transmission electron micrographs confirmed that the Rhizobium leguminosarum-white clover interaction was not influenced by F- concentrations >100 mg L-1 . The toxic F- concentration for Rhizobium leguminosarum determined in this study is orders of magnitude higher than the F- concentration in New Zealand agriculture soils under "normal conditions." There appears to be no indication of imminent risk of soil F to Rhizobium leguminosarum.
Keyphrases
  • heavy metals
  • climate change
  • human health
  • positron emission tomography
  • oxidative stress
  • risk assessment
  • plant growth
  • emergency department
  • pet imaging
  • water quality