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Fluorine and white clover: Assessing fluorine's impact on Rhizobium leguminosarum
Author(s) -
Geretharan Thangavelautham,
Jeyakumar Paramsothy,
Bretherton Michael,
Anderson Christopher W. N.
Publication year - 2020
Publication title -
journal of environmental quality
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.888
H-Index - 171
eISSN - 1537-2537
pISSN - 0047-2425
DOI - 10.1002/jeq2.20089
Subject(s) - rhizobium leguminosarum , rhizobium , trifolium repens , agronomy , biology , fertilizer , soil water , pasture , intercropping , chemistry , symbiosis , rhizobiaceae , horticulture , bacteria , ecology , inoculation , genetics
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 N 2 –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 (IC 10 ) 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 .