title: Soilless plant growth media influence the efficacy of phytohormones and phytohormone inhibitors.
abstract: Plant growth regulators, such as hormones and their respective biosynthesis inhibitors, are effective tools to elucidate the physiological function of phytohormones in plants. A problem of chemical treatments, however, is the potential for interaction of the active compound with the growth media substrate. We studied the interaction and efficacy of propiconazole, a potent and specific inhibitor of brassinosteroid biosynthesis, with common soilless greenhouse growth media for rice, sorghum, and maize. Many of the tested growth media interacted with propiconazole reducing its efficacy up to a hundred fold. To determine the molecular interaction of inhibitors with media substrates, Fourier Transform Infrared Spectroscopy and sorption isotherm analysis was applied. While mica clay substrates absorbed up to 1.3 mg of propiconazole per g substrate, calcined clays bound up to 12 mg of propiconazole per g substrate. The efficacy of the gibberellic acid biosynthesis inhibitor, uniconazole, and the most active brassinosteroid, brassinolide, was impacted similarly by the respective substrates. Conversely, gibberellic acid showed no distinct growth response in different media. Our results suggest that the reduction in efficacy of propiconazole, uniconazole, and brassinolide in bioassays when grown in calcined clay is caused by hydrophobic interactions between the plant growth regulators and the growth media. This was further confirmed by experiments using methanol-water solvent mixes with higher hydrophobicity values, which reduce the interaction of propiconazole and calcined clay.
authors.affiliation: Department of Horticulture and Landscape Architecture, Purdue University, West Lafayette, Indiana, United States of America.
authors.forename: Norman B
authors.initials: NB
authors.lastname: Best
authors.affiliation: Department of Horticulture and Landscape Architecture, Purdue University, West Lafayette, Indiana, United States of America; Department of Plant Biology, Carnegie Institution for Science, Stanford, California, United States of America.
authors.forename: Thomas
authors.initials: T
authors.lastname: Hartwig
authors.affiliation: Department of Horticulture and Landscape Architecture, Purdue University, West Lafayette, Indiana, United States of America; Plant Soil and Nutrition Research Unit, USDA ARS, Ithaca, New York, United States of America.
authors.forename: Joshua S
authors.initials: JS
authors.lastname: Budka
authors.affiliation: Department of Horticulture and Landscape Architecture, Purdue University, West Lafayette, Indiana, United States of America.
authors.forename: Brandon J
authors.initials: BJ
authors.lastname: Bishop
authors.affiliation: Department of Horticulture and Landscape Architecture, Purdue University, West Lafayette, Indiana, United States of America.
authors.forename: Elliot
authors.initials: E
authors.lastname: Brown
authors.affiliation: Department of Biology, Chicago State University, Chicago, Illinois, United States of America.
authors.forename: Devi P V
authors.initials: DP
authors.lastname: Potluri
authors.affiliation: Bindley Bioscience Center, Purdue University, West Lafayette, Indiana, United States of America.
authors.forename: Bruce R
authors.initials: BR
authors.lastname: Cooper
authors.affiliation: Department of Agronomy, Purdue University, West Lafayette, Indiana, United States of America.
authors.forename: Gnanasiri S
authors.initials: GS
authors.lastname: Premachandra
authors.affiliation: Department of Agronomy, Purdue University, West Lafayette, Indiana, United States of America.
authors.forename: Cliff T
authors.initials: CT
authors.lastname: Johnston
authors.affiliation: Department of Horticulture and Landscape Architecture, Purdue University, West Lafayette, Indiana, United States of America.
authors.forename: Burkhard
authors.initials: B
authors.lastname: Schulz
mesh_terms: D000327:Adsorption; D003470:Culture Media / Q000737:chemistry; D010641:Phenotype; D010937:Plant Growth Regulators / Q000737:chemistry / Q000494:pharmacology*; D010944:Plants / Q000187:drug effects*; D036226:Seedlings / Q000187:drug effects / Q000254:growth & development
chemical_list: D003470:Culture Media; D010937:Plant Growth Regulators