Uptake and xylem transport of fipronil in sunflower.
The phenylpyrazole insecticide, fipronil, is used in seed coating against Agriotes larvae, which infest mainly corn and sunflower. Coating the seeds of the cultivated plants with fipronil has proven its effectiveness against Agriotes populations. In the case of sunflower or even corn, the possible root uptake of this insecticide may lead to a toxic effect against pollinators such as honeybees. In the present report, the uptake and transport of fipronil inside the sunflower seedling was studied in the laboratory. In a first study, sunflower was cultivated on an aqueous medium containing fipronil. An intense root uptake of fipronil occurred, leading to a transport into leaves depending upon transpiration. In a second study, plants were cultivated on a soil in which fipronil was uniformly distributed. Under our soil conditions (20% organic carbon), the partition coefficient between soil and water (K(d)) was found to be equal to 386 +/- 30. The average rate of fipronil transfer from soil water to seedlings was from 2 to 2.6 times lower than water transfer. During the 3 week experiment, 55% of recovered labeled compounds was in the parent form and 35% had been converted to lipophilic metabolites, with either a 4-CF(3)-SO(2) or 4-CF(3)-S substituant, which are also very potent lipophilic insecticides. This paper suggests that the possible uptake of fipronil by sunflower seedlings under agronomic conditions is mainly controlled by the physicochemical characteristics of the seed-coating mixture.
Aajoud
Asmae
A
Equipe Pertubations Environnementales et Xénobiotiques, Laboratoire d'Ecologie Alpine, Université Joseph Fourier, BP53X, F-38041 Grenoble Cedex 09, France.
Raveton
Muriel
M
Aouadi
Heddia
H
Tissut
Michel
M
Ravanel
Patrick
P
D001692:Biological Transport; D002250:Carbon Radioisotopes; D006368:Helianthus / Q000378:metabolism*; D007306:Insecticides / Q000378:metabolism*; D018515:Plant Leaves / Q000737:chemistry / Q000378:metabolism; D018517:Plant Roots / Q000737:chemistry / Q000378:metabolism; D011720:Pyrazoles / Q000032:analysis / Q000378:metabolism*; D036226:Seedlings / Q000378:metabolism; D012987:Soil / Q000032:analysis; D014867:Water / Q000737:chemistry
D002250:Carbon Radioisotopes; D007306:Insecticides; D011720:Pyrazoles; D012987:Soil; D014867:Water; C082360:fipronil