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RESEARCH PRODUCT

Les paradoxes du glufosinate et glyphosate. Comportement dans l'ambroisie à feuilles d'armoise

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BEHAVIOUR OF GLUFOSINATE ANDGLYPHOSATE IN COMMONRAGWEED:APPARENT PARADOXAND SURPRISES We examined the foliar epidermis of commonragweed (Ambrosia artemisiifolia L.) plants and studied the behaviour of the herbicides glufosinate and glyphosate in this species. Both leaf surfaces exhibited 3 types of trichomes, according to their size and shape. Epicuticular waxes appeared amorphous, which may explain high levels of spray retention. Glufosinate and glyphosate were rapidly and almost completely taken up by common ragweed leaves; half maximum uptake was nearly reached after 5 and 3 h, respectively. The longest trichomes were stained with AgN03, indicating the presence of hydrophilic domains, which possibly facilitated the uptake of these very hydrophilic herbicides.Both were ambimobile, with 10-15%translocation out ofnthe treated leaves.Glufosinate was mainly directed towards the apical developing tissues, with low amounts reaching the roots. Glyphosate was directed towards the apical developing tissuesand the roots. The sensitivity of common ragweed to glufosinate and glyphosate can be explained by high spray retention, rapid and important foliar uptake, and appreciable migration out of the plant parts hit by the spray.