Comparative Diffusion of Atrazine inside Aqueous or Organic Matrices and inside Plant Seedlings

Several different matrices (water, n-butanol, n-octanol, lecithin, waxes, and suber) were chosen to measure [14C]atrazine diffusion rate and evaluate the specific diffusion parameter of this molecule. A simple experimen tal device was conceived for this purpose and two methods of calculation, deduced from Fickʹs law, were established and compared. The same device was used for diffusion measurements inside corn seedling fragments, either dead or alive. In inert matrices, the highest diffusion parameter found for atrazine was obtained for water (2.6 ± 0.9) 10-10 m2 s-1. For more lipophilic matrices, the value of the specific parameter decreased markedly, reaching only (1.2 ± 1) 10-12 m2 s-1 for glycerides and (2.5 ± 2.4) 10-13 m2 s-1 for paraffin. For dead corn roots or coleoptile, the diffusion parameter was close to that in water: (3.7 ± 2.1) 10-10 m2 s-1 and (9.6 ± 4) 10-10 m2 s-1. In living material, the movement of 14Clabeled compounds was much lower: (7.4 ± 4.6) 10-11 m2 s-1 and (1.6 ± 1.5) 10-11 m2 s-1. This was explained by atrazine hydroxylation in the presence of benzoxazinones, leading to a derivative which was accumulated inside the vacuole.