AbstractThe uptake from foliar deposits of 1014C‐labelled compounds into each of 10 species of field‐grown plants was measured 26 h after deposition by combustion of leaf tissue after removal of surface deposits. The compounds, which included eight pesticides, covered a wide range of lipophilicity and each was formulated in the same way; they were applied as droplets with a microsyringe. Uptake varied greatly between the species. All compounds were taken up well into maize andXanthium pennsylvanicum, whereas relatively little entered the leaves of apple or orange. Uptake into the six other species varied according to the compound. Amongst the eight non‐polar compounds, no relationship between the rate of uptake and molecular size was discerned, and only inX. pennsylvanicumwas uptake related to the partition coefficient and water solubility. Considering all the compounds, weak relationships were observed between molecular cross‐sectional area and uptake into four species. The range of the uptake rates (×130) was small compared with those of octan‐1‐ol‐water partition coefficients (×1010) and water solublities (×107) shown by the 10 compounds. Possible reasons for the absence of correlations between the uptake and the molecular properties considered are discussed. The results are consistent with either separate routes of cuticular entry for non‐polar and polar compounds, or a common route for both types of compound. The generally poor uptake by apple and orange leaves, which may be related to their thick cuticles, highlights the need to develop special formulations to optimise uptake
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