Systemic Translocation of14C-Labeled Metalaxyl in Tomato, Avocado, andPersea indica

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Abstract
Systemic translocation of 14C following treatment with 14C-metalaxyl was demonstrated in tomato, avocado (P. americana) and P. indica seedlings. In P. indica, the labeled fungicide was readily taken up by the roots and radioactivity was translocated uniformly to the aboveground parts of the plant. Metalaxyl concentrations ranging 67-106 .mu.g/g of dry P. indica root tissue were observed after the application of 1 mg of the fungicide as a soil drench. More than 90% of the foliar-applied fungicide remained in or on the surface of P. americana leaves up to 28 days after the last application. A small proportion of the applied fungicide was translocated downward to the roots. In tomato and P. indica plants, the labeled fungicide was translocated from a lower leaf to the upper leaves and from an upper leaf to the lower leaves. The uptake and subsequent translocation of the fungicide from the stem of avocado or tomato plants was superior to that from the leaves; after the fungicide was taken up by the stem, it was translocated laterally and upward to the leaves. Following leaf or stem application, only a very small proportion of the applied radioactivity was found in the roots (generally < 1%). Application of Triton B-1956 to P. indica leaves or of exogenous IAA with the labeled fungicide to avocado leaves did not enhance the uptake and downward translocation of the fungicide to the roots.