PICLORAM TRANSLOCATION AND REDISTRIBUTION IN SOYBEAN PLANTS FOLLOWING ROOT UPTAKE

The translocation pattern of root-absorbed radioactive picloram (4-amino-3,5,6-dichloropicolinic acid) in young soybean plants (Glycine max (L.) Merr., cv. Harosoy 63) was investigated. Picloram was rapidly transported from roots upward via the xylem, mainly to the primary leaves. These leaves almost immediately exported most of the picloram again via the ploem, primarily to the young apical leaves. Removal of the apical leaves or girdling the internode above the primary leaves reduced but did not prevent picloram export by the primary leaves. Amounts of root-absorbed picloram translocated from shoots back to the roots in split-stem plants were extremely small. In intact plants left for periods of up to 6 days, no change in the distribution of radioactivity took place after 1 or 2 days. © 1979.