Effect of MCPA on14C-Diclofop Uptake and Translocation

Experiments were conducted to determine the influence of the dimethylamine salt of MCPA {[(4-chloro-o-tolyl)oxy] acetic acid} pretreatment, darkness from 1 day prior to treatment until harvest, and exogenous sucrose on diclofop {2-[4-(2,4-dichlorophenoxy)phenoxyl] propanoic acid} glucose, and sucrose uptake and translocation by wild oat (Avena fatuaL.). Uptake of14C-diclofop label by wild oat foliage was not influenced by MCPA pretreatment, constant dark treatment, or the addition of exogenous sucrose. Total14C-diclofop and14C-glucose label uptake and translocation were similar whether 5 cm of the treated leaf tip were placed in distilled water or 1% (w/v) sucrose. Downward translocation of14C-diclofop,14C-sucrose, and14C-glucose label in the phloem of wild oat was reduced similarly by MCPA, constant dark treatments, or a combination of the two. Upward translocation of14C-diclofop label was greater and exudation of14C-diclofop label into the ‘tip’ solution was less than that of14C-sucrose or14C-glucose label, regardless of MCPA or constant dark treatments. Downward translocation of14C-diclofop label was reduced as much by MCPA topically applied to the wild oat leaf 1 cm above, 1 cm below, or with the diclofop as with the MCPA broadcast pretreatment.