Effect of Temperature on Picloram Absorption and Translocation in Leafy Spurge (Euphorbia esula)

Abstract

Temperature changes prior to picloram application affects its activity in leafy spurge. Absorption of14C picloram was directly correlated with temperature changes; each 1 C increase in air temperature 24 h before treatment resulted in a 1% increase of14C-picloram absorption in leafy spurge and vice versa. The greatest14C-picloram absorption averaged 47% of applied14C when the temperature increased from 18 C to 24 or 30 C 24 h before treatment compared to 33% when temperatures were constant. Translocation of14C picloram was more sensitive than absorption to temperature changes with 4.3 and 1% of applied14C-picloram translocated to the roots when the plants were maintained at 12 and 30 C, respectively. Even though absorption increased directly with temperature,14C-picloram translocation to the root system declined as temperature increased.