EFFECT OF TEMPERATURE ON PICLORAM ABSORPTION AND TRANSLOCATION IN LEAFY SPURGE (EUPHORBIA-ESULA)

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