Hydroponic tomato (Lycopersicon esculentum) response to dicamba in the nutrient media

A greenhouse study was conducted to determine the effects of sublethal dica mba concentrations in the nutrient media on hydroponically grown tomato pla nts. Tomato leaf area was the most sensitive vegetative growth parameter me asured in response to dicamba concentrations, ranging from 0 to 22 mug/L. L eaf area was reduced 31 and 76%, and specific leaf weights, a relative meas ure of leaf thickness (g/cm(2)), increased 26 and 121% after 30-d exposure to dicamba concentrations of 2.2 and 22 mug/L, respectively. In long-term e xperiments conducted until plants produced first ripe fruit, regression ana lysis indicated leaf area reductions of 8 and 66% from initial dicamba conc entrations of 1 and 10 mug/L, respectively. Reductions in total fruit fresh weight were highly correlated (r = 0.93) with leaf area reductions caused by dicamba. A hyperbolic regression model gave predicted losses in fruit fr esh weight per plant of 6% at 1 mug/L dicamba and 73% at 10 mug/L dicamba ( r(2) = 0.87). Results generally indicated that the level of dicamba in the nutrient media of hydroponically grown tomatoes that produced no observable effect was less than or equal to 1 mug/L.