Factors Affecting the Uptake of Endothall-14C by Hydrilla

Abstract

Placing hydrilla (Hydrilla verticillataRoyle) in 2.7 and 5.4 μM solutions of carbon-14-labeled endothali [7-ox = abicyclo(2,2,1)heptane-2,3-dicarboxylic acid] under controlled conditions resulted in a sigmoid-shaped uptake curve for both herbicide concentrations. Apical sections of hydrilla, which included the apical bud, absorbed greater amounts of endothall-14C than sections excised from the center of the plant below the apical bud. Low concentrations of copper as copper sulfate pentahydrate solutions of 0.4 and 2.0 μM in combination with endothall-14C increased the amount of radioactivity found in hydrilla, but copper concentrations of 4.0, 8.0, and 16.0 μM inhibited endothall-14C uptake. The greatest uptake by hydrilla in 5.4 and 2.7 μM solutions of endothall-14C exposed to temperatures of 10, 20, and 30 C occurred in the 20 and 30 C solutions, respectively. Endothall-14C uptake was studied under light intensities of 0, 540, 5400, and 21,500 lux. Uptake of radioactivity from 2.7 and 5.4 μM solutions of endothall-14C was greatest at 540 and 21,500 lux, respectively.