Elongating responses to herbicides of heterotrophic and photoautotrophic hairy roots derived from pak-bung plant

Abstract

The heterotrophic (HT) and photoautotrophic (PT) hairy roots of pak-bung were found to exhibit different elongating responses depending on the modes of actions of test herbicides. Treatment with 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU), an inhibitor of photosynthesis, decreased the tip elongation rate of the PT hairy roots, while no adverse effect was observed in the case of the HT hairy roots when DCMU were used at concentrations of 0.001–10 μmol/dm 3. The values of the median effective concentration (EC 50), defined as the herbicide concentration at which the tip elongation rate is decreased to 50% that of the herbicide-free control, were calculated. For the HT hairy roots: EC 50=1.8 (paraquat) and 1.4 μmol/dm 3 (pyributicarb), and for the PT hairy roots: EC 50=0.45 (DCMU), 0.37 (paraquat) and 1.2 μmol/dm 3 (pyributicarb).