Effects of different allelochemicals on root morphology of Arabidopsis thaliana

Non-linear regression analysis was applied to assess the phytotoxicity of trans-cinnamic acid, umbelliferone and coumarin on the whole root system of Arabidopsis thaliana and on the component root types (primary root and lateral roots). The different root types exhibited different sensitivities to these allelochemicals. At low concentrations, coumarin induced a hormetic effect on root elongation both in the whole root system and also on the lateral roots but not on primary root. This confirm coumarin's selective effect on particular root types. Conversely, both umbelliferone and trans-cinnamic acid caused only inhibitory effects (no hormetic effects) on the whole root system and also on its components. Allelochemicals phytotoxicity on the whole root system and on both root types showed the hierarchy: trans-cinnamic acid ≥ umbelliferone > coumarin.