Application of in vitro test system for evaluating the tolerance of Ageratum houstonianum and Petunia x hybrida to cadmium toxicity

Elena T. Iakimova, Denitza I. Milusheva, Bistra Y. Atanassova

Abstract: Cadmium (Cd) is a highly toxic heavy metal pollutant of the environment and biosphere. Phytoremediation of soils and waters contaminated with Cd and other heavy metals by the use of agricultural crops aimed for food is a hazardous approach. In this sense the ornamental plants can be an appropriate alternative. The current study was undertaken to develop in vitro test system for evaluating the physiological response to Cd stress of the annual ornamentals Ageratum houstonianum, cv. Blue Hawaii and Petunia x hybrida, cv. Lavender. In vitro cultured explants were exposed to a range of Cd concentrations exceeding the maximum permissible concentration (MPC), which for Cd in soil is 2 mg kg-1 dry matter. The stress impact was judged by the indices height and width of microplants, root length and diameter, fresh and dry biomass and the electrolyte leakage. The symptoms of toxicity were determined by visual observations. In vitro, the plants expressed different degree of tolerance at Cd levels exceeding MPC. Ageratum appeared medium tolerant to Cd concentrations elevated up to 5 x MPC whereas petunia showed lower tolerance and developed successfully only up to 2 x MPC. Pot experiments with ageratum were carried out to find out whether the in vitro established degree of tolerance may correspond to the response of whole plants grown on Cd contaminated substrate. In comparison to in vitro conditions, in vivo the plants tolerated even higher doses of Cd (up to 25 x MPC). The applied in vitro model system represents an innovative experimental approach suggested as promising tool for early diagnosis of the potential of annual ornamental plants to grow at conditions of Cd and other heavy metals stress. For establishing the potency of the examined plants for phytoremediation, further analyses of their phytoextraction capacity are envisaged.

Keywords: Ageratum houstonianum; cadmium; heavy metals; Petunia x hybrida; phytoremediation; tolerance

Date published: 2019-04-23