Responses of Arabidopsis thaliana seedlings in a Cd/Cu/Zn multi-pollution context

Seedlings of A. thaliana were exposed to cadmium, copper and zinc at two different concentrations, supplied separately or in combinations. The amounts of these metals were measured in shoots and roots, and a significant competition in cadmium and copper/zinc root uptake was observed. Microscopic analyses revealed that the root morphology was affected by metal exposure, probably because the levels of trans-zeatin riboside, dehydrozeatin riboside, indol-3-acetic acid, and the auxin/cytokinins ratio varied significantly amongst the metal-treated plants. RT-PCR analysis of some genes involved in auxin and cytokinin synthesis showed an up-regulated transcription after exposure to metals. Not least, phytochelatins appeared to play a possible role in zinc/copper homeostasis, other than in cadmium detoxification.