ABSTRACT
I. INTRODUCTION Heavy metal and other toxic metal cations are widespread pollutants that are phytotoxic. Most of them are absorbed by the plant roots, where they can accumulate. When the root tolerance is overloaded, the metals are translocated toward the leaves and affect the photosynthetic apparatus. Lower plants are also affected. In algae and cyanobacteria, the sensitivity to metal cations depends on their plasma membrane permeability and their capacity to bioaccumulate and is thus variable between species. Similarly, higher plants can be classified in three classes depending on their resistance to excess toxic divalent cations [1]. The first class of plants absorbs and translocates the ions as a function of metal concentration, the second class includes plants that are tolerant and that can exclude the metals at the root level, and the third class is represented by plants that can bioaccumulate heavy metals in their roots. The responses of the different plant species at the level of the photosynthetic electron transport system will thus be widely variable depending on species.
