Physiological response of Cistus salviifolius L. to high arsenic concentrations.

Arsenic is a trace element found in the environment which can be particularly toxic to living organisms. However, some plant species such as those of the genus Cistus are able to grow in soils with high As concentrations and could be used in the sustainable rehabilitation of mining areas through phytostabilization. In this work, the growth and the physiological response of Cistus salviifolius L. to As-induced oxidative stress at several concentrations (reaching 30 mg L^-1) in an hydroponic system were evaluated for 30 days. Several growth parameters, chlorophyll content, chemical composition, one indicator of oxidative stress (H₂O₂) and two of the major antioxidative metabolites (ascorbate and glutathione) were analysed. The toxic effect of As was better perceived in the plants submitted to treatments with concentrations of 20 and 30 mg As L^-1. Plants subjected to these treatments had higher concentration of As in roots and shoots. The concentrations of Ca, Mg, K and Fe in the plants as well as a large part of the evaluated growth parameters were also affected. Arsenic did not interfere with the ability of the plant to perform photosynthesis, as there were no significant differences in the contents of chlorophyll a, b and total between the different treatments. Plants from all treatments accumulated higher amount of As in roots than in shoots, and it was also in the roots that the concentrations of H₂O₂, AsA and GSH were higher. Cistus salviifolius showed high tolerance to As up to the concentration of 5 mg L^-1, which makes it a species with high potential to be used in the phytostabilization of soils contaminated with As and presenting high concentrations of the element in the soil solution.