The morphogenic responses and phytochelatin complexes induced by arsenic in Pteris vittata change in the presence of cadmium

Arsenic (As) and cadmium (Cd) are toxic elements frequently present simultaneously in the environment. Pteris vittata L. (Chinese brake fern) is a natural As hyperaccumulator, able to accumulate very high levels of As in the fronds. The fern is also capable to adsorb Cd and to accumulate it, at moderate levels, in the root. To date, the mechanisms triggered by the fern in the presence of As and Cd are poorly known, and it is unknown whether Cd alters the fern As hyperaccumulating capabilities. The research aim was to analyse the responses of P. vittata when exposed simultaneously to As and Cd. In particular, in this work it was investigated whether Cd alters the capabilities/strategies that the fern activates to hyperaccumulate As. Results showed that co-exposure to Cd and As negatively affects P. vittata by inducing cytohistological damage in the fronds, and reducing plant biomass. Cadmium presence increases As uptake but reduces As translocation to the frond. Co-exposure to Cd and As causes variations in the formation of As-phytochelatin complexes, mainly inducing the synthesis of long chain thiols binding As. Moreover, the co-exposure to Cd and As enhances extrusion of exudates containing As and Cd from the fronds. All together the data show that Cd alters the natural capabilities of the fern to hyperaccumulate As, but also suggest that P.vittata is able to contrast the toxicity due to As plus Cd, at least within defined limits.