Abstract
Polycyclic aromatic hydrocarbons constitute a large family of organic environmental pollutants. Hence, a particular attention has been attributed to all approaches involved in the reduction of their contamination in water and natural ecosystems. Plant tolerance, absorption, accumulation, and likely biodegradation of these pollutants, known as phytoremediation, have emerged as an efficient technique to remediate environments contaminated with polycyclic aromatic hydrocarbons. The present work was aimed to compare the tolerance to phenanthrene (a polycyclic aromatic hydrocarbon) in the two model plants: Arabidopsis thaliana (glycophyte) and Thellungiella salsuginea (halophyte). Our study showed that the development of these two species was reduced under phenanthrene stress, the effect being more pronounced in A. thaliana than in T. salsuginea. In parallel, results from the intrinsic quantum yield of photosystem II and chlorophyll concentrations were concomitant with those of growth and phenotypic changes, and confirmed the higher tolerance of T. salsuginea compared to that of A. thaliana. The intrinsic quantum yield of photosystem II was drastically decreased in the glycophyte, which indicates a marked disturbance in photosystem II performance. This induced a severe oxidative stress as shown by the utilization of specific reactive oxygen species probes. In parallel, the activities of glutathione reductase, gaiacol peroxidase, and superoxide dismutase were increased by 95, 73, and 36%, respectively, which indicates a marked phenanthrene-induced oxidative stress. In T. salsuginea, photosystem II performance was not significantly affected. This species showed less accumulated reactive oxygen species than A. thaliana. Its enzymatic antioxidant system showed few changes as superoxide dismutase was the only enzyme whose activity was enhanced (+34%). A much higher capacity of recovery was also noticed in this halophyte as compared to the glycophyte. Indeed, it seems that T. salsuginea accumulated phenanthrene in stomata, which suggests its possible volatilization. All these data, taken together, add new insight to the mechanisms involved in halophytic plant tolerance to abiotic stresses and their potential use in phytoremediation. (C) 2014 Elsevier B.V. All rights reserved.