Soil contamination and air pollution are currently two of global environmental problems that threat human health and terrestrial ecosystem. The increasing of heavy metal concentrations in soil and atmospheric ozone (O3) concentrations at ground level have been widely concerned with the accelerated industrialization and urbanization of China, particularly in the cities with old industrial bases. As one of the most toxic environmental pollutants, cadmium (Cd) has a strong influence on metabolic activities of trees by inducing a number of physiological changes.
In China, there are more than 7.0 million hm2 of poplar tree plantation, ranking top one in the world. They were often used for phytoremediation of polluted soils because of their fast growth, large biomass and deep root system.
Many researches were reported about the single effects of Cd or O3 stress on physiological and biochemical metabolisms of poplar species. However, little information is known about the combined effects and their interactive mechanisms of O3 and heavy metal on growth and physiological metabolism of tree species.
Associate professor XU Sheng, professor HE Xingyuan, professor CHEN Wei, doctor LI Bo, doctor LI Yan and doctor WANG Yijing from Institute of Applied Ecology (IAE), Chinese Academy of Sciences (CAS), and associate professor LI Pin from Research Center for Eco-environmental Sciences, CAS and associate professor YAN Kun from Yantai Institute of Coastal Zone Research, CAS, jointly characterized the interactive effects of soil cadmium (Cd) addition and O3 fumigation on visible injury and growth, photosynthesis, oxidative stress, antioxidant enzyme activities, abscisic acid content and bioaccumulation of Cd in Populus alba 'Berolinensis' saplings by using open top chambers in Shenyang city with developed heavy industry, Northeast China.
The results showed that high Cd pollution in soil increased the susceptibility of plants to O3 and exacerbated the adverse impact of elevated O3 on physiological metabolisms of poplar species. Interestingly, O3 increased the accumulation of heavy metal content in plant tissues. O3 and its combination with high Cd (500 mg kg-1) induced significant foliar injury symptoms, decreased root weight (41.6%) and total biomass (17.4%), inhibited net photosynthetic rate (50.7%) and stomatal conductance (37.5%). However, soil low Cd addition had no significant effect on photosynthesis and total biomass.
These findings provided increasing evidence that the combined stress of Cd and O3 showed a significant synergistic effect on growth and physiological changes of the tested hybrid poplar, and deepened our understanding on the response and adaptation mechanisms of multifactor stresses to plant and offered a reference for the afforestation and management of poplar forest in the high-O3 areas with heavy industrial cities.
This study entitled "Soil high Cd exacerbates the adverse impact of elevated O3 on Populus alba 'Berolinensis' L" was published in Ecotoxicology and Environmental Safety.
This research is financially supported by the National Natural Science Foundation of China.
Email: yueqian@iae.ac.cn
Publication Name: XU Sheng et al.
