Changes of Photosynthetic Performance of Brassica napus Affecting Cadmium Phytoextraction Performance under Elevated Temperature, CO2 and Drought

This study aimed to investigate the Cd-removal efficiency from the soil by rapes (Brassica napus L.) under changing climate conditions, i.e. elevated temperature and CO2 with or without additional drought stress. As photosynthesis is the most important primary metabolic process, determining plant growth, Cd-phytoextraction performance was evaluated through the changes in chlorophyll a fluorescence (ChlF) parameters that are widely used to quantify abiotic stress responses. The results showed that, with the less affected photochemical quantum yields and better general physiological state of PSII, well-watered rapes grown under elevated temperature and CO2 conditions produced significantly higher harvestable biomass and extracted significantly higher Cd content from the soil than those grown under ambient temperature and CO2 conditions. Drought fully negated this gain; however, Cd-phytoextraction performance by rapes under the combined impact of elevated temperature, CO2 and drought was not related to the changes of selected ChlF parameters, suggesting other restrictions to photosynthesis under additional drought stress than the reduced photochemical activity due to the decrease in electron transport flow.