Drought-free future climate conditions enhance cadmium phytoremediation capacity by Brassica napus through improved physiological status.

This study aimed to assess Cd phytoextraction efficiency in well-watered and drought-stressed B. napus plants under current climate (CC, 21/14 °C, 400 ppm CO) and future climate (FC, 25/18 °C, 800 ppm CO) conditions. The underlying physiological mechanisms underpinning the obtained results were investigated by studying Cd (1, 10, 50, and 100 mg kg) effect on B. napus photosynthetic performance and nutritional status. Only the Cd-50 and Cd-100 treatments caused visible leaf lesions, growth retardation, reductions in both gas exchange and chlorophyll fluorescence-related parameters, and disturbed mineral nutrient balance. Under CC conditions, well-watered plants were affected more than under FC conditions. The most important pathway by which Cd affected B. napus photosynthetic efficiency in well-watered plants was the damage to both photosystems, lowering photosynthetic electron transport. Meanwhile, non-stomatal and stomatal limitations were responsible for the higher reduction in the photosynthetic rate (P) of drought-stressed compared to well-watered plants. The significantly higher shoot dry weight, which had a strong positive relationship with P, was the main factor determining significantly higher shoot Cd accumulation in high Cd treatments in well-watered plants under FC conditions, resulting in a 65% (p < 0.05) higher soil Cd removal rate in the Cd-50 treatment.