Effect of elevated CO 2 concentration on photosynthetic characteristics of hyperaccumulator Sedum alfredii under cadmium stress

The combined effects of elevated CO 2 and cadmium (Cd) on photosynthetic rate, chlorophyll fluorescence and Cd accumulation in hyperaccumulator Sedum alfredii Hance were investigated to predict plant growth under Cd stress with rising atmospheric CO 2 concentration. Both pot and hydroponic experiments were conducted and the plants were grown under ambient (350 µL L −1 ) or elevated (800 µL L −1 ) CO 2 . Elevated CO 2 significantly ( P <  0.05) increased Pn (105%–149%), Pn max (38.8%–63.0%) and AQY (20.0%–34.8%) of S . alfredii in all the Cd treatments, but reduced chlorophyll concentration, dark respiration and photorespiration. After 10 days growth in medium with 50 µM Cd under elevated CO 2 , PSII activities were significantly enhanced ( P <  0.05) with Pm, Fv/Fm, Φ(II) and qP increased by 66.1%, 7.5%, 19.5% and 16.4%, respectively, as compared with ambient‐grown plants. Total Cd uptake in shoot of S. alfredii grown under elevated CO 2 was increased by 44.1%–48.5%, which was positively correlated with the increase in Pn. These results indicate that elevated CO 2 promoted the growth of S. alfredii due to increased photosynthetic carbon uptake rate and photosynthetic light‐use efficiency, and showed great potential to improve the phytoextraction of Cd by S. alfredii .