Is a C4 tropical grass still an option in the revegetation of iron ore tailings in face of climate change

Paspalum densum is a C4 tropical grass with a high potential for the rehabilitation of iron mining sites, but combined environmental factors can bring new and unexpected responses to this species. Here, we describe the effects of the iron solid particulate matter (SPMFe) deposition in P. densum under future scenarios of climate change with the increase in atmospheric CO2 concentration. The plants were exposed to two deposition rates of SPMFe (0 and 2.14 mg cm−2 d−1) in open-top chambers with two CO2 concentrations (380 and 700 μmol mol−1), with four replicates. The SPMFe deposition caused an increase in the leaf iron concentration, but without leaf bronzing. Besides that, the SPMFe deposition on the leaf surface caused a reduction in net photosynthesis, due to blockage of light radiation; and increased transpiration was considered a strategy to minimize the effect of overheating. The increase in atmospheric CO2 concentration resulted in a higher total leaf area. P. densum exhibited an efficient energy dissipation mechanism when exposed to excessive irradiance, which prevented photoinhibitory damage under SPMFe deposition. The increase in atmospheric CO2 concentration can positively impact the efficiency of photosystem II. The reduction in lipid peroxidation after exposure to SPMFe suggests that P. densum has an efficient mechanism for the elimination of reactive oxygen species. The high resistance presented by P. densum proves its potential for use in revegetation environments with high concentrations of iron and subject to particulate deposition, even in future climate change scenarios.