Accumulation and subcellular distribution of cadmium in rygegrass induced by Aspergillus niger TL-F2 and Aspergillus flavus TL-F3

Abstract

Although plant growth-promoting fungi can greatly accelerate the ryegrass bioaccumulation of cadmium (Cd), the underlying mechanisms are not yet well documented. Therefore, we performed a 20-days hydroponic experiment to investigate the effects of Aspergillus niger TL-F2 (A. niger TL-F2) and Aspergillus flavus TL-F3 (A. flavus TL-F3) on accumulation/subcellular distribution of Cd by annual ryegrass Dongmu 70 at different Cd concentrations (0, 2.5, and 5 mg L−1). Results indicated that both fungal strains promoted ryegrass biomass/growth by about 60%. Furthermore, we found that ryegrass roots (17.8–37.1 μg pot−1) had a significantly higher capability for Cd uptake than the shoots (1.66–5.45 μg pot−1) (p < 0.05). Of total Cd in ryegrass plants, 44–67% was in soluble form, 24–37% was in cell wall, and 8.5–25.5% was in organelles. Compared with non-fungus ryegrass, cell wall and soluble Cd fractions in fungus-inoculated roots increased and decreased by 13.5–44% and 21.5–26.4%, respectively. Besides, fungus inoculation generally increased the content of cell wall and soluble Cd fractions in ryegrass shoots. Altogether, the study concludes that inoculation of fungus in ryegrass is a promising approach to improve phytoremediation of Cd contaminated environments. Novelty statement Previous study by Han et al. (2018) examined the resistance of ryegrass plant to Cd stress after its inoculation with Aspergillus aculeatus. In this study, using a hydroponic experiment, we examined the effects of co-application of two species of Aspergillus fungi. i.e. A. niger TL-F2 and A. flavus TL-F3 on ryegrass growth/biomass, Cd absorption by ryegrass shoots and roots, and subcellular distribution of Cd in ryegrass roots and shoots.