Radon adsorption and air purification by Spanish moss (Tillandsia usneoides) and its metabolic response to radon exposure

Abstract

The capacity of Spanish moss (Tillandsia usneoides), an aerial plant, to adsorb radon (Rn) and absorb CO2 was assessed to analyze its capacity to remove pollutants from indoor air and to determine its radon (Rn) tolerance mechanism. Transcriptomics and metabolomics techniques were used to analyze the response of the plant to Rn exposure. Spanish moss absorbed indoor CO2 at night using the type of photosynthesis termed crassulacean acid metabolism. The CO2 absorption efficiency of the plant was mainly affected by the light duration and diurnal temperature differences. The highest purification efficiency was 48.25%, and the scales on the Spanish moss leaf surface were the key sites for Rn adsorption. Metabolome analysis showed that Rn exposure induced differential metabolites significantly enriched in the metabolism of lipids, amino acids, nucleotides, and carbohydrates. Transcriptome analysis showed significantly upregulated expression levels of functional genes in Rn-exposed leaves. Rn had significant effects on respiratory metabolism, as indicated by upregulated expression of metabolites and functional genes related to the glycolysis pathway, pyruvate oxidation, tricarboxylic acid cycle, and oxidative phosphorylation pathway. These responses indicated that the internal mechanism by which Spanish moss alleviates Rn stress involves an enhancement of cellular energy supplies and regulation of respiratory metabolic pathways to allow adaptation to Rn pollution.