Cadmium accumulation in duckweed relates to pH and oxalate synthesis in Cd shock

Abstract

Anthropogenic activities increase cadmium (Cd) pollution in aquatic systems. This study investigated how the pH change from 4.3 to 7.3 affected the absorption of Cd by the aquatic plant duckweed ( Lemna turionifera 5511). Here, the noninvasive microtest technique (NMT), high-performance liquid chromatography (HPLC), and transcriptome analysis were used to study the duckweed’s Cd absorption and the oxalic acid metabolism under different pH conditions. The results showed the highest Cd accumulation in duckweed with pH at 6.3. Furthermore, the Cd influx was higher at the root tip of duckweed cultured in a liquid medium at pH 6.3. Notably, Cd stress changed the pH value and H þ influx in duckweed roots, and significantly upregulated the Na þ /H þ exchange transporters. Moreover, duckweed was shown to have enhanced oxalate acid secretion and signifi-cantly upregulated biosynthesis-related genes under Cd stress. Therefore, these analyses suggest that Na þ /H þ exchange transporters and oxalic acid might affect Cd accumulation, which could provide new ideas for phytoremediating Cd pollution using duckweed.