Effects of NaCl application on cesium concentration, number, and size of epidermal bladder cells in quinoa plants

Abstract Quinoa (Chenopodium quinoa Willd.) plants possess epidermal bladder cells (EBCs) on the leaf surface that accumulate excess sodium (Na+). However, whether excess cesium (Cs+) is transported from the leaf to the EBCs has not been elucidated in quinoa plants. In this study, the Cs+ concentration of EBCs and leaves of quinoa plants grown in soil treated with high concentrations of NaCl was investigated via pot experiments. Three different treatments were performed: 9.75 g plot, and 19.50 g plot, and a control (with no added NaCl). In 9.75 g plot and 19.50 g plot, 9.75 g and 19.5 g of NaCl were applied to the soil, respectively. And 0.10 g of CsCl were applied to all pots. We observed that Na+ concentration in EBCs and leaves with and without EBCs increased with increasing NaCl concentration at the vegetative and flowering stages; Na+ concentration was lower in the EBCs than in both types of leaves at both growth stages. Cs+ concentration in EBCs and both types of leaves increased with increasing NaCl concentration; Cs+ concentration was higher in EBCs than in both types of leaves at both growth stages. However, NaCl application did not affect the number of EBCs at both growth stages, but the number of EBCs in older leaves was lower than that in younger leaves at both growth stages. Moreover, EBC diameter increased with NaCl application at both growth stages; the EBCs of younger leaves (1st leaf) were larger than those of older leaves (5th leaf) at both growth stages. Therefore, NaCl increased the Cs+-accumulation capacity of quinoa plants by increasing the size of the EBCs.