Application of sodium chloride improves quinoa (Chenopodium quinoa Willd.) growth and cesium accumulation under cesium stress

Abstract Quinoa contains epidermal bladder cells (leaf EBCs) on its surface that increase salt tolerance and facilitate the accumulation of unwanted substances. Additionally, cesium levels in the leaf EBCs are higher than in the leaf cells. Therefore, leaf EBCs are considered key for Cs absorption in quinoa. This study investigated whether, under Cs stress conditions 1) applying NaCl could restore quinoa growth and improve Cs absorption and 2) leaf EBCs maintained their Cs absorption capacity. K content in the leaf cells did not decrease upon CsCl treatment; therefore, CsCl-induced growth inhibition cannot be attributed to K deficiency. CsCl inhibited growth and this effect was rescued upon concomitant NaCl treatment. Cs content in the leaf cells was similar to or even higher than that when only CsCl was applied, suggesting that accumulated Cs in the leaf cells no longer inhibited growth or that Na had a growth-promoting effect. Phytoremediation of Cs can be achieved by applying NaCl, even when high soil Cs levels inhibit plant growth. Compared to leaf cells, Cs and K contents were higher in the leaf EBCs, regardless of CsCl treatment, indicating leaf EBC accumulation of these elements. Conversely, NaCl treatment led to higher Na content in the leaf cells than in the leaf EBCs, suggesting that when the internal Na content increases, quinoa does not actively transfer Na from the leaf cells to leaf EBCs. Therefore, leaf EBCs do not play a major role in salt tolerance in quinoa.