Differential responses to salt stress in ion dynamics, growth and seed yield of European quinoa varieties

•European sweet quinoa cultivars are extremely tolerant to salinity.•Quinoa varieties have a high capacity for ion exclusion under salinity.•Quinoa can adapt to increasing salinity stress by changing salinity response mechanisms.•Genotypic variation was found for salinity tolerance traits.•Epidermal bladder cells did not contribute substantially to ion exclusion. Quinoa is a nutritious seed crop with a great potential to grow in saline soils. Here, we studied ion concentrations in quinoa tissues throughout the life cycle of the plant, and linked ion dynamics to responses in growth parameters, seed yield and efficiency of photosynthesis under salinity (0–400 mM NaCl). Ion dynamics changed from high ion exclusion (>99 %, root contents lower than root medium and low accumulation of ions in the leaves) before flowering, to a build-up of ions during seed filling. This indicates a change in strategy in maintaining the necessary gradient of water potential from the root medium to the leaves. K+ concentrations in leaves also increased by more than 100 % in response to prolonged severe salt stress, which may point to a role of this ion in leaf osmotic adjustment. Accumulation of ions in epidermal bladder cells did not contribute substantially to Na+-exclusion as it was less than 6 % of the total Na+ taken up in leaves. Growth under salt stress was mostly impaired by anatomical adaptations (reduced SLA), while initial light use efficiency (Fv/Fm) and NAR were not affected. The variety Pasto showed a “survival strategy” to high salinity with higher ion exclusion and a higher reduction in transpiration than the other varieties, at the expense of lower biomass and seed yield.