The role of cotyledon metabolism in the establishment of quinoa (Chenopodium quinoa) seedlings growing under salinity

A growth chamber experiment was conducted to assess the effect of salinity on emergence, growth, water status, photosynthetic pigments, osmolyte accumulation, and ionic content of quinoa seedlings (Chenopodium quinoa). The aim was to test the hypothesis that quinoa seedlings are well adapted to grow under salinity due to their ability to adjust the metabolic functionality of their cotyledons. Seedlings were grown for 21 days at 250 mM NaCl from the start of the germination. Germination percentage and cotyledon area were not affected by salt whereas seedling height decreased 15%. FW increased in both control and salt-treated cotyledons, but the increase was higher under salinity. DW only increased in salt-treated cotyledons. The DW/FW ratio did not show significant differences between treatments. Relative water content, chlorophyll, carotenoids, lipids, and proteins were significantly lower under salinity. Total soluble sugars, sucrose and glucose concentrations were higher in salt-treated than in control cotyledons. Ion concentration showed a different distribution pattern. Na+ and Cl- concentrations were higher under salinity, while an inverse result was observed for K+ concentration. Proline and glycinebetaine concentrations increased under salinity, but the increase was higher in the former than the latter. The osmoprotective role of proline, glycinebetaine, and soluble sugars is discussed.