Abstract:

This research explored the resistance mechanism of quinoa （Chenopodium quinoa） seedlings under different salt-alkali stress levels， to provide reference data for its breeding， introduction and cultivation. It was envisaged the research would overcome the planting limitation of quinoa arising from to land salinization in northwest China. In this study， neutral salts （NaCl， Na₂SO₄） and alkaline salts （NaHCO₃， Na₂CO₃） mixed in different proportions with a concentration of 200 mmol·L^-1 were used as stress treatments. These included： A） NaCl∶Na₂SO₄ =1∶1， B） NaCl∶Na₂SO₄∶NaHCO₃ =1∶2∶1， C） NaCl∶Na₂SO₄∶NaHCO₃∶Na₂CO₃ =1∶9∶9∶1， D） NaCl∶Na₂SO₄∶NaHCO₃∶Na₂CO₃ =1∶1∶1∶1， E） NaCl∶Na₂SO₄∶NaHCO₃∶Na₂CO₃ =9∶1∶1∶9. This series was designed to provide gradually increasing pH as stress treatments. There was also a control （CK） treatment. The effects of the different saline-alkali stress levels on the growth of white quinoa seedlings， the levels of osmotic regulators， the activity of antioxidant enzymes and the expression of NHX1a and NHX1b genes related to Na⁺ compartmentalization were analyzed. It was found that with increased stress time， the plant height of quinoa was suppressed， and the root length and root∶shoot were promoted. Compared with CK， the plant height under treatment E was decreased by 15.39%， and the root length under treatment C was increased by 35.97% and the root∶shoot was increased by 53.10%. Across the salt concentration series， the content of malondialdehyde （MDA） in leaves increased initially and then decreased， and was low under treatment E. The contents of soluble sugar， soluble protein and proline （Pro） increased first and then decreased under the treatment of components A， B and C， and increased continuously under the treatment of components D and E. The superoxide dismutase and ascorbate peroxidase activities in the leaves initially increased and then decreased， peroxide enzyme activity progressively declined， catalase activity increased initially and then plateaued. The expression of Na⁺ compartmentalization-related genes NHX1a and NHX1b in leaves decreased initially and then increased， and the gene expression ranked in order treatment E>D>B>C>A. The results showed that as the proportion of alkaline salt in the saline solution was increased， the damage to quinoa seedlings progressively intensified， but quinoa has capacity to improve its own tolerance through salt tolerance mechanisms such as osmotic regulation， antioxidant production， and salt tolerance-related gene expression.

Key words: Chenopodium quinoa, mixed saline-alkali, seedling growth, physiological trait, gene expression