Comparative Effects Of Salt And Alkali Stresses On Osmotic Regulation Of Two Quinoa Cultivars

Soil salinization is a rising problem increasing at rapid pace.Soil salinity and alkalinity are the two main causes affecting crop production worldwide.In this study,two quinoa cultivars were selected for the experiment.The two quinoa cultivars were subjected to salt and alkali stresses to analyze the relative water content,inorganic ion content,proline and soluble sugar content.Salt and alkali stress concentrations used in the experiment were?NaCl:0,100,200 mM?and?NaHCO₃:0,50,100 mM?respectively for each variety.Ion contents of two quinoa cultivars had substantial changes under both stresses.Under salt and alkali stress,Na⁺concentrations in different parts of the two cultivars were increased in different degree.Under NaCl stress,Cl^-contents in different parts of two quinoa cultivars were increased with increase of stress intensity.Under NaHCO₃ stress,the change trends of Cl^-in leaves of two quinoa cultivars were similar to those under NaCl stress,while the Cl^-contents in shoots and roots were decreased with increase of stress intensity.Under the same conditions,the order of the contents of Na⁺and Cl^-in leaves of quinoa was followed the sequence:upper leaves<middle leaves<lower leaves.Under NaHCO₃ stress,Na⁺contents in leaves of Painbon were higher than those of Titicaca.And under NaCl stress,the content of Na⁺in Titicaca leaves was higher than those of Painbon.These results may be attributed to alkaline effects,probably due to an important adaptation for salinity.Under NaCl stress,the H₂PO₄^-contents in Titicaca were increased with the increase of salt concentration.In addition,the contents of K⁺,NO₃^-,H₂PO₄^-and SO₄^2-in stems and roots of two varieties of quinoa were also decreased.In contrast,salt and alkali stress had a relatively minor effect on the Contents of K⁺,NO₃^-,H₂PO₄^-and SO₄^2-in the leaves of two quinoa cultivars.Under the same conditions,the order of the contents of NO₃^-,H₂PO₄^-and SO₄^2-in the leaves of two quinoa species was followed the sequence:upper leaves>middle leaves>lower leaves.Under salt and alkali stress,the order of K⁺contents in the leaves was followed the sequence:upper leaves<middle leaves<lower leaves.Under NaCl stress,the proline contents in leaves of two quinoa cultivars were increased gradually.Under NaHCO₃ stress,the proline contents of Painbon cultivar were not increased significantly.On the contrary,the proline contents of Titicaca cultivar were decreased.This indicated that the accumulation and synthesis of proline was involved in osmotic adjustment of leaves,which was irrelevant to pH effect.In conclusion,the effect of alkali stress was much greater than that of salt stress.Compared with Titicaca,the tolerance of painbon to salt and alkali stress should be demonstrated in the future research.