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Sunflowers (Helianthus annuus L.) were treated with salt stress and salt-alkaline mixed stress,which were established by mixing proportions of NaCl,Na2SO4,NaHCO3 and Na2CO3.The physiological indices of seedlings stressed,including photosynthesis,growth and mineral element contents,were determined to compare differences in the physiological responses of sunflower to salt stress and salt-alkaline mixed stress.The results showed that the destructive effects of salt-alkaline mixed stress on growth and photosynthesis were more severe than those of salt stress.The contents of mineral elements in the plants stressed were significantly lower under salt-alkaline mixed stress than under salt stress.Data analysis indicated that both stresses caused ionic activity and free concentrations of some mineral elements to decline and even caused precipitation.This was coupled with a reduction of absorption capacity of roots.In conclusion,the mineral nutrition in sunflowers was affected under both salt and salt-alkaline mixed stresses,but the effects were more severe under saltalkaline mixed stress than salt stress.