Abstract:

【Objective】To comprehend the impacts of salt stress on seed germination,seedling growth,and physiological characteristics of salt tolerant and salt sensitive sunflower and to analyze the salt tolerant mechanism of sunflower from the perspectives of physiology and biochemistry.【Methods】Two sunflower inbred lines S05-10(salt tolerant)and 19S6(salt sensitive)were stressed with 50,100,150 and 200 mmol/L NaCl solutions,and distilled water treatment was used as control(CK). Germination percentage,plant height,proline content,malondialdehyde content,relative conductivity and SOD activity were measured. To analyze the effects of salt stress on seed germination,seedling growth and physiological characteristics of sunflower.【Results】Under 100,150,and 200 mmol/L NaCl stress,the germination rate of S05-10 and 19S6 significantly decreased,with the largest decreases being 55.68% and 82.11% when compared to CK(P<0.05). Under 200 mmol/L NaCl stress,the plant height of S05-10 and 19S6 reduced by 31.93% and 63.31%,respectively,compared to CK. Under 50-200 mmol/L NaCl stress,compared to CK,the proline content of S05-10 increased by 44.38%-142.62%,the malondialdehyde content increased by 7.12%-21.36%,and the relative conductivity of leaves increased by 0.04%-28.52%;while the proline content of 19S6 increased by 4.01%-19.74%,the malondialdehyde content increased by 5.00%-102.50% and the relative conductivity of leaves increased by 18.24%-28.96%. Under 100 and 150 mmol/L NaCl stress,the SOD activity of S05-10 increased by 17.77% and 20.43%,respectively,in comparison to CK. Under 50 to 200 mmol/L NaCl stress,the SOD activity of 19S6 was generally steady and increased by 1.86% to 3.73% compared to CK.【Conclusion】Under 100-200 mmol/L NaCl stress,sunflower seed germination and seedling growth were inhibited,with 19S6 showing more inhibition than S05-10 did. Under NaCl stress,19S6 suffered more serious salt damage,with serious leaf membrane lipid peroxidation and electrolyte leakage. The increase in malondialdehyde content and relative leaf conductivity were both significantly higher than those of S05-10. By accumulating more osmotic regulatory substances(proline)and boosting the activity of antioxidant enzymes(SOD)under NaCl stress,S05-10 reduced stress and improved salt tolerance. Under NaCl stress,19S6′s proline content and SOD activity did not change considerably,and its salt tolerance was evidently insufficient.

Key words: Sunflower, Salt stress, Salt tolerance, Salt sensitive, Seedling growth, Physiological characteristics