Responses Of Sweet Sorghum To Exogenous Salicylic Acid Under Salinity Stress Condition

Nowadays, the environment problem caused by fossil fuel is becoming severe. The bio-energy, which is sustainable and environmental-friendly is gaining more and more attention. In China, there is a large area of saline soil. It will be a win-win strategy to develop the energy crops industry on the saline soil. Sweet sorghum is one of the ideal energy crops. Although sweet sorghum has higher salt tolerance than normal crops, it still faces the problems of low germination rate, poor seedling establishment and inhibition of growth. The recent research shows that salicylic acid, as one of the phytohormones, can somehow alleviate the negative effects of abiotic stress. One salt tolerance genotype of sweet sorghum, Yajin 13, was used to investigate the effects of salinity and exogenous salicylic acid on its seed water uptake, germination and growth and physiological parameters of seedling. Then a pot experiment was done to investigate the effects of salicylic acid and salinity on the growth and theoretical yield of sweet sorghum.1. Effects of salinity and salicylic acid on water uptake and germination of sweet sorghum seedsThe quality of seed germination lays a solid foundation for an optimum plant population and crop establishment. Priming by exogenous salicylic acid might be one of the strategies that alleviate the negative effects of salt stress on seed germination. The seeds of Yajin 13 were pre-soaked with salicylic acid at different levels (0,0.362, and 0.724 mM) and cultured in water solutions at different salinity levels (0,50, and 100 mM) to investigate the effects on water uptake and germination process. The water uptake percentage and water uptake rate dropped quickly before 8 h, and then became stable after 12 h after water imbibition. During 8-12 h, seeds started physiology absorption of water and physical water uptake was finished. Salinity produced significant effects on water uptake and germination of sweet sorghum seeds, and pre-soaking salicylic acid alleviated the inhibitive effects of salinity. The 50 mM NaCl level did not inhibit seeds germination, but slightly promoted the growth of and growth. The 100 mM NaCl level significantly inhibited seed germination and the growth of shoots and roots. The germination index and seed vigor index were decreased by increasing salinity level. The 0.362 and 0.724 mM salicylic acid levels significantly promoted the germination of sweet sorghum seeds and the growth of shoots and roots. The 0.724 mM salicylic acid level had the best promotional effects on germination index and seed vigor index.2. Effects of salinity and salicylic acid on growth and physiology of sweet sorghum seedlingsSalt stress is one of the major abiotic stresses affecting physiological parameters at seedling stage. Reasonable application of exogenous hormones could be a way to the effects of salt stress. The seeds of Yajin 13 were pre-soaked at different salicylic acid levels (0,0.362, and 0.724 mM) and cultured in pots filled with sands treated with different salinity levels (0,50, and 100 mM) to investigate the effects of salinity and salicylic acid on growth and physiological parameters of sweet sorghum seedlings. The 50 mM NaCl level had rare negative effects on this sweet sorghum cultivar and seedling growth was even promoted. The 100 mM NaCl level significantly had negative effects by reducing emergence percentage and decreasing fresh and dry weight of shoots and roots. With the increased salinity level, the content of soluble protein and the activities of peroxidase (POD) and superoxide dismutase (SOD) followed an upward trend first and then a downward trend. Our study indicated that this sweet sorghum cultivar was salt tolerant, however the negative effects of salinity appeared with the increased salinity. Priming with salicylic acid at appropriate concentrations can significantly increase the emergence and the activities of catalase (CAT) and POD, but its positive effects were not as significant as they were in the germination trial. Compared with other levels,0.362 mM salicylic acid had better effects on regulating the growth of sweet sorghum.3. Effects of salinity and salicylic acid on growth parameters and theoretical yield of sweet sorghumThe stalk of sweet sorghum is rich in sugar juice as high as eight percent of stalk fresh weight. The juice can be easily converted into ethanol. The yield of ethanol from the stalk of sweet sorghum is 30%-40% higher than those produced from corn kernel and corn stalk. Sweet sorghum is one of the ideal crops that can grow on saline soils and can be used to develop bioenergy industry in China. In this study, a pot experiment was done to investigate the effects of salicylic acid (spray of 0 and 0.362 mM every 15 d after 30 d of seeding) and salinity (0,2.0 and 4.0 g NaCl/kg soil, corresponding to electrical conductivities of 0.3,2.3 and 4.7 dS/m) on the growth and theoretical yield of sweet sorghum. Plant height, stem diameter, leave number, LAI and fresh and dry weight of roots, stalk and leave were significantly decreased at the 4.7 dS/m salinity level. The sweet sorghum grew normally at the 2.3 dS/m salinity level. Regulating salicylic acid solution significantly promoted sweet sorghum growth under saline or non-saline conditions, and also increased the Brix of stalk, juice yield, sugar yield, and ethanol yield.