Sweet sorghum (
Sorghum bicolor
[L.] Moench) is a potential feedstock crop in biomass energy development, and is much more resistant to saline soils than crops. Healthy seed germination is critical for the growth cycle of plants, and determines the establishment of seedlings and subsequent crop production. High salinity conditions can result in difficulty for seed germination and delays the germination period. So, screening salt-tolerant genotypes and method for healthy seed germination under salinity stress are vital to crop production and food security. Therefore, a controlled study was conducted to explore the interactive amendment effects of exogenous gibberellic acid (GA
3) and salinity on seed germination process of sweet sorghum. Seeds were presoaked in different levels of GA
3 water solutions (0,144, 288, and 576 μM) and then cultivated in gradient NaCl solutions (0, 50 and 100 mM). The effects of salinity and external GA
3 on seed water uptake and germination characteristics were investigated. Compared with the effects of 0 μM GA
3 at 0 mM NaCl, slight salt stress of 50 mM NaCl improved the cumulative water uptake, germination and germination index, but high salinity level of 100 mM NaCl significantly inhibited these germination traits. However, either 100 mM NaCl or 576 μM GA
3 had significantly negative effects on seed cumulative water uptake, cumulative germination, germination index, and length of germ and radicle. The appropriate concentration of GA
3 prominently relieved salt stress and improved the seed germination of sorghum seeds, and the optimum concentration for seed germination of sweet sorghum was 288 μM GA
3 at each salinity level.
