Effect of seed priming on sorghum (Sorghum bicolor L.) seed germination and seedling growth under salt stress

Seeds of 2 sorghum (Sorghum bicolor L.) hybrid combinations of Tx623A × 89-363 (Sb1, a weak salt-tolerant cross combination) and Hei30A × Dalizao (Sb2, a strong salt-tolerant cross combination) were primed with 100 mmol·L-1 NaCl. The primed seeds were subjected to salt stresses of 4 NaCl concentrations (0, 50 mmol·L-1, 100 mmol·L-1 and 150 mmol·L-1) in a sand culture experiment. The effects of the seed priming and salt stress on seed germination and seedling growth under salt stress were then investigated. The results showed that with or without priming, seed emergence was significantly delayed. The rates of seed emergence and seedling survival also dropped significantly, while the seedling growth was inhibited, matter accumulation dropped with increased NaCl concentration. Compared with unprimed seeds under the same NaCl concentration, primed seeds had shorter emergence time, higher rates of emergence and seedling survival, higher dry/fresh shoot and root weight, higher contents of photo-synthetic pigments, and lower Na+/K+ ratio. The results suggested that seed priming promoted sorghum seed germination under salt stress, alleviated seedling damage by salt stress, accelerated seedling growth and increased seedling salt tolerance. Different effects were noted for cross combinations with different salt tolerance. The effects were much better for weaker salt-tolerant cross combina-tions.