Abstract:

This research explored the mitigative effect of ascorbic acid （AsA） and salicylic acid （SA） pelleting against NaCl stress during germination of alfalfa （Medicago sativa） seeds. Alfalfa seeds were coated with various concentrations of AsA （1， 2， 4， and 8 mmol·L^-1） and SA （1， 5， 10， and 20 mmol·L^-1） and then were pelleted. There were two control treatments： CK₁ comprised seeds without coating or pelleting； CK₂ comprised pelleted uncoated seeds. The germination performance of the various seed coating treatments was compared under NaCl exposure at 1.25% and 1.50% concentrations， so as to identify the seed coating formula which most effectively alleviated the effects of salt stress on germinating alfalfa seeds. It was found that the mean germination time was extended and germination percentage， germination potential， seedling length and seedling weight of CK₁ decreased significantly （P<0.05） under NaCl exposure at 1.25% and 1.50% concentrations. AsA had no obvious alleviation effect under 1.25% NaCl stress but the 4 mmol·L^-1 AsA treatment increased the germination percentage and seedling length of alfalfa seeds under 1.50% NaCl stress. The 1 mmol·L^-1 SA treatment increased germination potential， germination percentage and seedling length of alfalfa seeds under 1.50% NaCl stress， while the germination percentage of alfalfa seeds was decreased with 20 mmol·L^-1 SA treatment. These results show that the alleviation effect of AsA and SA coating on NaCl stress was dependent on the concentration of the AsA and SA seed coatings and the level of NaCl stress and that NaCl stress was alleviated in alfalfa seeds by 4 mmol·L^-1 AsA and 1 mmol·L^-1 SA coating and pelleting. These results provide reference data on the mitigation effects of AsA and SA coating and pelleting of alfalfa seeds subject to mitigating NaCl stress.

Key words: seed pelleting, alfalfa, ascorbic acid, salicylic acid, NaCl stress