Effects of NaCl stress on seed germination and seedling growth of two cold-season grasses

This study investigated the effects of NaCl on seed germination and seedling growth of infected Achnatherum inebrians and non-infected A. inebrians, Festuca arundinacea ‘Island’, and F. arundinacea ‘Hound 6’, to determine the tolerance level of single salt NaCl stress at seed germination stage and seedling growth stage and to conduct a comprehensive salt tolerance evaluation. In endophyte-infected A. inebrians and non-endophyte-infected A. inebrians, ‘Island’, and ‘Hound 6’ as the experimental material, the mass fractions of 0.1%, 0.3%, 0.5%, 0.7%, and 0.9% of the salt solution were used to process seeds, and germination rate, germination potential, vigor index and seedling height, and radicle length index, were measured to establish the related function equation to determine the tolerance values of four kinds of germplasms planted under saline conditions. The results showed that, compared with the control group, the germination rate, germination power, germination index, vigor index, seedling height, and radicle length decreased with increasing salt concentrations, whereas the root-cap ratio showed the opposite trend. Mild salt stress (0.1% and 0.3%) had a positive effect on seed germination and seedling growth (P < 0.05). In the germination stage, the appropriate salt tolerance concentrations of E + A. inebrians, E – A. inebrians, ‘Island’, and ‘Hound 6’ were 0.70%, 0.60%, 0.37%, and 0.49%, respectively. The salt-tolerance semi-lethal concentrations were 0.98%, 0.72%, 0.46%, and 0.61%, respectively, and the salt tolerance limit concentrations were 1.02%, 0.91%, 0.62%, and 0.87%, respectively. In the seedling stage, the salt tolerance thresholds of E + A. inebrians, E – A. inebrians, ‘Island’, and ‘Hound 6’ were 1.23%, 1.01%, 0.44%, and 1.09%, respectively. The comprehensive salt tolerance levels were; E + A. inebrians > F. arundinacea‘Hound 6’ > E – A. inebrians > F. arundinacea ‘Island’.