Average gas exchange indexes of the cotton blades of the control and five salt dust treatment groups (Mean ± SE) (n = 6).

Samples within one index with different lowercase letters a, b, c, d and e had significant differences between different salt dust treatment groups(P<0.05), while samples with matching lowercase letters had no significant differences. Average gas exchange indexes of the cotton blades of the control and five salt dust treatment groups (Mean ± SE) (n = 6).