Suaeda salsa is Adaptive to Chilling Stress under Salinity at Stages of Seed Germination and Seedling Establishment

Suaeda salsa L., a C3 euhalophytic herb, is a native of saline soils. This herb displays high resistance to salinity stress. In the present study, we investigated the interaction between low temperature and salinity on seed germination and seedling establishment. Low temperature (4 oC) conditions severely inhibited seed germination at 0 and 200 mM NaCl. The percent germination at 200 mM NaCl was higher than that at 0 mM NaCl. After 24 h of chilling stress, the fresh weight and dry weight of S. salsa seedlings at 0 mM NaCl was reduced, but the fresh weight and dry weight of S. salsa seedlings at 200 mM NaCl increased. APX and CAT activities decreased during chilling stress at both 0 and 200 mM NaCl, yet the activity of both enzymes was not affected as strongly at 200 mM NaCl compared to 0 mM NaCl. After a 12 h chilling treatment, the unsaturated fatty acid content and the double bond index (DBI) of DGDG, SQDG and PG major membrane lipids was significantly increased at 200 mM NaCl. The level of PG and the ratio of DGDG/MGDG in seedling leaves were also increased in the presence of 200 mM NaCl. These results suggest that S. salsa is more adaptive to chilling stress under 200 mM NaCl conditions at stage of seed germination and during seedling establishment.