Germination of dimorphic seeds of Suaeda moquinii under high salinity stress

Suaeda moquinii (Torrey) Greene (desert blite), a succulent shrub in the family Chenopodiaceae, is widely distributed in salt marshes of the western United States. Suaeda moquinii produces dimorphic seeds (soft brown and hard black). Both types of seeds were collected from a salt marsh in Faust, Utah. Experiments were conducted to determine the seed germination responses of the black and brown seeds to salinity and temperature. Brown seeds were found to be one of the most salt tolerant at the germination stage when compared to other halophytes. Brown seeds germinated (30%) at 1000 mM NaCl, but only a few black seeds germinated (8%) at 600 mM NaCl. Seed germination occurred in most saline treatments at the lowest thermoperiod (5-15 degreesC) tested. In some salinity treatments (600, 800, 1000 mM), further increases in temperature resulted in progressively decreased seed germination. Brown seeds germinated better and had a higher germination rate (germination velocity) than black seeds at all thermoperiods. The highest rate of germination of black seeds occurred at the lowest thermoperiod (5-15 degreesC). Recovery of germination for black seeds when transferred to distilled water after being in various salinity treatments for 20 days was nearly complete (82-100%) at the lowest thermoperiod (5-15 degreesC) but decreased with increase in the temperature. Brown seeds recovered substantially (59-97%) from salinity at all thermoperiods. Regression analyses indicated significant differences between the germination recovery of the black and brown seeds.