Dormancy, germination and viability of Salsola imbricata seeds in relation to light, temperature and salinity

Salsola imbricata Forssk., a leaf succulent perennial halophyte in the family Chenopodiaceae, is distributed both in coastal and inland areas of Karachi, Pakistan. Experiments were conducted in the laboratory to determine the effect of salinity, temperature and light on the germination of seeds. Different abiotic conditions including four temperature regimes (10-20, 15-25, 20-30, 25-35 degrees C) with five NaCl concentrations (0, 200, 400, 600, and 800 mM) were provided to S. imbricata seeds during germination under two light levels (12 h dark: 12 h light; and 24 h dark environment). Most seeds germinated in the non-saline control. Seed germination was progressively inhibited with an increase in salinity. About 8% seed germinated at 900 mM NaCl. Optimal germination was obtained at 15-25 degrees C and germination inhibition was greater at cooler temperature regime (10-20 degrees C). Light had little effect on the seed germination at all salinity and temperature treatments. When un-germinated seeds of S. imbricata were transferred from saline solutions to distilled water, the germination showed a temperature dependent recovery response. The highest recovery was obtained at 15-25 degrees C. Seeds lost their viability at cooler temperature regimes (10-20 degrees C) and under high salinity, however, poor recovery at warmer temperatures is attributed to the induction of seed dormancy.