High salt tolerance in germinating dimorphic seeds of Arthrocnemum indicum

Arthrocnemum indicum L. is a stem-succulent perennial in the family Chenopodiaceae and is widely distributed in the tidal marshes of Pakistan. Seeds were collected from a coastal salt marsh situated on the Arabian Sea coast at Sands Pit, Karachi, Pakistan. Arthrocnemum indicum produces dimorphic brown and black seeds, and brown seed was significantly (P < 0.05) heavier. Experiments were conducted to determine the effect of salinity and temperature on the germination of seeds. Results indicated that both seeds are highly salt tolerant, and 3% of the brown seeds germinated at 1000 mM NaCl. Germination was significantly higher at 15 degrees-25 degrees C thermoperiod at 600 and 800 mM NaCl. Rate of germination decreased with increase in salinity and there was no significant difference among various thermoperiods on the rate of germination in both seed types. When the seeds were transferred to distilled water after 20-d exposure to salinity, most recovered in 24 h, with recovery percentages at highest salinity varied from 72% to 86% at various thermoperiods.