Effect of water stress by polyethylene glycol 8000 and sodium chloride on germination of ephedra alata decne seeds

الملخص EN

Ephedra alata Decne is a perennial shrub and it is a very effective sand-binder.

In Saudi Arabia, the species is associated with sand dunes formation, especially the mobile, non-saline and low moisture content ones.

Its geographical distribution in Saudi Arabia includes the Northern, Eastern and Central regions.

The aims of this study were to determine the effects of temperature, water potential and Sodium Chloride on germination of E.

alata.

Seeds were collected from King Khalid Centre of Wildlife Research and Development at Thumama (80 km north east of Riyadh), Saudi Arabia.

Seeds were germinated at four alternating temperature regimes (8 / 22 ; 9 / 23 ; 13 / 27 and 18 / 35 °C).

Seeds were also germinated under stress of aqueous Polyethylene Glycol (PEG) solutions mixed to create water potentials of 0 ; 0.3; 0.6 ; 1.2 and 1.5 MPa.

Seed were also germinated in Sodium Chloride solutions of 0, 0.05, 0.1, 0.2 and 0.3 mol l-1.

Optimum germination was attained at 13/28 °C that corresponds to temperatures prevailing during spring time.

Seeds germinated in Polyethylene Glycol solutions exhibited significantly lower germination than control especially when water potential fell below 0.3 MPa.

Germination was also negatively affected by 0.1 mol l-1 Sodium Chloride solution or above.

Results indicated that the germination temperature responses of the nondormant seeds synchronize the event of germination with the season when four alternating temperature regimes (9 / 22, 10 / 24, 13 / 28 and 18 / 36 °C).

These alternating temperature regimes were selected after consideration of metrological data at station within the habitat range of the species (Table 1).

The seeds were germinated on filter papers placed in 10 cm diameter plastic dishes in dark incubators maintained at the appropriate temperature regimes.

Four replicates (20 seeds each) were used.

A seed was considered to have germinated when the radical emerged.

Germinated seeds were checked daily and discarded immediately until no seed had germinated for seven successive days; counting involved removal of germinator lid and that allowed a change of air and briefly exposed the seeds to light.