Germination of Francoeuria crispa (Compositae) from Saudi Arabia PDF

Keywords

Desert, Saudi Arabia, germination

Abstract

Francoeuria crispa is a perennial bushy desert plant. Its distribution in Saudi Arabia includes the Northern, Eastern, and Nefud regions, North Hijaz, South Hijaz and Eastern Najd. The freshly harvested seeds were germinated over a range of alternating temperatures (1S/8 , 21/10, 28114, 32116, 36121, and 42126°C) and also at varying salinity levels (2305.5, 4611, 9222.5, 18445, 27667 and 46112 ppm = 5, 10, 20, 40, 60 and 100 percent seawater, respectively) at two fluctuating temperature regimes: 21110 and 28114°C. The germination temperature responses of the nondormant seeds synchronize the event of germination with the season when environmental conditions are more favorable for subsequent growth and seedlings establishment. At 21110"C the seeds tolerated fairly high salinity levels which are far beyond those encountered and tolerated by the adult plants in their natural habitat. Increasing the incubation temperature to 28114°C reduced drastically the salt tolerance of the seeds. The inhibition of germination by excessive salinities (40, 60, and 100 per cent seawater) is due to the high osmotic potential of the medium. The ecological significance of the responses of the seeds to the various environmental variables is discussed.