Interactive effects of salinity, light and temperature on seed germination of sand dunes glycophyte Cyprus conglomeratus growing in the United Arab Emirates deserts

Cyperus conglomeralus is one of the most dominant evergreen plants on the unstable desert sand dunes of the Arabian Gulf region. This study assessed the effects of salinity, temperature and light of incubation, and their interactions on final germination, germination rate and recovery germination of this glycophytic sedge in the UAE deserts. The optimum germination for the non-saline treated seeds was in light and at 30/40°C. Germination in light was significantly greater than in darkness at higher temperatures, but did not differ at lower temperatures. Seeds of C. conglomeratus were very sensitive to salinity. Salinity tolerance depended on both light and temperature of incubation. Salinity tolerance at higher salinity levels was greatest at both higher temperatures and darkness. Germination in light was significantly reduced in 25 mM NaCl and almost inhibited in 50 - 100 mM NaCl, but dark germination either significantly increased or was not affected, especially at higher temperatures. No seeds recovered their germination after transfer from saline solutions to distilled water when placed at the lower temperatures, but recovery was observed at higher temperatures. The results are discussed in the light of the adaptive significance of germination behaviour for C. conglomeratus survival and adaptation in deserts.