Effects of temperature and different pre-treatments on seed germination of four Halimium species

The aim of this study was to understand the seed germination characteristics of four Halimium species [H. atriplicifolium (Lam.) Spach; H. halimifolium (L.) Willk.; H. ocymoides (Lam.) Willk.; H. umbellatum (L.) Spach ssp. viscosum (Willk.) O. Bolòs and Vigo], under different incubation temperatures and after various pretreatments for enhancing germination. Constant (15°C, 20°C or 25°C) and alternating 15/25°C temperature regimes and 16/8 hours light/dark photoperiod incubation conditions were used. Pretreatments applied were manual scarification, soaking in distilled water, boiling water, hot water, dry heat and sulphuric acid. Germination without pretreatment was low (<18%) and while some pretreatments improved germination, in all four species the highest germination percentages were obtained after manual scarification of seeds. While germination was not affected by temperature, germination rate was faster at 15°C and 20°C than at 25°C or 25/15°C. The physical dormancy caused by an impermeable hard seed coat appears to be the main reason for poor germination of untreated seeds of the four Halimium species studied.