Effects of different scarification methods on germination of Ziziphus spina-christi seeds

Trees are very important for local people in many rural areas of Africa. Ziziphus spina-christi (L.) Willd. is a multipurpose fruit tree species indigenous to Sudan. It is generally propagated by seeds which are slow to germinate and total germination percentage is low. Germination in related species was improved by either mechanical or acid scarification. Whether such methods are also effective in Z. spina-christi is, however, unknown. This study explored two mechanical methods (hilum abrasion using sand paper and cracking of the seedcoat) and three acid scarification treatments by the immersion of seeds in sulphuric acid (97%) for 30, 60 and 120 minutes. Emergence percentage was highest after immersing seeds in acid for 120 minutes, but was not significantly different from others scarification treatments, with the exception of the 30 minutes acid treatment. Mechanical and acid scarification, with the exception of the 30 minutes acid treatment, decreased days to first emergence (E-1st by 2-4 days, days to 50% emergence (E-50) by 12-10 days, and mean days to emergence (MDG) by 2-4 days. Cracking of the seedcoat resulted in lowest E-1st, E-50 and MDG. All treatments significantly increased total seedling fresh weight but not dry matter.