Seed Scarification Requirement in Doum (Hyphaene thebaica Mart.)

(Mohamed Abdel Wahab Alfredan and Yousef Saleh Siraj)

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Abstract

Seed dormancy is a means to allow seeds to initiate germination when conditions are normally favorable for germination and survival of the seedlings. Dormancy can be regulated by the environment or by the seed itself. The seed dormancy may be due to unfavorable environmental conditions or sometimes, some seeds may not germinate because of some inhibitory factor of the seed itself. Dormancy of seed due to inhibitory factors, are either due to hard seed coat (external) or physical of physiological status of the interior of the seed. Seed dormancy in Doum palm (H. thebaica Mart) belongs to the first type. Tropical tree species that produces seeds with hard seed coat such as Doum which is a common component of flora of the southwestern Saudi Arabia are restricted in their distribution in the region because of the prolong dormancy and poor germination rate. The treatment methods for scarification proved effective to reduce dormancy in Doum seed. Seeds soaked in water showed much lower germination than the seed soaked in water after mechanical or chemical scarification. The highest germination percentage (93%) was recorded by mechanically scarified seed for 30 min and then soaked in water for 24 hours. The sulphuric acid treated seed resulted in a low germination percentage (32%). The results indicated that the impermeability of the seed coat of Doum seeds and the need to activate the growth of the embryo by soaking the seed in hot water are related to the environmental conditions which affect growth and distribution of Doum in southwestern Saudi Arabia.
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