Drought tolerance of the dehydrated root of schismus arabicus seedlings and regrowth after rehydration, affected by caryopsis size and duration of dehydration

The unique drought tolerance of the single root of Schismus arabicus seedlings was compared with the roots of barley subjected to the same drought conditions. S. arabicus seedlings with roots and coleoptiles that were 1 to 2 mm or longercontinued to grow and develop into normal plants when rehydrated after various dry periods. Moreover, seedlings originating from larger caryopses grew faster than those from small caryopses. When seedlings of cultivated barley ‘Noga’ were dehydrated under the same conditions, none of the roots survived even after one day of drought. However, the barley seedlings survived because coleoptile growth was re-initiated following rehydration and new adventitious roots developed. S. arabicus is one of the very common annual plant species in large areas in theextreme deserts of the Saharo–Arabian phytogeographic region where the low rainfall and its distribution in winter are unpredictable. The ability of small portions of the S. arabicus soil seed bank to germinate after small amounts of rain, together with seedling drought tolerance for at least 29 days, may increase the chance of survival of this plant species. Seedlings originating from larger caryopses have even a higher chance of survival.