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 seedli ngs was compared with the roots of barley subjected to the same drought con ditions. S. arabicus seedlings with roots and coleoptiles that were I to 2 mm or longer continued to grow and develop into normal plants when rehydrat ed after various dry periods. Moreover, seedlings originating from larger c aryopses grew faster than those from small caryopses. When seedlings of cul tivated barley 'Noga' were dehydrated under the same conditions, none of th e roots survived even after one day of drought. However, the barley seedlin gs survived because coleoptile growth was re-initiated following rehydratio n and new adventitious roots developed. S. arabicus is one of the very comm on annual plant species in large areas in the extreme 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. arabi cus 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 caryopse s have even a higher chance of survival.