WATER RELATIONS BETWEEN 2 PERENNIAL SPECIES IN THE STEPPES OF SOUTHERN TUNISIA

In Tunisia, the rehabilitation of overgrazed and degraded rangelands i s being attempted through the reintroduction of various native perenni al plant species. We studied plant-water relations in two of the leadi ng candidate species, Seriphidium incultum (syn: Artemisia herba-alba) and Anthyllis henoniana, under conditions of water stress. Anythyllis was found to be adapted to water stress water reserves lying deep in the soil. In contrast, Seriphidium has adapted to drought by toleratin g very severe desiccation of its above-ground parts. Moreover, Seriphi dium individuals consists of several hydrologically independent subuni ts, with the result that one part of the plant can die without damagin g the rest of the plant. Relationships between xylem potential in the two species and soil water potential are also discussed.