Anastatica hierochuntica (Cruciferae) and Asteriscus pygmaeus (Compositae) were raised under different watering regimes. Relative growth and net assimilation rates were dependent on both age and watering regime. During seedling and juvenile stages, plants had more roots than shoots. Towards the end of the life cycle, there was a redistribution of resources from vegetative to reproductive structures. Plants could adjust the timing of phenological events and water use in accordance with the watering regime. Under high water treatments, A. hierochuntica was competitively inhibited, while under low water treatments A. pygmaeus was competitively inferior. -from Author