Growth, phenology, competition and conservation of two desert hygrochastic annuals raised under different watering regimes

Abstract

The two investigated species Anastatica hierochuntica L. Cruciferae and Asteriscus pygmaeus (DC.) Coss. et Dur. Compositae were raised under different watering regimes. Growth, phenology, resource allocation and competition for water were monitored. The following results were obtained: (1) The relative growth and net assimilation rates were dependent on both age and watering regime. (2) 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. (3) Plants were able to adjust the timing of phenological events and water use in accordance with the watering regime. (4) Under high water treatments, A. hierochuntica was competitively inhibited, while under low water treatments A. pygmaeus was competitively inferior. (5) Due to these species’ habitat accessibility there is a need to protect and safeguard their existence.