Survival strategies under extreme and complex environmental conditions: The aquatic resurrection plant Chamaegigas intrepidus

Chamaegigas intrepidus DINTER is a tiny poikilohydric member of the Scrophu lariaceae growing endemically in ephemeral rock pools on granite outcrops i n Central Namibia, Habitat conditions are characterised by (1) frequent and fast desiccation and rehydration during the rainy summer season, (2) compl ete dehydration during the dry winter season lasting up to 11 months, (3) i ntensive solar irradiation and high temperatures during the dry season, (4) diurnal oscillations of pH in the pool water up to 6 units, (5) extreme nu trient deficiencies, especially nitrogen. Anatomical, biochemical and physi ological adaptations to this complex of extreme environmental conditions ar e discussed such as contractive xylem, accumulation of abscisic acid, dehyd rins and carbohydrates during desiccation, and the role of amino acids, amm onium, urea and urease for nitrogen nutrition.