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The high north-central Chilean Andes present strong daily and seasonal temperature variations together with an extremely dry growing season, typical of mediterranean climates. Adesmia is highly diverse in terms of life-forms, and the most dominant plant genus in this region; therefore, it represents an opportunity to study plant responses to constraints imposed by water stress during the growing season. This paper characterizes variations in water relation parameters, which occur under low water availability conditions, and their effects on gas exchange characteristics in four Adesmia species with different life-forms and inhabiting different vegetation belts at different altitudes. Daily courses of gas exchange and water relations were performed on A. hystrix (3300 m), A. aegiceras (3300 and 3750 m), A. echinus (4200 m) and A. subterranea (3750 and 4200 m) in the growing season. Osmotic potential at full turgor and turgor loss and relative water content at turgor loss were also evaluated for each species. All Adesmia species show important stomatal control during most of the day as a response to law soil water availability. A. aegiceras, at both altitudes, exhibits maximum assimilation rates (6-8 mu mol m(-2)s(-1)) compared to the other three species (2-6 mu mol m(-2)s(-1)). Only A. hystrix at 3300 m and A. aegiceras at 3750 m lost turgor during the daily courses. Maximum CO2 assimilation rates are low compared to other species from mid-latitude high mountains.