Regulation of water use by four species of Cistus in the scrub vegetation of the Serra da Arrábida, Portugal
Plants of mediterranean ecosystems are subjected annually to prolonged periods of drought. The drought resistance of individual species occurring in these regions is conferred on them by both morphological and physiological adaptations which provide both drought avoidance and drought tolerance mechanisms (Levitt 1980). In parts of the Serra da Arrábida region, Cistus salvifolius, Cistus monspeliensis, Cistus albidus, and Cistus ladanifer are sympatric species, although in general, differences in habitat preference have been identified based on moisture availability. Cistus salvifolius, for example, is the most prevalent species on less exposed north facing mountain slopes. It occurs in a smaller growth form on drier south facing slopes together with the other three more thermophilic species. The present comparative study was undertaken to examine possible differences in drought resistance among these four Cistus species more closely. Over an annual cycle, the water relations and stomatal response of all four species were observed at monthly intervals in an attempt to identify differential responses to stress conditions.
KeywordsWater Potential Photosynthetically Active Radiation Transpiration Rate Leaf Conductance Xylem Water Potential
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