Adaptative strategies of psammophilous species

The psammophilous species have evolved different plant and leaf traits to cope with stress factors. They grow on a physiologically dried substrate characterized by a low capacity to water withhold, and a low nutrient content. Moreover, the sand raised by the wind, associated to high irradiance levels and high air temperatures in summer cause the erosion of the below-ground plant portion. Nevertheless, not all psammophilous species are able to withstand the same type or intensities of environmental stress. The main objective of our study is to analyze the phenological cycle, morphological and physiological leaf traits of the most representative species of the psammophilous vegetation developing inside the Presidential Estate of Castelporziano (41°45’N, 12°26’E, S – SW of Rome, Italy), in order to define their adaptative strategies. Cakile maritima Scop. subsp. maritima, Elymus farctus (Viv.) Runemark ex Melderis subsp. farctus, Ammophila arenaria (L.) Link subsp. australis (Mabille) Lainz, Ononis variegata L., Pancratium maritimum L., Eryngium maritimum L., Anthemis maritima L. were considered. Moreover, we want to determine the most discriminating traits defining their adaptive strategy. At phenological level, vegetative activity, flowering, fruiting and leaf senescence are analyzed, and the relative growth rate (RGR) is measured. At leaf level, leaf area and leaf dry mass, net photosynthesis and leaf water potential are analyzed. The structure of leaves has important implications for the performance of plants in specific habitats. The results on the whole underline the influence of air temperature on the beginning and the length of the phenophases. Among the considered species, C. maritima and A. maritima are the best adapted species to the low air temperature; moreover, their highest photosynthetic rates may be justified by the highest specific leaf area (SLA). The results allow us to hypothesize the response of the considered species to increasing stress factors including global change.