Ecophysiological adaptations of Asphodelus aestivus to Mediterranean climate periodicity: water relations and energetic status

During the course of a year, we studied the water and metabolic status of Asphodelus aestivus , a native geophyte of East Mediterranean, dominant in areas degraded by overgrazing and fire The species proved to be very efficient m storing water during the long summer drought At soil water content values around zero, in the upper part of the soil profile (10–20 cm in depth), the roots remained hydrated and turgid, their relative water content was > 60% and water potential > ‐ 1 6 MPa Accumulation of proline during winter in leaves (ca 5 mg g –1 dry weight) and tubers (though at significantly lower levels, ca 1.5 mg g –1 ) might be taken as evidence of a winter cold stress response Proline accumulation in tubers, under summer drought, was similar to that in winter Maximal values of caloric content were recorded in expanding leaves (ca 5600 cal g –1 dry weight) and minimal before leaf senescence In contrast, root caloric content remained fairly constant for most of the year (ca 4550 cal g –1 dry weight) in spite of drastic changes in the concentrations of soluble sugars, starch and lipids Long before senescence, photosynthetic products were translocated to the below ground system, where they were stored Drastic changes of the storage compounds were observed before emergence of the flowering stalk, far greater in magnitude than those before leaf emergence The below ground part of the species was found to be less susceptible to climatic stress and to constitute an energetically rather stable system The physiological processes of the species were well synchronised to the fluctuations of the Mediterranean climate