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, domi nant in areas degraded by overgrazing and fire. The species proved to be very efficient in storing water during the long summer drought. At soil water content values around zero, in the upper part of the soil p rofile (10-20 cm in depth), the roots remained hydrated and turgid; th eir relative water content was > 60% and water potential > -1.6 MPa, A ccumulation of proline during winter in leaves ica 5 mg g(-1) dry weig ht) 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 w inter. Maximal values of caloric content were recorded in expanding le aves (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 befo re 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 g reater in magnitude than those before leaf emergence, The below ground part of the species was found to be less susceptible to climatic stre ss and to constitute an energetically rather stable system. The physio logical processes of the species were well synchronised to the fluctua tions of the Mediterranean climate.