CHANGES IN THE ANTIOXIDATIVE METABOLISM INDUCED BY DROUGHT AND CD EXCESS IN THE LEAVES OF HOUSELEEK (SEMPERVIVUM TECTORUM L.)

Houseleek (Sempervivum tectorum L.), as a succulent CAM plant, withstands great water stress due to a CO sub(2)-concentrating mechanism. It is traditionally used as a medical plant, partly due to high foliar concentrations of phenolics. The aim of our research was to compare the response of S. tectorum plants to different abiotic stresses. Six months old S. tectorum L. plants were exposed to long term soil drought or cadmium excess for 5 months, in order to characterize the changes in the activities of peroxidases (POD), catalase (CAT), superoxide dismutase (SOD), phenolics concentration and pigments content. Cd treatment induced an increase in SOD, CAT and POD activities and concentration of total phenolics. POD activity increased with time of exposure to Cd, while the total chlorophyll content decreased and it is followed by an increase in Car/Chi ratio. Long term soil drought induced soluble phenolics accumulation and increase in CAT activity, but no change in pigments concentrations, POD and SOD activities. The role of SOD, CAT, POD and phenolics is discussed in relation to stress response and plant ageing.