An investigation on some medicinal compounds and PAL activity in two olive cultivars under cold stress

Olive (Olea europaea L.) is an evergreen tree, traditionally cultivated in the Mediterranean area. Olive tree cultivation is curtailed in cold areas because they can rarely tolerate temperatures at and below -12°C. In recent years, because of high demands for olive oil and its fruit, the cultivation of olive trees has been increased in Iran. To investigate the impact of cold stress on the content of total phenol, antioxidant activity and three major phenolic compounds including oleuropein, hydroxyl tyrosol and tyrosol and also phenylalanine ammonialyase (PAL) activity, one-year old olive cultivars of Sevillana and Frantoio were exposed to low temperatures of 10, 5, 0, -5, -10, -15, -20 and control 20°C for 12 h, gradually. The results indicated that total phenol content, antioxidant activity and PAL activity were increased under cold stress in both investigated cultivars. However, PAL activity in Sevillana showed significant decrease at and below -5°C while in Frantoio cultivar there was significant dwindling blew -10°C. Oleuropein content significantly increased during cold stress but, tyrosol and hydroxy tyrosol content decreased in both cultivars compared with the controls. According to the current results, Frantoio and Sevillana showed different resistance under cold stress, so that Frantoio was more resistant than Sevillana