Drought-induced oxidative stress in strawberry tree (Arbutus unedo L.) growing in Mediterranean field conditions

To study the relationship between drought and oxidative stress and mechanisms of photo- and antioxidative protection in strawberry tree (Arbutus unedo L.), the endogenous concentrations of xanthophyll cycle pigments, alpha-tocopherol and reduced and oxidized ascorbate were measured in 2-year-old plants exposed to a combination of water deficit, high light and high temperatures in Mediterranean field conditions. Under moderate stress (relative leaf water content [RWC] of ca. 68%), levels of photosynthetic pigments (chlorophylls and carotenoids) and ascorbate were kept constant, while alpha-tocopherol levels increased by ca. 50%. Under severe stress (RWC of ca. 53%): (i) alpha-tocopherol levels remained high, (ii) zeaxanthin concentrations increased by 75%, (iii) ascorbate increased by 54% and its redox state shifted towards its oxidized form, and (iv) chlorophylls, lutein and beta-carotene decreased by ca. 63, 61 and 75%, respectively. These results are consistent with the contentions that drought causes oxidative stress in A. unedo plants, and that mechanisms of photo- and antioxidative protection contribute to withstand drought-induced oxidative stress in this Mediterranean plant species. (C) 2004 Elsevier Ireland Ltd. All rights reserved.