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Artemisia monosperma plants were collected from three independent locations in Riyadh during the periods June 2009-February 2010. The goal of this study was to compare the physiological and biochemical strategies during temperature seasonal variation in Artemisia monosperma that is divergent in photosynthetic pigments and antioxidant system. Photosynthetic pigments, including chl a, b and carotenoids, were significantly varied according to temperature divergence in the different seasons. Tissue malondialdehyde (MDA) content used as an oxidative stress index was 2.3-fold enhanced in Artemisia monosperma collected during winter (9 degrees C), in comparison with plants collected during summer period (38 degrees C). Differences in accumulation of some antioxidant metabolite and enzyme activities during seasonal variations in temperature were investigated. Total ascorbate was markedly accumulated during winter period (especially at 9 and 15 degrees C). Antioxidant enzyme activities were also significantly enhanced in Artemisia monosperma during winter period compared with summer period. Different temperatures gave different results, which were quite significant (POD, P < 0.05; PPO, P < 0.05) showing an inverse trend in relation to the concentration of total phenols. Zymogram analysis showed the induction of two isozyme bands in A. monosperma subjected to high temperatures (38 and 47 degrees C.