This study was conducted to assess the induced-changes in the content of total phenolics and individual phenolic acids, total and individual polyamines and some organic acids in the leaves of two important Iranian grapevine cultivars under different durations of drought stress, and also to determine their involvement in grapevine drought tolerance. For this purpose, ‘Yaghuti’ as a drought-tolerant and ‘Bidanesefid’ as a drought-sensitive vine were subjected to 6, 12 and 18 days of drought stress. Our results showed that as compared to the respective control vines, 18 days drought stressed plants of ‘Yaghuti’ and ‘Bidanesefid’ had the highest concentration of total phenolics (31.55 vs. 27.40 mg.g-1Fw), total polyamines (98.40 vs. 70.11 ng.g-1Fw) and total organic acids (3.30 vs. 3.08 mg.100g-1Fw). Based on comparative analyses of individual phenolic acids, it seemed that in drought stress condition and especially in ‘Yaghuti’, Caffeic acid and Gallic acid could be used as biochemical markers of stress responses. In our study, only 18 days of drought stress resulted in a significant increase in spermidine concentration in ‘Yaghuti’ cultivar while putrescine and spermine concentration of this cultivar increased at the onset of stress, so it seemed that these two polyamines had a more important role in drought tolerance of ‘Yaghuti’. In the current study, different durations of drought stress remarkably increased the amounts of individual organic acids (tartaric, malic, oxalic and ascorbic acid) in both cultivars. The contents of quantified organic acids were not often significantly different between the two cultivars in the same durations of drought stress. Totally it seemed phenolic acids and polyamines were more effective markers for drought resistance investigation of vines.
