The effects of Vanillic Acid (VA) on germination, seedling and adult plant of rice (Oryza sativa L.) were investigated. Four cultivars, traditional (Taroom mahalli and Taroom deilamani) and improved (Shafagh and Onda) were studied. For germination, seeds were sterilized and then placed on Petri dish at 30°C at different concentrations (0, 10, 20 and 25 mM) for 7 days and growth factors of seedling were measured after 14 days. Seedling (10 days) planted in hydroponic medium including nutrient solution amended with 0, 25, 50 and 100 mg kg-1 VA. After 30 days, the growth factors were determined. α-amylase and peroxidase activities were assayed by Bernfeld and Maehly methods, respectively. Present results indicated that as a result of increasing concentrations of VA, germination percentage and germination rate as well as α-amylase activity markedly decreased except Onda in all cultivars. In all cultivars, seedling growth factors such as shoot length, fresh weight and dry weight as well as root have been reduced by increasing of VA. In adult plant, also shoot length, root length, shoot dry weight and root fresh weight were reduced by increasing concentrations of VA. Shoot fresh weight was decreased in Shafagh by increasing concentrations of VA; meanwhile, we have not observed any significant differences in the other cultivars. In the case of root dry weight, there were not significant differences in any cultivars. With increasing concentrations of VA, chlorophyll content reduced; on the contrary, peroxidase activity increased.

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