eng Oriental Scientific Publishing Company Biosciences Biotechnology Research Asia 0973-1245 2016-04-27 6 2 513 516 8652 article Habibeh zare 1 Payame Noor University, Lashkarak Highway, Nakhl street, Tehran 19569 (Iran). Drought is considered as one of the most important limiting factors for oil seed sunflower plant ( Hellianthus annuus L.) growth and productivity in Iran. On the basis of root and air organ dry weight as affected by drought stress exerted by poly ethylene glygohle 6000 ( PEG 6000) , out of 6 sunflower cultivars , arelatively tolerant ( Record ) and a sensitive cutivar ( uflor ) were selected . Their reponses to low water potential with respect to changes in activity of the antioxidant enzyme ascorbate peroxides, guagohtl peroxides , and its translocations . To the shoots and production of osmoprotection proline and soluble sugars were analyzed and compared . In low water potential increase ascorbate peroxidase activity , constitutively the enzyme activity was significantly higher in the toterant cultivar A significant increase in root proline content The increase was 2 to 3 times higher in the tolerant Record cultivar. Although the total soluble sugars in both cultivars tended to increase under low water potential The amounts accumulated were mostly comparable in both constitutively higher ascorbate peroxidase activity along with the higher rates of proline accumulation and total soluble sugars are taken as part of the mechanisms which confer drought tolerance to the sunflower cultivars. https://www.biotech-asia.org/vol6no2/some-physiological-responses-of-sunflower-helianthus-annuus-l-to-drought-stress-under-laboratory-conditions/ Drought stress; sunflower; ascorbate peroxide; proline; soluble sugars