The study was carried out in plant tissue culture laboratory, University of Baghdad during the period 2017-2019, as factorial experiment in complete randomized design, to study the effect of PEG at (0, 2, 4, 6 and 8%) on physiological and chemical changes in callus of three sunflower (Ishaqi 1, Aqmar and Al-haga) induced by the cultivation of the young stem in vitro under water stress. The content of callus cells of SOD, POD, CAT and APX enzymes as well as total dissolved carbohydrate were determined as indicators to determine the effect of PEG in callus tissue cells cultivated on medium equipped with the PEG concentrations. The results showed that cultivars were differs significantly, and A-haja variety was superior in increasing SOD to 12.26 absorption unit mg-1 protein, and the variety Ishaqi was superior in increasing POD, CAT and APX to 7.25, 11.54 and 0.4285 absorption unit mg-1 protein respectively. Aqmar variety was superior in increasing the total dissolved carbohydrate content to 0.34980 mg-1. PEG concentrations significantly affected enzyme activity, and 6% gave the highest efficacy of SOD and APX reached to 13.78 and 0.2976 absorption unit mg-1 protein respectively, while 8% PEG gave the highest effective of POD and CAT reached to 5.54 and 7.73 absorption unit mg-1 protein respectively. The total dissolved carbohydrate content achieved the highest mean at 8% PEG and reached to 0.31, 128 mg. g-1. The interaction caused significant effect and the highest SOD enzyme was obtained from Al-haja variety at 6% PEG, while POD, CAT, and APX enzymes (11.33, 16.30, and 0.5208 unit absorption mg-1 protein) were obtained …
