In order to develop nuclear energy uses in improvement of plants to dry condition and to investigate the effect of Gamma ray (800, 1000, 1200 gry and control) and PEG (-3, -6, -9 bar and control) on the length of root and shoot in two varieties of rapeseed (Sarigol and RGS003), an experiment was conducted in CRD design in factorial way at laboratory condition with 3 replication in 2011. The obtained results indicated that gamma ray had a significant effect on total fresh weight and turgescence weight (p<0.01). Drought stress affected significantly all 4 investigated traits (TFW, TW, TDW and RWC) with (p<0.01). The mutual effect of variety and PEG on total fresh weight and turgescence weight was significant (p<0.05) and this effect on RWC was significant, too (p<0.01). The obtained results revealed that the mutual effect of gamma ray with drought stress and variety on RWC was significant (p<0.05). The comparison of data mean showed that gamma ray on both traits namely TFW and TW led to weight loss and the highest weight is referred to the condition without application of gamma ray. The difference in TFW in 800, 1000, and 1200 gry dosages didn't prove to be significant. 800 gry dosage of gamma ray compared to other dosages indicated higher turgescence weight. The negative effect of drought stress on TFW was in a way that the highest TFW was observed in no stress condition and the least TFW was observed in -9 bar osmotic pressure. The drought stress had no effect on total dry weight of Sarigol, but increased the TDW of RGS003 so that the highest dry weight was observed in -3 bar osmotic pressure. The comparison of data mean indicated that the increase in negative osmotic pressure reduces the TW so that both varieties experience the highest weight in no stress condition and the least weight in -9 bar osmotic pressure. The application of ray had positive effect on increase of TDW in 800 and 1200 gry dosages.
