تاثیر تنش خشکی و اشعه ماوراء بنفش (UV-C) بر سیستم دفاع آنتی اکسیدانی آنزیمی و غیر آنزیمی در سه رقم گندم (Triticum aestivum L.)

Drought stress and ultraviolet radiation as stressful environmental factors have deleterious effects on physiological and growth of plants. Plants through specific physiological mechanisms confront with stressors factors that they cause the production of reactive oxygen species in plant cell. So in order to evaluation of the effect of drought stress and Ultraviolet on photosynthesis pigments and antioxidant defensive system of enzyme and non-enzyme in three varieties of wheat (Triticum aestivum L.), pot experimental  was conducted by using factorial based on completely randomized design (RCD) with three replications in Payme Noor university laboratory of Urmia in 2015. Treatments were drought stress in two levels (control and drought stress by applying 25% of field capacity) and ultraviolet radiation (control and UV-C) and three wheat varieties ("Zare", "Pishgham" and "Mihan"). In this study, morphological traits, photosynthetic pigments and enzymes affecting on defense system were studied. The results showed that under drought stress and UV rays, the content of flavonoids increased in " Mihan" and decreased significantly in "Pishgham" cultivar, while in the same conditions (drought stress and UV radiation), the content of anthocyanins increased significantly. Treatment drought stress and UV causes oxidative stress in different varieties of wheat. In addition drought stress increased phenolic compounds and cause to enhance antioxidant enzymes such as catalase activity, superoxide dismutase and peroxidase. The content of soluble sugars increased under drought stess conditions. Drought stress in comparison with optimum irrigation, stem lenth, root lenth, carotenoids and total chlorophyll about 16, 20, 25 and 25 percent significantly reduced, respectively. In drought stress condition, application UV increased proline amount in all three varieties about 31 percent but in optimum irrigation increasing was 22 percent. Increase the activity of antioxidant enzymes was observed in all three varieties, as well as the content of malondialdehyde and proline increased in all three varieties studied. UV radiation caused a significant reduction in the concentration of chlorophyll a, b and total chlorophyll. Also drought stress and UV reduced significantly root and stem dry weight, root and stem length. The interaction between drought stress and ultraviolet radiation increased damage to the plant. Also "Zare" variety according to increasing flavonoids and anthocyanin comparison with "Pishgham" and "Mihan" varieties was known as tolerant to drought stress.