Superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPX) are antioxidant enzymes which have important role in the metabolic reactive oxygen species (ROS) and defence against oxidative stress damage. Antioxidant enzymes activity increases in plant cells as a response to environmental stresses. The objective of this study was to evaluate the effects of micronutrients application on the antioxidant enzyme metabolism (SOD, CAT and GPX) in sunflower under drought stress. This experiment was carried out at Golmakan Agriculture Research Station (Iran) in 2005, using a split plot randomized complete block design with four replications. Irrigation as a main factor at three levels (normal, low stress and high stress) and six micronutrient treatments (control, Fe, Fe+Zn, Fe+Zn+Cu, Fe+Zn+Cu+Mn, Fe+Zn+Cu+Mn+B) as sub-plots within the main plots. Base fertilizers (N,P,K) and micronutrient treatments also used as required on the basis of the soil test. Results showed that the activity of these enzymes was significantly different (a= 5%) between control and stress treatments. The antioxidant enzymes concentrations were increased at 11-31% under high stress. Also there were significant differences (a= 5%) between control and micronutrient treatments under different enzyme concentrations. The antioxidant enzymes concentrations were increased at 48-89% level with Fe+Zn+ Cu+Mn treatment. The results showed that under drought stress micronutrients application increase drought resistance in sunflower.

In order to study effect of zeolite soil application and selenium foliar application on growth, yield and yield components of three canola cultivar under conditions of late season drought stress an experiment was conducted in two growing season in 2006 and 2007. Site study was field of Seed and Plant Improvement Institute, Karaj, Iran. The experimental design was a Randomized Complete Block arrangement in factorial split plot with three replications. Irrigation factors were chosen at two levels, included complete irrigation and irrigation holding at stem elongation stage. Zeolite was used at two levels, non application and 10 ton per hectare. Also selenium was sprayed at three concentrations, 0, 15 and 30 gr per liter from sodium selenate. These treatments were randomized in main plots while three canola cultivars ('Zarfam' , 'Okapi' and 'Sarigol') were randomized in sub plots. The results showed that, main effects of different irrigation levels have significant effect on all traits and drought stress decreased significantly all traits. Foliar application of selenium had significant and additive effect on plant height, number of pods in plant, number of seeds in pod, seed yield, biological yield, harvest index and oil yield. There was significant difference between zeolite application and non application on all traits except oil percent and harvest index. It was shown that canola cultivars were different in all of studied traits. Comparison of means showed that, four critical traits that is seed yield, biological yield, harvest index and oil yield were affected by experimental treatments. Different cultivars have different responses under unlike conditions inside upon traits. Under different treatment conditions especially drought stress, zeolite and selenium application have positive and significant effect on traits related to yield. In finally, zeolite and selenium application in dry lands that are exposure to late season drought stress can be helpful for yield improvement and prevent of decreasing yield.

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Problem statement: Drought stress significantly limits Canola (Brassica napus L.) growth and crop productivity. Hence, efficient management of soil moisture and study metabolic changes which occur in response to drought is important for agricultural production of this Crop. Approach: For a better understanding of drought tolerance mechanisms and improving soil water content management strategies, an experiment was laid out in a randomized complete block design with factorial spilt arrangement with tree replications. Results: Irrigation strategy and super absorbent application were allotted to main plots. Irrigation strategy had two levels: 80% of evaporation as control (I 1), drought stress started from flowering stage (I 2) Application of super absorbent had two levels: Non-application of super absorbent as control (S 1), application of super absorbent with 7% concentration. Cultivars (Rgs003 (V 1), Sarigol (V 2), Option500 (V 3), Hyola401 (V 4), Hyola330 (V 5), Hyola420 (V 6) were allotted to sub plots. Plants under water deficit stress and application of super absorbent showed a significant increase and decrease, respectively, in SOD, CAT and GPX activities in leaves compared with control plants. In this context, plants with higher levels of antioxidants showed higher resistance to these stress conditions and higher yield and dry matter allocation to grain filling process i.e. harvest index. Conclusion/Recommendations: Our results suggested that drought stress leads to production of oxygen radicals, which results in increased lipid peroxidation and oxidative stress in the plant. In conclusion of present study, Application of super absorbent polymer could reserve different amounts of water in itself and so increases the soil ability of water storing and preserving and at last in water deficiency, produce plant water need and approve its growth under postanthesis water deficiency.

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