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The experiments were laid out to understand the mechanisms causing yield limitations imposed by post-anthesis water and nitrogen deficiencies in plants with modified source-sink ratios. two soil-water regimes were allotted to the main plots. at anthesis, three levels of n were applied: none, 25% and 50% of total the n supply. Spike-halving caused reduction in grain yield at both water regimes and all n supply levels, showing that the reduction in grain number can not be compensated by a higher individual grain weight. Sink reduction by trimming 50% of the spikelets reduced grain number per ear by 38.5% and increased individual grain weight by 12.0%, which shows the plasticity in grain weight and grain set of wheat if sufficient assimilates are available. additional nitrogen supply at anthesis had no significant effect on the total aboveground biomass, but increased grain yield through more allocation of dry matter to grains. our findings suggest that for rainfed wheat with optimum n supply and supplemental irrigation, wheat growers should choose cultivars with a high grain number per ear and manage the crop to increase grain number per unit of land (sink capacity).

To determine the possible protective and enhancer role of selenium foliar application on oil yield, fatty acid composition and glucosinolate content of rapeseed cultivars under late-season thermal stress, a factorial split-plot experiment based on randomized complete block design with three replications was carried out in Karaj, Iran during the two growing seasons 2014–2015 and 2015–2016. Three sowing dates (Oct. 7 as normal planting date), (Oct. 17 as semi-late planting date), (Oct. 27 as late planting date) and two selenium foliar application (non-application as control and sodium selenate as foliar application) were factorially randomized to main plots, and rapeseed cultivars were allocated to sub-plots. Plant materials were six cultivars including three hybrids and three Iranian open pollinated varieties. Late-season thermal stress caused by late planting date reduced oil yield, oil content, oleic acid, linoleic acid, palmitic acid and increased linolenic acid, erucic acid and glucosinolate content of investigated cultivars. The results of this study demonstrated that the highest amount of oil yield, oil content, oleic acid, linoleic acid, palmitic acid and the lowest amount of erucic acid and glucosinolate content were observed in L72 cultivar in both control and selenium application treatments. This study provided new important findings about the supportive and enhancer role of selenium in the form of sodium selenate on quantity and quality of oil in rapeseed plant.

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.

Wheat yields in the semi-arid regions are not only limited by inadequate water supply, but also by n shortage late in the cropping season. it becomes clear that the physiological response of genotypes to drought stress should be included in studies investigating the interaction between n and water management (ahmadi and Baker 2001, Saint Pierre et al. 2008). Fan and li (2001) demonstrated that depending on the level of n supply, n fertilization could increase the agronomic n-use efficiency of winter wheat, which significantly reduced with the severeness of drought stress.Efficient n use is crucial for economic wheat production and the prevention of n emissions to ground and surface water (Spiertz et al. 2006, Spiertz 2009, therefore, optimizing irrigation regimes and nitrogen management taking into account crop phenology will produce optimum grain yields (Karam et al. 2009).improving attainable yields of wheat under stress conditions requires knowledge of yield-determining physiological processes such as adaptation to environments with a broad range of climatic and edaphic variation, diversity in plant traits and plasticity in source-sink relationships (reynolds and trethowan 2007, Barnabas et al. 2008). Fan et al. (2005 found that both leaf photosynthesis and grain starch accumulation could be promoted by nitrogen supply under drought conditions. Madani et al. (2010) demonstrated that late nitrogen supply at anthesis did