and objectives: Flooding conditions refer to the condition in which part of the plant stem below the water. Flooding causes stomata closure and reduction in oxygen concentration in the plant root. It is involved in the formation of reactive oxygen species. Active oxygen species cause oxidative stress. Oxidative stress causes severe membrane damage, lipid peroxidation and antioxidant activity reduction. This causes electrolyte leakage and finally cell death. On the other hand chlorophyll a and b

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... content, especially chlorophyll b reduced at the plant. The sum of these factors reduced the performance of the plant during the flood period. Proper nutrition can reduce the devastating effects of flash flooding on plant, this study was conducted to investigate the effect of different dietary regimes flooding and antioxidant characteristics, Chlorophyll fluorescence, chlorophyll content (a,b), leaves carotenoids and seed yield of soybean (Glycine max (L.) Merr) DPX cv. Materials and methods: The experiment was conducted in factorial arrangement with completely randomized design with three replications in the Gorgan University of Agricultural Sciences and Natural resource in 2012. Treatments include nitrogen treatments at three levels of (1. Do not inoculate plus nitrogen, 2. Inoculated with bacteria (Bradyrhizobium japonicum) 3. Non-inoculated without fertilizer), severely flooded in four levels (0, 5, 10 and 15 days) and the flooding stress was applied during reproductive stage (R2), respectively. Plant traits such as the antioxidant activity (catalase, peroxidase enzyme, ascorbate peroxidase and ascorbic acid), chlorophyll (a, b) content, leaves carotenoids, chlorophyll fluorescence and grain yield in soybean was measured. Results: Based on the results of this experiment the maximum activity of the ascorbate peroxidase enzyme was observed at the non-inoculated and nitrogen * Corresponding author; m.khadempir87@yahoo.com 2 application treatment without flooding condition. Peroxidase and catalase enzyme activity at all levels of nutrition treatment increased up to 5 days flooding, but in 10 and 15 days flooding the activity of these two enzymes declined. The amount of ascorbic acid production (from 0 to 15 days) in all three levels of nitrogen supply was increased. The chlorophyll fluorescence, chlorophyll content (a, b) and carotenoids showed a decreasing trend under the flooding stress. Chlorophyll b reduction was much more than chlorophyll a by increasing the flooding duration, then chlorophyll b to a ratio reduced, drastically. The results of this experiment showed that the highest and the lowest yield was observed at non-inoculated with nitrogen treatment without flooding (32.30 g plant -1 ), and at non-inoculated treatment without fertilizer with 15 days flooding (2.10 g plant -1 ), respectively. Conclusion: The results of this experiment indicated that there is a strong relationship between the amount of available nitrogen and the function of the stress tolerance mechanisms (the production of antioxidant enzymes, pigments, auxiliaries, etc.) during flooding in soybean; in this case, higher available nitrogen for the plant increase flooding tolerance and reduce crop yield damage. 14 Kg ha -1 , with average yield 3478 Kg ha -1 . In this study, all points were in the range of 85% from 1:1line. The value of R 2 was 0.67. In addition, values of RMSD and CV were 521 kg/ha and 3.9%, respectively. To evaluate the model and compare it with the reality, some statistics were used. These statistics are based on the difference between simulated and measured amounts and the correlation between them. Conclusion: Therefore, it was concluded that this model has suitable precision for predicting yield under Gorgan conditions. Obviously, models can be useful when they are applied by physiological and ecological analysis, experiments, and empirical measurements of system. Abstract Background and objectives: Quinoa (Chenopodium quinoa Willd.) is a member of Amaranthaceae family that originated in the Andean region in Bolivia, Chile and Peru five thousands of years and it has a tiny and round seeds. Quinoa in different combinations of diet used as food, as well as how to cook like rice grains and known as the Inca rice in the South American countries. World Food Organization compared quinoa with dry milk because of its high nutritional value. According to quinoa tolerance to drought and salinity, the most important factor that quinoa suitable for cultivation in arid and desert-prone culture is early maturity because at the end of the growing season, drought is a major problem for quinoa culture, early maturity is an important strategy to reduce drought effects. Materials and methods: In order to identify the variety with higher yield and early maturity, five genotypes of the quinoa include of Ames13737 (QA1), Ames13724 (QA2), PI634919 (QP1), PI51055 (QP2) and PI665272 (QP3) have received from National Salinity Research Center and planted in Agricultural Sciences and Natural Resources of Gorgan university under greenhouse condition in a completely randomized design with five replications. Some different morphophenological traits related to yield (1000-grain weight, plant height, stem height, ear no. per main inflorescence and stem diameter) and early-maturity (germination (days), days to 4-leaf stage, days to inflorescence formation, days to inflorescence colouring, days to pollination, days to milky stage and days to physiological maturity) were evaluated. 20 (August 9 th ) performed a higher number of grain/ panicle (74.93), as the main component of grain yield, with a maximum grain yield (4194.7 kg/ha). We found that traits such as panicle/plant and panicle harvest index (PHI) were in maximum level in 1 st and 2 nd dates (19 th and 29 th August) of transplanting. Conclusion: According to the results of testing two factors of interest, including transplanting dates and nitrogen application rates we found that through transplanting of this cultivar earlier on 9 th August in summer that climate factors affecting plant growth such as temperature and radiation which are in optimum condition could be suitable field practices in a rice-rice cultivation system, will produce the optimum amount of grain yield.