Water Water deficit especially after heading is one of the most effective factors of wheat yield loss in Iran and across the world and identifying the physiological traits related to plant resilience is of great importance in screening for tolerant varieties. The objective of this study was to evaluate the variation in stem reserves accumulation capacity and its relationship with remobilization in some wheat cultivars. 22 wheat cultivars were cultivated in a split plot design with three replications, full irrigation and 40% of field capacity being main plots. The amount of accumulation and remobilization was estimated by measuring internodes weight and stem soluble carbohydrates content (WSC). Significant genotypic variation among cultivars was observed under both normal and drought conditions. Maximum accumulation was found in lower internodes followed by peduncle and penultimate using dry weight measurement method. In WSC measurement method, however, maximum accumulation was observed in penultimate followed by lower internodes and peduncle. Cultivars ranking based on accumulation was also different in two methods. Drought stress caused decline in internodes weight, WSC and yield and remobilization efficiency. The specific stem weight had the highest correlation with remobilization. Significant correlation was found between grain yield and remobilization, specific stem weight and WSC.

In order to evaluate the effects of leaf defoliation on assimilate remobilization in wheat under water deficit stress, a field experiment was carried out as a split split plot based on randomized complete block design with three replications at College of Agriculture, Shiraz University during 2013-2014 growing season. The treatments included water stress: normal irrigation and cutting-off irrigation at anthesis as main plot, wheat cultivars: Pishtaz, Chamran and Marvdasht as sub plot, and levels of source manipulation: non-defoliation, defoliation at mid-stem elongation or mid-anthesis as sub sub plots. The results showed that leaf defoliation, especially at stem elongation reduced grain yield significantly (Pishtaz 19. 2%, Chamran 24. 7% and Marvdasht 24. 9%). The highest remobilization was also obtained from leaf defoliation treatment at stem elongation, so that defoliation at stem elongation increased proportion of stem and ear in grain yield by 1. 6 and 1. 4 times, respectively; however, it could not compensate yield loss resulted from leaf defoliation. Pishtaz and Marvdasht cultivars had the highest and the lowest remobilization, respectively. Water deficit enhanced remobilization and relative proportion of stem and ear in yield, so that mean of relative proportion of stem and ear in grain yield were 9. 1% and 6. 8% under normal and 15. 2% and 26. 3% under water stress conditions, respectively, meanwhile relative proportion was greater for Pishtaz cultivar. In general, water deficit stress and leaf defoliation, especially at early growth season increased remobilization before flowering and proportion of ear and stem storage in grain yield.

Wheat is the first cereal and the most important crop in the world, and due to the increasing population growth, its production is expected to increase every year. Meanwhile, Iran is considered to have a Mediterranean climate and is part of the arid and semi-arid regions of the world due to its geographical location. Under the Mediterranean climate, grain filling of wheat and other cereal usually occurs when the average temperature of the environment increases and the amount of available moisture is reduced, which would disrupt the photosynthesis and reduce the production of photoassimilates during the current photosynthesis process. However, at the same time, the demand for photosynthetic materials for grain filling and also demand for respiration of the live biomass of plant increases, and current photosynthesis does not respond to them. Therefore, the carbon needed to fill the growing grains is provided from other carbon-based sources, such as the remobilization of stored carbohydrates in the stem internodes before anthesis stage. Therefore, studying the factors affecting the transfer of photoassimilates from different parts of the plant, can provide us with a solution that can be used more effectively to reduce the damage to drought stress and the optimal yield of wheat.

Mutant genetic materials are valuable tools for understanding the physiology of remobilization and could be useful in the breeding of drought tolerant varieties. Two advanced mutant lines of bread wheat (T-67-60 and T-65-7-1) along with their wild type (Tabasi Cv. ) were planted at two moisture conditions (normal and 30-40% of field capacity) as a factorial experiment in format of completely randomized design with three replications. Drought treatment initiated at full heading stage (Zadoks 60) and soluble carbohydrates were measured 5 times (0, 7, 14, 21 and 28 days after anthesis) in the stem internodes, separately. Based on the results it could be said that changes in the receiving signals for senescence phenomena under drought stress, capability of the sink, the rate of the reserves assimilated before anthesis and the use of reserves capacity over stem are the factors affecting the differences of genotypes in remobilization of stem soluble carbohydrates under drought stress. It seems that under drought stress mutant line T-65-7-1 was significantly better than wild type cultivar in terms of remobilization and its efficiency and also for faster receiving signals of senescence (as a stimulating factor of remobilization), higher capability of the sink (more grain yield) and higher reserve capacity (higher maximum soluble carbohydrate concentration and specific content). Also, mutant line T-65-7-1 has utilized full ability of all parts of the stem for remobilizing soluble carbohydrates during grain filling.

To study the effect of salinity stress on some physiological traits in wheat cultivars (Triticum aestivum L.), a factorial experiment based on randomized complete block design with three replicates was performed at 2017 in the research greenhouse of Agronomy Department, University of Tehran. Salinity treatments at two levels; control (1.2 dS/m) and sodium chloride treatment (16 dS/m) and seven wheat cultivars, Rowshan, Inia-66, Mahdavi, Khazar-1, Karaj-2, Ghods and Shole were the experimental treatments. According to the results, relative water content, yield and its components and potassium/sodium ratio decreased in all genotypes while Na+ content and remobilization of carbohydrates were increased. Salt resistant varieties, Roshan and Inia-66, had the highest level of relative water content, remobilization of soluble carbohydrates and number of grains per spike. In addition, Roshan cultivar showed the highest potassium concentration and K+/Na+ in the shoots, while Ghods and Sholeh as sensitive cultivars had the highest sodium concentration in the shoots. Findings showed that the ability of a cultivar to remobilize soluble carbohydrates is one of the traits that determine salt stress tolerance, hence, this trait is suitable for evaluating salt tolerance of wheat cultivars in the future investigations.

Stem reserve remobilization is very important to keep the grain yield in wheat under terminal drought but the importance of this mechanism is unclear under terminal salinity. In this research stem reserve remobilization under terminal salinity were studied in greenhouse on four genotypes (No14 and No49, different in remobilization, and Bam as salt-tolerant and Ghods as salt-sensitive cultivars). Saline water (EC=15 dSm-1) was applied from anthesis. The experiment was conducted using a completely randomized design with factorial arrangement with three replications. Stem sampling was done five times with seven days intervals from anthesis, and stem dry weight, weight density and total water soluble carbohydrates (WSC), remobilization and its efficiency and grain yield were measured. The results showed that the highest grain yield, remobilization and contribution of remobilization in yield production were related to Bam and the most yield loss was related to Ghods. Based on the results, Bam with the highest remobilization efficiency had the most WSC production and remobilization under stress. A significant positive correlation between remobilization and yield production under terminal salinity showed that in spite of application of saline water at anthesis stage and continuation of photosynthesis up to the middle of the grain filling period, remobilization also had a great contribution on yield production in tolerant genotypes under salt stress.

In order to study the nitrogen remobilization of rice genotypes under different nitrogen fertilizer levels, a field experiment was carried out in the rice research institute (Rasht/Iran) during 1999-2000. A split-plot design based on randomized complete blocks with four replicates was used. Three nitrogen levels, includes of 0, 150 and 300 kg/ha as the main plots and three rice genotypes includes of 424,506 and 507 as the sub plots were applied. The results showed that nitrogen remobilization had significant differences among different levels of nitrogen. Moreover the interaction between nitrogen treatment and genotype had significant effects on nitrogen remobilization. Different part of shoot of rice genotypes showed different responses related to remobilization of nitrogen, and contribution of grain nitrogen from leaves was more contributed than other parts. There were negative correlations between grain yield and nitrogen remobilization. While there were positive and significant correlations between grain yield and harvest index and days number to 50% an thesis. Also correlation coefficient between nitrogen remobilization and biomass were negative and significant. Moreover, correlation coefficients between nitrogen remobilization and day's number to maturity were positive and significant.

This experiment has been performed to study the effect of seed sowing density and different amounts of nitrogen fertilizer application on the remobilization indices in wheat (Qaboos cultivar) in the field of Gonbad Kavous Agricultural and Natural Resources Research Station in two years (2018-19 and 2019-20) in three replications and as a split-plot in a randomized complete block design. The main plots include pure nitrogen at four levels, i. e., 0 (control), 46, 92, and 138 kg/ha of nitrogen from urea fertilizer source), and the subplots are planting density at six levels (150, 225, 300, 375, 450, and 525 seed/m2). The remobilization photosynthetic assimilate separately from leaves, main stem (without leaves), and seedless spike components are examined to study the process of photosynthetic material transfer to seed. Results show that there has been significant differences among planting density, nitrogen fertilizer, and interaction of planting density× fertilizer treatments in terms of grain nitrogen percentage and remobilization traits of wheat. The highest percentage of grain nitrogen (1. 87%) has been obtained in the treatment of 138 kg/ha nitrogen and 450 seed/m2. In the first year, the highest remobilization from the plant is observed in the treatment of 92 kg/ha nitrogen and 375 seeds/m2 (0. 528 gr/plant), and in the second year, in the control, the highest remobilization is observed in the planting density of 300 seeds/m2 (0. 345 gr/plant), and then with increasing planting density, the remobilization from the plant is reduced.

In order to study the effect of salinity stress and nitrogen forms on nitrogen remobilization from root to shoot following defoliation and shoot dry matter production, a research in the form of factorial experiment based on randomized block, was designed in three replications. Treatments include: 1) nitrogen forms containing a) biological N fixation (N1), b) 6mM NH4NO3 (N2), c) biological N fixation+, 6mM NH4NO3 (N3), 2) salinity in two levels containing 1/1 ds/m (S0) and 12 ds/m (S1) and 3) two Iranian alfalfa cultivars (Bami and Gharehyonjeh). Salinity stress decreased nitrogen availability in root and shoot, nitrogen remobilization and shoot dry matter. Percentage of this reduction in Ghareyonjeh cultivar was higher than Bami cultivar. According to positive correlation between nitrogen remobilization to shoot following defoliation and shoot dry matter production (r=0.86), it was hypothesized that the effect of salinity on reduction of alfalfa shoot regrowth resulted from reduction in nitrogen remobilization. The highest nitrogen remobilization was related to N2 and N3 treatments although the percent of remobilization in N1 treatment was higher. Due to salinity, amount of nitrogen remobilization decreased in all nitrogen forms but percentage of this reduction was higher in N2 and N3 treatments. Percentage of increase in sodium content due to salinity in N2 and N3 treatments was higher than N1. According to appositive correlation between root sodium content and nitrogen remobilization (r=-0.83), it is possible that greater decrease in nitrogen remobilization and shoot dry matter production following defoliation in N2 and N3 treatments resulted from greater increase in sodium content in these treatments.

In order to investigate the effect of mycorrhizl fungi on dry matter remobilization of barley in dryland conditions, a field experiment has been carried out in factorial analysis based on randomized complete block design with three replications at the farm station of Sarablah Agricultural Research Cente, Ilam during 2019-2020 cropping season. Experimental factors include different barley cultivars (Mahali, Mahoor, Khoram, and Fardan) and fertilizer application is the control (without fertilizer application), 50% P chemical fertilizer, mycorrhizal fungi (Glomus mosseae, Glomus etunicatum and Rhizophagus irregularis), mycorrhizal fungi along with 50% P chemical fertilizer and 100% P chemical fertilizer. The results of this study indicate that the interaction of cultivar along with fertilizer application have had significant influence on dry matter remobilization efficiency from spike, contribution of spike reserves to grain yield, dry matter remobilization efficiency from stem, contribution of stem reserves to grain yield, current photosynthesis rate, contribution of current photosynthesis, and grain filling rate. Thus, the interaction of Fardan cultivar and mycorrhizal fungi along with 50% P chemical fertilizer has had the highest dry matter remobilization effeciency from spike, contribution of spike reserves to grain yield, current photosynthesis rate, contribution of current photosynthesis, and grain filling rate. In return, in this study the highest stem dry matter remobilization effeciency, contribution of stem reserves to grain yield, have been obtained from the interaction of Mahali cultivar along with control treatment. According to the results, in dryland conditions of the region, new cultivar of Fardan as well as mycorrhizal fungi along with 50% P chemical fertilizer can be recommended.