In order to examine the impact of drought stress and re-irrigation on chlorophyll fluorescence parameters and physiological traits of three wheat cultivars at five levels of irrigation, an experiment was performed in a factorial arrangement with complete randomized design in three replications. The traits comprised of chlorophyll fluorescence parameters (F0, Fm, Fv and Fv/Fm) and physiological characteristics included relative water content, leaf temperature and relative content of chlorophyll were measured .The results showed that the relative water content and chlorophyll relative content were decreased but leaf temperature was increased under drought stress. Similarly, the chlorophyll fluorescence parameters Fm, Fv and Fv/Fm increased but F0 decreased under drought stress and these changes in tolerant cultivars were less severe than susceptible cultivar. The re-irrigation treatment caused these traits in the stressed plants to be similar to normal conditions, where it was lower for susceptible cultivars than the resistant cultivar. The results of correlation among all traits showed significant positive and negative relations, that the highest indices was recorded between Fm and Fv parameters (r=0.991**) and between Fv/Fm. and F0 (r=0.926**).

Drought stress is an important yield-restricting factor in arid and semi-arid areas. Drought tolerance is a multigenic character and it occurs in various stages of growth. Since the mutagenesis is a fast and safe method, it can be used to diversify genetic contents of plant with the purpose of enhancing quantitative and qualitative traits. In this research, expression pattern of some genes involved in ABA-independent pathway in Tabasi Cultivar (drought sensitive) and mutant line T65-58-8 (drought tolerant, treated with 250 gray gamma radiation) were evaluated under drought stress conditions at maturity stage. In order to study the expression of genes involved in production of proline (P5CS, P5CR and P5CDH) and measuring its amount under drought stress and re-irrigation condition, seeds of two genotypes mentioned above were cultured in 24 cm pots. At the anthesis stage, irrigation was stopped until wilting symptoms appeared, then sampling from flag leaf was done at appropriate intervals (two, three, four, five and six days after irrigation stoppage) and also 12 hours, three, four and five days after re-watering. The control treatment underwent sampling simultaneously. The study was conducted as a factorial experiment based on completely randomized design with two biological replicates. The results demonstrated that the increment of drought stress led to higher expression of P5CS gene in Tabasi cultivar compared to the mutant line, while P5CR gene was more expressed in the latter. The expression of P5CDH in mutant line decreased, while Tabasi cultivar showed an increase in this regard. After re-irrigation, the expression of P5CS and P5CR in both genotypes decreased compared to the control, whereas P5CDH gene was expressed less and more in mutant line and Tabasi cultivar, respectively. Also, the results indicated that proline concentration in the mutant line increases more than Tabasi cultivar under drought stress, while it decreases in both genotypes as a result of re-irrigation. In general, mutant line T-65-58-8 adopts better remedial responses for expression of genes involved in proline production compared to Tabasi cultivar so as to remain undamaged, and it is probable that the osmolyte pathway underwent some changes as result of exposure to gamma rays.

Water deficiency or drought is among the most important factors in reducing crop production (Heidari, et al., 2013). Water deficiency or water stress occurs when transpiration is more than water absorption (Alizadeh, 2008). One of the methods that researchers have been studying to increase water use efficiency and performance over the last decade is the use of superabsorbent polymers and deficit irrigation (Khyrabadi, et al., 2014). The superabsorbent polymer is a kind of hydrocarbon, which absorbs water several times as much as its own weight. Due to the drying of the root environment, the water inside these polymers is gradually evacuated and placed at the disposal of the plan, thus the soil will remain moist for a long time without the need for re-irrigation (Abedi Kupai, And Sohrsb, 2005). Considering that the most important advantage of superabsorbent application is reducing the effect of drought stress, this study investigated the effect of deficit irrigation and different levels of superabsorbent on yield, yield components and water use efficiency of lettuce.

This study was conducted in 2015 as a factorial randomized complete block design with four replications to assess the effects of sodium nitroprusside on reducing the drought damage on morphological and physiological parameters of three grapevine cultivars (Yaghooti, Askari and Bidane sefid). Water deficit treatments were applied at four levels including: full irrigation (100% FC), moderate stress (60% FC), severe stress (30% FC) and re-irrigation after severe stress treatment and foliar application of sodium nitroprusside (SNP) (at 0, 0.5 and 1 mM). Water stress decreased plant height, stem diameter, chlorophyll content, relative water content and membrane stability, whereas significantly enhanced total soluble sugars, carotenoids, proline content, guaiacol peroxidase, ascorbic peroxidase and catalase activities. Based on the responses of cultivars to different levels of drought stress, it can be concluded that Yaghooti seems to be a more resistant cultivar to water stress compared to Askari and Bidanesefid cultivars. Foliar applications of SNP significantly decreased the negative effects of water stress in grapevine cultivars and increased plant height, stem diameter, chlorophyll content, relative water content, membrane stability, total soluble sugars, carotenoids, proline content, guaiacol peroxidase, ascorbic peroxidase and catalase activity. Therefore, application of SNP (especially at 0.5 mM) can reduce adverse effects of drought stress and improve growth in grape cultivars.

Climate change and rainfall patterns pose a serious ‎threat to the world's food supply to a growing population. Water scarcity is ‎currently limiting food security and economic prosperity in many parts of the ‎world. One of the solutions of the increasing the water productivity is ‎cultivation of the drought-resistant medicinal plants. Forest savory is one of ‎the native medicinal plants of Iran, which contains valuable medicinal and ‎chemical compounds. The aim of this study was to investigate the trend of ‎changes in antioxidant enzymes of two forest savory chemotypes under ‎drought stress conditions, re-watering and selenium foliar application.‎

‎In the present study forest savory chemotypes of “carvacrol/thymol/p-‎Cymene” (Darkesh chemotype) and “thymol/p-Cymene/carvacrol” (Pono ‎chemotype) with herbarium code of MPH-1347 were used. The experiment ‎was conducted in the form of a split plot experiment based on a randomized ‎complete block design. Drought were applied at 3 levels (control, moderate ‎stress (25 days without irrigation) and severe stress (40 days without ‎irrigation). selenium treatments was applied at 3 levels (0, 5 and 20 mg) as ‎foliar application. Re-irrigation was performed immediately after drought ‎stress. In order to measure enzymatic activity variation of plant 3 stages the ‎sampling was done. Including: at the end of drought stress of each treatments, ‎‎1 day and 5 days after re-watering.‎

Re-irrigation acts as a mechanism to restore physiological functions ‎that have been reduced by water stress. In other words, recovery is an ‎important component for adaptation of plants. In present study, drought stress ‎was not significantly altered the enzymatic activity of measured antioxidant ‎enzymes (except catalase in “Peno” chemotype) in both chemotypes. There ‎was also no significant reaction to selenium foliar application in different ‎levels. On the other hand, the study of changes in enzyme activity before and ‎after re-irrigation showed that, although the enzyme activity tended to reduce ‎after re-irrigation, but in the shortest possible time the activity of enzymes ‎reached to pre-irrigation conditions indicates the high resistance of this plant ‎species to drought. Also, the plant's response to drought levels and supportive ‎treatments in the two chemotypes had almost the same trend.‎

The lack of response of important antioxidant enzymes of forest ‎savory to drought stress and supportive treatments stated that this plant as a ‎drought-tolerant plant containing is suitable for cultivation in areas with ‎limited water resources and irregular rainfall. Therefore, it is suggested that ‎this plant be used for cultivation in low water conditions of Shahrood and ‎similar areas.‎

In order to study the photosynthesis, gas exchange and chlorophyll content of bean by application of Brassinosteroid, an experiment was conducted during 2016-2017 at the research farm of the University of Zanjan, in split factorial base on randomized complete block design with three replications. In this experiment, irrigation levels (in two levels of optimal irrigation and drought stress) were applied to main plots and bean cultivars (at two levels of Kusha cultivar and COS16 genotype) and different levels of Brassinosteroid (at four levels of 0, 2, 4 and 6 μM) were allocated to sub plots as factorial. In the flowering stage, by cutting irrigation, drought stress was applied and simultaneously with drought stress, bean plants, were sprayed with Brassinosteroid (Epibrassinolide) at the indicated concentrations. The results showed that drought stress had negative effects on the intercellular CO2 concentration, transpiration rate, stomatal conductance, photosynthesis rate and chlorophyll content, but with the elimination of drought stress and re-irrigation, the plants were recovered. The use of Epibrassinolide minimized the negative effects of drought stress on photosynthesis, gas exchange, chlorophyll content and seed yield of bean. The highest seed yield was obtained by application of 2 μM of Epibrassinolide (with an average of 2068.2 kg.h-1). Therefore, the use of this hormone can be suggested as a solution to increase drought stress resistance and increase the seed yield of bean under optimal irrigation and drought stress conditions.

Rapid and efficient recovery from water deficit stress may be one of the key determinants of drought adaptation in plants. The present study was designed to investigate drought stress tolerance and recovery in promising lentil lines at the flowering stage. For this, a factorial experiment based on the completely randomized design was conducted with three replications. The factors included 6 lentil lines, drought stress (control (irrigation at 80% FC or 20% moisture depletion), medium stress (irrigation at 55% FC or 45% moisture depletion), and severe stress (irrigation at 30% FC or 70% moisture depletion)), and three sampling times (three and six days after drought, and recovery (two days after re-irrigation)). Drought stress caused a decrease in chlorophyll a, chlorophyll b, total chlorophyll, carotenoid, protein, yield, and yield components. The reduction of these traits was more remarkable at six days after stress. However, during the recovery time remarkable increase was observed in these traits. The results showed that the correlation between H2O2 and MDA was significant and positive. Furthermore, drought stress increased the amount of proline, H2O2, and MDA, which resulted in an increase in the activity of antioxidant enzymes (catalase, polyphenol oxidase, and peroxidase). An increase in the intensity and duration of the drought stress also caused an increase in H2O2 and MDA content and the activity of antioxidant enzymes. In addition, in the recovery conditions, a significant reduction in the destructive effects of stress (H2O2, MDA content) and the activity of antioxidant enzymes was visible. The results of the present study indicated that the effects of drought stress on lentil lines yield and yield components (seed number, number of pods, 100-seed weight, and seed yield) were varied. Drought stress at the flowering stage decreased the number of seeds and pods per plant, and 100-seed weight, which led to yield losses. Although line 2 had the highest yield under normal and drought stress conditions, line 1 exhibited the lowest yield under stress conditions. Based on the results of this experiment, line 2 seems to be a suitable line for culture in the regions challenged with water deficit stress.

Seedling wheat spirit are tolerant to strict dehydration up to the 4th day following imbibitions. The aim of present study is investigation of responsive proteins to drought stress and recovery in seeds attached to four day seedlings. The test was done by drought stress using interruption of irrigation in two time points (10 and 20 days) and recovery for 3 and 7 days in a growth chamber. All the experiments were conducted based on Completely Randomized Design (CRD) with three replications.Seedlings attached to seedlings were examined for physiological and protein assays. Physiological traits showed strict drought stress level on seed and recovery could return seedlings to normal condition. 2DE done on seed of all treatments and replicates and 657 protein spots were reproducibly detected by Ag No3  staining from seeds. Finally, after significance test, 130 spots were detected by searching protein data banks. Drought stress has increased the expression of genes involved in the production of defense proteins (proline increase), the breakdown ofseed storage compounds, and the production of proteins that are effective in structural changes in the cell wall. On the other hand, reduced expression of proteins effective in respiration and protein breakdown has reduced energy consumption in cells under stress. Under re-irrigation conditions, increased expression of proteins effective in carbohydrate metabolism has led to the consumption of nutrients in seeds (reduction of seed weight) and the production of new structural proteins (presence of new leaves and roots).

In order to investigate different lines of durum wheat for water stress tolerance, an experiment was carried out in the greenhouse in the form of a split plot design in a Randomized complete block design with three replications using 20 lines of durum wheat at two levels of water stress (40% and 70% of the amount of available water was completely drained in 0.4 and 0.7 levels of stress, respectively and re-irrigation was performed) and a control level (complete irrigation). Also, water-soluble and salt-soluble proteins were extracted and SDS-PAGE was done. Measured traits were photosynthetic pigments (chlorophyll a, chlorophyll b, chlorophyll a/b, total chlorophyll and carotenoids), soluble sugar and prolin content. The results of the analysis of variance showed that there was a significant difference between the studied lines at different levels of stress. The results of comparing the mean of the studied traits showed that in total, lines 16 and 5 have the highest value in most of the traits and lines 10 and 18 have the lowest value in most of the traits. Also, the results obtained from the cluster analysis indicated that due to the higher mean values compared to the other lines both in stress-free and stress conditions, lines 16 and 5 (Mra-1/4/Aus1/3/Scar/GdoVZ579//BitI, TRN//21563/AA/3/BD2080/4/BD2339/5/RASCON_37/TARRO_2//) have a higher performance stability in the different environmental conditions. Furthermore, the results of molecular analysis of the studied proteins showed that in water and salt soluble proteins based on matrix similarity and genetic distance of straw, the lowest genetic distance was between genotypes 18 and 19 (0.32) and the highest genetic distance was between genotypes 16 and 8 (0.98). Finally, it can be concluded that there is a significant genetic diversity between the studied cultivars and this diversity can be used in plant breeding.

Wheat (Triticum aestivum L.) is one of the most important grains used in the world and its production is reduced in different regions due to drought stress. the plant antioxidant system can scavenge the reactive oxygen species (ROS) produced under drought. Induction of mutation using gamma ray is one of the common methods for genetic modification and identification of tolerant and resistant mutants. Mutant T65-58-8 is one of these drought tolerant genotypes that has been obtained by irradiation to Tabasi wheat genotype. The wheat plant needs irrigation during the flowering stage and drought stress is very important in this stage. In this study, in the flowering stage, the enzymes superoxide dismutase (SOD), catalase (CAT), glutathione reductase (GR) and glutathione peroxidase (GPX) involved in the mechanisms of tolerance to oxidative damage of ROS in the flag leaf were studied and the expression of the genes related to these enzymes was investigated using RNAseq. method.

Drought stress was applied based on field capacity (FC). The experiment was performed as a factorial experiment in a completely randomized design with three replications. Factors studied in this experiment include genotype at two levels (Tabasi parent and Mutant T65-58-8) and drought stress at 5 levels (100% FC or control, 75%, 22%, re-sampling from control pots at 18% FC and sampling after re-irrigation to the pot when had 90% FC). Wheat growth stages can be studied by Zadoks index. SOD activity was measured by Minami and Yoshikawa method, CAT activity by Aebi method, GR activity by Foyer and Halliwell method and GPX activity by Hopkins and Tudhope method. RNA sequencing was performed using Illumina NovaSeq 6000. Gene expression was obtained based on sequencing data by Bowtie2, Tophat2, HTseq-count and Featurecount softwares. After normalization by generating FPKM, Log2FC gene expression was calculated.

Examination of superoxide dismutase (SOD), catalase (CAT), glutathione reductase (GR) and glutathione peroxidase (GPX) indices showed a significant difference (p<0.01). Comparisons showed that SOD and CAT activity was higher in the mutant genotype at all stress levels. In the Tabasi genotype, re-irrigation increased the activity of SOD and CAT enzymes compared to the activity of this enzyme in field capacity 18%. In the study of GR and GPX enzymes, it was found that in both genotypes, the activity of this enzymes ancreases with increasing drought stress. In the Tabasi genotype, irrigation reduced the activity of GR enzyme and in the Tabasi and mutant genotypes, re-irrigation did not reduce the activity of GPX enzyme. Examination of GPX activity showed that this enzyme has a constant activity in mutant genotype under drought stress conditions. Examination of 21 genes related to SOD enzymes showed that six genes named FSD3(1), CSD1(2), FSD2(2) and CCS(1) mutant genotype had significant expression changes in drought stress conditions compared to the control. 6 catalase-related CAT1(3) and CAT2(3) genes from 14 genes related to CAT also had a significant increase in mutant genotype under drought stress compared to the control. One CAT1 gene and two CAT2 genes in mutant genotype had more expression in drought conditions than Tabasi genotype. 7 genes called CSA associated with GPX from 16 genes related to GPX also had a significant increase in mutant genotype under drought stress compared to the control. H2O2, KCN, chloroform-ethanol, sodium azide (NaN3), metal ions, carbohydrates, polyethylene glycol affect the activity of SOD. NaN3, amines, potassium cyanide and salicylic acid affect the activity of CAT. Gold, vitamin-E and selenium can also affect GPX activity.

The study shows that the activity of SOD, CAT and GPX enzymes in both genotypes has increased under drought stress conditions. However, comparison of the expression of known genes related to these three enzymes shows that only some of these known genes have been altered. One FSD3 gene, two CSD1 genes, two FSD2 genes and one CCS gene had significant expression changes in the mutant genotype under drought stress compared to the control. This could be considered as confirmation of the increase in superoxide dismutase activity in the mutant genotype under drought stress, but the difference in expression of these 6 genes in the mutant genotype under drought stress compared to the Tabasi genotype under drought stress was not significant. This indicates that other factors in the mutant genotype under drought stress have increased the activity of SOD enzyme or limited the production or activity of this enzyme in the Tabasi genotype under drought stress. from the 6 altered genes expressed in the mutant genotype under drought stress compared to the control, one gene called CAT1 and two genes called CAT2 in the mutant genotype under drought stress showed more expression than the Tabasi genotype under drought stress. These genes can be introduced as genes involved in more tolerance of mutant genotype to drought stress than Tabasi genotype under drought stress. 7 genes called CSA had a significant change in expression in the mutant genotype under drought stress compared to the control, but these genes were not significantly different in the mutant genotype compared to the Tabasi under drought stress. Comparison of glutathione reductase enzyme in mutant and Tabasi genotypes in drought condition showed that the activity of this enzyme in the two genotypes was not significantly different. The activity of SOD, CAT and GPX enzymes can be inhibited or intensified by chemical agents and compounds.