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Limited water for irrigation and the coincidence of early growth of sugar beet (Beta vulgaris L.) with the late growth of winter cereals in the Northeast (NE) of Iran, force farmers, to allocate their limited irrigation water to the cereal crops and thus their sugar beet crop is subjected to an early water stress. Finding cultivars which are able to withstand early water stress without a significant yield reduction is critical to the farmers’ economy. This study was conducted over a two-year period (1998 and 1999) to evaluate the response of nine sugar beet genotypes to drought stress and to determine the crop traits associated with drought resistance. The results showed that stomatal conductance, leaf-air temperature difference and proline accumulation were associated with levels of water stress in sugar beet genotypes. Among these indices, leaf-air temperature difference was a more precise parameter to measure. A negative correlation between Δ T (leaf -air temperature) and stomatal conductance was found. The correlation coefficients for 1998 and 1999 were -0.87 and -0.58, respectively. There was a positive correlation between Δ T and proline accumulation in sugar beet genotypes. The correlation coefficients for the 1998 and 1999 experiments were 0.61 and 0.49, respectively. The shoot: root ratio (S:R) measured at the end of the stress period showed that genotypes with a lower S:R often had a greater stomatal conductance. In general, genotypes with a lower S:R at the end of the stress period usually had a greater root dry weight. The correlation coefficients of S:R with root dry weight at the end of the stress period were -0.96 and -0.65 for 1998 and 1999, respectively.

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Water stress is a serious environmental problem throughout the world. It is a conse-quence of both drought and salinity which may be relieved by breeding cultivars that can tolerate low soil water potentials. Alfalfa (Medicago sativa L.) is normally grown in arid and semi-arid zones. One approach to improving the ability of the crop tolerate drought is to make use of the variation provided by tissue culture derived from somaclonal varia-tion. Seedlings of a moderately salt tolerant line CUF 101-1S derived from the commercial variety CUF 101 were used as a source of explants to initiate and regenerate tissue cul-tures. Regenerant plantlets were allowed to grow to maturity, selfed, and set seed. These seeds (R1) were germinated and grown in a nutrient medium containing 0, 200 and 250 g l-1 polyethylene glycol (PEG) 6000 and additional calcium as CaCl2 (4.0 mol m-3) for 14 days to assess their ability to withstand stress in the progeny generation. Tolerance to PEG was assessed using measurements of root and shoot lengths. Proline levels and activ-ity of the antioxidant enzymes, catalase (EC 1.11.1.6) and glutathione reductase (GR) (EC 1.6.4.2) were also determined. Selected somaclones were more tolerant than the parent. A large increase in the level of proline was observed in the somaclones compared with the parent variety in response to PEG stress. The activity of catalase and glutathione reduc-tase increased in the tolerant genotypes but remained unchanged in the parent when they were subjected to PEG stress.

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Abstract:
Aim: With global warming and limited water resources in the world, especially in arid lands of Iran, managing the production of forest seedlings in the country's nurseries is facing a special challenge. In this regard, the study of drought tolerant plants to select them in the mass seedling production programs can be useful.
Material and methods: Potted seedlings of Persian oak (Quercus brantii Lindl.), pistachio (Pistacia atlantica Desf.), Judas-tree (Cercis siliquastrum L.) and black poplar (Populus nigra L.) exposed to a normal irrigation scheme (100% field capacity) and drought-stressed (30% field capacity) conditions were examined over a period of 120 days in a greenhouse of Bam Khorramabad Nursery to judge their tolerance for drought stress.
Findings: Drought-tressed seedlings from all species had a lower content of chlorophyll a, chlorophyll b, total chlorophyll and carotenoids compared to the control plots, but the content of proline and malondialdehyde (MDA) did, however, increase. Under stress conditions, MDA content in black poplar, Judas-tree, Persian oak and pistachio was 174, 121, 105 and 102% higher than the control seedlings, respectively, and this increase in black poplar over other species ranged from 93.5 to 176.5%.
Conclusion: This study confirms that among four tree species, black poplar has lowest tolerance to drought stress. Thus, Persian oak, pistachio and Judas-tree, should be prioritized in the mass seedling production programs of nurseries in arid areas suffering from limited water resources, due to their higher tolerance to water scarcity.

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The effects of sodium chloride and Zn rates and sources on the growth and chemical composition of lowland rice (Oryza sativa L.) were studied using calcareous soil in a greenhouse experiment. The treatments comprised 5 levels of NaCl (0, 12.5, 25, 37.5 and 50 mmol kg-1 soil), three Zn rates (0, 5 and 10 mg kg-1 soil) and two Zn sources (ZnSO4, 2H2O and ZnEDTA). Applied salinity decreased shoot dry weight, leaf area and chloro-phyll concentration, whereas Zn supply significantly increased these growth parameters. However, the enhancing effect of soil Zn fertilization was more pronounced at lower NaCl levels than under higher salt stress, irrespective of Zn sources. Concentrations of Zn, P and K were significantly decreased and those of Na and Cl increased in NaCl-treated plants. Zn application markedly increased Zn concentration and decreased Na and Cl and P accumulation in shoots. Moreover, there was a significant difference between the two Zn sources to affect rice growth. Free proline increased but reducing sugars de-creased with an increase in the levels of substrate NaCl. However, Zn-untreated rice con-tained higher proline and reducing sugars than Zn-treated plants. Furthermore, an in-crease in proline was greater in the presence than in the absence of Zn and with ZnSO4 than with ZnEDTA. It is concluded that a decrease in soil osmotic potential, nutrient im-balance and excessive plant accumulation of Na and Cl in NaCl-treated plants caused growth suppression, whilst Zn supply decreased the suppressing effects of excess salt on rice growth. Therefore, it is recommended that for growing rice in saline soils that are low in available Zn, Zn should be supplied in a adequate quantities.

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Salicylic acid has been found to play an important role in the regulation of plant growth and development in response to environmental stresses. In the present study, the effect of salicylic acid (SA) (0 and 0.1 mM) on growth parameters and some physiological characteristics of two strawberry cultivars ("Kurdistan" and "Queen Elisa") was investigated under drought stress treatments (-0.1 and -1 MPa). Experimental design was factorial based on completely randomized design with three replications. Results showed that drought stress decreased leaf area, leaf dry matter, shoot dry matter, total dry matter, relative water content, stomatal conductance, yield, and fruit weight. Salicylic acid application increased total leaf area and leaf and shoot dry matter in both cultivars. Leaf number, root dry matter, total dry matter, yield and fruit weight were increased by SA application in "Kurdistan" under drought stress. "Kurdistan" cultivar had higher RWC than "Queen Elisa" and SA application increased RWC, proline and soluble carbohydrate in "Kurdistan" compared to "Queen Elisa" under drought stress conditions. RWC, proline and soluble carbohydrate of “Queen Elisa" did not change with SA spray. Total soluble protein was not affected in "Kurdistan" under drought stress, while "Queen Elisa" showed a reduction in total protein. SA application increased catalase and peroxidase activity in both cultivars under drought stress. In conclusion, “Kurdistan” was less susceptible to drought stress than “Queen Elisa” because “Kurdistan” showed less reduction in leaf number and area, crown, and total dry matter compared to “Queen Elisa”. SA application altered some physiological responses of both cultivars under drought stress. The effect of SA was more pronounced in "Kurdistan” than "Queen Elisa".

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In this study, we assessed the relative contribution of organic and inorganic solutes to osmotic adjustment (OA) in three almond rootstocks subjected to four levels of soil salinity. The results showed that leaf water and osmotic potentials were affected by salinity in GF677 and Bitter almond, but less so in GN15, suggesting a higher selectivity for K⁺ and Ca²⁺ against Na⁺ in this latter rootstock. GN15 excluded Na⁺ and accumulated Cl^-. Nevertheless, in this rootstock, Cl^- and Na⁺ were the main osmolytes involved in OA, while the osmotic role of K⁺, Ca²⁺ and Mg²⁺ was small. Proline had the highest relative contribution of organic solutes to OA in the leaves of GN15 and GF677, while in Bitter almond it was not effective. The role of soluble sugars was rather marginal in terms of OA in all three genotypes. All three rootstocks displayed a degree of OA in the presence of high NaCl concentrations in the growth medium, but used different osmolytes to achieve it. Therefore, breeders should be careful in choosing biochemical parameters to assess OA capability of Prunus genotypes. 

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As sesame is a somewhat neglected crop, information concerning its response to salinity is lacking. The effects of NaCl stress were studied on seven genotypes of Sesamum indicum L. The 6-weeks-old sesame seedlings were treated with different NaCl concentrations (0, 30, and 60 mM). The NaCl caused significant decreases in fresh and dry mass of all genotypes; however responses of genotypes to the salt were significantly different. Based on the data obtained for fresh and dry mass accumulation, the genotypes were divided into two groups: i.e. salt-tolerant (Ardestan, Varamin, and Darab) and salt-sensitive (Naz-Takshakheh, Naz-Chandshakheh, Yekta and Oltan). Lipid peroxidation was recorded to be the lowest in cv. ‘Varamin’, ‘Darab’, and ‘Ardestan’ (tolerant group), whereas it was recorded to be maximum in genotypes ‘Naz-Takshakhe’, ‘Naz-Chandshakhe’, ‘Oltan’ and ‘Yekta’ (sensitive group) in the 60 mM NaCl treatment. In both 30 and 60 mM NaCl treatments, the activities of SuperOxide Dismutase (SOD), Catalase (CAT), Ascorbate Peroxidase (APX) and Glutathione Reductase (GR) were found to be higher in the tolerant group, compared to the sensitive group of genotypes. The accumulation of proline in the sesame leaves under saline conditions was higher in tolerant group, compared to the sensitive genotypes. It seems that in the salt-tolerant genotypes of sesame, increases in antioxidant enzymes activities and proline accumulation, along with a lower lipid peroxidation at cellular membranes, led to a higher level of tolerance to the salt.

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This study was carried out to evaluate the effects of salinity stress (16 dS m^-1) on proline accumulation and expression pattern of three genes involved in the proline synthesis (P5CS, P5CR) and degradation (PDH) in the fourth and the flag leaves. The experimental treatments consisted of two levels of salinity stress including 1.6 (control) and 16 dS m^-1 and three wheat cultivars, namely, Hirmand and Chamran (as tolerant cultivars) and Atrak (as sensitive). These were arranged as factorial based on a Completely Randomized Design with three replications. There was an increase in Na⁺ concentration and decrease in K⁺ concentration in salinity stress compared to the control condition in the fourth and the flag leaves of all cultivars. However, the tolerant cultivars showed lower level of Na⁺ concentration and higher level of K⁺ concentration and K⁺/ Na⁺ ratio. Seemingly, the increase in proline accumulation was due to P5CS, P5CR up-regulation and PDH down-regulation. On the other hand, the higher proline degradation in the fourth leaf of the tolerant cultivars was probably due to the provision of a source for energy or nitrogen, which helped to enhance the yield of these cultivars under salinity stress.

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This study investigated the effects of foliar application of normal and nanoparticles of zinc oxide (ZnO) on the growth, proline content, and some antioxidant enzyme activities of sunflower cultivars at different salinity levels. Treatments included five cultivars (Helianthus annuus L. cvs. Alstar, Olsion, Yourflor, Hysun36, and Hysun33), two salinity levels (0 and 100 mM NaCl), and three foliar applications (none-sprayed, ZnO normal and nanoparticles at a rate of 2 g/L). Olsion showed the highest proline content and superoxide dismutase activity (SOD) among the studied cultivars under saline condition. Foliar spray of ZnO improved SOD activity and shoot dry weight of sunflower. Nanoparticles of ZnO had positive effect on biomass production of sunflower plants compared to the normal form. According to the result, Olsion and Hysun33 cultivars were suitable for saline conditions, whereas Hysun36 was appropriate for normal condition.

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Drought stress reduces growth and productivity of crops in arid and semiarid regions, such as Iran. Methyl Jasmonate (MeJA) is involved in regulating plants growth and their immune responses. The main purpose of this study was to evaluate the effects of MeJA on growth and some physiological responses of summer savory (Satureja hortensis) plant under drought stress condition. Treatments consisted of three levels of drought stress including stress free conditions, mild stress and severe stress, and four concentrations of MeJA (0, 75, 150, and 225 μM). The results showed that drought stress and MeJA application had a significant effect on morphological, physiological, and biochemical parameters. In drought conditions, some growth parameters, namely, relative water content and essential oil yield decreased and antioxidant activity, proline content, and essential oil percentage increased. The results suggest that MeJA application under drought stress can improve growth parameters as well as relative water content, proline content, antioxidant activity, and essential oil percentage and yield. The best protection appeared to be obtained from plants treated with MeJA at 75 μM.

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Ziziphus spina-christi are distributed in arid and semi-arid regions of world. Most of these areas are subjected to soil salinity. So, the aim of this study was to find out the effects of different NaCl concentrations on Z. spina-christi seedlings growth, in the presence of a number of single and dual AMF inoculums, to provide some information about possible effects of AMF under salinity condition. For this purpose, the study was conducted in nursery using 4×3 factorial scheme (4 salinity levels; 0, 50, 100 and 150 mM and 3 mycorrhiza treatments; non-mycorrhizal plant, G. fasciculatum and Funneliformis mosseae+G. fasciculatum inoculated plants). Our results revealed that salinity has negative effects on root length colonization, growth parameters, chlorophyll content, nutrients absorption and results in Na, proline, superoxide dismutase, peroxidase and catalase activity increment but mycorrhizal plants maintained higher growth characteristics, chlorophyll content, nutrients, root colonization and enzymes activity, proline and Na ion reduction and these effects in dual inoculum were significantly different from single inoculum fungi. According to the results dual-inoculated plants are more tolerative to salinity compared to single-inoculated and not-inoculated seedlings. Indicating that Z. spina-christi plantation in saline soil would give us the best result if we use dual inoculated plants. It could be said that in saline soils Z. spina-christi dual-inoculated with mycorrhiza is tolerative and more efficient.

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 Sorghum [Sorghum bicolor (L.) Moench] is moderately tolerant to salinity and it is important as a candidate crop for both fodder and grain in salt-affected areas. This pot experiment was conducted at Research Greenhouse of College of Agriculture, Shiraz University, Iran, to evaluate the relative effectiveness of biochemical traits and stress tolerance indices contributing to genotypic differences in salinity tolerance in 30 lines and 14 cultivars of sorghum. In addition, a new indicator, Storage Factor Index (SFI), was defined and used to quantify the Na⁺ partitioning between shoot and root. Among the indices, stress tolerance index was found useful as a selection criterion. Furthermore, the tolerant genotypes had higher K⁺/Na⁺ ratio in shoot and root with greater SFI, indicating that most of Na⁺ was stored in their roots. Although peroxidase and superoxide dismutase were enhanced under salinity conditions in both sensitive and tolerant genotypes, only Catalase (CAT) activity was found to be promoted in tolerant lines/cultivars. Proline accumulation did not appear to be related to salinity tolerance in sorghum lines/cultivars. Overall, our findings suggested that salinity tolerance in sorghum genotypes was not only associated with Na⁺ exclusion from the shoot, but also with the enhancement of CAT activity.

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In the last decades, resistance to salt stress has been studied intensively in plants. Many ornamental plants have widespread presence in green areas of coastal regions. In such regions, plants are subject to seawater aerosol and surfactants, both of which are frequent in the coastal areas of Mediterranean environment. The objective of this study was to investigate the antioxidant enzyme activities of two ornamental plants, namely, Callistemon and Viburnum, under the effects of these stressful conditions. To analyze the performance of these plants stressed by 8 weeks treatments with seawater aerosol and surfactants, we measured the antioxidative defense mechanism, considered as enzymatic response, Proline (Pro) levels, Chlorophyll (Chl) and MalonDiAldehyde (MDA) contents. To better understand the response mechanisms, two different growing periods were studied: from January to March and from May to July. The higher temperatures of the second period negatively affected the response of the plants. Salt stress considerably reduced the chlorophyll content in both species, especially in the second period. In particular, the sea aerosol treatments caused 29% and about 45% reduction in Callistemon and Viburnum plants, respectively. The amount of Pro in Viburnum was very small (154.35 nmol g^-1) compared to Callistemon (1466.94 nmol g^-1). An opposite trend was noticed for MDA. ROS-scavenging enzymes, such as SuperOxide Dismutase (SOD), catalase (CAT), and Glutathione Peroxidase (GPX) in plants exposed to treatment with sea aerosol plus anionic surfactant were significantly higher. Between the two species, Viburnum showed more efficient action mechanisms to overcome aerosol stress.
 

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This study primarily aimed to identify and suggest appropriate rapeseed cultivars and their optimum sowing time. A factorial split-plot experiment was conducted in a complete randomized block design with three replications during two years (2014-2016). The study was carried out using six rapeseed cultivars, namely, Elvis, HL2012, L155, KR2, HW113 and Danob, three sowing dates (October 7, 17, and 27), and two concentrations of glycinebetaine (0 as control and 0.2%). The sowing dates and the GlycineBetaine (GB) were allotted to main plots and the six cultivars were allotted to subplots. The HL2012 cultivar had the highest seed yield (4,584 kg ha^-1), seed oil content (44.6%) and seed oil yield (2,060 kg ha^-1), which were achieved optimally in the first sowing date. Application of GB increased the average seed yield from 4,089 to 4,419 (kg ha^-1), seed oil from 44 to 44.4% and seed oil yield from 1,818 to 1,976 (kg/ha). The amounts of proline and soluble carbohydrates in the plants increased from the first to the third sowing dates. The early sowing date and the application of GB had positive effects on the quantity and quality of rapeseed oil. The results of cluster analysis showed that three of the six cultivars could be suitable for cultivation in Karaj, Iran.
 

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This study was conducted to investigate the response of four barley cultivars (Reyhan03, Yousef, Afzal, and Khatam) to salinity stress at 0 (control), 100, 200 and 300 mM levels as a factorial experiment, within the randomized complete block design in three replications in a greenhouse, using the Hoagland solution. The physiological and biochemical properties including dry weight and RWC, photosynthesis pigments, K⁺/Na⁺, osmotic adjustments (soluble sugars, glycine betaine, proline), hydrogen peroxide and antioxidants enzymes (catalase and peroxidase) in root and shoot of barley cultivars were evaluated in saline and non-saline conditions. To determine the relationship between growth performance and the physiological and biochemical properties, the correlation between the properties and causality analysis was examined. Results obtained from comparing the mean among the treatment combinations showed that the salinity stress reduced the dry weight, photosynthesis pigments, and K⁺/Na⁺, while it increased the soluble sugars, glycine betaine, proline, H₂O₂, catalase and peroxidase in the root and shoot of barley cultivars. Correlation analysis indicated that potassium in the shoot had the most positive and significant correlation coefficient (r= 0.86) with the dry matter of shoot. The stepwise regression analysis showed that the root dry weight, catalase of root and shoot, H₂O₂ of shoot and K⁺/Na⁺ of shoot contributed to the performance. Causality analysis revealed that the root dry weight, K⁺/Na⁺ of shoot, and catalase of shoot were highly important as they had a direct positive and significant impacts on the performance of shoot dry matter.

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The effect of nutrient solutions with varying nitrogen forms was evaluated on yield and quality of coriander (cv. Punjab Sugandh) grown in soilless medium under polyhouse conditions. Crop was sown on three dates viz., October (main season), February, and July (off-season), respectively. In polyhouse, N (Nitrogen) was supplied in variable ratios of NO₃^- to NH₄⁺ viz; 100:0 (T1), 75:25 (T2), 50:50 (T3), 25:75 (T4), 0:100 (T5), respectively, keeping total N content constant. Fresh foliage was harvested 3 times in each season at 30 days interval starting from date of sowing. At each harvest, plant growth quality parameters including activity of antioxidants enzymes were determined. Irrespective of the seasons, the yield was significantly higher in polyhouse than soil-grown crop, and among the nutrient solutions, the solution of T2 recorded significantly higher yield as well as growth and quality parameters during all the season. It could be concluded that NO₃^- to NH₄⁺ ratio of 75:25 in the nutrient solution improved both yield and quality and is thus most suitable for coriander crop.

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This investigation was conducted to determine the effects of salinity stress on some physiological and biochemical parameters of common bean (Phaseolus vulgaris L.). Three levels of NaCl (0, 100, and 200 mM) were applied to four common bean genotypes. In the subsequent steps, chlorophyll content, relative water content (RWC), electrolyte leakage index (ELI), Na⁺ and K⁺ concentrations, the K/Na ratio, malondialdehyde (MDA) content, total protein content, and proline concentration were determined and compared. Moreover, the activity of antioxidant enzymes catalase (CAT), ascorbate peroxidase (APX), polyphenol oxidase (PPO), and guaiacol peroxidase (GPX) were analyzed. Content of Chl a, Chl b and carotenoid decreased by increasing the intensity of salinity stress along with the SPAD value. RWC dropped and ELI incremented by augmenting salinity together with the K/Na ratio. The results revealed that MDA and proline concentrations significantly increased under the mentioned conditions. Activities of antioxidant defense enzymes were altered notably. Total protein content mitigated under salt stress. Jules and 201 were detected as tolerant genotypes during this experiment.

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Soil salinity is one of the most important environmental constraints that reduce plant growth and productivity. This study aimed to investigate the effects of various NaCl concentrations on the physiological properties of grape cultivars. NaCl was added at three levels (0, 25, and 50 mM) to Murashige and Skoog medium under in vitro conditions to assess various effects on 21 grape cultivars. Effects of salinity stress were investigated on ascorbate peroxidase, catalase, and superoxide dismutase activities, as well as malondialdehyde, protein, proline, chlorophyll A and B contents, of all samples. The results showed that with an increase in salinity, the amount of antioxidant enzymes, proline content, and protein increased in cv. Rasha, suggesting that it was more tolerant than the other cultivars. Malondialdehyde and Electrolyte leakage accumulation also increased in all cultivars, but this increase was higher in salinity-sensitive cultivars, such as hybrids and wild cultivars than resistant cultivars. During salinity stress, chlorophyll content decreased, and the lowest decrease in chlorophyll content was recorded in cv. Rasha, compared to other cultivars. This research demonstrated that the resistance of cv. Rasha, H6 and H4 to salinity stress was due to its ability to adjust proline, protein content, and antioxidant enzymes.