جستجوی مقالات مرتبط با کلیدواژه « پایداری غشاء » در نشریات گروه « زراعت »

Wheat is a major staple food crop in the world. Although all abiotic stresses adversely affect the wheat growth and production, water scarcity imposes the most severe effects on this crop. Drought stress is also believed to affect the uptake, transport and accumulation of key inorganic nutrients in plants. Silicon occurs abundantly in soils, but in the field of plant growth the other inorganic elements for plant growth are more important than Silicon. However, Silicon plays an effective role in plants under stressful conditions. Silicon entails useful effects in plants under water-deficit treatments, with respect to drought-induced regulation of metabolic processes and water relations. Of several plant growth regulators, Cycocel (CCC) is believed to be very effective in masking the adverse effects of different abiotic and biotic stresses on crops as well as being an essential component of the signal-transduction pathways operating in plants exposed to environmental cues including drought stress. Exogenously applied CCC is believed to affect absorption and transport of nutrients, stomata regulation, growth and photosynthetic rate, chlorophyll synthesis and transpiration. The literature has little information on the role of Silicon and CCC applied in combination in alleviating drought-induced injurious effects on plants. Therefore, in the present study, we appraised the effects of exogenous Silicon and CCC applied individually or in combination on wheat growth and grain yield under water-deficit conditions.

This study was carried out in Tiran province, Isfahan, Iran during 2018-2019, as a split-split plot design in randomized complete block with three replications. The main plots considered irrigation regimes (full irrigation and 40% field capacity irrigated), sub-plots considered Silicon and cycocel application (control, 3.6 g l-1 Silicon, 210 mg l-1 Cycocel, and 3.6 g l-1 Silicon + 210 mg l-1 Cycocel) and sub-sub plots considered two wheat cultivar (Sirvan and Chamran). All measurements based on fresh plant samples were done before the grain-filling stage. Measurements included relative water content, soluble sugars and soluble proteins; activities of peroxidase, ascorbate peroxidase, catalase, superoxide dismutase, levels of hydrogen peroxide, malondialdehyde, concentrations of Ca, K and Mg and leaf water potential. At maturity, yield and yield components were measured. Statistical analysis of data was performed using the MINITAB statistical software.

Drought stress caused a considerable reduction in yield and yield components and relative water content of both cultivars. Application of Silicon and cycocel effectively improved these parameters in water-deficit treatments. Moreover, water-limited conditions markedly promoted the activities of key antioxidant enzymes including peroxidase, ascorbate peroxidase, catalase and superoxide dismutase, while enhancing the accumulation of soluble sugars, potassium, magnesium and calcium in leaf tissues. Application of Silicon and cycocel further enhanced the activities of the key antioxidant enzymes and accumulation of osmolytes, and decreased the levels of H2O2 and malondialdehyde in drought stressed plants. Synergistic effects of Silicon + cycocel application on yield and physiological parameters were apparent compared with Silicon or cycocel applied separately. Water-stress alleviation and yield improvement in the wheat cultivars by Silicon and cycocel application was attributable to partly improved osmotic adjustment and antioxidant activity as well as to more favorable water status under stress conditions.

Foliar application of Silicon, CCC and especially the combination Silicon + CCC, markedly improved grain yield and yield components of the two wheat cultivars under water-deficit. In Silicon, CCC and Silicon + CCC treatments, grain yield was 15.63%, 16.60% and 24.32% higher respectively, than with no foliar application under water stress in cv. Chamran, and 10.25%, 16.02% and 19.25% higher in cv. Sirvan. The results of the study highlight the role of Silicon and CCC application in regulating water-stress response of wheat, suggesting that Silicon and CCC are involved in physiological activities. These results showed positive effects of Silicon and CCC in terms of increased antioxidant activity as well as relative water content and leaf water potential. In addition, Silicon and CCC stimulated the active accumulation of some osmolytes in leaves of water-stressed wheat plants, which suggests enhanced osmoregulation ability. The synergistic effects of Silicon + CCC application on yield and physiological parameters were greater than of Silicon or CCC applied separately. Therefore, proper application of Silicon and CCC might result in increased production of wheat, particularly in dryland areas.

Drought stress is one of the most important factors limiting plant growth. Salicylic acid is a phenolic compound produced by plants that plays an important role in regulating various plant processes. Research has shown that external application of salicylic acid can increase plant tolerance to some abiotic stresses such as osmotic stress, drought, salinity, ozone and ultraviolet rays. The aim of this study was to investigate the interaction of drought stress and foliar application of salicylic acid on some physiological and biochemical parameters in bean genotypes.

To investigate the effect of salicylic acid on the physiological and biochemical trait of bean genotypes under drought stress, a factorial experiment based on randomized complete block design with three replicates was performed at 2020 in the research greenhouse of Agronomy and Plant Breeding, of the College of Agriculture and Natural Resources, University of Tehran in Karaj. The treatments included two genotyps of common bean (167drought tolerant and Naz drought sensitive), two levels of drought stress, 80% of field capacity (as control), and 40% of field capacity (severe drought stress) as well as two concentrations of salicylic acid 0, 1 mM. After applying the treatments, various physiological and biochemical traits were evaluated.

The results showed that drought stress significantly reduced ion leakage and significantly increased ion leakage, hydrogen peroxide and malondialdehyde in both genotypes. These changes under drought stress were far greater in Naz genotype than in genotype 167. Foliar application of salicylic acid reduced the amount of malondialdehyde, ion leakage and hydrogen peroxide and increased the activity of antioxidant enzymes, proline and relative content at all drought levels. The reduction of these changes in leaf foliar application by salicylic acid in Naz genotype was much greater than genotype 167.

The results showed that that foliar application of salicylic acid was able to maintain the leaf water status (relative leaf water content), maintain cell membrane stability (by reducing ion and malondialdehyde leakage), increase the amount of compatible solutions (proline) as well as increasing the Antioxidant enzymes activity (superoxide dismutase, catalase, ascorbate peroxidase and guaiacol peroxidase) in both bean genotypes and thus, reduce the negative effects of drought stress and make the plant more resistant. Therefore, the foliar application of 1 mM salicylic acid can be used to reduce the destructive effects of drought stress on bean genotypes.

In order to investigate the interaction effect of vermicompost and sodium chloride on some characteristics of fennel as a medicinal plant, a factorial experiment was conducted in a randomized complete block design in the greenhouse conditions. Experimental treatments consisted of four levels of salinity (0, 40, 80 and 120mM sodium chloride) and two levels of vermicompost (0 and 5% volumetric), which were applied to four fennel landraces of Urmia, Shiraz, Bushehr and Mashhad. Plants were harvested five weeks after planting and then some of their traits were measured. According to the results of this experiment, vermicompost application induced a significant increase in the dry weight of shoot, chlorophyll a, chlorophyll b, total chlorophyll, carotenoids, magnesium, iron, phosphate, nitrate, membrane stability index, relative water content, and a decrease in the malondialdehyde and other aldehydes of shoot in most studied fennel landraces. In contrast, under salt stress condition (without vermicompost), reverse results were obtained. The highest and the lowest effects of 120 mM sodium chloride on shoot dry weight in the studied fennel landraces were observed in Mashhad (more than two fold) and Shiraz (about 58 percent) landraces, respectively. Nevertheless, the results of interaction between vermicompost and salinity showed that dry weight of shoot, photosynthetic pigments, mineral elements, membrane stability index and relative water content of fennel were significantly increased in the presence of some salinity levels under vermicompost treatment. Malondialdehyde and other aldehydes were also reduced in these conditions. Under combined application of vermicompost and 120 mM sodium chloride, shoot dry weight of Shiraz landrace was increased more than two fold, the highest increase of this trait among the fennel landraces.

Wheat has more distribution range than any crop in the word due to its wide adaptation to different climatic conditions. Occurrence of environmental stresses during wheat growth period significantly reduces its yield in most of its cultivated areas. Among different stresses, cold stress is one of the environmental factors that limiting the cultivation of wheat in the cold and the mountainous areas. Cold stress causes changes in physiological and biochemical traits in plants. This research was conduct to evaluation of some physiological and biochemical traits that related to cold tolerance in different wheat genotypes in semi cold winter region.

This study was conducted at research farm and laboratory crop physiology, Department of Plant Production and Genetics, Razi University, Kermanshah, Iran during 2013-2014 cropping cycles. The farm experiment was a Randomized Complete Block Design (RCBD) with three replications. Sowing date was mid-November. The purpose of field cultivation was to induce the normal induction of cold acclimation in different wheat cultivars under natural field conditions. In this research 12 bread wheat cultivars such as: Norstar, Zarin, Kavir, Baz, Sivand, Alvand, Pishgam, Pishtaz, Orum, Shahryar, Bahar and Parsi were evaluated. These cultivars were purposefully selected from different wheat growth types of spring, autumn and qualitative cultivars. Then, at different stages of cold acclimation, the crowns of the studied cultivars were transferred to the laboratory and in order to evaluation of physiological traits were studied under different temperatures in thermogradient freezer. To this end, a Factorial experiment based on Completely Randomized Design (CRD) with three replications was used. In this experiment, the first factor was 12 above mentioned wheat cultivars, and second treatment was five temperature treatments (+3, -3, -6, -9 and -12 ○C).

The results showed that, winter and facultative cultivars had more crown soluble proteins, membrane stability and antioxidant enzymes activity (peroxidase, superoxide dismutase and catalase) than spring cultivars. The LT50 average was -6.5 ○C. In the meantime, LT50 in winter and facultative wheat cultivars was -8.5 ○C and in spring cultivars was -4.7 ○C. The soluble proteins and catalase activity had the highest positive and significant correlation with cold tolerance.

In general, physiological and biochemical characteristics in winter and facultative cultivars (Norstar, Zarin, Orum, and Alvand) were more associated with cold tolerance than the others. In this research, Norstar cultivar with LT50= -14 ○C and Orum cultivar with LT50= -11.5 ○C were identified as resistant cultivars to cold stress.

Low yield and instability, is one of the most important issues in chickpea cultivation. The adverse environmental conditions have affected the crop yield; in this regard, one of the most important factors is salinity stress that reduces crop yield. Meanwhile, microorganisms have a high ability to mitigation the adverse effects of salinity. In addition, the coexistence of beneficial bacteria and fungi creates a potential for a decrease of salinity stress impacts on plants. Mycorrhizal fungi belonging to the branch Glomeromycota, one of the oldest living organisms introduced to coexist with plants on land and in salinity. These fungi are widely found in saline soils. Research has shown that mycorrhizal arbuscular fungi increase salinity tolerance and prevent yield loss. Studies have shown that the coexistence of mycorrhizal arbuscular fungi with crop roots increases the activity of antioxidant enzymes and this expansion of activity to the plant helps to reduce the effects of salinity stress. With regard to the beneficial effects of mycorrhizal fungi on reducing salinity effects in crops, this study aimed to evaluate salt tolerance in chickpea using native mycorrhizal fungi to improve soil properties and its sustainable production under saline conditions.

This study was performed in 2016 as factorial based on completely randomized block design with three replications in the research glasshouse of the College of Agriculture, Ferdowsi University of Mashhad. Salinity stress treatments included four levels (tap water [control], 6, 6 and 9 dS.m-1 sodium chloride) and mycorrhiza species at three levels (native mass, Piriformospora indica as endophyte, and Gigospera margareta). Four weeks after applying salt stress, maximum quantum efficiency of PSII photochemistry (F'v/F'm) II, stomatal conductance, SPAD index, relative water content (RWC) of leaves, and membrane stability index in the youngest fully expanded leaf were measured. In addition, morphological traits, including plant height, lowest branch height, number of branch number, and number of leaves per plant were measured. At the end of the experiment, the shoot fresh and dry weight, length, volume and dry weight of root were measured, finally root colonization was assessed.

The maximum quantum efficiency of PSII photochemistry (F'v/F'm) affected by different levels of salinity and mycorrhiza application. The highest and lowest maximum quantum efficiency of PSII photochemistry (F'v/F'm) levels were related to 9 dS.m-1 salinity treatment with mycorrhiza Piriformospora indica and control treatment with Gigospera margareta species, the difference between which was 4.5 times. In addition, the highest amount of gas exchange was observed in the Piriformospora indica species. The highest SPAD index was related to treatment with Piriformospora indica fungi in non-stress conditions and the highest salinity stress level. Moreover, application of Piriformospora indica fungal species increased RWC by 4.54% and 9.20%, compared to the use of mycorrhiza native mass and Gigospera margareta species, respectively. Application of Piriformospora indica showed superiority in membrane stability index relative to Gigaspora margareta in all treatments of salinity stress, with the exception of 9 dS.m-1 treatment. However, no significant difference was observed between mycorrhiza treatments in 9 dS.m-1 of salinity stress. Root inoculation with Piriformospora indica increased plant height by 12.7%, compared to mycorrhiza native mass. At all levels of salinity stress, Piriformospora indica increased shoot fresh weight, compared to native mass and Gigospera margareta treatments. Furthermore, the least and highest decrease in root length was observed in Piriformospora indica and Gigospera margareta treatments, respectively. Among mycorrhiza fungi treatments, Piriformospora indica produced the highest root volume, compared to native mass and Gigospera margareta treatments with a difference of 10.9% and 36.4% between them. In addition, in non saline treatment with Piriformospora indica had the highest percentage of root colonization (54.66).

According to the results of the study, most traits evaluated in the study were affected by increased intensity of salinity stress. In addition, increased salinity had a negative impact on root development due to increased soil osmotic potential and toxicity, which ultimately reduced plant growth. Moreover, mycorrhiza inoculation had a significant, positive effect on the photosynthetic system of photosystem II, shoot and root dry weight, ratio of shoot to root, root length and percentage of colonization, root volume, root fresh weight, RWC and membrane stability index. Inoculation of commercial species of mycorrhiza under salt stress increased plant salinity tolerance.

The root of liquorice contains a large amount of glycyrrhizic acid which are known to have various food, industrial, cosmetic and pharmaceutical applications. Regarding to spreading of salinity in arid and semi-arid regions, to assay the tolerance levels of salinity in germination and vegetative stages and the effect of salt stress on the concentration of glycyrrhizic acid in liquorice plant, an experiment performed based on a randomized complete design with at least three replications. Salt stress applied at four levels including 0, 100, 200 and 300 mM NaCl. Our results at the germination stage showed that NaCl at 100 mM level caused a significant decrease in germination rate and percentage and the length of primary root and hypocotyl were diminished. While 200 and 300 mM levels of NaCl inhibited the germination. The results at vegetative stage showed that high salinity levels decrease the root/shoot dry weight ratio, plant yield, protein content and the K/Na, Ca/Na, Mg/Na ratios of shoot and root while the concentration of 300 mM NaCl caused a significant increase in root dry weight and shoot malondialdehyde and total phenol content in comparison with control. Also, the high concentrations of salinity increased the concentration of glycyrrhizic acid in roots. According to measured results at germination and vegetative stages of liquorice plant, it can be concluded that salt tolerance is a developmental stage specific phenomenon. Also, that cultivation of liquorice in saline soils potentially could increase glycyrrhizic acid accumulation in liquorice roots.

Chickpea is one of the most important legumes in Iran. Despite the abundance of cultivated lands in Iran by chickpea, yield per hectare is considerably lower than world average. Environment conditions of chickpea cultivation in infertile, arid and semiarid regions limit the yield production in Iran. Salt stress, resulted from salts accumulation in soil solution is one the limiting factors for chickpea cultivation in arid and semiarid areas. Chickpea is a salt sensitive plant and yield loss is one of the most potential impacts of salinity on chickpea. Polyamines are low molecular weight polycationic molecules, which play important roles in a number of plant physiological processes, including resistance to various stresses. Recently, the role of polyamines, unique polycationic metabolite, was proved as a regulator of growth and plant membrane transport. They also act as a source of reactive oxygen species (ROS) and ROS scavenger and activator of key antioxidant enzymes. Moreover, they are involved in plant stress tolerance. The present study was conducted to investigate the ameliorating effect of spermine and spermidine spraying on yield and yield components of salt treated chickpea plants.
 

The experiment was performed as factorial based on a randomized complete block design with three replications in research farm of Khartooran Shahrood (salinity 5.7 dS m-1). Spermine was sprayed at three levels (0 (control), 0.25 and 0.50 mM) and spermidine also at three levels (0 (control), 0.25 and 0.50 mM) in three stages including four-leaf, flowering and pod-filling stages. Some attributes such as relative water content, membrane stability index and activity of catalase, polyphenol oxidase and guaiacol peroxidase enzymes, plant height, number of branches per plant, number of pods per plant, number of seeds per pod and seed yield were measured.
 

The results showed that foliar spray of spermine at the concentration of 0.50 mM increased membrane stability index (15%) and plant height (23%) in comparison with the unsprayed plants. Moreover, foliar spray of spermidine at the concentration of 0.50 mM significantly increased membrane stability index (17%), plant height (31%), number of branches (52%), number of pods per plant (27%), 100- seed weight (16%) and seed yield (15%), when compared to unsprayed plants. Sodium chloride treatment disturbs membrane integrity and leads to ionic imbalances in plants. On the other hand, polyamines as one of the most important growth regulators, play key roles in regulating membrane functions by attachment to anionic sites or to the negatively charged phospholipid head groups on membranes. Their exogenous consumption probably not only reduces absorption of hazardous ions such as Na+ and Cl-, disturbing normal functions of plant cells and reducing growth, but also protect membranes against the stress injuries caused by salt stress. Furthermore, polyamines are able to reverse the inhibitory effect of salinity stress on plant growth by increasing cell division and cell size. Salt stress declines nutrients transportation to growing shoots and also reduces chlorophyll contents which both leads to growth reduction in plants, while polyamines not only accumulate in thylakoid membranes and increase their integrity under stress but also leads to chlorophyll maintenance and by increasing cell division in root tips elevates nutrient absorption and help plants to keep normal growth. Nutrient and carbohydrate deficiency under saline stress is one of probable reasons for abscission of flowers and branch reduction leading to yield reduction which all can be reversed by exogenous polyamine application. Concerning relative water content (RWC) and enzymes activity, interaction of spermine and spermidine had significant effects on RWC and activity of polyphenol oxidase, catalase and guaiacol peroxidase enzymes. ROS scavenging will reduce their major impact on damages to the biomolecules such as membrane lipids, proteins, chloroplast pigments, enzymes and nucleic acids. Polyamines can act as osmoprotectants to increase water absorption under deficit water condition. They also act as ROS scavenger and activator of key ROS scavenging enzymes.
 

In general, foliar spraying with spermidine was more effective than spermine in mitigating the deleterious effects of salt stress and maintaining the different characteristics of chickpea. Furthermore, application of the concentration of 0.50 mM of both polyamines was more effective than 0.25 mM.

The dragonhead plant is herbaceous that originated in middle Asia and about 66 compound are identified in this plant which the most important compounds are Geranyl acetate, Geranial, Geraniol and Nearl. Application of growth regulator lead to increases of plant resistance against biotic and abiotic stress and is involved as a strategy to prevents adverse effects of environmental stress. According to semi-sensitivity of dragonhead plant to drought condition, its medicinal importance as well as, its industrial widespread use, this study was conducted to evaluate dragonhead essential oil yield and its compound under drought condition and also, to evaluate physiological aspect of drought resistance.
Material and A split plot experiment with two factors moisture levels (normal and stress) and hormone treatment (control, 600 and 1200 µm cycocel and 800 and 1600 µm salicylic acid) was conducted in based of completely randomized block design with four repeats. Two moisture regimes (normal and drought stress) were main factors. In drought stress, plants were irrigated before flowering stage and after that irrigation was stopped in drought stress treatment until end of experiment. Different levels of salicylic acid (800 and 1600 µm) and cycocel (600 and 1200 µm) and control were sub factors which was applied once, two days before drought treatment.
Findings :Membrane stability was negatively correlated to essential oil yield and chlorophyll content index and positively correlated to proline content. In normal condition, there were differences between hormone levels and essential oil yield, so that treatment with salicylic acid 1600 µM lead to highest amount of essential oil yield and treatment with cycocel 1200 µM had no effects on essential oil yield in comparison with untreated plants, moreover treatment with salicylic acid 800 µM and cycocel 600 µM adversely affect essential oil yield than untreated plants. The analysis of essential oil under stress conditions showed that most of the decomposed compounds under these conditions were less than that control and none of the growth regulators have not been able to increase the amount of compounds that have been reduced in stress conditions. Unlike other compounds Geraniol Influenced by growth regulators in stress conditions there was a significant increase compared to the control and Geranyl acetate Was increased influenced by Cycocele 1200 µm and Salicylic acid 1600 µm. And for compounds Neral and Geranial in stress conditions for all levels of growth regulators observation was not found.Under drought condition, Geraniol was significantly increased by application of all hormones treatment than untreated plants while Geranyl acetate was significantly increased only by application of salicylic acid 1600 µM and cycocel 1200 µM.
The results of this research showed that by increasing the amount of proline, which is a positive reaction to drought stress the percentage of essential oil also increases. Correlation results revealed that Essential oil yield has a positive and significant relationship with chlorophyll content index and with membrane stability has a negative and significant relationship. This indicates that Essential oil yield has a positive relationship with the plant's greenness. That is, the plant has the more leaves and limiting conditions affect the plant less the plant will have a higher essential oil yield. Under stress conditions, there is no difference between levels of growth regulators but there are differences between levels of growth regulators in normal conditions for essential oil yield. So that salicylic acid 1600 had the highest essential oil yield. Analysis of essential oil under drought condition indicated that, the most of compounds had higher content under normal condition and any hormonal treatment compensated this decrease. In contrast, Geraniol significantly increased by hormonal treatments under drought than normal condition; thus it could by concluded that in drought condition, application of higher dose of hormones will increase essential oil compounds.

Sunflower is one of the five important oil plants in Iran that because of the relative resistance to drought stress and high oil quality (absence of cholesterol) had a wide range of country land that devoted to the cultivation of this crop. Drought stress is one of the most important factors that limiting the growth and yield of many crops, especially in the arid and semi-arid region in the world.The use of micro-nutrients is one of the ways to reduce the negative effects of water stress on crops. This research was carried out to investigate the response of sunflower to the foliar application of iron (Fe) and zinc (Zn) micro fertilizers under drought stress conditions and to evaluate the role of these nutrients for reducing drought stress damages and plant tolerance to the drought stress.
Material and This experiment was carried out as a split-plot based on randomized completely block design with three replications in Zarghan Agricultural Research Station, Fars province in spring and summer of 2014. The irrigation interval in three levels (irrigation after 60, 120 and 180 mm evaporation from A-class pan evaporation) were used as the main plot and foliar application of micronutrients in four levels (foliar application with water (control), ferrous sulfate (3 g L-1) zinc sulfate (3 g L-1) and the combination of ferrous sulfate and zinc sulfate each one at a rate of (3 g L-1)) served as the subplot. In this experiment, physiological traits (chlorophyll content, proline, soluble carbohydrates, relative water content and electrolyte leakage percent of leaf), morphological traits (leaf area index and height) as well as grain yield were evaluated. The results showed that the main effects of irrigation interval and foliar application were significant for all traits, but their interactions only were significant for proline and soluble carbohydrates. Delaying in irrigation from 60 to 180 mm evaporation significantly decreased 5.6, 31.2, 37.5, 17 and 37 percent relative water content (RWC), chlorophyll content, plant height, leaf area index (LAI) and grain yield, respectively. With the delaying in irrigation also, leaf electrolyte leakage increased by 20 percent. In foliar application treatments, compared to the control, the foliar application of Fe and Zn caused to increase the RWC, chlorophyll content, proline and soluble sugars content of leaves, plant height, LAI and grain yield and oil as well as reduced electrolyte leakage in leaf significantly. The interactions mean comparison of irrigation and foliar application on proline and soluble carbohydrates showed that in all three levels of irrigation use of Fe and Zinc together increased these traits. Foliar application of Fe and Zn improved physiological traits under drought stress condition. Hence, the increase in metabolites particularly soluble carbohydrates and reducing lipid peroxidation, by foliar application of these two elements, could have a positive effect on the mechanisms of drought tolerance and increased sunflower grain yield and oil.

Chlorophyll, RWC, electrolyte leakage and seed performance of three maize hybrid varieties under draught and chilling stress conditions were examined. The experiment was carried out in split-split plots using random completely blocks design with three replications in 2013-2014 in research farm and greenhouse Mashhad University of Ferdowsi, Agronomy Faculty. The main plot was chilling stress at two levels (present and absence of chilling stress); the subplot were drought stress at three levels (100% irritation, 75% irritation, and 50% irritation); sub-subplot was maize hybrid variety (single cross 704, single cross 400, and single cross 260). Results showed that stress conditions affected SPAD so that draught stress declined RWC and stability of cytoplasm membrane. The highest RWC and stability of cytoplasmic membrane were seen in single cross 260 and 400. Mutual effects of the treatments showed that the chilling and 100% irritation single cross 704 treatments had the highest SPAD. In addition, SPAD, RWC, and electrolyte leakage at the end of season decreased relative to the emergence time of male inflorescence. In presence of chilling and draught stresses, single cross 400 had higher performance comparing with the two other hybrids. This, in turn, indicates better performance of such treatment comparing with the other hybrids.

Scientific data on the hulled wheats is scarce. Therefore, changes in some physiological attributes including carotenoids concentration, antioxidant enzymes activity, malondialdehyde content (MDA), cell membrane stability index (MSI) and grain yield in a hulled tetraploid wheat (i.e. "Joneghan") and a durum wheat cultivar (i.e. "Yavaroos") in response to salinity and plant growth promoting rhizobacteria (PGPR) were studied using a split-factorial based on randomized complete block design at Research Farm, Isfahan University of Technology, Isfahan, Iran in 2013. Three levels of irrigation water salinity (control, 100 and 200 mM of NaCl) were chosen as main plots and the two tetraploid wheat genotypes and three PGPR strains (550, 57 and UW3) and bacteria-free control were considered as subplots. Salinity led to significant decreases in grain yield/m2 (nearly 30%), activity of the antioxidative enzymes of catalase (CAT), peroxidase (POX) and ascorbate peroxidase (APOX) and carotenoids concentration. Salinity led to a decrease in MSI and an increase in MDA content, indicating salt-induced damages to the cells. Bacterial strains left different effects on the above-mentioned traits. Strain 550 led to 44% increase in grain yield of the two genotypes at the absence of salt, though strain UW3 led to 24% increase in grain yield of the genotypes, when grown at the presence of 200 mM of NaCl. Though, the bacterial strains led to increase in MSI of the salt-treated plants. From the data obtained in the present field study we can conclude that the PGPR efficacy in the mitigating salt stress in tetraploid wheat is genotype-, salt level- and strain-specific. The "Joneghan" hulled tetraploid wheat was out-performed by the "Yavaroos" durum wheat, though its yield penalty due to saline water did not appear to differ from that of the latter genotype.

A field experiment was carried out to study the yield and physiological responses of rapeseed (Brassica napus L.) to boron application and high temperature stress due to late planting, in Ramin Agriculture and Natural Resources University of Khuzestan at 2013-2014. The experimental design was a split plots design in RCBD with four replications. Planting dates (18 November, 3 December, 17 December and 30 December) were placed in main plots and boron application treatments (control, 10 kg B.ha-1 incorporated with soil, boron spraying at 8 leaf stage and budding stages) were placed in sub plots. Planting date had significant effect on relative water content (RWC), cell membrane stability, peroxidase enzyme activity, leaf area index (LAI), canopy’s temperature, grain yield and dry matter. In addition, boron application had significant effect on LAI, peroxidase enzyme activity and yield. Late planting caused to decrease the grain yield and dry matter related to increased canopy’s temperature at flowering stages. Delayed planting from 18 November to 30 December, result in decreased grain yield about 60.5 percent. Boron application incorporated with soil caused to increased grain yield about 23 percent in comparison to control. High temperature stress due to late planting caused to decreased RWC, cell membrane stability and LAI in flowering stage. Generally, highest grain yield (4579.7 kg.ha-1) was obtained from planting at 18 November and 10 kg boron.ha-1 incorporated with soil, and lowest grain yield was obtained from planting at 30 December and without boron application.

In order to investigation of the effect of freezing stress on electrolyte leakage of two fennel landraces that grown on the field, a factorial experiment based on completely randomized design was conducted with three replications in Agricultural College, Ferdowsi University of Mashhad in 2004. Treatments were two fennel landraces (Khorasan and Kerman), two planting dates and six temperatures (0,-3,-6,-9,-12,-15°C). Seedlings were selected in 4-6 leaf stage from the field and transferred to the laboratory and different organs of seedlings (root, leaf and crown) were investigated for cytoplasmice membrane stability. Results indicated that electrolyte leakage percent of fennel landraces and those organs significantly affected by lowering temperature. LT50 in Kerman landrace was lower then Khorasan landrace and LT50 of second planting date was lower then first planting date in two landraces, and LT50 of crown was the lowest. According to the importance of the effect of cold injury on fennel, additional investigations are requested.

To evaluate the effect of supplemental irrigation on nutrient uptake, water relations and drought tolerance of safflower, an experiment with four levels of irrigation (no irrigation, irrigation at the heading, flowering and both heading and flowering stages) and three safflower cultivars (Gila, Isfahan local and PI-537636) was conducted as a split plot based on randomized complete block design with three replications at Ardebil Agricultural Research Station during 2008. Irrigation showed significant impact on leaf potassium content, relative water content, leaf water potential and membrane stability. There were significant differences amongst cultivars in terms of sodium, potassium, and calcium content, leaf water potential as well as membrane stability and a significant interaction was also observed between irrigation and cultivar on leaf water potential and membrane stability. The highest water potential (0.57 MPa) and membrane stability (95.3%) was obtained by Gila cultivar when irrigated at heading and flowering stages. PI-537636 genotype showed superiority based on stress susceptibility (SSI) and tolerance (TOL), while Isfahan local variety was superior in terms of the stress tolerance index (STI) and geometric mean productivity (GMP). However, given the fact that the best cultivars are those producing high yields under normal conditions with the minimum yield reduction under drought stress, Isfahan local variety was the preferable cultivar under drought stress conditions.