selenium

Introduction:

Stevia rebaudiana Bertoni is a herbaceous plant from the family Asteraceae and used as a valuable sweetener in food industry and as anti-inflammatory, antioxidant, antipyretic, anti-fungal, and antibacterial agent in medicine and pharmacology. Piriformospora indica is an endophytic fungus, which is mainly used to improve plant growth and the amount of secondary metabolites. Selenium (Se) as an micronutrient increases the antioxidant properties and plant growth and its nano form (SeNPs) is considered as a synthetic antioxidant. To evaluate the effect of Piriformospora indica inoculation and selenium nanoparticles foliar application at two concentrations of 5 and 10 mg/l on biological activities of the methanolic extract of the regenerated S. rebaudiana plants, an experiment was conducted in 2020 in Plant Physiology Research Laboratory of the Bu-Ali Sina University of Hamadan in a factorial arrangement based on completely randomized design with three replications. 

Materials and Methods:

To investigate the effects of endophytic fungus P. indica and SeNPs application, in vitro regenerated Stevia plantlets were inoculated with P. indica and foliar sprayed with SeNPs at two concentrations of 5 and 10 mg/l. Plant samples were harvested at vegetative and initial flowering stages and used for further analyses. After measuring the growth parameters, total phenol content and antioxidant activity were evaluated by Folin-Ciocalteu and DPPH radical scavenging assays, respectively. In addition, antibacterial activity of the plant methanolic extracts was studied by disc diffusion method. 

Results and Discussion:

Inoculation of P. indica and application of SeNPs together resulted in plant growth improvement and also increase in total phenol content and antioxidant activity of the Stevia plants especially at vegetative stage. In addition, the studied extracts represented good antibacterial activity against two gram-positive bacteria, Bacillus thuringiensis and Staphylococcus aureus, and one gram-negative bacterium, Escherichia coli. The highest antioxidant and antibacterial activities were observed in the Stevia plants inoculated with P. indica and also treated with SeNPs. 

Conclusion:

Regarded to the results of the present study, P. indica inoculation and SeNPs application could result to the benefits in Stevia plants. Hence, it can be concluded that the biotic and non-biotic elicitors of P. indica and SeNPs can improve the antioxidant and antimicrobial activities of the Stevia plants by increasing the amount of total phenolic compounds.

In order to evaluate the effect of foliar application of some chemicals on antioxidant enzymes activity and chlorophyll fluorescence of sunflower in different irrigation conditions as well as identifying compounds’ effectiveness in reducing the adverse effects of drought stress, this experiment has been conducted at the Agricultural Research Center of Hamedan, Iran, between 2015 and 2016. Three irrigation and six foliar application treatments are evaluated in a split plot experiment based on randomized complete block design with three replications. Irrigation treatments consist of 60%, 80%, and 100% plant water requirement and foliar application treatments include abscisic acid 40 μM, Selenium 20 mg/L, Salicylic acid 500 μM, SNP 100 μM, Glycine betaine 100 mM, and the control. Results show that by decreasing the irrigation water, the activity of superoxide dismutase, peroxidase, and catalase enzymes rise sharply, while the maximum photochemical efficiency of photosystem II and grain yield decline. The interaction effect of irrigation × foliar application on the activity of antioxidant enzymes and grain yield is significant, but not so on chlorophyll fluorescence. In deficit irrigation treatments, foliar application of all chemical compounds significantly boost the activity of antioxidant enzymes, compared to the control. Application of salicylic acid raises the maximum photochemical efficiency of photosystem II and grain yield, at all irrigation conditions. Under 60%, 80%, and 100% irrigation conditions, salicylic acid application increases grain yield by 24.3%, 10.1%, and 4.9%, respectively.

Saffron ‏(‏Crocus sativus L.‎‏)‏ is one of the most expensive agricultural and pharmaceutical products in the world, which has a special place among export products. In this study, in order to investigate the effect of some chemical and biological fertilizers on the yield and quality of saffron, a factorial experiment was conducted in a completely randomized design with three replications. Treatments included two levels of EM (Effective Microorganisms) fertilizer (With and without fertilizer), Two levels of selenium (0 and 1 mg/l) and Three levels of phosphorus (0, 25 and 50 mg/l). The studied factors included number of flowers, fresh and dry weight of flower, fresh and dry weight of stigma. Also, chemical analysis of stigma including crocin, picrocrocin and safranal was performed according to the national standard of Iranian saffron. The results showed that the application of EM fertilizer in selenium treated plants caused a significant increase in the number of saffron flowers. Stigma dry weight in EM fertilizer treated plants and concentration of 50 mg/l phosphorus in the presence of selenium was significantly higher than the absence of selenium. The results also showed that the application of selenium with EM fertilizer at the highest phosphorus level caused a significant increase in flower dry weight and fresh stigma weight. Based on the results of this study, the amount of picrocrocin in plants treated with a concentration of 50 mg/l phosphorus was significantly higher than the control treatment. Also, the use of phosphorus increased the amount of safranal.

Drought stress is the most important factor in crop yield reduction. It is important to know how to cope with drought. This experiment is carried out to investigate the effect of organic growth stimulator (Hamoon green) on yield and some physiological indices of safflower under drought stress, during 2017-2018 in university of Zabol (Chahnime) as a split plot, based on RCBD with three replications. Experimental treatments include drought factor based on plant growth stages at three levels (complete irrigation throughout the growing season, irrigation up to terminal bud forms, and irrigation up to completed flowering) and spraying factor of organic growth stimulator at 4 levels (pure water), the foliar application has been Hamoon green 1 liter in 10 liters + calcium, Hamoon green 1 liter in 20 liters + calcium and Hamoon green 1 liter in 30 liters+ calcium. Results show that drought has reduced the height, 1000-seed weight, and oil percentage, by 44.41%, 31.24%, and 17.10%, respectively. Spraying hamoon green 1 liter in 10 liters+ calcium leads to an increase of 18.03%, 13.90%, and 13.74% for the above traits, compared to the control. The highest grain yield (1882.55 kg.ha-1), chlorophyll a, b, total and carotenoids (3.49, 0.94, 4.44, and 7.37 mg.gr-1 fw, respectively), selenium content (5.18 mg.kg-1 fw) and seed calcium content (2.91%) are obtained from hamoon green 1 liter in 10 liter + calcium and complete irrigation treatment. In general, it seems that by spraying 1 liter per 10 liters+ calcium, a good performance can be achieved.

Drought is one of the most important factors limiting crop yield and foliar application of phytoprotectants is an important management strategy for increasing crop resistance to drought stress. This research was conducted at Rice Research Station of Tonekabon, Iran, in 2018 by using a split-plot based on a Randomized Complete Block Design (RCBD) with three replicates. Main plots were irrigation regimes [common irrigation (control), and irrigation withold from tillering stage (45 days after transplanting)] and subplots were foliar application of phytoprotectants (control, selenium, silicon, ascorbic acid, salicylic acid). The results showed that irrigation withold from tillering stage caused a 29.3% reduction in grain yield in the absence of foliar application. Drought stress decreased plant height, tiller number and 1000-grain weight by 15.5, 14.95 and 3.34%, respectively. Drought stress increased proline content by 115%. Also, in the irrigation withold from tillering stage, foliar application with selenium, silicon, ascorbic acid, and salicylic acid led to increase in floret fertility percentage and 1000-grain weight, thereby increasing the grain yield up to 32.6, 31.9, 35.3 and 33.3%, respectively, compared to no foliar application (control). In general, the results of this study showed that foliar application of phytoprotectants can reduce the adverse effects of drought stress and improve the grain yield of rice under drought stress conditions.

In order to investigation the effect of planting date and foliar application Zinc sulfate and Selenium on tolerance to high temperature on two Wheat cultivars one experiment was carried out in a split factorial experiment based on a complete randomized block design with three replications at the experimental farm of Shahid Chamran University of Ahvaz during a growing season 2017-2018. Three factors were investigated in this experiment. initial factor including three planting date (Nov 11, Des 11, Jan 10). The solution type was used as the second factor: 1- foliar application with tap water (control), 2- foliar application with selenium (4 mg/lit), 3- foliar application with zinc sulfate (0.04%) and third factor including two wheat cultivars (Chamran and Star). According to the results in planting date of 20 January, the number of grains per spike decreased in the foliar application treatments by zinc solfate 10%, Selenium 36% and control 33% compared to similar treatments in the planting date of November 20th. In the planting date of January 20, the decrease in grain yield compared to the planting date of November 20th was 49.3% in the control treatment and 49.9% in the selenium treatment While in zinc sulfate treatment, yield reduction was 20.19%. According to the results obtained in folia application, Zn sulfate increased grain yield in two wheat cultivars by increasing the number of grains per spike, 1000- grain weight and grain filling duration.

The negative effects of heat stress on plants are seriously problems, which often cause damage to crops throughout the world. High temperature driven degradation of chlorophyll reduces photosynthetic capacity. Moreover, impaired transport of photosynthate (carbohydrate mobilization) from green organs (source) to anther tissues (sink) leads to high pollen mortality and thereby decreases grain yield. In environmental stress, plant tolerance should be increased. Therefore some chemical compounds are used to improve the metabolic activity of the plant, which calcium chloride is one of them. For this purpose, the present experiment was conducted to investigate the effect of calcium chloride and selenium foliar application on reducing the effects of heat stress on yield and yield components of two wheat cultivars.

This experiment was carried out as a split factorial experiment based on a randomized complete block design with three replications at the experimental farm of Shahid Chamran University of Ahvaz during growing season 2017-2018. Three factors were investigated in this experiment. First factor including three planting dates (Nov 11, Dec 11, and Jan 10) was allocated in main plot. The second factor was three solution types  ( foliar application of tap water (control), foliar application of selenium (4 mg L-1), and foliar application of calcium chloride (10 mM) and third factor was two wheat cultivars (Chamran and Star) which were assigned in sub plots.

According to the results of third planting date, the highest number of grains per spike (36) was obtained in the foliar application of calcium chloride and the least number of seeds per spike (25) was observed in control and selenium foliar application treatments. In calcium chloride foliar application in third planting date, the number of grains per spike decreased by 12% compared to the first planting date but in the control and selenium foliar application treatments, the number of grains per spike decreased by 36%. In the third planting date, the difference between treatments was more evident in grain yield. So, in this planting date, the decrease in grain yield compared to the first planting date was 49.3% and 49.9% in the control and selenium foliar application treatments, while in calcium chloride foliar application, yield reduction was 23.8%. In all three planting dates, when calcium chloride was used as foliar application, the grain filling duration was longer than treatments of control and selenium foliar application. Grain filling duration was prolonged when calcium chloride applied. This could be one of the most important factors that resulted in lower 1000 grain weight and grain yield than the other treatments. While in this condition, there is sufficient time to carry out photosynthesis and transfer the material to the filling grains. Finally, it can be concluded that the calcium chloride application can have a significant effect on reduction the effects of last season's heat stress on wheat by reducing the negative effects of heat stress during pollination, increasing the grain filling period and 1000 grain weight. The number of smaller seeds per spike indicates the effect of heat stress on the plant and reduced fertility of the seeds due to lack of proper inoculation and lack of sufficient photosynthetic material and the competition between the seeds for absorption of food. Increasing yield in calcium chloride treated plants can be due to better photosynthetic activity in these conditions. Because the use of calcium chloride increases the efficiency of the photosystem II and ultimately improves the function of photosynthesis.

Calcium chloride may increase the 1000 grain weight by improving the transfer of photosynthetic products from leaves to seeds as physiological reservoirs, as well as increased grain filling duration. Therefore, it can be concluded that the calcium chloride application can have a significant effect on reducing the effects of last-season heat stress on wheat by reducing the negative effects of heat stress during pollination, increasing the grain filling duration and 1000 grain weight.

Many solutions have been introduced to enhance drought tolerance. Exogenous applications of various chemicals such as compatible solutes, growth regulators and stress-messenger molecules have been considered during recent years. Glycine betaine (GB) is one of the most effective osmoprotectants. The physiological and antioxidant properties of selenium (SE) have become of higher importance for biologists. Salicylic acid (SA) plays an important role in the abiotic stresses tolerant. Nitric oxide plays an important role in many physiological and vegetative processes such as seed germination, stomatal closure, root development, aging and adaptation to several stress types. Sodium nitroprusside (SNP) is commonly used as a nitric oxide releasing agent in plants. Abscisic acid (ABA), as a messenger, plays a role in responding to drought and other environmental stresses, as well as in many physiological processes such as photosynthesis and regulation of stomatal opening and closure. The aim of this study was to compare the influence of some chemicals as foliar application in order to reduce the adverse effects of drought stress in sunflower. This experiment was conducted at the Agricultural Research Center of Hamedan, Iran, during 2015-2016. Three irrigation and six foliar application treatments were evaluated in a split plot experiment. Irrigation treatments consisted of 60%, 80% and 100% of crop water requirement and foliar application treatments included: abscisic acid 40 M, Selenium 20 mg L-1, Salicylic acid 500 M, SNP 100 μM, Glycine betaine 100 mM, and control. An infrared gas analyzer (IRGA, Lci, ADC Biosientific Ltd, Hoddeston, UK) was used in order to measure the photosynthesis rate, stomatal conductance, transpiration rate, leaf temperature and sub-stomatal CO2 concentration. Photosynthetic water use efficiency was calculated from photosynthesis rate divided by transpiration rate. The leaf relative water content (RWC) was calculated as the follows:RWC (%) = [(FW - DW.) / (TW – DW)] × 100
Where FW is the leaf fresh weight, DW is the leaf dry weight and TW indicates the leaf turgid weight.
Combined analysis of variance of two years data was done using SAS statistical software. The comparison of means was carried out by Duncan's multiple range test at 5% of probability level. Effects of irrigation and foliar application on stomatal conductivity and transpiration rate were significant. Stomatal conductivity and transpiration rate were decreased by decreasing irrigation amount. The lowest rate of stomatal conductivity and transpiration rate in all irrigation conditions were resulted from ABA. Leaf temperature and RWC were affected by irrigation and foliar application. The lowest leaf temperature was obtained under normal irrigation. The highest RWC (90.8%) was attributed to normal irrigation. Applying 80% and 60% of crop water requirement reduced RWC about 10% and 28.5%, respectively. Foliar application of chemicals increased RWC. The effects of irrigation and irrigation × foliar application on photosynthesis rate were significant. The photosynthesis rate decreased with decreasing the irrigation amount. Sub-stomatal CO2 concentration decreased under 80% of crop water requirement and it increased in 60% of crop water requirement. Under normal irrigation conditions, photosynthetic water use efficiency enhanced by foliar application of SA, but under water deficit conditions, foliar application with all compounds promoted photosynthetic water use efficiency. Decreasing of irrigation water had significant effects on gas exchange and photosynthetic properties of sunflower and caused a sharp decline in stomatal conductance and transpiration rate. Furthermore, RWC and photosynthesis rate were decreased, but leaf temperature were increased simultaneously. By decreasing irrigation, the sub-stomatal CO2 concentration initially reduced and continued to increase with more water limitation, while the photosynthetic water use efficiency was increasing gradually. Foliar application with chemicals affected on gas exchange and photosynthetic properties of sunflower. The lowest stomatal conductance and transpiration rate, and the highest amount of RWC were obtained by foliar application of ABA and SNP. In normal irrigation, SA improved photosynthesis rate, but ABA, SNP and SE reduced the sub-stomatal CO2 concentration and photosynthetic rate. Under low irrigation, foliar application of all chemicals increased photosynthesis rate and reduced the sub-stomatal CO2 concentration. SA had a more positive impact rather than other compounds.

Selenium is a beneficial element with antioxidant and antivirus function and it can increase plant growthand tolerance to environmental stress.Inthis study, the effects of selenium in stress conditions caused by heavy metals cadmium, nickel and lead in cucumber (Cucumis sativus L. cv Super Dominus) was investigated.The research was conducted using a completely randomized design with factorial arrangement in three replications for two germination tests .The first experiment was carried out to determine the optimal effectiveness of selenium and heavy metal toxicity threshold levels, Which contains levels of selenium (0, 4, 6, 8, 10 mgL-1) from sodium selenate, cadmium (0, 10, 15, 20, 25 µM) from cadmium chloride, nickel (0, 50, 100, 150, 200 µM) from nickel chloride and lead (0, 20, 40, 60, 100 µM) from lead chloride sources. The second experiment were consisted of two levels of selenium (0, 8 mgL-1) and toxicity threshold levels of heavy metals, including cadmium (0, 25 µM), nickel (0, 200 µM) and lead (0, 100 µM) treatments.The results showed that the germination index was significantly reduced as presence of toxic concentrations of heavy metals in the medium of cucumber seed germination. However, the application of selenium was improves the rate and percentage of germination, increase the length of shoot and root and seedling wet and dry weight in stress condition.Selenium was significantly increased cell membrane stability and decrease malondialdehyde under stress condition.Selenium improved antioxidant activity and increase activity of catalase, ascorbate peroxidase and guaiacol peroxidase enzyms in heavy metal toxicity condition .In general, the results of this study showed that the optimum concentration of selenium was reduces symptoms of toxicity due to the presence of heavy metals incucumber seedgermination mediumas  improving germination, growth and antioxidant activity.

  Agricultural soils in Iran, as in many other countries, are slightly to moderately contaminated by cadmium. According to some published reports, the average content of cadmium in some agricultural products and soils of Iran was found to be above the FAO/WHO guidelines. Abiotic stresses including cadmium stress can lead to overproduction of reactive oxygen species (ROS) causing progressive oxidative damage and ultimately cell death. In order to reduce cadmium-induced toxicity and alleviate some adverse effects of this metal on plants, a number of strategies including phytoremediation have been developed. Meanwhile, it was found that application of some elements such as calcium could diminish adverse effects of heavy metals in plants. In addition to calcium, selenium due to its potential in mitigation of cadmium toxicity has gained increased attention in recent decades. Selenium, as an antioxidant, plays an important role in the maintenance of human health, and on the other hand, many soils and, consequently, the crops produced in them suffer from the deficiency of this element. Although some studies have reported protective roles of selenium in plants subjected to cadmium stress, due to the limited reports on the effects of selenium on wheat exposed to cadmium stress particularly under Iranian soils conditions, the present study was conducted. In winter 2015, a pot experiment was carried out based on a completely randomized design in factorial arrangement with three replications for each treatment at research greenhouse of agriculture faculty of Ferdowsi university of Mashhad, Iran. The site is situated at 36°2′ North latitude, 59°4′ East longitude at an altitude of 999.2 m above mean sea level. The experiment included four levels of selenium (0, 0.5, 1, and 4 mg kg -1 soil, in the form of sodium selenite) and three levels of cadmium (0, 5, 15 mg kg -1 soil, in the form of cadmium nitrate). Soil weighing 6 kg was put into polyethylene pots, irrigated with distilled water to field capacity each three days and left over for 45 days to attain equilibrium. Eight seeds of wheat (Triticum aestivum L. cv. Falat) were sown per pot and thinned to four plants after the seedlings of wheat were well established. Sixty days after germination, newly expanded leaf samples from each pot were taken for determination of leaf pigments, proline and enzyme activity. Meanwhile, shoots from each pot were harvested from 1 cm above the soil and rinsed four times (twice with distilled water, once with 20 mM EDTA and again once with distilled water). The samples were wiped with paper and oven-dried at 50 °C for one week. Finally, dry weight of the shoots was measured. Cadmium stress, selenium application, and their interactions had a significant effect on photosynthetic pigments concentration, proline content, catalase activity and shoot dry weight. Results showed that as cadmium concentration in soil increased, chlorophyll a, b concentration, carotenoids content, catalase activity and shoot dry weight decreased. In contrast, the accumulation of proline in the plants was stimulated after the cadmium treatment, by 25 % in the presence of the highest cadmium level, as compared to the lowest cadmium level. Selenium application exerted its positive influence on some physiological parameters in plants exposed to cadmium stress. Chlorophyll b concentration and enzyme activity were higher in plants treated simultaneously with selenium and cadmium as compared with plants treated solely with cadmium. However, selenium did not show positive effect on chlorophyll a concentration, carotenoid content and shoot dry weight in plants grown under cadmium stress. Meanwhile, selenium at high concentration had no beneficial effect on wheat but also led to a significant decrease in photosynthetic pigments content, enzyme activity and shoot dry weight. The results of the present study revealed that cadmium stress negatively affected physiological parameters of wheat and decreased photosynthetic pigments concentration, catalase activity and shoot dry weight. In contrast, selenium supplementation at low concentration could improve partially some physiological responses in wheat under cadmium stress.

To evaluate the effect of selenium (from sodium selenate) on increasing efficiency at water deficit condition a research was conducted in Karaj 1 wheat cultivar in 2014-2015 cropping year with split plot based on completely randomize block design with four replications in Karaj. Irrigation treatments with two levels, normal (I1) and interruption of irrigation at mid flowering (110 days after planting) (I2), which were assigned to main plots and selenium foliar application with six concentrations: 0 (S0), 5 (3.12 micro g.) (S1), 10 (6.24 micro g.) (S2), 15 (9.36 micro g.) (S3), 20 (12.5 micro g.) (S4) and 25 (15.62 micro g,) of sodium selenate per plant (S5) g.ha-1 to sub plots. The results showed that water deficit increased the rate of superoxide dismutase, catalase, glutathione peroxidase and malondialdehyde marker. Foliar application of selenium, increased contents of antioxidant (anti oxidation) enzymes under stress condition and was maximum in 20 g. selenium per ha-1. Content of malondialdehyde was decreased and caused significant increase in grain yield. Increasing antioxidants and reduction of malondialdehyde at normal condition was lower. On the other hand, negative effect of malondialdehyde on yield components, cellular membrane stability and antioxidant enzymes at humidity stress condition was higher than normal condition. Significant increase of cytoplasmic membrane stability, grain yield, grain weight and selenium content of seed was obtained when 15 and 20 g. selenium ha-1 were used as compared with those of higher and lower rates of selenium usage under water deficit and normal irrigation. Suppression of free oxygen radicals, and enzyme induction defense mechanisms against oxidative damage has been effective. Therefore, use of exogenous compounds such as selenium may increase the antioxidant capacity of plant against stress.

Selenium is an essential nutrient, but its role in the plants need more research. For this purpose a factorial experiment in a completely randomized design with three replications was carried in the Shahed University of Tehran in 2015. The first factor was different concentrations of Selenium (0, 0.5, 1, 1.5 and 2 percent) and the second factor of priming time (0, 8, 16, 24 and 32 hours). The results indicate that the effect of the concentration and priming time was significant on germination percentage, germination rate, mean daily germination, germination uniformity, germination value, seedling length and vigor index. The interaction of concentration in priming time had a significant effect on the level of one percent on traits of germination rate, mean time germination, daily germination rate, germination uniformity and seedling length. With increasing concentrations of selenium from 0 to 2%, were observed significant increases in germination percentage, germination rate, mean daily germination, germination value, and seed vigor index. So that the highest average traits observed in concentrations of 2% and lowest in 0%. The highest germination rate in priming for 8 and 24 hours in concentration of 2% with an average of 4.50 and 4.33 seeds per day, respectively. With increase of priming time increased germination uniformity and seed vigor and highest average of two traits was 24 and 32 hours priming. Generally, priming with 2% concentration for 24 hours had significantly increased germination index and seed vigor of Stevia.

Drought stress is one of the major factors limiting crop yield in dry-lands. To investigate the effect of sources and different rates of selenium on physiological traits, yield and yield components of wheat and barley in dry lands a factorial experiment based on complete randomized block design with three replicates was carried out at the Research Station of Islamic Azad University, Arak Branch, in 2014-2015. Experimental factors were selenium sources with two levels, (sodium selenate and sodium selenite), selenium rates with three levels, (0, 18 and 36 g.ha-1) and two crop plant (wheat and barley). The result showed that, foliar application of wheat with 18 g.ha-1 sodium selenite increased the grains per spike by 9.4% as compared to control and foliar application of barley with 18 and 36 g.ha-1 of sodium selenite increased the grains per spike by 8 and 12%, as compared to control, respectively. Two times foliar applications of these two plants with sodium selenate and sodium selenite increased their relative water content. Foliar application by 18 g/ha of selenium increased the grain yield from 1776.31 kg.ha-1 in control to 1889.92 kg.ha-1, while grain yield was decreased (about 1539.62 kg.ha-1) as compared to control when 36 g.ha-1 of selenium was used. It could be concluded that foliar application of 18 g.ha-1 selenium as sodium selenite or sodium selenite in wheat and barley during stem elongation and emergence of spike increases grain yield in dry land condition.

In order to evaluate the effect of zeolite application and selenium spraying on some physiological traits and grain yield in medicinal pumpkin (Cucurbita pepo L.) under different moisture regimes, a study was conducted in a factorial experiment based on randomized complete block design with three replications during 2010 in Takestan at Gazvin province, Iran. The three levels of irrigation factors including normal irrigation based on 60mm evaporation from class A pan (control), withhold irrigation at the flowering and fruit formation stages, zeolite factors including two levels of non-application and use of 10 tons per hectare and selenium was sprayed at two concentration in zero and 30 grams per liter per hectare. The results showed that water deficit stress decreased stomatal conductivity, carotenoid content, chlorophyll a, total chlorophyll, grain yield and increased proline concentration and chlorophyll b content. Zeolite application of 10 tons per hectare under water deficit stress conditions had desirable effect on chlorophyll a and chlorophyll b content and grain yield, also improved traits as stomatal conductivity and reduced proline concentration. The highest grain yield (1329 kg.ha-1) was obtained with zeolite and selenium application together at normal irrigation conditions. According to the results, it seems that application of zeoilite and selenium in areas that are subjected to water deficit stress can be useful in improving plant growth and production.

Selenium (Se) is an essential element for humans and animals. However, its effects are less known on plants. In this study, the effect of different sources and levels of selenium was studied on growth and some physiological characteristics of onion in hydroponic system, it is done in order to have a good and an acceptable quality character, and does not have a problem for human and plant. The treatments included four levels of selenium nanoparticles (2, 5, 10 and 30 mgL-1) and three concentrations of sodium selenite (2, 4 and 8 mgL-1) and sodium selenate (1, 2, and 3 mgL-1), each treatment were separately performed in a completely randomized design with three replicates. Results showed that in seedling stage different levels of nano-selenium, sodium selenite and sodium selenate were significantly effected on leaf fresh weight, root fresh weight, root dry weight, pseudostem fresh weight and also bulb weight, bulb diameter and length of bulbs. Sodium selenite and sodium selenate were significantly effected on leaf chlorophyll content and total selenium bulb. The highest leaf chlorophyll content was observed at low levels of sodium selenite and sodium selenate by increasing selenium concentration in nutrient solution, leaf chlorophyll content were decreased in comparison with control. The content of total selenium bulb increased with increasing sodium selenite and sodium selenate concentration in nutrient solution, However increase in plants treated with sodium selenate was more than plants treated with sodium selenite.

In order to study the effects different treatments of priming on yield and yield components of rainfed wheat, a field experimental was carried with three replications in the Research Station of Islamic Azad University, Arak Branch, Iran in 2014. The experimental treatments were control, seed priming with distillate water, priming with rates of 1, 2 and 3 mg l-1 Se alone and along with foliar application of distillate water and selenium. The result showed seed priming with 1 and 2 mg l-1 Se along with foliar application of selenium increased seedling emergence percentage by 47.64 and 41.5% as compared with control, respectively. The maximum number of grain per spike) was obtained from seed priming with 2 mg l-1 Se along with foliar application of Se, That was increased number of grain per spike by 18.2% as compared with control. The maximum of 1000 grain weight was record for foliar application with distillate water. Seed priming with 2 mg l-1 Se along with foliar application of Se increased 1000 grain weight by 9.4% as compared with control. Seed priming with 1 and 2 mg l-1 Se along with foliar application of Se and priming with distillate water along with foliar application of selenium increased grain yield by 16.7, 19 and 17.9% as compared with control.

Selenium is an essential element for human and animal heath, with antioxidant and anti-cancer properties. Although, researchers have found it to increase vegetative growth. It is not considered to be essential for higher plants. In order to evaluate the effect of selenium and sulfur on growth and yield of three cultivars of spring wheat a factorial experiment based on randomized complete block design with three replicates was conducted in pots at the Agricultural Faculty of Islamic Azad University, Tabriz Branch, Iran, during 2009-2010. Treatments were 3 cultivars of spring wheat (Karaj, Pishtaz and Sepahan), 5 levels of selenium (0, 0.2, 2, 5 and 10 mg/kg) in the form of sodium selenate used and 4 levels of elemental sulfur (0, 50, 100 and 150 mg/kg). Results showed that 0.2 and 2 mg Se/kg of soil increased growth and yield in all three cultivars, but 5 and 10 mg Se/kg of soil without sulfur, caused toxicity symptoms, white spots on leaf margins, while its toxicity decreased when 50 and 100 mg S/kg of soil was used and toxicity disappeared by using 150 mg S/kg of soil. This indicates that low levels of Se may have positive effects on growth and yield of wheat through meaningful interaction between Se and sulfur.

An experiment was conducted to study the effect of organic and inorganic antioxidant on Gompertz non-linear function in broilers reared under heat stress. So, 180 one-day old chickens (male and female) were used in a completely randomized block design with 6 treatments and 3 replicates. The experimental diets were (T1) control diet; (T2) control diet + 5 gr.kg-1 turmeric powder; (T3) control diet + 10 gr.kg-1 turmeric powder; (T4) control diet + 0.3 mg.kg-1 sodium selenite; (T5) control diet + 0.3 mg.kg-1 sodium selenite +5 gr.kg-1 turmeric powder; and (T6) control diet + 0.3 mg.kg-1 sodium selenite +10 gr.kg-1 turmeric powder. Broilers were subjected to heat stress (35 ºC) during the fifth and sixth weeks. The results showed that diets including 10 gr.kg-1 turmeric powder significantly increased final weight (Wf), weight at inflection time (Wt) and time at inflection time (t) (p<0.05). However, the difference between 10 and 5 gr.kg-1 turmeric powder levels was not significant. The interaction between selenium and sex was significant on Wf in such a way that male chickens fed with selenium had higher Wf.