فهرست مطالب ali ashraf soltani

Basil (Ocimum basilicum), as an annual plant, belongs to the family Lamiaceae, native to Asia (Iran, India, Pakistan, Thailand, etc.) and grows in warm and semi-warm regions. Arsenic (As) is a highly dangerous heavy metal for plants and human. This quasi-metal is widely distributed in the earth's crust, and also is the twentieth most abundant element in the earth's crust. Selenium (Se) is a non-metallic chemical element and also has similarities to arsenic. Global interest in the biological effects of selenium on the environment and the food chain is growing because selenium is essential as a micronutrient for many organisms, including humans and other animals (although it is toxic in high concentrations). Given that arsenic is one of the most important factors limiting crop production in the agricultural sector, it seems necessary to conduct researches in this field to eliminate or reduce the toxic effects of these element on agricultural plants.           

In this study, the effect of selenium on increasing the tolerance rate of basil plant against arsenic heavy metal stress was investigated as a factorial experiment based on completely randomized design under greenhouse condition. The first factor included arsenic-contaminated soil (4576 mg kg-1) and non-contaminated soil, and the second factor included different concentrations of selenium treatment (0, 5 and 10 mg L-1 selenium sodium). Foliar application of selenium was conducted at two stages. The first stage of foliar application was carried out at 4-leaf stage and the second stage of foliar application was done two weeks after the first stage. Leaf number, leaf area, stem height, fresh and dry weight of leaf and stem, chlorophyll and carotenoid content, free proline content, phenol, flavonoid and anthocyanin content, electrolyte leakage and antioxidant enzymes activity were evaluated at the end of the experiment.

The results showed that arsenic stress negatively affected the morphological traits such as leaf number and area, fresh and dry weight of leaf, fresh and dry weight of stem and plant height, but selenium treatment alleviated the toxicity of arsenic and increased the values of these traits, so that treated plants had higher values of morphological characteristics comparing to control plants under arsenic heavy metal stress. The highest values of morphological traits were observed in plants treated with the highest concentration of selenium (10 mg L-1). In terms of physiological traits, arsenic heavy metal stress reduced the values of some of these traits, so that the lowest amounts of chlorophyll a, chlorophyll b and total chlorophyll, anthocyanin, phenol, and flavonoids were recorded in plants grown in arsenic-contaminated soil without foliar application of selenium. On the other hand, the lowest activity rates of guaiacol peroxidase, catalase and ascorbate peroxidase were observed in plants grown in non-contaminated soil and without selenium foliar application. Also, the both arsenic stress and selenium treatment increased proline accumulation and soluble sugars content of treated plants comparing to control plants. Heavy metal stress increases the production and accumulation of reactive oxygen species (ROS) and damages the membrane structure resulting in more electrolyte leakage. Selenium application led to increasing plant resistance rate against arsenic stress, mainly by enhancing cells antioxidant capacity and osmotic potential.

Considering basil is one of the most important aromatic vegetables which has fresh consumption, crispness and wateriness of its leaves and young shoots is one of the most important commercially traits which directly affect crop marketability. Considering arsenic stress has a negative effect on leaf morphological traits (number, area, fresh weight and dry weight) and stem characteristics (fresh weight, dry weight and height), it is recommended to use selenium foliar application as an efficient technique to overcome adverse effects of arsenic stress on basil production in regions with contaminated soils.

Summer savory (Satureja hortensis L.) is an annual medicinal herb, belonging to the family of Labiatae. This plant is native to the Mediterranean region and is cultivated extensively in France, Hungary, Spain, and Iran. Drought is one of the most important environmental factors responsible for decreasing global production and performance, especially in areas with low and irregular rainfall. Morphological indices such as plant height, stem length, yield, leaf area, and many of the growth traits of the plant are affected by drought stress.

A factorial layout based on a randomized complete block design with three replications was conducted at the Research Farm at the Mohaghegh Ardabili University, Iran, during 2016-2017. Treatments included three levels of drought stress (Full irrigation (s1), Water cut at 50% of flowering (s2), and Water cut in early stages of flowering (s3) and four vermicompost levels (including 0, 1, 1.5 and 2 t. ha-1). Plants were fully irrigated until eight weeks after seeding, and then drought stress was started at the early stage of flowering and 50 % flowering of plants. Fully irrigated plants throughout the growing season considered as control. The sampling was performed from cultivated plants, by the random collection of 3 individual samples. Samples to evaluate the morphophysiological, biochemical, and yield characteristics were taken at the full flowering stage. Traits such as plant height, dry stem weight, lateral branches, relative water content, electrolyte leakage, chlorophyll fluorescence, chlorophyll a, chlorophyll b, total chlorophyll, carotenoid, proline, protein, Catalase, and peroxidase antioxidant enzymes were measured and assessed. Data were analyzes using SAS V9.2. Mean comparison of results was made using Duncan's multiple range test at P≤0.05 levels.

Morphological traits: The results of the analysis of variance the effects of various vermicompost levels and drought stress and their interaction have been presented. The results showed that the effect of drought stress and vermicompost on plant height and shoot dry weight were significant at the 5% probability level. However, no significant effect was observed on the number of lateral branches. Also, the interaction of drought stress and vermicompost fertilizer treatments was substantial for plant height and dry weight of stem at a 5% probability level.The photosynthetic pigments: The results of the analysis of variance showed that the interaction of drought stress and vermicompost on chlorophyll fluorescence, chlorophyll a, chlorophyll b, and carotenoid was significant at 5% probability level, but the total chlorophyll has a considerable effect. The highest chlorophyll a (23.33 mg.kg-1), chlorophyll b (17.24 mg.g-1) and carotenoid (8.08 mg.g-1) in full irrigation treatment and two tons per hectare of vermicompost and minimum chlorophyll a (17.73 mg.kg-1), chlorophyll b (96.6 mg.g-1) and carotenoid (5.5 mg.g-1) in Water cut in early stages of flowering and Without the application of vermicompost (control).Proline: Based on the results of the analysis of variance, the effect of drought stress and vermicompost on the proline content of Satureja plant was significant at 5% probability level. The results showed that with increasing drought stress, the amount of proline in leaf was raised. However, with the use of vermicompost, leaf proline decreased, with the highest amount of proline (0.226 μg.g-1) in Water cut in early stages of flowering (severe stress) and without application of vermicompost (control) and low proline (0.15 μg.g-1) in Full irrigation (control) and vermicompost treatment (2 t.ha-1) were obtained. Investigating the drought stress on German chamomile plant, researchers reported that drought stress increased proline accumulation in the leaf (Ghaedi Jeshni et al., 2017). It was reported that increasing the amount of drought stress in sorghum increased the amount of proline in the leaf (Esmaeilpour et al., 2013).

Based on the results, it can be concluded that vermicompost 2 t. ha-1 can improve the medicinal plant growth and yield under severe drought irrigation regimes.
 

Assess the diversity of the understanding of ecosystem function; maintain genetic resources, checking environmental changes, and success or failure will help natural resource management programs. Over-grazing and uncontrolled usage of rangelands are the most common and the most important factor of rangeland degradation which causes a reduction in species diversity.

In order to investigate the effect of different grazing intensities on species diversity and uniformity in the rangelands of the southeastern slopes of Sabalan, three habitats with different grazing managements including light, medium and severe grazing were selected and one square meter plots along three 200-meter transects were sampled. In each plot, the list of available species, canopy percentage and number of individuals of each plot were recorded. Simpson, Shannon and Brillon diversity indices and Camargo, Simpson and Smith-Wilson uniformity indices were calculated.

The results showed that the area with medium to light grazing intensity has the highest diversity and uniformity compared to the area with heavy grazing intensity which indicates favorable conditions for the establishment of several species. 

Discussion and Conclusions

Due to the significant effect of grazing intensity on diversity and richness indices, it is necessary for rangeland managers to control grazing intensity through management methods to maintain the diversity of rangeland ecosystems. Therefore, it is enough to target the management based on moderate grazing and bring the areas with intense grazing to the conditions of moderate grazing so that the good and tasty species gradually replace the woody and poor species. Desirable species and plant species and woody species are poor.

The most current way for measuring the soil fragmentation is determination of mean weight diameter (MWD). In this study, the adaptive neuro-fuzzy inference system (ANFIS) was used to predict of range soil fragmentation affected by different grazing intensities, distance from village and sampling depth. Present study conducted at 2015 in 3 adjacent rural areas (Alvars, Aldashin and Asbe marz) in Darvishchai watershed in Ardabil County. The studied parameters on the soil fragmentation including different grazing intensities in 3 levels (low, medium and high intensity), distance from village in 3 levels (200, 400 and 600 meters) and the soil sampling depths in 2 levels (0-15cm and 15-30cm). Obtained data were transferred to MATLAB software for the development of ANFIS models. For evaluating the models operation, mean squares error (MSE) and correlation (R2) were used. The result of best ANFIS model in prediction of soil fragmentation was compared with results of regression model. The results show that different grazing intensities, distance from village, sampling depth and their combinations had significant effect on the soil fragmentation. Increase of grazing intensity resulted in increment of soil fragmentation. With increment the distance from village from 200 to 400 meters, soil fragmentation decreased but with increment of distance, increased. Soil fragmentation in all conditions was higher at depth of 0-15 cm than depth of 15-30 cm. ANFIS model had more precision in prediction of soil fragmentation (R2=0.96) relative to regression model (R2=0.76).

  The effect of plant growth promoting bacteria on increasing wheat yield has been demonstrated. Nevertheless, the effect of these bacteria on soil biological quality particularly in the stress conditions such as soil salinity was seldom studied. Therefore, the aim of this study was to investigate the effect of these bacteria on improving biological indices of soil under cultivation of wheat and salinity condition. In order to investigate the effect of inoculation with plant growth promoting bacteria (PGPB) on some soil biological indices and wheat growth parameters under salinity stress, a factorial experiment was conducted based on completely randomized design with three replications. The factors were salinity at four levels, control, 6, 8 and 10 dS.m-1, inoculation with plant growth promoting bacteria at three level, no-inoculation, and inoculation with Pseudomonas putida and inoculation with Pseudomonas fluoresces. After the growth period, the plant yield parameters such as the root volume, root and shoot fresh and dry weight, were measured. The organic carbon, microbial biomass carbon, respiration and substrate–induced respiration was also determined. The results showed that the soil biological indices and plant growth parameters significantly decreased as the soil salinity increased; however inoculation with the bacteria significantly increased plant growth parameters. The inoculation with P. fluorescens and P.putida compared to the control (without inoculation) increased root volume by 83% and 25%, root dry weight by 38% and 7%, and root fresh weight by 52% and 50%, in the salinity level of 6 dS.m-1 respectively. The highest microbial biomass carbon (1997 mg Cmic. Kg-1 dry soil) was observed in inoculation with P.putida. Inoculation with P. fluorescens could also increase soil microbial biomass carbon in the control from 987 to 1765 mg Cmic. Kg-1 dry soil. Compared to no-inoculation, inoculation with both bacteria in all salinity levels increased soil basal respiration and substrate-induced respiration. It could be concluded that the presence of plant growth promoting bacteria not only increased plant growth parameters under salinity stress, but also they improved soil biological indices such as soil microbial biomass carbon, basal respiration, and substrate-induced respiration and thereby indirectly enhanced plant growth conditions and increased plant yield quantity and quality. It could be concluded that the presence of plant growth promoting bacteria not only increased plant growth parameters under salinity stress, but also they improved soil biological indices such as soil microbial biomass carbon, basal respiration, and substrate-induced respiration and thereby indirectly enhanced plant growth conditions and increased plant yield quantity and quality.

To evaluate the effects of grazing on some physical and chemical properties of soil, in the summer rangelands of southern slopes of Sabalan, three regions with different grazing intensity were selected after field observation and 27 soil samples were randomly taken along three 200-m transects. Soil samples were taken from the depths of 15-0, 30-15 and 45-30 cm and transported to laboratory and soil properties such as texture, organic matter, organic carbon, phosphorus, potassium, EC and pH were measured. Analysis of variance and mean comparison were made using Duncan's test. Results showed that no significant difference was found for soil pH and phosphorus among the grazing intensity treatments and soil depths; however, significant differences were observed for other variables. The results showed that organic matter content decreased with increasing of grazing intensity and the lowest content was recorded for the 30-45 cm soil depth in the heavy grazing area. According to the results of this research it can be concluded that soil structure is degraded with increased grazing intensity; therefore, a balanced grazing need to be taken into account in summer rangelands to prevent soil degradation.

In order to investigate the effects of the inoculation with P. putida, R. leguminosarum bv. phaseoli and F. mosseae on yield and nutrient uptake of Common Bean (Phaseolus vulgaris L.), a greenhouse experiment in a completely randomized factorial design with 3 treatment including a: microorganism in four level (no inoculation, P. putida, F. mosseae and mix inoculation of fungi and bacteria), B: Zn in two level (0 and 10 mg.kg-1) and C: Nitrogen in two leve (inoculation with R. leguminosarum and adding 70 mg.kg-1 nitrogen in form of NH4NO3) with four replication was conducted. The results of experiment indicated that the concentration of P, K, Zn, Cu and Mn in shoots of plants and shoot dry matter, shoot wet matter, seed dry weight, seed number and thousand seed weight affected by simultaneous inoculation of F. mosseae and P. putida. The concurrent inoculation of F. mosseae P. putida R. leguminosarum bv. phaseoli significantly increased the Mn concentration in shoots of plants and seed number. Uptake of N, P, K, Fe, Zn, Cu and Mn significantly affected by synchronous inoculation of F. mosseae and P. putida. The concurrent inoculation of F. mosseae P. putida R. leguminosarum bv. Phaseoli had no significant effect on nutrient uptake. Maximum thousand seed weight was obtained in rhizobium treatment which represents the role of effective and efficient rhizobium bacteria in reduction of nitrogen fertilizers use without yield loss.

Fluorescent Pseudomonads are one of the most important plant growth promoting bacteria which exists in the rhizosphere of different crops, having different growth stimulating properties that can improve plant growth. Production of high concentrations of IAA is one of the typical characteristics for most of these bacteria. In order to evaluate the ability of auxin production by various strains of Pseudomonas fluorescens in different time period (in TSB and DF medium) and also to determine the effects of these strains on the growth of maize, a greenhouse experiment was done in a completely randomized design. The results showed that all isolates were able to produce IAA. The average amount of IAA in TSB medium ranged between 0.04 to 34.3 mg.l-1. The lowest and the highest IAA produced on fifth day by p13 and p26 isolates respectively. IAA production by the isolates in DF medium varid between 0.043 to 6.03 mg.l-1. Significant correlation between auxin production in both medium in different days showed that manner of auxin production by isolates were the same and isolates that have a high potential to produce auxin in both medium, produced higher amounts of auxin compared to inefficient isolates. The results of greenhouse experiment showed that the isolates inoculation increased shoot dry weight up to 100 percent while shoot length, leaf area and chlorophyll increased by 53.1, 57.2 and 22.3 percent respectively. Root dry weight was decreased by inoculation of most isolates. The results showed a significant positive correlation between the productions of IAA in both rich TSB and minimal DF medium. This correlation suggests that both media can be used for selection of superior strains.