فصلنامه گیاه و زیست بوم
پیاپی 45 (زمستان 1394)

This experiment was conducted in an attempt to study the vegetation and the impact of physiographic, soil, and geological factors on the distribution of plant communities in Manesht region in Ilam province. To analyze and determine the ecologic groups, 125 square sampling plots with an area of 400 square meters was collected from the region following a systematic-random design. To determine the soil factors, two soil samples (0–30 and 30-90 cm deep) were collected from each land unit and the parameters such as soil texture, pH, EC, saturated moisture, lime, organic matter content, N, P, K, bulk density, and partial density were measured. Using TWINSPAN, the vegetation of the study area was classified. Afterwards, PCA and CCA procedures were used to investigate relationship between the vegetation and the environmental factors and to determine the most effective factors. The results of PCA and CCA analyses revealed a significant relationship between the distribution of the ecologic groups and the plant species with the physiographic, soil, and geological factors. The most significant environmental factors contributing to the distribution of the ecologic groups in the region included the geologic formation and the organic and lime matters. The CCA result was entirely consistent with the PCA, but CCA shows more details about the relationship between species and the environment while PCA illustrates the relationship between the ecologic groups, the prominent species, and the environmental factors.

1. Department of Rangeland and Watershed Management, University of Mohaghegh Ardabili, Ardabil, Iran.
2. Department of Soil Sciences, University of Mohaghegh Ardabili, Ardabil, Iran.
Abstract
This study was conducted in an attempt to investigate the relationship between the distribution of Artemisia austriaca Jacq. and some environmental characteristics in the southeast slopes of Sabalan. The density parameter was selected as the dependent variable with elevation, slope and aspect, rainfall and temperature, the percentage of clay, sand and silt, pH, organic materials, potassium, phosphorous, lime, electrical conductivity, bare soil, rock, gravel, litter, and the total canopy cover as the independent variables. Following systematic-random method, samples were collected from the roadsides in proper distances based on a 40-meter transect, each containing 5 plots of 1×1 m2 soil samples for recording the parameters. After producing related maps in the geographical information system, the topographic and climatic parameters were extracted for each site. The soil parameters were determined in the soil lab. Data was analyzed using t-test, cluster analysis, and discriminant analysis to determine the effective environmental factors in the distribution of species by means of SPSS16 and PCORD4. The results indicated that factors such as elevation, rainfall, temperature, and bare soil in the first place, and potassium, organic matter, and lime in the second place, and the geographical directions, the percentage of rock and gravels, slope, phosphorus, the percentage of litters, clay, and sand, electrical conductivity, and pH were amongst the environmental factors affecting the distribution of A.austriaca.

This study was conducted on an area of about 3000 hectares in the northern slopes of the Gareen Mountain in the Northeast of Delfan County. Initially, the plant species observed in the region were collected during the growing season and the families, genera, and species of each were determined on the basis of the common plant taxonomy methods using different published flora and other identification resources. After that, the medicinal species and their used organs were identified. On the basis of the IUCN and Red data book of Iran, the conservational classes of each species were analyzed. The results indicated that the most important family forms with respect to the number of species are Poaceae with 24 species (15.78%), Asteraceae and Lamiaceae each of them with 23 species (15.13%), Brassicaceae with 20 species (13.16%), Fabaceae with 13 species (8.55%), and Apiaceae with 6 species (3.95%). The life form comprised: hemichryptophytes with 40.79%, Therophytes with 39.47%, Geophytes with 7.24%, Phanerophytes with 5.92%, Chamaephytes with 4.61%, and Cryptophytes 1.97%. The results of the geographical distribution of the plants in the region illustrated that the majority of the species (54.61%) belong to Irano-Touranian region. Out of the 152 identified plant species in this region, 75 species are medicinal and belong to 25 families, the most important of which are: Asteraceae with 16 species, Lamiaceae with 10 species, Fabaceae with 7 species, Poaceae with 6 species, and Apiaceae and Brassicaceae each with 5 species. Additionally, with the analysis of rare and endangered species, four conservational categories were identified. These included: LR or Low Risk (13 species), DD or Data Deficient (2 species), Vu or Vulnerable (1 species), and En or Endangered status (1 species).

Aluminum is the most important factor in limiting plant growth in acid soils. Attention to its toxicity and impact on reducing the efficiency of agricultural products is important. Due to its large amount of protein, soybean is considered as a significant source of food. Researchers are looking for ways to increase the resistance of different plant species against the growing concentrations of heavy metals. According to previous research, adding GA to the cultivation medium reduces the toxic effects of heavy metals. In the present study, the effects of aluminum chloride (AlCl3) stress in (0, 50, 100, 150, and 200 µmolar) concentrations and their interaction effect with gibberellics (GA3) at 0 and 50 µmolar concentrations on soybean (Glycine max (L.) Merr.) was explored during 25 days in a hydroponically cultivated environment and the activity of some of the antioxidant enzymes was analyzed. The results showed that, in the presence of GA, the growth inhibitor effects were reduced due to the presence of aluminum. Aluminum decreased the activity of antioxidant enzymes in the plants. GA increased the activity of catalase (CAT), superoxide dismutase (SOD), guaiacol peroxidase (GPX), and ascorbate peroxidase (APX) enzymes. The findings of this study illustrated that the use of GA in different aluminum treatments removed many of the toxic effects of aluminum in soybean plants.

Algae are highly taken into consideration because of their nutritional value and different applications. Nowadays, Algae are also considered as a source for generating energy. Light intensity, carbon dioxide, and the amount of nitrate are important restrictive factors in microalgae growth. Today, efficient photobioreactors are used for increasing the mass of micro-algae. However, one of the limiting factors in the cultivation of micro-algae is the biomass movement and the appropriate application of nutrients. In this research, the tubular photobioreactor designed in Islamic Azad University, Varamin branch, is evaluated. For so doing, by fixing some of the factors affecting the growth such as temperature and pH, the impact of different amounts of sodium nitrate, light, and carbon dioxide on microalgae growth in tubular photobioreactor was explored. A factorial experiment with three replications was carried out with different amount of NaNo3 (0.75, 15, and 3mM), CO2 (0.2, 0.35, and 0.5Lit /S) and light intensity (150, 200, and 250 µ.mol.photon/m2.s). The results showed that the growth of microalgae significantly increased by increasing CO2 and NaNO3 quantities (at p

This study was carried out to investigate the allelopathic effects of Eucalyptus camaldulensis on germination and early seedling growth of Festuca arundinacea under laboratory condition in order to determine the effect of pretreatments with gibberellic and salicylic acids on decreasing the destructive effects of allelopathic compounds. The chemical stimulators used in this study included: three levels of gibberellic acid (125, 250, and 500 ppm), three levels of salicylic acid (100, 200, and 300 mg/L) and 5 levels of allelopathic compounds of Eucalyptus camaldulensis (0, 25, 50, 75, and 100 %). The experiment was carried out in a factorial completely randomized design with four replications. The obtained data was analyzed using MSTAT-C software and the comparison of means was performed by Duncan test. The results of variance analysis and comparison of means indicated that Eucalyptus camaldulensis extract had inhibitive effect on germination and the early seedling growth of Festuca arundinacea. Early seedling growth of Festuca arundinacea was increased by the pretreatment of seeds in chemical stimulators. The highest effect on growth parameters belonged to gibberellic acid. The interaction effects of allelopathic levels and pretreatment with chemical stimulators were significance on the germination percentage and speed, root, shoot and plant length, and the seed vigor index.

In an attempt to study the effect of different amounts of zeolite and nitrogen on the agronomic traits of sunflower at different planting dates, a factorial experiment with three replications was carried out in a randomized complete-block design in Qazvin Agricultural Research Station in 2011. The experiment factors included: three planting dates (D1: 5 May, D2: 20 May, and D3: 4 June, 2011), three levels of nitrogen (N1: 50 kg/ha, N2: 75 kg/ha, and N3: 100 kg/ha), and two levels of zeolite (Z1: 0 t/ha and Z2: 10 t/ha). Farrokh cultivar was planted in this design. The analyzed traits in the experiment included the economic yield of the seed, the biological yield, oil yield, and the harvest index. The results indicated that the highest seed yield (3188 kg/ha) belonged to the first planting date with 100 kg/ha nitrogen and 10 t/ha zeolite and the lowest seed yield (740 kg/ha) related to the third planting date with 50 kg/ha nitrogen in the absence of zeolite. The highest harvest index (22/96 %) was obtained from the first planting date.

Glossy buckthorn (Frangula alnus), one of endangered medicinal plants, is native to the northern parts of Iran. The present study was carried out in an attempt to investigate and eliminate the physical and physiological dormancy in glossy buckthorn seeds. First, seed viability was analyzed by means of triphenyl tetrazolium chloride test. Then, the permeability and the presence of resistant tissues in the seed crust were analyzed. The mechanical and chemical scarification treatments, respectively with sand paper, knife, and concentrated sulfuric acid (for 2, 4, 8, 20, and 30 minutes), were used to break the physical dormancy of the seeds. For breaking deep physiological dormancy, different concentrations (125, 250, and 500 mg/l) of gibberellic acid and potassium nitrate (100, 200, and 400 mg/l) along with the selected scarification treatments (sharp knife, sand paper, and sulfuric acid) were applied. To determine the chilling requirements, the seeds were treated for 75, 81, 86, 96, and 101 days at 5 ◦C in humid conditions and were then planted. The results of the tetrazolium test confirmed the viability of a high percentage of the seeds. Furthermore, the microscopic analyses illustrated the presence of sclereid layers in the seed crust. The mechanical scarification (with sand paper and knife) and sulfuric acid (30 minutes) treatments significantly increased the permeability of the seed crust. Analyzing the interaction effect of seed crust scarification and chemical treatment for breaking deep physiological dormancy confirmed the significant effect of the scarification treatment with sand paper and knife. Furthermore, the gibberellic acid treatment at 500 mg/l concentration had the greatest impact on breaking the deep physiological dormancy. Analyzing the impact of stratification time on seed germination revealed that the time required for the stratification was more than 100 days.

In order to determine the most appropriate amount of exposure and irrigation for the breeding of wild pistachio (Pistacia atlantica zohary) seed plants in the nursery, the effect of three light treatments (100, 50, and 20%) with four replications (0, two, five, and ten days irrigation) on seed plants was explored in the first year of planting, in a split-plot design in which light comprised the main plot and the irrigation treatments formed the sub-plots. The results obtained at the end of a growing season indicated that the impact of different light treatments was significant for the seed germination (at 5% level), the height and diameter growth traits, and the number of seedling, subsidiary branches, and leaves (scattered at 1% level). The effect of different irrigation treatments on germination traits, subsidiary branches, leaves, the collar diameter (at 1% level), and the growth height (at 5% level) was significant. Furthermore, the interaction effect of light and irrigation was significant for the buds, subsidiary branches, and diameter and height growth yields (at 1% level) as well as the number of leaves (at 5% level). The maximum number of buds, leaves, subsidiary branches, and diameter and height growth belonged to 100% light and two days irrigation treatments. The study was carried out on wild pistachio seed plants during the first year of growth. To monitor the changes in the results, the study should continue until the seedlings are planted in the field.