جستجوی مقالات مرتبط با کلیدواژه « frequency » در نشریات گروه « زیست شناسی »

Identifying and introducing the plants of a region is particularly and locally important, which includes the possibility of accessing specific plant species in a certain place and time, determining the potential and vegetative capabilities of the region, the possibility of increasing the density of the species of the region, the possibility of obtaining a new plant species or species, and identifying the destructive factors of the region’s plants. The most obvious classification to explain and describe the structure of plants is to specify the life form of each plant species in each different plant community. The purpose of this research is to investigate the flora, life form, geographical distribution and some characteristics of plants in plant communities. in order to analyze the vegetation status at the central Alborz protected area in Alborz province. In this research, 101 plots were collected and a total of 152 plant species were identified. The identified species belong to 103 genera from 30 families. Asteraceae family with 16 genera and 21 species includes the largest existing taxon in the study area, followed by Poaceae and Fabaceae families with 14 and 12 genera and 18 and 17 species, respectively. The genera Salvia with 8 species and Astragalus with 7 species had the highest species diversity among the identified genera. The dominant vegetative form among the identified species was herbaceous, and tree and shrub elements had the least identified form. According to the Raunkiaer system, hemicryptophyte plants with 51.3% (79 species), therophyte plants with 29% (44 species), cryptophyte plants with 9.9%, chamaephyte plants with 6.6%, and phanaerophyte plants with 2.6% were the most abundant biological forms in this range, respectively. Also, the highest abundance of plant species according to the vegetation area is Irano-Touranian (81 species) and Irano-Touranian/ Hyrcanian (33 species). In general, it can be concluded from this study that the plant community in this area is heterogeneous because all the identified species were in presence code class I with an abundance percentage of 0 to 20%. Also, considering that the study area has a relatively high flora, it can be used to evaluate the current situation and predict the future situation of the region.

In this study, we investigated the effects of sediment grain size and seasonal change on the structure of macrobenthic communities in the south and southeastern shorelines of the Caspian Sea for one year using a hand corer. Sediment sampling was performed at four stations (Sari, Sisangan, Khajeh Nafs-Ashuradeh, and Bandar-e-Turkmen wharf) with different substrates. Results of PERMANOVA analysis showed a significant interaction effect between the season and the sampling station. The dominant species composition varied in each station at different seasons. Stenogammarus sp. and A. improvisus and P. eichwaldiana contributed to 100% dissimilarity between Bandar-e-Turkmen and Farahabad shorelines in summer, winter, and spring. In all seasons, Stenogammarus sp. was dominantly present in most sampling replications with a uniform frequency at the Sari shoreline. C. albidus and C. littoralis species were dominant in Khajeh Nafs-Ashuradeh and Sisangan stations during four seasons, respectively. Based on dbRDA plots, the sediment organic matter and electrical conductivity in summer; salinity, pH, and silt percentage in autumn; sediment organic matter and pH in winter; and organic matter and percentage of clay in spring had a substantial role in the distribution of macrobenthos and their frequency differences.

Alibilagh region, situated in the western side of Tandoureh National Park, is one of the impressive views in Dargaz town. In the point of view of distribution of lichens, the site is valuable because of the existence of hills, rocky highlands, old trees and broken trunks. However, the investigation of Alibolagh’s lichens is restricted to 18 species. The present research was done with the goals of the identification of more corticolous lichens and the investigation of distribution of the lichens on the bark of trunks and twigs and also finding the probable relation between the heights of the place of vegetation from the soil surface. Laboratory identifications were done on the base of standard macro-microscopy methods and the current chemical tests. The statistical analysis was done by using SPSS. 17 species identified included four new reports Lecanora albellula, Parmelia sulcata, Phaeophyscia cilita and Physcia caesia for Rzavi Khorasan province. The statistical analysis showed that Teloschistaceae and Physciaceae have the most frequency on the trunks and twigs. Also there is no meaningful relation between the height of the establishment of the thalli on the substrate and the species.

In order to investigate morphological traits of hoary cress populations, seeds of 40 populations were collected from different parts of Iran in 2013 and were sown in pots at the same condition. At the end of growth season, fifteen morphological traits were measured. Germination rate and germination percentage were also measured in laboratory. Unweighted pair-group method of arithmetic averages (UPGMA) was performed to determine the individual relationship among populations of hoary cress. Five groups were classified based on the cluster analysis of populations of hoary cress which were mainly in accordance with geographic origins. Populations belonging to the northern latitudes had lower growth due to the decline in average daily cumulative annual radiation and air temperature with increasing latitude. These variations among populations may affect their responsee to specific herbicides. Factor analysis based on PCA revealed that three factors comprise almost 88.97% of total variations that the proportion of the first, second and third components were 67.39%,12.97% and 8.60%, respectively. Fresh and dry above ground and below ground weight, total fresh and dry weight and leaf length possessed the highest positive correlation with the first factor. Leaf width, stem height, silicle width, germination rate and germination percentage possessed the positive correlation with the second factor. Dry weight of aboveground / belowground ratio and number of stem (negative) possessed the highest correlation with the third factor.

It is clear that DNA concentration and biological detection devices have many applications in the fields of genetics and biotechnology. For this goal, some similar devices have been designed working with the laser light which the disadvantages of them are high prices and the use of significant amounts of sample volume. But this designed device which works with LED light has very cheap manufacturing cost. The amounts of DNA used in this device are very low, about a few micro-liters and measurement of small, fast and portable it is also the advantages of these devices. The Data recorded as voltage versus time and the Fourier transform the frequency domain. From the frequency curve, by using the Byrlambrt it is possible to obtain the relative concentrations of DNA, viruses and assays measuring DNA damage and many other applications. By use of this device, the concentration of DNA colored with three different pigments was measured.

This study was done on artificial reefs in Khuzestan coastal waters in Bahrakan region from 2004 to 2006. Visual stationary census of fishes was done from four reef areas and also one area as control site. In general 15 families of fishes were observed. Sparidae with 3 species were the most diverse family. Serranidae (85%) was the most abundant family during the study period. Some species such as Epinephelus coioides، Neopomacentrue Sindensis، Scolopsis sp. and Diplodus sargus were frequently observed around the artificial reefs. The number of species (58%) and frequency (49%) of economic fishes in the mixed structure sites were more than other reef structure and showed increasing trend but no significant difference were observed (p>0. 05). The percentage of species number between stations and season had no significant difference (p>0. 05) but the relative frequency of species had significant difference between season (p>0. 05).