فصلنامه گیاه و زیست بوم
پیاپی 35 (تابستان 1392)

Dead trees are considered as valuable nutritional resources in forests. By being a part of food cycles, providing nutritional materials, and keeping moisture, they prepare a desirable environment for seed germination and seedling growth. This study was carried out in Chelir district in Kheiroud forest — one of the four districts under the administration of the Department of the Natural Resources of the University of Tehran — for investigating the effect of dead trees on forest soil. To explore and compare tN, tC, pH, and C/N ratios at two different layers, i.e. the humus and the mineral (in 10 cm depth below humus) layers, samples were gathered in 12 replications from dead trees (with 4 decay degree) and the forest soil (without dead trees) as the witness group. The aforementioned factors were measured and their C/N ratio was estimated under the laboratory condition. The results of the T-test indicated that the tN of the humus layer in dead trees was significantly different from that of the witness group at P<0.05 and the tC, pH, and C/N of the humus layer at P<0.01. There was also a significant difference between tN, tC, and C/N of the mineral layer at P<0.01, but no significant difference was discerned in the pH of these layers. In addition, a review of the paired-group test showed that there was a significant difference between dead tree and forest treatments regarding tC. However, there was no significant difference regarding tN between the two treatments.

Today, heavy metal pollution of the biosphere has created environmental problems. Phytoremediation refers to the technique of using plants to remove pollution from the environment and to transfer them harmlessly, which becomes possible with the accumulation of heavy metals in various plant tissues and organs.In this study, 45 three-year old seedlings of Pinus sylvestris were put under the same condition at the end of March 2011, in Karaj. Using lead nitrate salt and water, different concentrations of (i.e. zero (control), 800, and 1600 mg/Kg) soluble were prepared and evenly added, in two occasions, to the soil of the seedlings at the end of June. The extracts obtained from root, stem, and leaf organs as well as the soil posts at the end of November were measured using the ICP device. Data obtained from a completely randomized design with 15 replications were analyzed using one-way ANOVA. The results indicated that P.sylvestris is a suitable species for lead phytoremediation. The accumulation of lead in root and shoot was more at the concentration of 800 ppm, whereas the highest amount of lead accumulation belonged to root and leave at the concentration of 1600 ppm. The comparison of different soil horizons demonstrated that the lead element was mostly accumulated in the surface horizon.

The foundation of pastureland management is based on the pastoralist life style. Using the science of rangeland management without a deep understanding of the traditional nomadic and rural life results in range management methods with a pseudo-scientific appearance. BoyerAhmad, as the biggest tribe in kohgiluyeh-va-Boyerahmad, settles in all of the geographical regions of the province during different seasons of the year. For investigating the ecological viewpoint of the people of Boyerahmad tribes with respect to the plant species used by their livestock, a floristic list of the plants of the area under study was developed, on the basis of which a questionnaire was designed regarding the plant species used by the livestock and was distributed among the Boyerahmad tribes. Cocran method was applied to determine the sample size. The reliability and validity of the questionnaire were measured using Cronbach’s alpha and the contact method, respectively. In the next phase, to validate the accuracy of the ecological viewpoints of Boyerahmad tribes, data obtained from the questionnaire were analyzed scientifically using two-way ANOVA (at 95% confidence interval) in a completely randomized design. Generally speaking, the results indicated that even though people’s viewpoint did not exactly match with that of administer, it was relatively similar to it. The fact that the major species identified by people were also similar to those used by the livestock in the experiment indicated that although people of Boyerahmad tribes did not theoretically deal with ecology, they scientifically and practically understand it. Hence, their viewpoints, which are formed over a long time, can be applied as a practical model.

To select the best seeds in wheat cluster (Triticum aestivum L. var. PBW-343), the amount of magnesium and potassium in different parts of the grain clusters were measured. The spikelets of the grain cluster were divided into basal, central, and apical parts and then the seeds of the spikelets were divided into basal (bold) and apical (small) parts. The changes in the amount of magnesium and potassium during the fourteenth and the twenty-eighth days as well as the maturity period were measured. Magnesium and potassium concentrations were at the lowest level during the fourteenth day. The highest amount of magnesium and potassium reservations in the cluster was measured during the maturity period. The amount of magnesium during the experiment was higher in the basal seeds of the central spikelets of the cluster in comparison to the seeds of the other parts. The results indicated that since there was no significant difference between the basal seeds of the central and the basal spikelets, they can be placed in one group. Similarly, the amount of potassium was higher in the basal seeds of the central spikelets of the cluster in comparison to the seeds of the other parts and given that there was no significant difference between the basal seeds of the central and basal spikelets in this regard, they can be placed in one group. The results of this experiment revealed that a wider range of crops can be used for corrective works in comparison to the work of other researchers.

Artemisia annua belongs to the Asteraceae family and is a medicinal annual herb that contains an anti-malaria compound called Artemisinin. In the present study, the variation of Artemisinin content was investigated in seven populations of A.annua collected from different regions in the north of Iran. The leaves of different populations were shade dried and then extracts were obtained from 1g of each leave sample. Artemisinin content in extracts was measured using HPLC-UV and the standard sample. The analysis of the amount of Artemisinin content obtained from different populations indicated that the highest and lowest amounts respectively belonged to the populations collected from Noshahr with 0/195% of dried leaf and Havigh with 0/053%. The results demonstrated a relatively low variation in the amount of Artemisinin content in populations of A.annua. The amount of Artemisinin content measured in this study is significant in comparison to the samples obtained from the other parts of the world.

Each of the rangeland species has certain production during the months of grazing and different years. In addition, the grazing livestock consumes certain amounts of forage during each period of the grazing season and different years which varies depending on the conditions and different races. Rangeland and livestock management would not be feasible without understanding the production characteristics of plants and the amount of forage intake during the grazing period. In an attempt to investigate the vegetative and productive characteristics and the consumption rate of Ziziphora clinopodioides forage by the livestock at different stages of phenology, the present experiment was carried out during four years in Urmia-Garebagh rangelands. With the beginning of the grazing season and the entering of livestock into the rangeland, the remaining forage from the graze was harvested, at one-month intervals, until the livestock left the rangeland. The consumption rate was determined by subtracting the amounts of the harvested forage from the fenced plot forage. To explore the effect of study years as well as the harvest months on the production and consumption of the species under analysis, the obtained data were analyzed. The results of ANOVA combined variance analysis indicated that there was a significant difference between the months under analysis and that the highest amount of production and consumption occurred in the fourth year. However, the consumption rate of forage in second month was the highest throughout the grazing season. Generally speaking, it can be claimed that the temperature and rainfall are two significant factors in the amount of production and consumptions of this species.

Soybean is one of the oil seeds whose cultivation is important for preventing the import of oil and replacing meat protein with it. Given that the soybean cultivated in Iran is usually Fe-deficient due to the calcareous soil used for the cultivation and considering the role of Fe in soybean, the present experiment evaluated the effect of different rate and sources of Fe-fertilizer on soybean yield. A randomized complete block design with 4 replication and 5 treatments (0, 2, and 5 kg Fe-sulfate per 1000 liter and 5 and 10 kg/ha Fe-Sequestrin) was selected. After cultivating and farming, and for reducing the peripheral effects, soybeans were harvested from the center of each plot and their yield and yield components were determined. The obtained data were then analyzed. The results indicated that the application of 5 and 10 kg Fe-Sequestrin per hectare with the mean yield of 1845 and 2845 kg/ha significantly increased the yield (at P<0.05) in comparison to its non-application condition in the control group with the mean yield of 1542 kg/ha. The thousand-seed weight in 10 kg/ha Fe-Sequestrine and Fe-Sulfate foliar application (5 per 1000) demonstrated a significant increase.

One of the significant factors in seed germination is the altitude of seed source from the sea level which may significantly affect plant size or growth due to the differences in the environmental factors such as humidity, temperature, the intensity and quality of light, day length, and soil chemicals. This experiment was conducted to evaluate the effect of seed source (from the sea level) and salinity stress on Fortuynia bungei Boiss germination. An experiment was carried out in three replications, following a factorial, completely randomized design. The factors included: (1) seed source at two levels (Siyahkooh-Yazd, Ravar-Kerman) and (2) salinity stress at six levels (0, 25, 50, 75, 100, and 125 mM NaCl). The results indicated that germination percentage and rate, seed vigor, and stem length in both habitats were significantly reduced (p<0.01) with an increase in the amount of salinity. However, the amount of the reduction of these attributes varied depending on the seed source. In addition, the percentage and rate of germination were significantly different (p<0.01) in two habitats and the seeds obtained from Siyahkooh demonstrated a better performance.

Verticillium wilt is one of the most important vascular diseases of olive. For this reason, investigating different aspects of this disease such as distribution, biology, pathogenicity, and disease management have always been considered significant. In an attempt to investigate host-pathogen interaction, the present experiment was carried out to study the histopathology of olive (cultivar Zard) inoculated by Verticillium dahliae. Root-dipping method for 30 minutes was used for the inoculation of the seedlings by spore suspension with concentration 109 spore/ml. Four to twelve weeks after inoculation, with the occurrence of wilt symptoms, transversal sections were prepared from various parts of the stem and root. Then, very thin transversal sections were prepared and after different stages of staining, microscopic slides were prepared. The results of the microscopic investigations indicated that the causal agent of Verticillium wilt has caused disorders in the physiology through spreading into vessels, obstruction of xylem vessels, and their destruction. The casual agent also resulted in disorder in the flowing of vascular sap and caused shoot wilt. The results indicated that the seedlings obstructed the vessels and prevented the spread of pathogen with producing tylose. The pathogenicity and defensive mechanisms associated with host-pathogen interaction and their roles in susceptibility rate of the olive to Verticillium wilt have been discussed in this research.