فصلنامه گیاه و زیست بوم
پیاپی 36 (پاییز 1392)

The protected region of Western Dena is located in the southern part of Zagros mountain range in Kohgilouyeh and Boyer Ahmad province. Western Dena is one of the richest areas of Iran in terms of biodiversity. The purpose of this study is to investigate the changes in the biodiversity, arrangement, and formation of plants at the heights of Dena mountain range. Samples were collected following a random-systematic data collection procedure. Thirty plots were identified using the least level of species method. The coverage percentages of each species as well as the dominant ones were determined in each sample plot. Information regarding the height, direction, the percentage of the slope was recorded in each sample plot. The floristic investigation of 30 sample plots indicated that 212 sample plants belonging to 24 plant families exist in Western Dena region, out of which 41 are endemic, 12 are rare, 1 is vulnerable, and 7 belong to one-genus species. The results revealed that the heighest range for the growth of Phanrophytes, Comfites, and Geophites was 3150-2242, 3350-4050, and 2514-2926 m respectively. The Hemicrytophytes and Trophites grow in all of the heights. The most influential factor in the degree of plant coverage in the region was the height. The slope percentage was in the second place regarding the significance. There are four arrangements of trees, bushes, pulvinate plants, and herbaceous plants in the region. In addition, there are 117 species of Hemicryptophytic vegetation (55%), 44 Therophytic vegetation forms (21%), 17 Chamephytic vegetation forms (8%), 17 Geophytic vegetation forms (8%), and 17 vegetation species of Phanerophytes.

The present experiment was carried out to evaluate the tolerance of Sedlitzia rosmarinus against salinity and drought stresses that resulted from polyethylene glycol (PEG) and NaCl during germination and the early seedling stages of plant development. This study was conducted in the research laboratory of the Faculty of Agriculture in Islamic Azad University, Pishva-Varamin in the summer of 2010. The seeds under study were collected by the assistance of the research centre of Kashan during 2010. The pace and percentage of germination as well as the length of rootlet were measured as the significant parameters. The study was conducted following a completely randomized factorial design including drought treatment with polyethylene glycol 6000 (PEG6000) at five levels and salinity treatment at six levels with three replications. Data obtained from the last days of the experiment were analyzed. The results indicated that increasing the salinity and drought stresses generally reduces the growth indices. It was observed that the length of root decreases parallel with an increase in drought stress up to the third treatment. After that, the length of rootlet increases with an increase in drought stress. Similar results were also obtained from the salinity stress. However, the degree of the changes was not as significant as those of drought stress. The same condition also exists for the percent and pace of germination. Hence, it can be claimed that the interaction effect of salinity and drought significantly affected the length of rootlet, plumule, and germination at different levels. In addition, an increase in salinity and drought stresses explicitly reduces the page of germination and the length of rootlet and plumule.

Priming exercise is significant, especially in dry areas where seed germination encounters problems due to the due to lack of soil moisture, because of its role in increasing seed germination speed. The impact of osmopriming on germination of lentil (ILL6199) seeds was analyzed in the laboratory of the Faculty of Agriculture in Islamic Azad University, Qaemshahr Branch, in 2010, following a completely randomized factorial design experiment with three replications. The factors which were analyzed included: polyethylene glycol (PEG) with concentrations of 5 and 10%, potassium nitrate (KNO3) with concentrations of 1 and 2%, Coloryd potasyom (KCl) with concentrations of 2 and 4%, and the duration of 4, 8 and 12 hours. The results indicated that the maximum length of root and shoot under 5% PEG was obtained during 4 hours, but the highest ratio of root to shoot length R/S and dry weight (R/S) obtained from priming with PEG and KNO3 concentrations of 5, 10, and 2% during the 12- and 8-hour period. The highest germination rate was obtained from 5% PEG priming.

The identification of rangeland species and getting more information about their ecological traits substantially help range management. The present study aims to investigate the impact of cutting on the ecological traits of juncus maritimus. The experiment was carried out during a 9-week period, following a completely randomized factorial design with four treatments and 10 replications. All of the aboveground organs in the plant under the study were cut 6 cm above pots’ soil surface in four cutting treatments, i.e. frequent cutting (once a week), moderate cutting (once every 2 weeks), limited cutting (once every 4 weeks), and control (cutting just at end of the experiment). The results indicated that repeating the cutting treatment reduced total and root dry matter weights of the plant. Changes in dry matter weight resulted in some changes in plant dry mater dedication. Accordingly, the least amount of dry matter dedication was obtained from the roots of cut plants compared to the control ones. The findings also indicated that the cutting stress resulting from the cuts in different treatments had a significant effect on the amount of total dry matter, shoot and roots organs, tillering, and the total rhizome length. These traits in the cutting treatments significantly differed from those of the control group. Generally speaking, the species under study was unable to regenerate its defoliated organs against cutting (i.e. livestock graze).

This study was carried out in an attempt to develop a response curve for Astragalus verus Olivier with respect to some environmental gradients using None Parametric Multiplicative Regression (NPMR) method. The potential distribution maps of the species in Fereydunshahr rangelands of Isfahan province were developed using Logistic Regression (LR) and Ecological-Niche Factor Analysis (ENFA) methods. To construct these two models, thirty one environmental variables (including edaphic, climatic, and physiographic variables) in the studied area were mapped. Then, drawing on these maps and the maps of the environmental variables, NPMR approach was used to provide a response curve for the species. The predictive NPMR models can provide response curves for species against various environmental gradients without any assumed pattern and can determine the ecological amplitude of the species. The results obtained from the maps of the potential habitats (LR and ENFA) and the response curve indicated that the appropriate habitat for Astragalus verus in the region under study was an area with moderate to relatively heavy soil texture (44 to 48 percent clay content), moderate slope (10 to 20 percent), low electrical conductivity (less than 0.3 dS/m), saturated water content between 45 to 47%, and a pH amounting to 7.5. Similar approaches can be used to allocate appropriate areas for the rehabilitation and protection of valuable native plant species.

The present study investigated the potential of carbon sequestration in Pistcia atlantica, Acer monspessulanum, Amygdalus scoparia and Ephedra procera in Bagh-e Shadi Herat in Yazd province. The carbon sequestration in P. atlantica was analyzed in both protected and under-graze areas. For selecting the trees, the diameter classes sampling procedure was applied and the species were classified into four classes based on their diameters. One tree from each diameter class was randomly selected, cut, and different parts of the tree (i.e. root, trunk, branches, and leaves) were separately weighed. To estimate the mean weight of the litter in each plot, a (1 m2) sample plot was randomly chosen and the amount of litter was carefully collected and weighed. The samples were dried, and then the percentage of the organic carbon was determined using the furnace combustion method. By determining the ash weight and having the initial weight as well as the ratio of the organic carbon to the organic material, the degree of carbon sequestration was calculated separately for each plant. The results indicated that the amount of carbon sequestration in Pistacia was 6.232 and 4.461 ton in the protected and under-graze areas respectively but these differences were not significant. Comparing carbon sequestration in different species revealed that Amygdalus and Ephedra respectively contained the highest and the lowest amount of carbon sequestration. To summarize, it can be claimed that the species under study play an important role in carbon sequestration in the forests out of the North of Iran.

One of the major problems in Juniprus excelsa habitats in Iran is the lack of regeneration, which threatens their revival and future. The dispersion of these regenerations is not similar under all of the trees. The soil and its components play a significant role in their formation. Plant roots and microorganisms produce soil enzymes. Their existence in different cycles of soil releases and makes the essential elements for the plants and regenerations available. This experiment was carried out to study and compare the possible role of soil enzymes in rhizosphere of Juniperus tree with and without regeneration in Chaharbagh habitat in Gorgan. Samples were obtained from rhizosphere soil of the trees with and without regeneration. The activity of acid and alkaline phosphatase, dehydrogenase, urease, and the microbial biomass enzymes were measured using reaction with substrate by the means of spectrophotometer. The results indicated that the activity of these enzymes and the microbial biomass were more in the rhizosphere of trees with regeneration compared to those without regeneration. This may be due to the existence of more microorganisms such as mycorrhizal fungi in the root of these trees and better absorption of food substances.

Green algae (Enteromorpha sp.) belongs to the chlorophyta branch and has a parenchymal structure and can be widely found in the sea bed of the Caspian Sea. In this study Enteromorpha sp. algae in the sea bed was collected, separated, and identified. After the treatment, during the stage of measuring photosynthetic pigments, the concentration of the chlorophylls a, b, and total as well as beta carotene was determined. Then, the amounts of lipid peroxidation and the activity of enzymes were calculated. The results of photosynthesis pigment measurement indicated that, at high concentrations of mercury (100 mg l-1), the rate of different types of chlorophyll was not significantly different from the control. However, with an increase in the concentration of mercury, the degree of photosynthesis pigments significantly decreased. The activity of the enzymes was different with respect to the time period and the concentration of the treatment. The activity of all of the enzymes significantly decreases during the treatments with high concentrations of mercury, whereas the activity of different enzymes follows different patterns at lower concentrations. In Ascorbate peroxidase, the activity of enzyme decreased with an increase in the concentration. In 100 and 200 mg l-1 concentrations, enzyme activity significantly increased. Enzyme responses in Peroxidase were different from the other enzymes. The only significant increase in enzyme activity was observed at 100 mg l-1 concentration treatment. Polyphenoloxidase enzyme only had a high activity at 200 mg l-1 concentration treatment. Investigating the degree of lipid peroxidation activity indicated that its amount was more than the control at different treatments. No significant different was found between the concentrations of Malondialdehyde at 3 100, 200, and 300 mg l-1 treatments.

Considering the environmental effects of using pesticides and the gradual decrease in the amount of crops, the potential of allelopathic plant extracts can be used for biological controlling and releasing the allelochemical substances from leaves, seeds, roots, and stems of the living plants or plant substances that are getting decomposed. This study was carried out under the laboratory and greenhouse conditions, in an attempt to investigate the effect of hydro-alcoholic extracts obtained from the roots and shoots of annual wormwood (Artemisia annua L.) medicinal plant on the germination and growth of four types of weeds including Avena fatua L., Chenopodium album L., Setaria viridis L., and Amaranthus retroflexus L. The treatments included the extracts of annual wormwood in six concentrations (0.1, 0.25, 0.5, 1, 2.5 and 5%) and the distilled water as the control. The results indicated that different concentrations of the extracts of annual wormwood significantly decrease the germination percentage as well as the length of radicle and plumule in weed seeds under the laboratory condition. In addition, different concentrations of the extract resulted in a significant decrease in the growth percentage of the seeds, the height, and wet and dry weights of weed bushes under the greenhouse condition. The laboratory results revealed that the seed germination in Avena fatua L., Chenopodium album L., Setaria viridis L., and Amaranthus retroflexus L. stopped using extracts with concentrations of 0.25, 0.5, 0.5, and more than 2.5% respectively. The greenhouse results indicated that the annual wormwood extract with 1% concentration respectively reduces the germination percentage of the seeds of Avena fatua L., Chenopodium album L., Setaria viridis L., and Amaranthus retroflexus L. to 64, 84, 43, and 65% in comparison to the control. It was also found that a 5% concentration of the extract nearly stopped the seed germination in Avena fatua L. and Setaria viridis L. On the basis of the results, it can be claimed that the extracts of the annual wormwood have strong allelopathic effects and inhibit germination and growth of the weeds, a quality which can be applied in producing natural pesticides.