فصلنامه گیاه و زیست بوم
پیاپی 34 (بهار 1392)

One of the problems in most of the Juniprus excelsa habitats is the lack of regeneration which presents itself as a challenge for their revival and future. The dispersion of these regenerations is not similar under all of the trees. The soil and its components also play a significant role in their formation. The plant roots and micro-organisms produce soil enzymes. Hence, their presence in different food cycles of the soil might release the nutritional elements and make them available for plants and their regeneration. The present study was carried out in Chahar-Bagh habitat of Gorgan in an attempt to investigate and compare the possible influence of the soil enzymes and microbial biomass on the rhizosphere of the Juniperus trees with/out regeneration. Samples were collected from the soil around the roots of trees with/out regeneration. After extracting the juice, the activity of the acid and alkaline phosphatase, dehydrogenase, and urease was measured using the substrate and microbial biomass reactions by means of a spectrophotometer. The results indicated that these enzymes and the microbial biomass had more activity in the trees with regeneration in comparison to those without regeneration. This might be due to the existence of more micro-organisms such as mycorrhizal fungi in the root of these trees and the better absorption of food elements and materials.

The limitation of the resources in economy can be considered as one of the main reasons behind the attentions to the productivity in all of the areas of management, particularly that of seed collecting. The purpose of the present research is evaluating the performance of the seed-collecting groups in the jungles of the north of Iran. Data was collected from 89 questionnaires which analyzed the seeds of deciduous and coniferous trees. From among the 9 seed-collecting groups, the highest productivity rates were respectively for Mazandaran Wood and Paper Company, Pylambara nursery, and Katoul Yew Wood Industry Company with 7.5, 6.25, and 5.71 units per labor-hour. From among the remaining groups, Farim nursery had the lowest rate of productivity with 1.76 units per labor-hour. Analyzing the amount of the collected species of seeds indicated that only in Noshahr Contracting Company the productivity of labor force was beyond the standard level and the rest were below the standard. Acer capadosicum collected in Noshahr and Najarpoor Contracting Companies was beyond the standard level. The amount of the collected oak was higher than the standard level in five contracting companies and nurseries including Noshahr, Mazandaran Wood and Paper Company, Katoul New Wood Industry Company, Safrabasteh nursery, and Najarpoor Company. Alder species collected in Farim Wood Company, Katoul New Wood Industry Company, and Neka Wood Company were beyond the standard level. The amount of the collected wild cherry appeared to be above the standard level in Pylambara nursery and Company, Mazandaran Wood and Paper Company, Katoul New Wood Industry Company, and Mazand Flower and Fruit Company. Tilia species were collected at the standard level in Pylambara nursery and Mazandaran Wood and Paper Company. Finally, none of the companies and nurseries had collected fraxinus at the standard level and its amount was below the standard. Some of the main reasons behind the failure in achieving the standard levels in collecting seeds might be non-appropriate human force combination, education, and workers’ age range.

Stipa hohenackeriana Trin. and Rupr. is one of the proper forage plants for supplying the required forage for animals and soil conservation in different rangelands, particularly those in Kordan region. The present study was carried out in Kordan rangelands of Alborz, during five years, in an attempt to analyze the productive features as well as the consumption rate of the forage of Stipa hohenackeriana Trin. and Rupr. Accordingly, during the grazing season and as soon as the livestock entered the rangelands, the amount of the forage remained from livestock graze was harvested at one-month intervals until the livestock left the rangelands. The consumption rate was determined by subtracting the harvested forage from the grazed rangelands and those obtained from the fenced plot. Afterwards, for investigating the effect of the harvest years and month on the production and consumption of the species under analysis in the study area, the obtained amounts were analyzed. Generally speaking, the results indicated that the highest and the least amounts of Stipa hohenackeriana were produced in the fourth and the first years, respectively. A similar result was obtained regarding the consumption rate. In addition, it was found that Stipa hohenackeriana’s growth and forage production periods were in spring. The growth and production rates of this plant were maximal in April and gradually decreased toward July. The forage of this plant was extensively grazed by livestock during May. It appears that by the completion of the stages of growth, the plant turns woody and this reduces the tendency of livestock for eating it. As a result, less amount is consumed by livestock.

Aaran and Bidgol’s Rige-Boland sandy dunes with the surface area of about 168000 hectares are located in most northern part of Isfahan. The most important natural habitats of the study area are Populus euphratica woodlands, the sandy soils containing sulphate compounds, the profile of neogene hills, waterways and seasonal river beds, salty and wet regions, desert playa adjacent to the sandy dunes, destroyed lands, ponds, and the kanat margins. The study area is at least 780 m and at most 1100 m above the sea level. The average annual rainfall is about 120 mm, 52% of which occurs in the winter. The average annual temperature ranges between –13 and +48 0C. In the present field study, all of the existing plants in the habitats were collected and identified during two growth seasons. One hundred and ninety seven plant species were identified in different habitats including: one alga, three gymnosperms, and 190 angyosperms (including 164 species of dicotyledons and 26 species of monocotyledons). The identified plants belonged to 40 families and 139 genera. The plant families which had the highest number of species were Chenopodiaceae (with 32 species), Brassicaceae (with 23 species), Papilionaceae (with 13 species), and Boraginaceae (with 12 species). The important life forms of the area based on Raunkiaer system are as follows: Therophytes (with 108 species, 54.9%), Hemichryptophytes (with 32 species, 16.3%), and Phanerophytes (with 27 species, 13.5%). The analysis of the geographical dispersion of the plants in sandy dunes indicated that the species with Irano–Turanian region’s geographical dispersion had the highest degree of dispersion, i.e. 118 species (60.7 %).

The none-hunting area of Gomishan international wetland is located between 53o 54' 34" of eastern longitude and 37 o 9' 9" of northern latitudes in the north west of Golestan. It covers an area of 14000 hectares and is considered as the wetland ecosystem of the province. The minimum and maximum elevations of the area under study are -16 and 40 m, respectively. The collected samples were identified on the basis of the common plant taxonomies and the application of the indispensable resources and the family, genera, and species of each of them were determined. The names of the taxonomies of the region were provided in alphabetical, family, and the scientific name orders. Generally speaking, 28 families, 77 genera, and 93 plant species were identified, of which the most frequent species belonged to Poaceae (with 18 species), Chenopodiaceae (with 13 species), and Asteraceae (with 11 species). From among different plants in this region, Therophytes has the most frequent life form with 61 species and 65.6%. Investigating the geographical distribution of the species indicated that 34.4% (i.e. 32 species) belong to Irano-Turanian region, 16.1% belong to Irano-Turanian, Mediterranean, and Euro-Siberian regions, and 12.9% were considered as multi-regional.

In an attempt to investigate the effect of different moisture treatments and nitrogen levels on the seed yield of Hashemi Tarom rice (Oryza sativ L.), a field experiment was carried out in 2009 in Neka, Mazandaran. The study was conducted in strip split slots with 4 replications following CRBD design. The main factor, i.e. the moisture treatments including waterlogging I1(control), irrigation disruption at tillering stages I2 (15 days), flowering stage I3 (15 days), and the seed filling stage I4 (15 days), and the peripheral factor, i.e. the four nitrogen levels (0, 50, 100 and 150 kg of nitrogen per hectare) in the form urea, were applied. The analysis of variance indicated that the irrigation and nitrogen fertilizer had a significant effect on the seed yield, fertile florets, floret sterility, and the number of fertile tillers. The results of the Duncan test (at P<0.05) revealed that the waterlogging treatment along with the consumption of 150 kg of nitrogen resulted in the highest increase in the total yield and yield components; hence, were placed in group a. Furthermore, it was found that the interaction effect of irrigation and nitrogen levels was significantly different in all of the traits of the fertile florets, the sterile florets, the panicle length, and the fertile tillers. The results indicated that despite the high degree of water consumption, the waterlogging method appears to be the most efficient method for rice irrigation.

In an attempt to investigate the effect of shading (source limitation) on dry matter remobilization, yield, and yield components of different rice cultivars, a field experiment was carried out in the research farm of the Agricultural Services Centers of Rezvanshahr during 2007-2008. The study followed a factorial, randomize-complex-block design. The variety and treatment factors, which were respectively at two (Hashemi and Hybrid I) and four (control, light shading, moderate shading, and heavy shading) levels, were carried out in three replications. The treatments in the present study began 10 days before anthesis and ended 10 days after it. The analysis of the results indicated that the shading treatments had a significant effect (at P<0.01) on the seed yield, biological yield, harvest index, the panicle length, the number of grains in each panicle, the number of spikelet on the panicle, and 1000-grain weight. The highest and lowest grain yields belonged to the Hybrid I in the control condition with an average of 8962/3 kg/ha and Hashemi in the heavy shading condition with an average of 1503/3 kg/ha, respectively. The heavy shading treatment had the lowest yield in both types of cultivars. The shading treatments had a significant effect (at P<0.01) on the remobilization of stem and leaves’ dry matter. From among the aerial parts of the plant, the stem had the highest share in the remobilization process. Hashemi cultivar had the least amount of dry matter remobilization probably due to its limited sink space and production capacity. Generally speaking, the results revealed that Hashemi cultivar had a more limited sink space in comparison to the Hybrid I.

Canola as one of the significant oil-seed plants in mild climates has the capability to adapt itself to a wide range of climatic conditions. Canola oil has a high nutritional quality due to its unsaturated fatty and cholesterol-free acids. From among different kinds of oil-seed plants, canola has a high degree of variability in its fatty acids. The present study investigated the effect of different concentrations of lead (pbCl2) and zinc (ZnCl2) on some of the growth parameters of brassica napus L. A number of similar seeds were selected for the study. Two ml of zn, pb solutions and distilled water (as check) were added to each plate containing five seeds. The plates were then incubated in darkness at 25. The solutions were arranged everyday and the germination speed was measured after 3 to 4 days. After the germination, the plates were kept under the same condition for 10 to 14 days. Afterwards, the grown seeds were taken out of the plates and their wet weight was measured. The dry weight was counted after 72 hours. After twenty days of cultivation, the seed were treated with different concentrations of pbcl2 (0.50, 2.50, 4.50 and 6.50) and zncl2 (5.0, 10.0, 15.0 and 20.0) for 45 days and then were used for investigating the growth parameters. An increase in the amount of the lead and zinc of the cultivation environment resulted in a decrease in the percent and rate of germination, the wet and dry weights, the root length, and the hipocuticule length in all of the treatments.

The developments in the field of biology as well as the significance of protecting the environment and the high demands for food supplies have led the researchers to consider the application of biological tools in agriculture. The present study investigated the impact of 5 Trichoderma harzianum isolates on the growth of cucumber under greenhouse conditions, using a completely randomized design (CRD) with six replications. Three different concentrations, i.e. 0.5%, 1%, and 1.5% inoculums per pot, were applied. The growth parameters used in the study included: the plant length, stem thickness, and shoot and root fresh/dry weights. The results of Duncan multiple range test (DMRT) indicated that some Trichoderma harzianum isolates had a significant effect on the growth parameters of cucumber. From among the isolates, T1 had the greatest impact on plant-growth with 25.8% increase in shoot’s fresh weight, 22.8% in shoot’s dry weight, 20.4% in root’s fresh weight, 21.5% in root’s dry weight, 18.4% in leaf number, 4.8% in stem diameter, and 22.4% in plant length. In addition, the isolates had the highest growth impact at 1.5% inoculums per pot concentration. The outcome of this study revealed that the aforementioned isolates can be applied as growth stimuli in crop production.