جستجوی مقالات مرتبط با کلیدواژه « تنش خشکی » در نشریات گروه « جنگلداری »

Wild Pistachio (Pistacia atlantica var. mutica Rech. f.) is an important tree species in the forests of Iran that has faced many challenges in its natural restoration. This study investigated the interaction effects of Funneliformis mosseae, MycoRoot biofertilizer, and Pseudomonas fluorescens on Pistacia atlantica seedlings under two water treatments: 100% field capacity as a non-stress treatment and 50% field capacity as a drought stress treatment. Decreased soil moisture reduced the growth (root collar diameter, shoot and root fresh weight, shoot dry weight) of Pistacia atlantica seedlings. The interaction of mycorrhizal fungi and phosphate-solubilizing bacteria on seedling growth, as well as chlorophyll, carotenoid, and leaf proline content, was significant at the 5% level. The highest stem height was observed in the combined treatment of Funneliformis mosseae and Pseudomonas fluorescens (24.54 cm) under non-stress conditions, while the shortest belonged to the control treatment (8.8 cm) under drought stress conditions. Proline content in seedlings inoculated with Funneliformis mosseae in the presence of Pseudomonas fluorescens was higher (8.87 μmol/g) than other treatments, and this treatment was more effective in reducing drought stress symptoms than other treatments. Under non-stress conditions, the presence of Pseudomonas fluorescens alone did not play a significant role in improving seedling growth, but its positive effects on growth appeared when interacting with mycorrhizal fungi and during drought. Although this research observed that mycorrhizal and bacterial seedlings had better growth than control seedlings and that microorganisms had the same effect as irrigation on some growth characteristics, it is necessary to conduct similar additional experiments in nurseries and natural habitats on P. atlantica seedlings using different irrigation levels to confirm these results.

Recognition of the available moisture content and its changes in the habitat can be a dynamic ecological indicator. The aim of this study was evaluating the soil moisture storage volume with the distribution model of the Turc in the oak forest located in the Meleh-Siah Ilam.

The research was conducted from October 2013 to September 2015. Monthly rainfall and temperature data, monthly solar radiation, water holding capacity map and DEM of the region were used as input data.  To validate the soil moisture data from the water balance model, 33 humidity sensors 110 cm were installed in different locations of the habitat. Then, soil moisture was measured with TDR moisture meter in monthly time step. To evaluate the model, the mean absolute error (MAE) and mean error deviation (MBE) statistics were used and the results were analyzed.

The results showed that the accuracy of the model in estimating soil moisture in wet months is low and is overestimated, and Suitable in a dry month. Other results showed that in the first and second year of the study, precipitation was 680 mm and 383 mm, respectively and the share of evapotranspiration from precipitation is 56% and 77%, respectively. Also, in the study site the available water capacity of the soil is 125 mm, which the maximum in March and the downtrend continued until September and reached a minimum of zero. Other results indicate that the vegetation in the study area was drought tolerant in the first year (normal in terms of rainfall), in two months of August and September and increased in the second year (drought), in the months of July, August, September and October. The results also showed that 73% of the dried oak stands correspond to the areas that Soil moisture reached below the wilting point (15%) in September.

Therefore, reducing soil moisture in droughts has played an important role in the drying of oak bases and effect of the intensity and persistence of drought periods on the drying of oak trees needs further investigation.

Paulownia fortunei (Seem.) Hemsl is one of the fastest growing tree species of Paulownia genus, which is a suitable option for wood farming and agroforestry in north of Iran. Drought is one of the most important factors limiting the growth and survival of this species, which can cause severe damage to its performance in the nursery and planting area. This study intends while to investigate the growth and survival response of this species seedling to changes in soil moisture, to consider the possibility of using foliar spray of salicylic acid and ascorbic acid to increase drought resistance of P. fortunei in seedling stage.

In this study, 225 seedlings were selected, and were transplanted in 3 liter pots filled with suitable soil, and were examined after establishment under 3 levels of soil moisture (90%, 60% and 30% of field capacity) and 5 levels of foliar spray (control, 1 and 10 mM ascorbic acid, 100 and 150 mg.l-1 salicylic acid), using two-factor factorial experiment with 3 replications for 4 month. Survival of seedlings and growth characteristics, including stem height, collar root diameter, chlorophyll, and specific area of leaves, and also length and number of main and lateral roots for each seedling were measured at the end of the study. Collected data were analyzed using two-way analysis of variance, Duncan multiple comparison of means, and simple linear regression method at 95% confidence level.

The results showed that in all foliar spraying treatments, a decreasing and significant linear relationship was observed between soil moisture and seedling survival. So that at 30% moisture level (severe drought) salicylic acid foliar spray treatment increased the survival of seedlings by 7 times. Also, lessening of soil moisture from 90% to 60% caused a significant reduction in growth traits of stems and leaves of seedlings, The results showed that the effects of foliar spray on seedling root properties are strongly affected by soil moisture, so that at 90% moisture level, foliar spray reduces root area and number of first order lateral roots, nevertheless, at 30% moisture level, seedlings were treated with foliar spray of salicylic acid at a concentration of 150 mg.l-1 and ascorbic acid at a concentration of 10 mM, showed the highest mean values of root area, total root length and number of first order lateral roots.

P. fortunei seedlings are very sensitive to changes in soil moisture. Also, the use of foliar spray, especially in the treatment of salicylic acid with a concentration of 150 mg.l-1 improves the survival and growth characteristics of this species seedling under water scarcity conditions.

In this study, Populous deltoides seedlings were exposed to drought stress for four months. Cuttings of poplar clones were collected from the terminal shoot in the Chamestan Research Station, Mazandaran Province, Iran. Cuttings were planted in plastic pots under the control environment of Ghaemshahr Horticultural Research Station in June. After three growing months, seedlings of uniform height were chosen. Then potted seedlings included treatment 20 under the control environment in five clone levels (P.d.63/10, P.d.63/51, P.d.73/51, P.d.69/55, P.d.77/51) and four drought stress levels (four periods of irrigation, 3, 6, 9, 12 days) with three replicates were investigated using a factorial experiment under randomized complete block design. Results showed that water stress affected and reduced growth, survival, seedling growth (plant height, diameter, leaf area), biomass, net photosynthesis, and transpiration. However, P.d.69/55 clone seedling growth was appropriate in addition to optimal survival. However, comparisons amongst clones showed that the maximum rate of survival was achieved in 63/10 clone, but growth was less than that of 69/55 and 63/51 clones. Avoidance mechanisms in different clones caused the resistance of seedlings to drought. But among clones, P.d.69/55, P.d.63/51, P.d. 63/10 were relatively tolerant of drought. This study showed that the 9-day irrigation interval was the most suitable treatment for P. deltoids clones, also 77/51 clone was drought-susceptible with a 12-day irrigation interval. These results suggest that a selection of these clone seedlings for drought tolerance when water is limited with sandy loam soil in order to seedling production in nursery and wood cultivation conditions in the north of Iran. Thus particularly applies for 69/55 clone, which is also used the 9-day irrigation interval.

This study was conducted to investigate effect of different irrigation and shade treatments on arial and root biomass, leaf area and viability of Caucasian hackberry Seedlings in Shorab nursery, Khoramabad, Lorestan province, Iran. Firstly, 30 Celtis caucasica trees was selected in around of Shorab village forests and then seeds were collected from different directions of trees. Seeds were planted on plots in November and budded in April next year and afterwards plots were irrigated daily until starting treatments. After that, four irrigation treatments (daily, once in every two, three and four days) and three shade treatments (full light, semi and full shade) with three replications and 30 pots per replicate (overally, 1080 expirmental units) were applied on them during five months period. Then, leaf length and width, leaf area, viability, arial and root biomass were measured and analysed in split test model by multi way ANOVA. Results showed interations of irrigation and shade have significant effects on biomass, leaf length and leaf width (p<0.05). Irrigation have significant effect on viability of seedlings in full light, but this effect is not significant in semi shade and full shade. Also, by reducing light, viability of seedlings is decreased. Regarding to results, could be inferred that growth and viability of seedlings are better in full light compared to other treatments which this shows Celtis caucasica is extremlly light demand species and high levels of light are important for its growth.

This study was conducted to investigate the different irrigation and shade treatments on seedling production of Celtis caucasica in Shorab nursery, Khoramabad city, Iran. For this purpose, 30 Celtis caucasica trees were selected in around of Shorab village forests and then seeds were collected from four directions of trees. After investigating the seeds quality, seeds were planted on pots in Novamber and budded in April next year and afterwards pots were irrigated daily until starting treatments. Then, four irrigation treatments (control, once in every two, three and four days) and three shade treatments (full light, semi shade and full shade) with three replicates and 30 pots per replicate (totally, 1080 experimental units) were applied for five months. Based on results, seed survival of this species was 84 percent. Shade, irrigation and interactions effects of these treatments have significant effects on seedling height, root length and collar diameter of Celtis caucasica after the end of one growing season and their interactions are significant as well (p

Physiological response of different species to drought stress can help to recognize the effective mechanisms in drought stress and choose the best species for planting in dry lands of Iran. This study investigated the physiological mechanisms of Robinia pseudoacacia L. seedlings in draught conditions. An experiment was carried out in a completely randomized block with one treatment (irrigation) at five levels (1, 3, 5, 7, and 9 -day intervals) with five replicates in one-year-old seedlings of Robinia pseudoacacia L. The effects of drought stress, chlorophyll fluorescence parameters (Fv/Fm, Fm & F0), pigments concentrate (total chlorophyle, chlorophyle ‘a’ and ‘b’), and proline content of leaves were measured with sampling from leaves of mentioned treatments. Drought stress caused a significant reduction in maximum photochemical efficiency of photosystem II (Fv/Fm), maximum fluorescence (Fm) and minimum fluorescence (F0) (p

The response of plants to water available for strategy codification of water resources and irrigation is very important. In this study, evapotranspiration, crop coefficient, yield and water use efficiency in two species of Eucalyptus (Eucalyptus flocktoniae (Maiden) Maiden, E. leucoxylon F. Muell.) through lysimeter experiments were determinated under different soil moisture levels (100%, 70% and 40% of field capacity). The research was designed as a factorial experiment on a completely randomized design with three replications in Yazd climatic conditions. The results showed that with increasing soil moisture in both species, evapotranspiration increased, so that there were significant differences between the different levels of soil moisture treatments (p

Drought stress is one of the most important factors reducing the plant growth and yield. Due to the complexity of factors affecting the drought tolerance or resistance in plants and access to relevant mechanisms, researchers are faced with challenges. Studying the root development can be considered as an important indicator in this regard. On the basis of this study how the development of two species of Eucalyptus roots under drought conditions and at different depths in lysimetric conditions were taken into account. Drought stress was applied in three irrigation levels, including: 100% field capacity (control), 70% field capacity (moderate stress) and 40% field capacity (sever stress) in three replicates. Effects of drought stress on root weight development were studied in six deeps, including: 0-20, 20-40, 40-60, 60-80, 80-100 and 100-120 cm. The results showed that increasing drought stress reduced the roots development in both species significantly. E. micortheca produced more roots than E. sargentii in varying levels of drought stress. The roots of E. microtheca had more deep penetration than E. sargentii in all drought stress treatments. Due to the reasons mentioned, E. microtheca is more resistant to drought stress than E. sargentii.

Willows due to the rapid growth rate, low nutrient requirements, resistance to many pollutants, and environmental stresses are ideal candidates for developing the landscapes and reducing the environmental degradation. The purpose of this study was to determine the response of Salix alba seedling to water deficit conditions. This experiment was set up as complete randomized design with five irrigation periods (2, 4, 6, 8 and 10 days) in three replicates (each replicate containes five pots) for four months. Results indicated a high survival rate for Salix seedlings, whereas under extremely drought stress (10-day irrigation) it was always greater than 73%. Height and collar diameter growth, above-ground and under-ground biomass, number of leaves and root volume decreased with increasing the irrigation period but no changes occurred in leaf area, specific leaf area, root length and root:shoot ratio. Regarding to the economy of water resources, 6- and 8-day irrigation periods, due to high survival (100%) and favorable growth of seedlings, can be considered for raising salix alba seedlings in this region and/or in climatic regions similar to the research site.

Trees are an important source of wild germplasm for sustainable forestry. Wild pear germplasm (Pyrus boisseriana) was collected from a forest ecosystem and resistance potential to drought stress was surveyed in a greenhouse. In six-month seedlings, signs of leaf rolling appeared after 18 days without water (drought simulation). Gas exchange parameters, such as net photosynthesis, stomatal conductance, and transpiration, decreased with increasing drought over the time. Decreasing net photosynthesis caused negative effects on growth and leaf expansion and caused the seedlings to drop their leaves. In contrast, however, there was no effect of drought on root and shoot biomass, compared to control plants. Mean xylem water potential was -0.66 and -2.22 for control and stressed seedlings respectively. The Xylem water potential led to decreasing of RWC (%) and finally electrolyte leakage increased by 45%. We did not observe any negative effect of drought on chlorophylls a and b, but the carotenoid content increased. We found no increase in the proline content of the stressed plants. Finally, wild pear are able to tolerate drought for about 18 days, by decreasing some physiological parameters (gas exchange, xylem water potential, and relative water content), and by increasing some antioxidant systems like carotenoid . Additional research, but with field populations, and with studies of gene and protein expression, are necessary before wild pear can be used as a source of germplasm.

This study was conducted to study of morpho-physiological responses of Robinia pseudoacacia L. seedlings under drought stress by irrigation period at 4 levels (intervals of 4, 8, 12 and 16 days). The experiment was performed as completely randomized design in a greenhouse environment. Results indicated that all studied traits were affected by water stress, except water use efficiency (WUE). The greatest value of most traits was observed in 4-day irrigation. Seedlings treated by 12- day irrigation had the largest root length. The biggest root dry weight belonged to seedlings irrigated in intervals of 4 and 8 days. Irrigation periods of 8 and 16 days remained the highest water use efficiently (WUE) and electronic leakage (EL) for seedlings, respectively. Generally, seedlings with 4-day irrigation period indicated the best response to drought stress. Of course, 8-day irrigation period showed a relatively well response to water stress especially in terms of survival and growth parameters whereas it can be considered as an appropriate and economic irrigation. Similar investigations can be performed in forest nurseries where climate is adapted for R. pseudoacacia growing.

Walnut has a high economic value because of the good quality of wood and fruits. So this species has been harvested since many years ago till today and has been introduced as a protected species. The performance of Juglans regia increases in wet years، but reduces in dry years، hence paying attention to physiological and morphological parameters in order to identify the genomic regions related to drought resistant is important for breeding programs in walnut. In this study، genetic diversity by SSR markers has been evaluated. Also، the association of used primers with physiological and morphological traits were analyzed before and after drought stress. 10 SSR primer pairs generated 53 alleles in 62 walnut seedlings. All locies showed significant difference (p≤0. 01) from the Hardy-Weinberg. Dendrogram of the Neighbour-Joining method showed that 62 walnut seedlings divided to four main groups. Analyses of population structure by Structure 2. 3. 1 software identified two sub populations (k=2). Based on association mapping analysis، by using MLM (mixed liner model) method، transpiration، conductance and photosynthesis have been controlled by WGA9 and WGA69 locies in normal condition. In stress condition WGA1 loci showed relationship with CO2 concentration that was covered %75 of variations of this trait. The results of this study can be used in breeding programs of Juglans regia to identify drought resistant varieties.

Drought stress is the main factor affecting on plant growth in dry and sub-dry regions and had the most importance than other abiotic stresses at seedling establishment. So، today''s، the great amounts of biological researches are about drought stresses. In this study، the effect of drought stresses (100، 75، 50 and 25% field capacity) on seedling survival، growth (height، basal diameter، leaf area، root length، root volume and root length/ height) and physiological activities (photosynthesis، transpiration، stomatal conduction، leaf surface temperature and gas exchange) of P. atlantica seedlings were investigated in greenhouse condition. The results showed that drought stress had significant effects on morphological and physiological characteristics of Pistacia atlantica seedlings. So that، drought decreased survival، height growth، basal diameter، leaf surface، photosynthesis، transpiration، stomatal conduction and gas exchange of P. atlantica seedlings. Drought stress hadn’t significant effects on root length، root/height and leaf surface temperature of seedlings.

Drought stress is one of the most important environmental factors limiting plant growth and development so finding the new techniques to evaluate the drought tolerance in plants, would be valuable. The purpose of this study was the application of chlorophyll fluorescence technique as a reliable method for rapid assessment of drought stress in hackberry seedlings (Celtis caucasica L.). An experiment was designed as completely randomized block with one factor (irrigation), at five levels (1, 3, 5, 7 and 9 days) with five replicates. Chlorophyll fluorescence parameters (Fv/Fm, Fm & F0), and the proline content of leaves in one-year-old seedlings of Celtis caucasica were measured. The results indicated that maximum fluorescence (Fm) had a significant reduction in the 9 days treatment. Also maximum photochemical efficiency of photosystem II (Fv/Fm) showed a significant downward trend since the 5 days treatment, while the minimum fluorescence (F0) was not significantly affected by drought. Increasing the intensity of drought was resulted in proline accumulation in leaves from 1.7 (µmol/gfw) in the 1 day treatment to 72.95 in the 9 days treatment. In afforestations and urban green spaces, measurement of chlorophyll fluorescence is a reliable method for identification of well-adapted species to environmental stress.

Climate change is defined as long term and irreversible changes in the climatic behavior of a region. Many studies have been conducted in different regions of the world on climate change. The results of these studies show considerable changes in climatic factors especially in precipitation and temperature. In this research، the trend of changes in annual and seasonal rainfall and temperature in 24 synoptic stations over a 50-year data period (1956-2005) was investigated in Iran. The Mann- Kendall test and linear regression technique were used to analyze the trend of changes in climatic factors. The results showed both increasing and decreasing trends in annual rainfall at various regions of Iran. Annual rainfall in northern slopes of Alborz and western slopes of the Zagros Mountain as well as in eastern and southeast parts of Iran had a decreasing trend while in the central of Iran the trend of changes was increasing. In southern region of Iran the rainfall had an increasing trend. The results also showed that temperature in most of the studied stations over the considered period was increasing. The highest and lowest changes in temperature were seen in the mean temperature of summer and winter، respectively. Ahwaz and Khorramabad stations had a decreasing trend and over all seasons would go toward more cooling. The temperature trend in Oromiye was decreasing in autumn and summer while Shahrekord and Bandar abbas had the same trend in summer and winter.

Christ thorn (Ziziphus spina-christi) is a forest tree species that grows wild in the arid and semiarid areas of Asia and Africa where rural populations intensively use its fruits، leaves، bark، and wood. The death of a large number of seedlings with root rot symptoms has been observed since 2008 in Kazerunand Lamer nurseries in Fars Provience of Iran. Necrosis of internal skin and crown were also detected in the infected plants. Some isolates of Fusarium oxysporum were recovered through plating the infected tissues on the PDA medium which were found to be pathogenic on the Christ thorn seedlings through Kock’s postulate. Since Christ thornis cultivated in the arid areas and damping-off of the seedlings is a common disease in these areas، the present study was conducted to study the co-effects of water stress and the pathogen on the plant seedlings. The effects of F. oxysporum infection and the levels of irrigation frequencies (every 2، 3، 5 and 8 days) was studied through using a factorial experiment that was arranged in a randomized complete block design with four replications. Some morpho-physiological features of the seedlings such as height، leaf number، leaf height، and width were measured. The results of this experiment indicated that the growth response of Christ thorn to drought stress depends on the levels of irrigation applied. Compared to the unstressed control، the interaction of F. oxysporum and water stress reduced the seedling height and leaf numbers up to more than 50%.

Eucalyptus (E.camaldulensis Dehnh) is one of the major plant species in Iran covering vast areas of plantations. This is a fast-growing species with high tolerance to harsh environmental conditions. Nevertheless the water deficiency in soil can be effective on the quality and quantity of plant growth. To study the effect of soil drought stress on water relationship in Eucalyptus (E.camaldulensis Dehnh), an experiment was carried out using weight and drainage Lysimeters in natural condition. The trials were implemented in Shahid Sadoghi control desert research station in Yazd for three years. The experiment was done with three treatments, 100% (control), 70% (medium stress) and 40% (high stress) field capacity (FC) in three replicates as complete randomize design. The results showed that the plant physiological behaviors including water potential, relative water content (RWC) and soluble sugar in leaves were affected by water availability for plant. Increasing the amount of soil moisture was not significantly effective on soluble sugar levels in roots and leaves proline levels (P-value> 0.05). By increasing the amount of soil moisture, the relative water content (P-value <0.001) increased. Increasing the amount of soil moisture reduced the water potential (P-value <0.001) and the amount of soluble sugars in leaves (P-value <0.001). These results showed that the osmotic adjustment through increases of soluble sugars in leaves, decreased the leaf water potential and increased drought resistance in this plant, although this ability is low. With these conditions, this plant could not be considered as drought-resistant plant.

In order to investigate the impact of drought stress, a trail was carried out in a factorial experiment in the base of randomized complete design on traits such as pigments and photosynthesis in five Eucalyptus species (E. globulus, E. largiflorens, E. robusta, E. sideroxylon, E. tereticornis). Drought treatments contained polyethylene glycol solution with five levels (0, -1, -3, -6, -12 bar). In this investigation characteristics such as: chlorophyll and carotenoids, photosynthesis rate, leaf water potential and stomata number were studied. Most of the traits were significantly decreased under water stress condition. The highest amount of chlorophyll, carotenoids, photosynthesis and leaf water potential were related to control plants of different species. Results showed that these traits caused lower reduce under drought stress condition in E. largiflorens. Whereas these traits have positive correlation with resistance to drought, consequently E. largiflorens were most resistance species to drought stress. E. sideroxylon and E. tereticornis with high reduce in traits were sensitive species to drought under drought stress condition. E. globulus and E. robusta were relative high resistance species to drought stress.

The effect of arbuscular mycorrhizae fungi (AMF) on morphological and physiological characteristics of Pistacia khinjuk under drought stress were studied in Ilam, Iran. First, the mycorrhizae fungi associated with Pistacia khinjuk trees were isolated and identified and then their effects on morphological and physiological characteristics of Pistacia khinjuk under greenhouse condition were assayed. It was found that survival of seedling was not affected by mycorrhizae and irrigation, but other physiological and morphological characteristics were affected, separately. Therefore, mycorrhizae as well as irrigation increased root collar diameter, seedling height, terminal growth, leaf number, refresh weight of shoot and root, root volume, leaf area, photosynthesis and transpiration. In contrast to irrigation, AMF didn’t effect on root length, root dry weight, leaf surface temperature, stomatal conductance and photosynthesis. So, we can propose that in dry and sub dry region, for best success in afforestation, seedling is better to be associated with AMF.