نشریه روابط خاک و گیاه
پیاپی 21 (بهار 1394)

Rhizosphere is a small zone with different biological and chemical properties from bulk soil. In this research، kinetics of zinc (Zn) release was compared in wheat (Rowshan Back Cross) rhizosphere and bulk soil in 10 calcareous soils by using rhizobox at greenhouse conditions. The rhizosphere and bulk soil samples were extracted with DTPA-TEA for 1 to 504 h at 25±1 0C. In addition، available Zn was evaluated by chemical extractions (DTPA-TEA، AB-DTPA and Mehlich 3). Results showed that the amount of available Zn، cumulative released Zn and rate of Zn release in the rhizosphere soils were significantly (p<0. 05) higher than the bulk soils. Power equation was the best descriptive of Zn release in rhizosphere and bulk soils. In addition، parabolic diffusion، first order and simple Elovich equations could be used to describe kinetics of Zn release. The obtained correlation coefficients between wheat responses and characteristics of Zn release showed that higher significant correlations in the rhizosphere soils were found as compared to the bulk soils.

Iran is one of the countries that is located in world''s arid and semi-arid regions and is constantly subjected to water shortage. One of the effective methods for reducing water consumption and increasing production in agricultural sector is greenhouse culture. By using proper irrigation management in greenhouse، we are able to utilize water، soil and fertilizer to produce high yield and quality products. In the present study، a split-plots experiment was conducted as randomized complete blocks design with three replications، during 2010 and 2011، in Agricultural and Natural Resources Research Center، Isfahan، Iran. Irrigation frequency at 3 levels (once each 1، 2 and 3 days) was considered as the main plot and the subplots were irrigation depth at three levels (75% ETc، 100% ETc and 125% ETc). Results revealed that effect of depth of irrigation was significant on yield، number of fruits per plant and mean weight of a tomato، but the effect on water use efficiency (WUE) was not significant. The highest yield (6. 77 kg/m2) and the lowest yield (4. 52 kg/m2) were observed in 125% ETc and 75% ETc treatments، respectively. The amount of consumed water in these treatments was 0. 3 and 0. 19 m3/m2، respectively. WUE in the treatments ranged from 25 to 28 kg/m3. Lack of significant effect of various irrigation water depths on WUE، though the effect was significant on yield، indicates that the crops have been under-irrigated. It was found that the abovementioned traits were not significantly affected by applying irrigation frequency treatments. Soil analysis at the end of the experiment showed that salinity in the soil surface of the pots was more than lower depths، which is due to surface water evaporation and acculation of the salts. Salinity in F1 treatment was very high (8 dS/m)، though the pots were irrigated once a day. This shows that everyday irrigation، but with low depth of irrigation، has not been able to leach salts to deeper depths. Based on the obtained results، water shortage، practical simplicity and labor saving، the 125% ETc treatment with 3-day irrigation frequency are recomanded.

Stevia)Stevia rebaudiana Bertoni) leaves are strong natural sweeteners، with no calories، which can be used as a substitute for sugar in food and beverage industries. When the day length is less than 13 hours، stevia goes to flowering stage and the content of sweetening substances decreases. In low temperatures، this plant goes to dormancy phase. It would be possible to produce stevia leaves all year round in the greenhouse by adjusting the photoperiod and temperature. This study was conducted as a factorial experiment، based on completely randomized design with two factors. Treatments were 3 photoperiods (short winter days، interrupting nights for 1. 5 hours at midnight، and long days) and 3 levels of vermicompost (0، 10 and 20% v/v) as substrate. According to the results، flowering was observed only in the control plants kept in winter short days. The highest leaf yield was produced in 20% vermicompost treatment with interrupting nights. In the same treatment، the amount of chlorophyll a، total chlorophyll and carotenoid content was increased، while chlorophyll b content was decreased. Therefore، in this experiment، by increasing the day length or interrupting the nights، stevia plants were kept in the growing phase، and adding vermicompost at 20% level to the growth medium improved plant growth and increased the leaf yield.

Increasing of water consumption and demand for irrigation water in agriculture has led to an increase in reuse of treated، or even raw، municipal and industrial wastewater in many countries. Heavy metals (HMs) in these unconventional waters are one of the sources of pollution of water، soil and plant. HM toxicity in plants may eventually cause disturbances in plant growth. Accumulation of HMs in plants has health problems for human beings and animals which consume these plants. In this research، uptake of cadmium (Cd) by three vegetables (cress (Lepidium sativum L.)، lettuce (Lactuca sativa L.) and tomato (Solanum lycopersicum L.) from a contaminated soil was studied. The experimental design was completely randomized. For each plant، two soil treatments (control soil and contaminated soil by 100 mg/L Cd) and five replications were considered. After planting، growing and harvesting، and preparation of the samples، Cd uptake in roots and shoots was measured. Results showed that mean Cd uptake by all three plants was significantly different from the control treatment. Maximum uptake of Cd belonged to tomato، whereas lettuce had the lowest uptake. Transfer coefficient of Cd from soil into cress، lettuce and tomato was 1. 3، 0. 33 and 0. 65، respectively. Although transfer coefficient of Cd to lettuce is lower than the other two plants، but consumption of lettuce per person is much greater than cress. Hence، irrigation management of polluted wastewater is important.

Mining، industrial and agricultural activities can result in considerable soil pollution by heavy metals (HMs). One of the methods to control this pollution is application of adsorbent minerals. The purpose of this study was to compare the effects of adsorbent minerals (bentonite، zeolite and sepiolite) on transfer of some heavy metals (i. e.، Pb، Zn and Cd) from soil to tissues of sunflower (Heliantus annuus L.). Treatments included: Non-polluted soil، HM-polluted soil، polluted soil + bentonite، polluted soil + zeolite، and polluted soil + sepiolite. Sunflower seeds were planted in different pots containing the above treated soils. After 70 days of growth، plants were harvested and HMs content was measured. Results revealed that the uptake of HMs from non-polluted soil was lower than that of other treatments. In the polluted soil + sepiolite treatment، the added sepiolite increased plant Cd and Zn uptake by 0. 37 and 7. 17 mg/kg، respectively. However، the differences in HMs uptake were not significant for other treatments. Zeolite addition decreased plant uptake of Zn and Cd by about 12 and 0. 21 mg/kg، respectively، while bentonite addition reduced Pb uptake by about 3. 05 mg/kg، without any significant difference for the other treatments. Zn uptake was higher by about 12. 2 mg/kg in plant shoots as compared to plant roots. On the contrary، the roots took up higher amounts of Cd and Pb، as compared to the shoots. Despite high concentration of the HMs in the polluted soils، considerable tendency of sunflower for uptake، and a high adsorption capacity of the applied minerals، the HMs uptake by sunflower and surface adsorption by the minerals were very low، probably due to HMs precipitation in the soil.

This study was conducted to assess the effects of two species of arbuscular mycorrhiza fungi (Glomus mosseae and G. intraradices) on growth of young plantlets of two olive cultivars (Koroneiki and Valanolia). Recently rooted cuttings were inoculated with the mycorrhiza، planted in pots containing sterile soil and located in the greenhouse. Eighteen months following inoculation، some morphological، physical and biochemical traits were studied. The results showed that inoculated plantlets with both mycorrhizal fungi species had taller height، more shoots، thicker stems، longer internodes and more leaves as compared to control plantlets. They also had more fresh and dry weight of stem، but showed lower amount of fresh and dry weight of roots. Mycorrhiza inoculation significantly increased total chlorophyll، carotenoids and phenol content of leaf، but there were no significant difference in the amount of iron and phosphorus in the leaf. In all the studied traits، there wasn''t any difference between the two mycorrhiza species. Percent of root colonization in both mycorrhiza fungi was found to be higher than control.

Soilless culture in greenhouse is being developed in Iran، as in many countries of the world. This study was conducted to evaluate the possibility of applying sawdust as well as the effect of adding bentonite and pumice on vegetative growth of bell pepper cv. Inspratian. The experiment was conducted as a completely randomized blocks design with 8 treatments and 4 replications، in greenhouse of College of Agriculture، Isfahan University of Technology. The planting media consisted of different v/v ratios [100% sawdust، sawdust+ pumice at the ratios of 5، 10 and 15%، sawdust+ bentonite at the ratios of 5، 10 and 15%، and a common planting medium (85% peat+ 15% perlite) as control]. Results showed that after peat، in most cases، plants grown in sawdust+ pumice showed better vegetative growth as compared to those of pure sawdust or sawdust+ bentonite. For example، the highest fresh and dry weight of shoots and dry weight of roots were in 85% sawdust+15% pumice treatment. The results also showed that after peat، the highest chlorophyll content was determined in 95% sawdust+ 5% pumice and 90% sawdust+ 10% bentonite media. The lowest chlorophyll content was related to 100% sawdust medium. After peat treatment، the earliest flowering، fruiting and color establishment was observed in 85% sawdust+ 15% pumice، which was not significantly different from 95% sawdust+ 5% and 90% sawdust+ 10% pumice.

Plant growth promoting rhizobacteria are known as an alternative to chemical fertilizers، which are able to reduce the harmful effects of non-biological stresses such as salinity and increase soil fertility and crop production. This study was conducted to investigate the effect of inoculation of Pseudomonas fluorescens strain FY32 on a number of morphological characters in canola cultivars under salt stress. Thereby، a split split-plot design with three replications was applied in hydroponic cultivation system. Six bacterial inoculated (Pseudomonas flourescens FY32) and non-inoculated canola cultivars were subjected to sodium chloride salt stress at three levels (0، 150 and 300 mM). Based on the ANOVA results، inoculation effects under different salinity levels on canola cultivars، compared to non-inoculated treatments، were statistically significant on plant fresh weight، dry weight of leaf، stem and total plant، leaf area and root length. Also، three-way interaction effects of salinity، bacteria and cultivar on plant height and root volume were significant (P<0. 01). Sodium، potassium and proline concentration in leaves and roots of inoculated plants had significant difference with non-inoculated plants at different levels of salinity. The highest rate of proline and potassium ion was observed in canola cultivars inoculated with Pseudomonas fluorescens under both salinity levels. It can be concluded that inoculation of canola plants with Pseudomonas flourescense (containing ACC- deaminase gene) could improve their growth and development in case of salinity stress.

In order to investigate the effect of combination of chemical and biological fertilizers on dry matter، uptake and efficiency of nitrogen (N)، phosphorus (P) and zinc (Zn) by fenugreek (Trigonella foenum- graecum)، an experiment was conducted as randomized complete blocks design with three replications in the Research Greenhouse of Shahrekord University. Eight fertilizer treatments consisted of control (no fertilizer)، urea fertilizer (UF)، UF+ zinc sulfate (ZS)، UF+ Azotobacter (Az)، UF+ mycorrhiza (My)، UF+ ZS+ Az، UF+ ZS+ My and UF+ ZS+ Az+ My. Results indicated that there was significant difference (P≤ 0. 05) among different fertilizer treatments for agronomic efficiency of N، P and Zn. The highest agronomic efficiency of N، P and Zn (60، 96 and 198 g/g، respectively) was achieved in UF+ZS+Az treatment. The highest P-uptake efficiency (18. 7 %) was observed in UF+My treatment and it had significant (P≤ 0. 05) difference with other treatments، except UF+ZS treatment. The highest Zn physiologic efficiency was obtained in UF+ZS، which had no significant difference with UF+ ZS+ Az and UF+ ZS+ Az+ My. Maximum dry matter (292 g/m2) was produced in UF+ ZS+ Az treatment. In general، application of biofertilizers، especially Azotobacter، integrated with urea and zinc sulfate not only is effective in increasing dry matter، but also can increase productivity of fenugreek by increasing chemical fertilizers’ efficiency in greenhouse culture.

Nowadays، cultivation of medicinal plants in the greenhouse and use of appropriate strategies to improve the response to environmental stresses on one hand، and growth of medicinal compounds on the other hand، has been under consideration. In this research، effect of exogenous putrescine on resistance of Datura stramonium plant to salinity stress was evaluated through studying growth parameters، amount of chlorophyll a، b، soluble carbohydrates and alkaloid compounds in roots and shoots of this plant. Seeds of Datura plant were grown in a mixture of soil and sand. After 35 days، the plants were transferred to Hoagland solution. Different concentrations of NaCl (0، 20، 40 and 60 mM) and putrescine (0. 01 and 0. 05 mM) were added to Hoagland solution، depending on the treatment type، in the form of 10 independent and combined treatments، based on randomized complete blocks design. After 15 days، shoots and roots of treated plants were evaluated. Results showed that with increasing salt concentration، the shoot length، fresh and dry weight of roots and chlorophyll a، b content were decreased. On the other hand، dry and fresh weight of shoots، chlorophyll a، b، soluble carbohydrates and alkaloid compounds were significantly increased with putrescine application in the treatments which contained salt. This research confirmed the positive role of exogenous putrescine in improving the growth، increased chlorophyll pigments، soluble carbohydrates and alkaloid compounds of Datura medicinal plant in saline conditions.

In order to evaluate the effects of salt stress and putrescine on some morphological and biochemical traits and pigment content of pot marigold plant، an experiment was conducted under greenhouse conditions based on completely randomized design، using four levels of sodium chloride (1، 3، 6 and 9 dS/m) and three levels of putrescine (0، 1 and 2 mM). Sodium chloride was applied on the soil، while putrescine solution was sprayed on the leaves. Results showed that salt stress reduced all growth parameters and pigment content significantly، while increased the amount of reduced sugars in leaves and roots. Application of putrescine had significant effect on all biochemical parameters and pigment content; but had no effect on the number and diameter of flowers. Spraying of 2 mM putrescine، under salt stress level of 9 dS/m، increased fresh flower weight، shoot dry weight، chlorophyll a، total chlorophyll، leaf cartenoides and reduced sugars by 29، 27، 35، 32، 17 and 15 percent، respectively، compared to control treatment. Based on the results of this experiment، it was concluded that application of putrescine improves the growth، biochemical traits and pigment content of marigold plant under salt stress conditions.

To study the activity of some antioxidant enzymes and accumulation of compatible osmolytes affected by different concentrations of chromium (Cr+3) (0، 5، 10، 15 and 20 mg/kg soil) combined with different levels of manure (0، 10 and 20 ton/ha) in basil (O. basilicum L.)، a factorial experiment، based on completely randomized design with four replications، was carried out at Research Greenhouse of Zabol University in 2012. Results of this study indicated that increasing the level of Cr+3 from 0 to 20 mg/kg soil، when 20 ton/ha manure was applied، decreased the activity of catalase (CAT)، ascorbate peroxidase (APX) and glutathione peroxidase (GPX) enzymes decreased from 0. 008، 0. 537 and 0. 081 to 0. 006، 0. 305 and 0. 071 µmol H2O2/mg protein، respectively. This may be caused by the improvement in physiological activities of the plant in the presence of organic compounds. It seems that application of different amounts of manure led to an increase in leaf proline and carbohydrates content، via availability of macro- and- micro nutrients، especially nitrogen، even when different levels of Cr3+ heavy metal existed in the growth medium. The obtained correlation coefficients indicated a significant positive relationship between most physiological traits، and the highest correlation coefficient (0. 84) was found between proline and soluble carbohydrates. It appears that organic compounds، such as manure، have considerable potential to reduce the harmful effects of Cr3+ heavy metal and improve physiological indices of basil.

In order to study of the effect of combined biologic and priming on growth characteristics and phosphorus (P) and potassium (K) concentrations in Nigella sativa L.، an experiment was carried out in the greenhouse of Agriculture Faculty، University of Birjand with factorial CRD statistical design in 2011. Factors were 1- Bacteria treatments a (Pseudomonas sp 168)، b (Pseudomonas sp 187)، c (compose of Pseudomonas sp 168 and Pseudomonas sp 187) and d (without Bacteria treatment)، 2- priming with KH2PO4 (50 mM concentration) and without priming. Soil sample was taken from Bidokht village and sieved through a 4-mm and transported to pots of 3 kg (pH=7. 8 and ECe= 1 dS/m). Pots were irrigated based on field capacity moisture. Results showed that biologic treatments caused، significant increase in shoot dry weight and both P and K concentrations of shoot. Priming had excessive effect of biologic fertilizer on those of two elements concentrations in shoot of Nigella sativa L. in sixth week and shoot dry weight as well. Highest shoot concentration of K and P was observed in (Pseudomonas sp 168+priming) and (Pseudomonas sp 168+187+priming) respectively. Therefore، combine application of priming and biologic seed treatments can be useful method for increasing of P and K concentration in medicinal plants.

Water stress is a global crisis and is considered a serious threat for agriculture. Superabsorbent polymers، through improving soil physical conditions، prevent moisture stress in arid and semi-arid areas. To evaluate the effects of a natural superabsorbent (bentonite) and a synthetic superabsorbent (A200) on growth of lettuce، a factorial experiment in a completely randomized design with four replications was conducted. The amount of each superabsorbent at 3 levels (0، 0. 15 and 0. 3% w/w) and 2 levels of water stress (60 and 100% of field capacity) were tested. The results showed that in 100% of field capacity treatment، leaf relative water content، chlorophyll index and stomatal conductance were more than 60% of field capacity treatment. Electrolyte leakage، vitamin C، total soluble solids and chlorophyll b were higher in 60% of field capacity treatment. Application of 0. 3% bentonite decreased electrolyte leakage، vitamin C and soluble solids by 74، 19 and 31 percent، respectively، and increased relative water content، chlorophyll index، stomatal conductance and total chlorophyll content by 3، 2، 22 and 8 percent، respectively، relative to the control. While، application of 0. 3% of superabsorbent A200 decreased electrolyte leakage، vitamin C and soluble solids by 28، 18 and 37 percent، respectively، and increased relative water content، chlorophyll index، stomatal conductance and total chlorophyll content by 6، 32، 25 and 42 percent، respectively، as compared to the control treatment. These results indicated that bentonite can reduce the negative impacts of drought stress as much as artificial superabsorbent.

In order to investigate the effects of mycorrhizal symbiosis on some soil hydraulic properties and nutrients uptake by spring barley، a greenhouse experiment was conducted based on a completely randomized blocks design with four replications، using two mycorrhizl fungi including Glomus intraradices (GI) and Glomus etunicatum (GE) and non-mycorrhizal (control) treatments، in an alkaline coarse-textured soil. Results showed that GE and GI significantly increased (P< 0. 01) field capacity (FC) water content by 24. 7 and 12. 6%، permanent wilting point (PWP) water content by 20. 1 and 11. 1%، available water capacity (AWC) by 27. 1 and 13. 3%، micropores by 14. 1 and 5%، mesopores by 27. 8 and 20. 8% and decreased macropores by 17. 3 and 9. 5% and saturated hydraulic conductivity by 88. 2 and 68. 8% relative to the control، respectively. Also، GE and GI fungi significantly increased (P< 0. 01) uptake of phosphorus in barely seeds by 44. 1 and 20. 3% and in stem by 181 and 50. 6% and potassium in seeds by 290. 8 and 167. 9%، respectively. It is concluded that mycorrhizal symbiosis، as a biological and sustainable method، improved hydraulic and chemical quality of the alkaline coarse-textured soil.