Chemical and physical characteristics of wheat root mucilage influenced by Serendipita indica symbiosis: a comparison among four cultivars.

Although there is evidence to suggest that the endophytic fungus Serendipita indica plays a crucial role in enhancing plant tolerance against biotic/abiotic stressors, less is known about the impacts of this symbiosis association on root mucilage chemical composition and its physical functions. The mucilage of inoculated and non-inoculated seedlings of four wheat cultivars (i.e., Roshan, Ghods, Kavir and Pishtaz) were extracted using an aeroponic method. Total solute concentration (TCm), carbon content (Cmucilage), electrical conductivity (EC), pH, fatty acids, surface tension (σm), and viscosity (ηm) of mucilage were measured. Ghods and Kavir had the highest and lowest root colonization percents, respectively. Saturated fatty acids, including palmitic and stearic acids, were dominant over unsaturated fatty acids in wheat root mucilage. However, their compositions were significantly different among wheat cultivars. S. indica colonization, especially for Ghods, increased the TCm, Cmucilage, and palmitic acid. Moreover, root mucilage of S. indica-inoculated Ghods had lower σm and greater ηm. An increased amount of powerful surfactants like palmitic acid in the mucilage of S. indica inoculated treatments led to lower σm and greater ηm. Such studies provide further support for the idea that plant-released mucilage plays a major role in modifying the physical environment of the rhizosphere. This knowledge toward truly understanding the rhizosphere can be potentially used for improving the rhizosphere soil quality and increasing crop growth and yield.

Oxygen diffusion in biochar-based mixtures as plant growth media: Experimental and modelling.

A large amount of agricultural waste is produced annually. Producing biochar is an excellent solution for waste management, resource recovery, emission reduction, energy production, reduction in transportation and enhancing carbon sequestration. This study was done to investigate the aeration status of biochar-based growth media as compared with the commercial soilless medium of cocopeat-perlite. Biochars from oven-dried residues were produced by slow pyrolysis at 300 (B300) and 500°C (B500) with a rate of 2°C min-1 and using a continuous inflow of nitrogen. Sawdust (Sd), wheat straw (WS), rice hull (Rh), palm bunches (Plm) and sugarcane bagasse (SC), their biochars, vermiculite (V) and zeolite (Z) were used to prepare 13 mixed growth media. Oxygen diffusion coefficient (Dp) of media was measured at six matric potentials (h) of -5, -10, -15, -20, -40 and -60 hPa. Troeh et al. (1982) model was fitted to Dp/D0 versus air-filled porosity (AFP) data. Although AFP was more than 0.1 m3 m-3 for some media, the Dp/D0 was very low. Considering optimum Dp/D0 (i.e. 0.010-0.015) for growth substrates at h = -8 hPa, aeration status of four media (cocopeat-perlite, Rh-SCB300-Z, Sd-SCB300-Z and WSB500-Rh-V) was optimum. Highest Dp/D0 at h = -8 hPa was observed for Rh-SCB300-Z. The AFP at h = -10 hPa was highest for Rh-SCB300-Z, cocopeat-perlite and WSB500-Rh-V. Biochar-based media with good aeration status and water retention can be a suitable substitute for commercial soilless culture in greenhouse production. Overall, WSB500-Rh-V is a suitable substitute for cocopeat-perlite.

Maize water status and physiological traits as affected by root endophytic fungus Piriformospora indica under combined drought and mechanical stresses.

MAIN CONCLUSION: Under combined drought and mechanical stresses, mechanical stress primarily controlled physiological responses of maize. Piriformospora indica mitigated the adverse effects of stresses, and inoculated maize experienced less oxidative damage and had better adaptation to stressful conditions. The objective of this study was to investigate the effect of maize root colonization by an endophytic fungus P. indica on plant water status, physiological traits and root morphology under combined drought and mechanical stresses. Seedlings of inoculated and non-inoculated maize (Zea mays L., cv. single cross 704) were cultivated in growth chambers filled with moistened siliceous sand at a matric suction of 20 hPa. Drought stress was induced using PEG 6000 solution with osmotic potentials of 0, - 0.3 and - 0.5 MPa. Mechanical stress (i.e., penetration resistances of 1.05, 4.23 and 6.34 MPa) was exerted by placing weights on the surface of the sand medium. After 30 days, leaf water potential (LWP) and relative water content (RWC), root and shoot fresh weights, root volume (RV) and diameter (RD), leaf proline content, leaf area (LA) and catalase (CAT) and ascorbate peroxidase (APX) activities were measured. The results show that exposure to individual drought and mechanical stresses led to higher RD and proline content and lower plant biomass, RV and LA. Moreover, increasing drought and mechanical stress severity increased APX activity by about 1.9- and 3.1-fold compared with the control. When plants were exposed to combined stresses, mechanical stress played the dominant role in controlling plant responses. P. indica-inoculated plants are better adapted to individual and combined stresses. The inoculated plants had greater RV, LA, RWC, LWP and proline content under stressful conditions. In comparison with non-inoculated plants, inoculated plants showed lower CAT and APX activities which means that they experienced less oxidative stress induced by stressful conditions.

Erodibility of calcareous soils as influenced by land use and intrinsic soil properties in a semiarid region of central Iran.

The most important properties affecting the soil loss and runoff were investigated, and the effects of land use on the soil properties, together with the erodibility indices in a semiarid zone, central Iran, were evaluated. The locations of 100 positions were acquired by cLHS and 0-5-cm surface soil layer samples were used for laboratory analyses from the Borujen Region, Chaharmahal-Va-Bakhtiari Province, central Iran. To measure in situ runoff and soil erodibility of three different land uses comprising dryland, irrigated farming, and rangeland, a portable rainfall simulator was used. The results showed that the high variations (coefficient of variation, CV) were obtained for electrical conductivity (EC), mean weight diameter (MWD), soil organic carbon (SOC), and soil erodibility indices including runoff volume, soil loss, and sediment concentration (CV ~ 43.6-77.4%). Soil erodibility indices showed positive and significant correlations with bulk density and negative correlations with SOC, MWD, clay content, and soil shear strength in the area under investigation. The values of runoff in the dryland, irrigated farming, and rangeland were found 1.5, 28.9, and 58.7 cm3; soil loss in the dryland, irrigated farming, and rangeland were observed 0.25, 2.96, and 76.8 g; and the amount of sediment concentration in the dryland, irrigated farming, and rangeland were found 0.01, 0.11, and 0.15 g cm-3. It is suggested that further investigations should be carried out on soil erodibility and the potential of sediment yield in various land uses with varying topography and soil properties in semiarid regions of Iran facing the high risk of soil loss.

Effect of pyrolysis temperature on chemical and physical properties of sewage sludge biochar.

The objective of this study was to evaluate the effects of pyrolysis temperatures (300, 400, 500, 600 and 700°C) on properties of biochar produced from an urban sewage sludge. Biochar yield significantly decreased from 72.5% at 300°C to 52.9% at 700°C, whereas an increase in temperature increased the gas yield. Biochar pH and electrical conductivity increased by 3.8 and 1.4 dS m⁻¹, proportionally to the increment of temperature. Biochar produced at low temperatures had higher total nitrogen and total organic carbon content but a lower C/N ratio, calcium carbonate equivalent, and total P, K and Na contents. Total and diethylene triamine penta acetic acid (DTPA)-extractable concentrations of Fe, Zn, Cu, Mn, Ni, Cr and Pb increased with increment of temperature. Lower DTPA-extractable concentrations of Fe, Zn, Cu, Mn, Ni and Pb were found in biochars compared to the sewage sludge. Pyrolysis decreased bulk density, whereas particle density and porosity increment was observed upon pyrolysis with increment of temperature. Sewage sludge saturated water content (θs ) was 130.4 g 100g⁻¹ and significantly greater than biochar, but biochar θs significantly increased with temperature (95.7 versus 105.4 g 100g⁻¹ at 300 and 700°C, respectively). Pyrolysis decreased the biochar's water repellency, assessed by molarity of ethanol droplet (MED), compared to the sewage sludge. The lowest MED of 0.2 and water repellency rating of 3 were found for the biochar produced at 700°C. Based on our results and considering the energy consumption, pyrolysis temperature in the range of 300-400°C may be suggested for sewage sludge pyrolysis.

Effects of upstream activities of Tigris-Euphrates River Basin on water and soil resources of Shatt al-Arab Border River.

The Tigris-Euphrates River Basin (TERB) is one of the key transboundary basins among the developing countries in the Middle East which has been significantly damaged by mismanagement, exploitation for energy production and unsustainable water use. This study aimed to evaluate the water and soil resources in the lower parts of this basin. More specifically, how the area of the Shatt al-Arab River (SAR) formed at the confluence of the Tigris and Euphrates rivers is affected in terms of quality by upstream activities. Four mathematical models of hydrodynamics, advection-dispersion in the river, and convection-dispersion in soil were used in conjunction with assessment of soil salinization by irrigation water. The soil salinization based on direct saltwater infiltration from riverbanks and soil salinization by irrigation with river water were predicted after simulating the intrusion of saline seawater by considering the tidal conditions of the SAR. The results showed that by applying six optimistic and probable scenarios of freshwater inflows for the future, changes in the water and soil quality in downstream riparian countries (Iran and Iraq) reflect this basin's developments and water allocation upstream. Regarding the possible scenario of maximum inflow reduction in the future, the findings of this study can be used to create a comprehensive view of the current condition and development challenges. This emphasizes the need for participatory crisis mitigation strategies between the upstream and downstream countries.

Application of response surface methodology (RSM) for optimizing coagulation process of paper recycling wastewater using Ocimum basilicum.

The wastewater produced in a pulp and paper industry is one of the most polluted industrial wastewaters, and therefore its treatment requires complex processes. One of the simple and feasible processes in pulp and paper wastewater treatment is coagulation and flocculation. Overusing a chemical coagulant can produce a large volume of sludge and increase costs and health concerns. Therefore, the use of natural and plant-based coagulants has been recently attracted the attention of researchers. One of the advantages of using Ocimum basilicum as a coagulant is a reduction in the amount of chemical coagulant required. In this study, the effect of basil mucilage has been investigated as a plant-based coagulant together with alum for treatment of paper recycling wastewater. Response surface methodology (RSM) was used to optimize the process of chemical coagulation based on a central composite rotatable design (CCRD). Quadratic models for colour reduction and TSS removal with coefficients of determination of R2 > 96 were obtained using the analysis of variance. Under optimal conditions, removal efficiencies of colour and total suspended solids (TSS) were 85% and 82%, respectively.

Feasibility of agricultural residues and their biochars for plant growing media: Physical and hydraulic properties.

This study was conducted to examine feasibility of using some agricultural residues and their biochars as substitutes for commercial horticultural growing media as cocopeat, sand, perlite, zeolite, pumice, vermiculite and rockwool. Biochars of wheat straw, sawdust, rice hull, sugarcane bagasse and date palm bunches were produced at 300 and 500 °C. Following substrate properties were determined: easily available water (EAW) defined by the difference between water contents (θ) at absolute matric potentials (h) of 10 and 50 hPa (EAW = θ10 - θ50), air after irrigation (AIR = θ0 - θ10), water holding capacity (WHC = θ10), water buffering capacity (WBC = θ50 - θ100), saturated water content (θs), bulk density (BD), total porosity (TP), water drop penetration time (WDPT), pH and electrical conductivity (EC). A classification system was developed to evaluate the substrates as horticultural growing media. Higher pyrolysis temperature produced biochars with higher pH, EC, TP, θs, WHC, EAW, and WBC and lower biochar yield, AIR, BD and WDPT. Sugarcane bagasse biochars had higher θs, TP and WBC and lower BD than other biochars. Comparison among organic residues and inorganic substrates showed that highest TP, θs and EAW were observed in rockwool, whereas, among organic residues, maximum values of these properties were achieved for sugarcane bagasse, wheat straw and sawdust, respectively. Considering pH, EC, BD, TP, EAW, AIR, WBC and WDPT, wheat straw and sawdust were classified as very good substrates similar to cocopeat and rockwool. Other organic residues were placed in good class. Wheat straw and date palm bunches biochars produced at 500 °C and sugarcane bagasse and rice hull biochars were good growing media and can be suitable candidates for amendments or replacements of commercial growing media.

Effect of the fungus Piriformospora indica on physiological characteristics and root morphology of wheat under combined drought and mechanical stresses.

This study was done to evaluate the effects of the root-colonizing endophytic fungus Piriformospora indica on wheat growth under combined drought and mechanical stresses. Inoculated (colonized) and non-inoculated (uncolonized) wheat (Triticum aestivum L. cv. Chamran) seedlings were planted in growth chambers filled with moist sand (at a matric suction of 20 hPa). Slight, moderate and severe mechanical stresses (i.e., penetration resistance, Qp, of 1.17, 4.17 and 5.96 MPa, respectively) were produced by a dead-load technique (i.e., placing a weight on the sand surface) in the root medium. Slight, moderate and severe drought stresses were induced using PEG 6000 solutions with osmotic potentials of 0, -0.3 and -0.5 MPa, respectively. After 30 days, plant physiological characteristics and root morphology were measured. An increase in Qp from 1.17 to 5.96 MPa led to greater leaf proline concentration and root diameter, and lower relative water content (RWC), leaf water potential (LWP), chlorophyll contents and root volume. Moreover, severe drought stress decreased root and shoot fresh weights, root volume, leaf area, RWC, LWP and chlorophyll content compared to control. Catalase (CAT) and ascorbate peroxidase (APX) activities under severe drought stress were about 1.5 and 2.9 times greater than control. Interaction of the stresses showed that mechanical stress primarily controls plant water status and physiological responses. However, endophyte presence mitigated the adverse effects of individual and combined stresses on plant growth. Colonized plants were better adapted and had greater root length and volume, RWC, LWP and chlorophyll contents under stressful conditions due to higher absorption sites for water and nutrients. Compared with uncolonized plants, colonized plants showed lower CAT activity implying that wheat inoculated with P. indica was more tolerant and experienced less oxidative damage induced by drought and/or mechanical stress.