A Model for the Development of the Rhizobial and Arbuscular Mycorrhizal Symbioses in Legumes and Its Use to Understand the Roles of Ethylene in the Establishment of these two Symbioses

We propose a model depicting the development of nodulation and arbuscular mycorrhizae. Both processes are dissected into many steps, using Pisum sativum L. nodulation mutants as a guideline. For nodulation, we distinguish two main developmental programs, one epidermal and one cortical. Whereas Nod factors alone affect the cortical program, bacteria are required to trigger the epidermal events. We propose that the two programs of the rhizobial symbiosis evolved separately and that, over time, they came to function together. The distinction between these two programs does not exist for arbuscular mycorrhizae development despite events occurring in both root tissues. Mutations that affect both symbioses are restricted to the epidermal program. We propose here sites of action and potential roles for ethylene during the formation of the two symbioses with a specific hypothesis for nodule organogenesis. Assuming the epidermis does not make ethylene, the microsymbionts probably first encounter a regulatory level of ethylene at the epidermis–outermost cortical cell layer interface. Depending on the hormone concentrations there, infection will either progress or be blocked. In the former case, ethylene affects the cortex cytoskeleton, allowing reorganization that facilitates infection; in the latter case, ethylene acts on several enzymes that interfere with infection thread growth, causing it to abort. Throughout this review, the difficulty of generalizing the roles of ethylene is emphasized and numerous examples are given to demonstrate the diversity that exists in plants

Effects of soil compaction on plant growth, phosphorus uptake and morphological characteristics of vesicular-arbuscular mycorrhizal colonization of Trifolium subterraneum

We investigated the effect of soil compaction and phosphorus (P) application on morphological characteristics of mycorrhizal colonization and growth responses, to determine the reasons for reduced responses observed in our previous work with compacted soil. Growth, phosphorus (P) uptake and intensity of vesicular–arbuscular (VA) mycorrhizal colonization were studied in clover plants (Trifolium subterraneum L.) with and without VA mycorrhizal colonization at two P applications and three levels of soil compaction. Phosphorus was supplied either at constant mass concentration (mg P kg⁻¹ soil) or at constant volume concentration (mg P dm−3 soil). Increasing bulk density of the soil from 1•1 to 1.6 Mg m⁻³ significantly decreased root length and shoot d. wt, but increased the diameter of both main axes and first order lateral roots regardless of P application. Total P uptake and shoot d. wt of clover plants colonized by Glomus intraradices (Schenck & Smith) were significantly greater than those of non-mycorrhizal plants at all levels of soil compaction and both P applications. However, soil compaction to a bulk density of 1.6 Mg m⁻³ (penetrometer resistance = 3.5 MPa at a matric potential of − 33 kPa) significantly decreased mycorrhizal growth response. There was no evidence that the increased volume concentration of P at high bulk densities was responsible for the reduced responses. Soil compaction had no significant effect on the fraction of root length containing arbuscules and vesicles, but total root length colonized by arbuscules, vesicles or by any combination of arbuscules, vesicles and intra-radical hyphae significantly decreased as soil compaction was increased. The air-filled porosity of highly compacted soil, which varied from 0.07 to 0.11 over the range of matric potentials encountered (− 33 and − 100 kPa), had no significant effect on the intensity of internal colonization

The effect of soil compaction on growth and P uptake by Trifolium subterraneum: interactions with mycorrhizal colonisation

The effects of vesicular-arbuscular mycorrhizal (VAM) colonisation on phosphorus (P) uptake and growth of clover (Trifolium subterraneum L.) in response to soil compaction were studied in three pot experiments. P uptake and growth of the plants decreased as the bulk density of the soil increased from 1.0 to 1.6 Mg m⁻³. The strongest effects of soil compaction on P uptake and plant growth were observed at the highest P application (60 mg kg⁻¹ soil). The main observation of this study was that at low P application (15 mg kg⁻¹ soil), P uptake and shoot dry weight of the plants colonised by Glomus intraradices were greater than those of non-mycorrhizal plants at similar levels of compaction of the soil. However, the mycorrhizal growth response decreased proportionately as soil compaction was increased. Decreased total P uptake and shoot dry weight of mycorrhizal clover in compacted soil were attributed to the reduction in the root length. Soil compaction had no significant effect on the percentage of root length colonised. However, total root length colonised was lower (6.6 m pot⁻¹) in highly compacted soil than in slightly compacted soil (27.8 m pot⁻¹). The oxygen content of the soil atmosphere measured shortly before the plants were harvested varied from 0.18 m³m⁻³ in slightly compacted soil (1.0 Mg m⁻³) to 0.10 m³m⁻³ in highly compacted soil (1.6 Mg m⁻³)

Influence of Arbuscular Mycorrhizal Fungi and Drought Stress on Some Macro Nutrient Uptake in Three Leek Genotypes with Different Root Morphology

Introduction: Drought stress is one of the main problems in agricultural productions in arid and semiarid regions such as Iran. Lack of water influences on most of plant physiological processes such as photosynthes, cellular development and uptake and transmission of nutrients in plants. Some approaches such as selection of resistance cultivars to drought stress, and selection of dripped irrigation have been applied in order to increase the irrigation efficiency. In recent years, biological approaches such as mycorrhizal symbiosis have been used to alleviate the detrimental effects of drought stress. Mycorrhizal symbioses increase the absorption of nutrients, especially phosphorus, and reduce the adverse effects of environmental stresses. It can also improve the host plant growth and yield. The percentage of mycorrhizal dependency of host plants depends on different environmental factors (such as light intensity, temperature, soil conditions), as well as morphological and physiological characteristics of plants. 1n 2010, a greenhouse pot experiment was conducted at University of Agriculture and Natural Resources Ramin. The effect of mycorrhizal inoculation on root morphology of three leek genotypes and uptake of phosphorous, calcium and potassium in shoot and root were studied. Materials and Methods: The experiment was conducted in a completely randomized design consisting of a 3×3×2 factorial combination. Experimental factors included three levels of soil moisture (40, 60 and 80% of available water in the soil), two mycorrhizal status (with and without fungus Glomus intraradices) and three leek genotypes including: Shadegan (with low root branching, short and thin root length), Esfahan (with abundant root branching and long root length) and Porrum (with low root branching, short and thick root length). The treatments were replicated four times. The soil was autoclaved at 121°C and15 PSI for 15 minutes and gently packed into PVC pots, 200 mm long and 150 mm in diameter. Leek seeds were sterilized with sodium hypochlorite (NaOCl) solution (10%) for 20 min. Two hundred grams of inoculum (spore, hyphae, mycorrhizal clover of root fragments and soil) were placed in deep of plant root. Each pot received 10 cm-3 nutrients solution, free of P weekly. Plants equally watered for one mounth then, drought stresses were applied. Leeks were harvested 12 weeks after planting. Sub-samples of roots were taken for determination of root length were cleared in 10% (w/v) KOH solution and then were stained with trypan blue and root colonization was studied using modified Phillips & Hayman. The colonized root length was determined by binocular and gridline intersect method of Tennant. Phosphorus concentrations were measured by the method of colorimetery with a spectrophotometer. Potassium and calcium concentrations were determined by flame photometer and titration with vercin (Ethylene diamine tetra acetic acid: EDTA), respectively. The statistical analysis was performed using MSTAT-C statistical software and means were compared by Duncan’s multiple range test at the significance level of

Effects of soil compaction on phosphorus uptake and growth of Trifolium subterraneum colonized by four species of vesicular-arbuscular mycorrhizal fungi

The ability of four species of vesicular–arbuscular mycorrhizal (VAM) fungi to increase phosphorus uptake and growth of clover plants (Trifolium subterraneum L.) at different levels of soil compaction and P application was studied in a pot experiment. Dry matter in the shoots and roots of clover plants decreased with increasing soil compaction. Colonization by Glomus intraradices Schenck & Smith and Glomus sp. City Beach WUM16 increased plant growth and P uptake up to a bulk density of 1•60 Mg m⁻³, although the response was smaller as soil compaction was increased. Glomus etunicatum Becker & Gerdeman and Glomus mosseae (Nicol. & Gerd.) Gerdemann & Trappe had no effect on the shoot d. wt and P uptake when the bulk density of the soil was ≥1•40 and ≥1•60 Mg m⁻³, respectively. Soil compaction to a bulk density of 1•60 Mg m⁻³ had no effect on the percentage of root length colonized by G. intraradices and Glomus sp. City Beach, but total root length colonized decreased as soil compaction was increased. Decreased P uptake and growth of clover plants colonized by G. intraradices and Glomus sp. City Beach, with increasing soil compaction up to a bulk density of 1•60 Mg m⁻³, was mainly attributed to a significant reduction in total root length colonized and in the hyphal biomass. Soil compaction, which increased bulk density from 1•20 to 1•75 Mg m⁻³, reduced the O₂ content of the soil atmosphere from 0•16 to 0•05 m3 m⁻³. The absence of any observable mycorrhizal growth response to any of the four species of VAM fungi in highly compacted soil (bulk density = 1•75 Mg m⁻³) was attributed to the significant decrease in the O₂ content of the soil atmosphere, change in soil pore size distribution and, presumably, to ethylene production

Meperidine (pethidine) versus morphine in acute pain management of opioid-dependent patients

Hassan Solhi,1 Hossein Sanaei-Zadeh,2 Sadra Solhi,1 Mohammad Ali Azizi Nadian,1 Morteza Gharibi,3 Bahman Sadeghi Sedeh4 1Department of Internal Medicine, Arak University of Medical Sciences, Arak, 2Emergency Room, Division of Medical Toxicology, Hazrat Ali-Asghar (p) Hospital, Shiraz University of Medical Sciences, Shiraz, 3Department of Emergency Medicine, Arak University of Medical Sciences, 4Department of Social Medicine, Arak University of Medical Sciences, Arak, Iran Abstract: The present study aimed to evaluate the effectiveness of morphine and meperidine (pethidine) as pain relief in opioid-dependent patients with acute pain. A total of 122 opioid-dependent patients with acute pain were included in the study. Their pain severity was assessed, using visual analog scale (VAS) scores ranging from 0 to 10. The patients randomly received intravenous morphine (up to 0.15 mg/kg) or meperidine (up to 1.5 mg/kg) for pain control by patient control analgesia (PCA) pump. The clinical opioid withdrawal scale (COWS) was employed for the assessment of withdrawal symptoms. The pain relief and the emergence of withdrawal symptoms were measured at 15, 30, and 60 minutes after drug administration. The patients who received morphine reported a better pain control compared to those who received meperidine (mean ± standard deviation [SD] VAS scores 4.11±1.90 vs 5.85±2.08 at the end of the study; P<0.001). On the other hand, the patients who received meperidine indicated prominent withdrawal symptoms (mean ± SD COWS scores 4.80±2.18 vs. 1.98±0.82 at the end of the study; P<0.001). Our findings revealed that morphine can be recommended in acute pain management of opioid-dependent patients. In addition, emergency physicians should ask their patients about any drug dependence before selecting the appropriate drug for their acute pain management. Keywords: pain management, meperidine, morphine, opioid dependency, withdrawal symptom