Arbuscular Mycorrhiza Inoculation Research Articles

Effect of arbuscular mycorrhiza and organic matter type toward growth and yield of sorghum on Oxisol Tuntang

Utilization Oxisol as plant growth media for sorghum is still limited. The main problems of the cultivation in Oxisol are low pH, high soluble form of Al, Mn, Fe, low organic matter (OM) and lack of nutrients especially P. The purpose of the present research was to examine the effect of arbuscular mycorrhiza (AM) and OM type toward the growth and yield of sorghum on Oxisol Tuntang. The pot experiment was conducted in greenhouse using factorial completely randomized design with two factors of AM inoculation and OM type with three replications. The first factor was inoculation of AM: without and with AM inoculation. The second factor was OM type: without OM, elephant grass compost, cow dung compost, worm castings and goat manure. The inoculation of AM in interaction with OM significantly increased AM colonization, spore density, leaf number, dry weight, water uptake, P concentration, P uptake and grain mass. Interaction of AM with worm castings and interaction of AM with goat manure indicated the same higher effect on sorghum growth and yield, compared with the interaction of AM with elephant grass compost and interaction of AM with cow dung compost. The control treatment showed the lowest plant performance.

Role of putrescine (Put) in imparting salt tolerance through modulation of put metabolism, mycorrhizal and rhizobial symbioses in Cajanus cajan (L.) Millsp.

Salt stress is a major environmental constraint that limits growth and nitrogen-fixation in legumes. Role of putrescine (Put) and arbuscular mycorrhiza (AM) in improving functional efficiency of legumes has gained importance in recent years. Present investigations assessed the impact of Put (1 mM) seed priming and/or Rhizophagus irregularis inoculation on growth, mycorrhizal and rhizobial symbioses with an emphasis to correlate the same with nodular Put metabolism in pigeonpea (Cajanus cajan L.) genotypes (Tolerant-Pusa 2001 and Sensitive-Pusa 991) under salt stress. Salinity declined plant biomass, with greater negative effects on roots than shoots which reduced the mycorrhizal colonization as well as nodulation ability of Sinorhizobium fredii AR-4. The decline in nitrogen-fixing efficiency could be correlated with increase in Na+ concentrations in roots as well as nodules. Salinity reduced endogenous Put by increasing diamine oxidase (DAO) as well as decreasing arginine decarboxylase (ADC) as well as ornithine decarboxylase (ODC) activities in nodules. Put priming enhanced per cent mycorrhizal colonization which further increased the rhizobial symbiotic efficiency, more in Pusa 2001 than Pusa 991. Both Put priming and AM inoculations reduced Na+ uptake and improved nutrient status especially P in both underground organs, with AM more effective than Put. The further decline in Na+ uptake was recorded when both amendments were given together which enhanced nitrogen-fixing ability of nodules by modulating anabolic and catabolic enzyme activities responsible for Put biosynthesis. Hence, +Put+AM can be used as an effective strategy to improve symbiotic potential and arrest nodule senescence in pigeonpea under salt stress.

Arbuscular Mycorrhizal Symbiosis with Arundo donax Decreases Root Respiration and Increases Both Photosynthesis and Plant Biomass Accumulation.

The effect of arbuscular mycorrhiza (AM) symbiosis on plant growth is associated with the balance between costs and benefits. A feedback regulation loop has been described in which the higher carbohydrate cost to plants for AM symbiosis is compensated by increases in their photosynthetic rates. Nevertheless, plant carbon balance depends both on photosynthetic carbon uptake and respiratory carbon consumption. The hypothesis behind this research was that the role of respiration in plant growth under AM symbiosis may be as important as that of photosynthesis. This hypothesis was tested in Arundo donax L. plantlets inoculated with Rhizophagus irregularis and Funneliformis mosseae. We tested the effects of AM inoculation on both photosynthetic capacity and in vivo leaf and root respiration. Additionally, analyses of the primary metabolism and ion content were performed in both leaves and roots. AM inoculation increased photosynthesis through increased CO2 diffusion and electron transport in the chloroplast. Moreover, respiration decreased only in AM roots via the cytochrome oxidase pathway (COP) as measured by the oxygen isotope technique. This decline in the COP can be related to the reduced respiratory metabolism and substrates (sugars and tricarboxylic acid cycle intermediates) observed in roots.

Poor-Soil Rhizosphere Enriched with Different Microbial Activities Influence the Availability of Base Elements

Understanding the ecology of soil rhizosphere is essential to enhancing soil ecosystem and plants productivity. Poor-soil properties can limit rhizosphere microbial composition, interactions and plants productivity. Furthermore, the presence of plant exudates and microbial interation can change the rhizosphere dynamic. In the current study, we used two types of soils, rich nutrient soil represented by potting-soil and poor-soil represented with nutrient-deprived poor-soil. The two types of soil were inoculated with five microbial combinations using plant growth promoting bacteria (PGPB, Pseudomonas fluorescens) and mycorrhiza, and planted with two-day-old sorghum bicolor and Setaria italica (Foxtail millet) seedlings. Soil elements analyses were conducted 60 days after planting. The availability of exchangeable base alkali elements (Ca, Mg, Na) were measured and compared. Na was exclusively affected by PGPB inoculation in both soil types. Ca and Mg increased highest when associated with arbuscular inoculation, exclusively, in comparison to association with PGPB or Ectomycorrhiza in both soil types when planted with sorghum. Whereas, the same elements Ca and Mg, increased highest when associated with arbuscular mycorrhiza inoculation whether combined with PGPB or ectomycorrhiza when in soil planted with Setaria italica. The mycorrhiza increased Ca and Mg availability when combined with PGPB. Naincrease was associated only with PGPB inoculation solely in both soil types. The use of arbuscular mycorrhiza inoculation combined with PGPB is ecofriendly method to enrich rhizosphere in poor-soil and eliminate the need to use any chemical fertilizers.

Response of Sesbania sesban to arbuscular mycorrhiza inoculation

The effects of arbuscular mycorrhiza inoculation - Glomus mossaea, G. fasciculatum, G. macrocarpum, G. etunicatum, Acaulospora muricata and Scutellospora heterogama, on dry matter (DM) yield, and chemical composition of Sesbania sesban were evaluated under greenhouse conditions. The most effectives fungi on DM yields were S. heterogama and A. muricata, which provided increases of 155 and 140%, in relation to the control. Root colonization was affected by arbuscular mycorrhiza inoculation. Plants inoculated with G. fasciculatum, S. heterogama and G. mossaea had the highest levels of root colonization. The highest N contents were obtained with G. mossaea and G. etunicatum, while plants inoculated with S. heterogama and A. muricata exhibited higher N uptake. The highest P contents were recorded with the inoculation of G. mossaea and A. muricata, however the higher uptake were obtained with S. heterogama and A. muricata. This study showed that several arbuscular mycorrhiza fungi were effective in increasing DM yield, and N and P uptake of S. sesban. The most efficient species were S. heterogama and A. muricata.

Role of Arbuscular Mycorrhiza in Alleviating Salinity Stress in Wheat (Triticum aestivum L.) Grown Under Ambient and Elevated CO2

AbstractPlant growth and development are influenced by future elevated atmospheric CO2 concentration and increased salinity stress. AM (arbuscular mycorrhiza) symbiosis has been shown to improve plant growth and resistance to environmental stresses. The aim of this study was to investigate the potential role of AM fungus in alleviating salinity stress in wheat (Triticum aestivum L.) plants grown under ambient and elevated CO2 concentrations. Wheat plants inoculated or not inoculated with AM fungus were grown in two glasshouses with different CO2 concentrations (400 and 700 μmol l−1) and salinity levels (0, 9.5 and 19.0 dS m−1). Results showed that salinity stress decreased and elevated CO2 increased AM colonization. AM inoculation increased plant dry weight under elevated CO2 and salinity stress. Stomatal conductance, density, size and aperture of AM plants were greater than non‐AM plants. AM fungi enhanced NUE by altering plant C assimilation and N uptake. AM plants had higher soluble sugar concentration and [K+]: [Na+] ratio compared with non‐AM plants. It is concluded that AM symbiosis improves wheat plant growth at vegetative stages through increasing stomatal conductance, enhancing NUE, accumulating soluble sugar, and improving ion homeostasis in wheat plants grown at elevated CO2 and salinity stress.

The Arbuscular Mycorrhiza Rhizophagus intraradices Reduces the Negative Effects of Arsenic on Soybean Plants

Arsenic (As) in soils causes several detrimental effects, including death. Arsenic toxicity in soybean plants (Glycine max L.) has been little studied. Arbuscular mycorrhiza (AM) increase the tolerance of host plants to abiotic stress, like As. We investigated the effects of AM fungi on soybean grown in As-contaminated soils. A pot experiment was carried out in a glasshouse, at random with five replications. We applied three levels of As (0, 25, and 50 mg As kg−1), inoculated and non-inoculated with the AM fungus Rhizophagus intraradices (N.C. Schenck & G.S. Sm.) C. Walker & A. Schüßler. Plant parameters and mycorrhizal colonization were measured. Arsenic in the substrate, roots, and leaves was quantified. Arsenic negatively affected the AM percentage of spore germination and hyphal length. As also affected soybean plants negatively: an extreme treatment caused a reduction of more than 77.47% in aerial biomass, 68.19% in plant height, 78.35% in number of leaves, and 44.96% reduction in root length, and delayed the phenological evolution. Mycorrhizal inoculation improved all of these parameters, and decreased plant As accumulation (from 7.8 mg As kg−1 to 6.0 mg As kg−1). AM inoculation showed potential to reduce As toxicity in contaminated areas. The AM fungi decreased As concentration in plants following different ways: dilution effect, less As intake by roots, and improving soybean tolerance to As.

Effects of soil pH and arbuscular mycorrhiza (AM) inoculation on growth and chemical composition of chia (Salvia hispanica L.) leaves

In this study, chemical composition and growth responses of chia plants (Salvia hispanica L.) to inoculation with an arbuscular mycorrhiza (AM, Glomus mosseae, Nicol. & Gerd.) fungal inoculum (namely MC10) under the influence of soil pH were investigated. The experiment project included six treatments, i.e., control-non-arbuscular mycorrhiza fungi (NAMF, pH 7.1), control-arbuscular mycorrhiza fungi (AMF, pH 7.1), acid-NAMF (pH 5.1), acid-AMF (pH 5.1), alkaline-NAMF (pH 8.2), and alkaline-AMF (pH 8.2). Stunted growth and leaf chlorosis were noticed mainly in plants grown in soil with acidic pH. An increase in fresh biomass was attained in plants amended with AM fungi in alkaline soil pH. Alkaline sandy soil with low levels of available P stimulated AMF colonization of chia roots, which subsequently enhanced P uptake and translocation in plant tissues. Total proteins, carbohydrates, and total fat content in leaves increased in AMF-inoculated plants in neutral and alkaline soil pH, while only fat content enhanced under acidic soil pH. MC10 inoculum resulted in reduced levels of total phenolics under alkaline conditions, whereas under acidic soil resulted in increased levels compared to the non-inoculated plants. The predominant fatty acids of chia leaves were palmitic (18.3 %), a-linolenic (17.1 %), pentadecenoic (11.0 %), linoleic (7.5 %), oleic (7.5 %), and stearic (6.3 %). Higher concentration of stearic, oleic, linoleic, and a-linolenic acids was observed in the leaves of chia plants grown on control (neutral pH) and alkaline soil in the presence of the MC10 inoculum. Alkaline soil combined with AM inoculation enhanced the nutritional value of chia leaves.

Effect of Arbuscular Mycorrhiza Fungi Inoculation on Growth and Uptake of Mineral Nutrition in Ipomoea aquatica

A green house experiment was conducted to investigate the effect of arbuscular mycorrhiza inoculation on plant growth and uptake of mineral nutrition in Ipomoea aquatica considering the objective of using environmental friendly biofertilizer instead of chemical fertilizer. A common leafy vegetable plant Ipomoea aquatica was grown with mycorrhiza and without mycorrhiza for 42 days. After harvest the plants were analyzed for mineral nutrition concentration. Plant fresh weight, dry weight, macronutrient (P, K, Mg, Na), micronutrient (Fe, Mn, Zn) concentration was higher in arbuscular mycorrhiza inoculated plant than non-mycorrhiza inoculated plant. For sustainable agriculture, introducing biofertilizer by using arbuscular mycorrhiza inoculation would be one of the most efficient techniques for replacing chemical fertilizer to meet the nutrient deficiency in nutrient deficient soils of Bangladesh.

Field inoculation of arbuscular mycorrhiza on maize (Zea mays L.) under low inputs: preliminary study on quantitative and qualitative aspects

Arbuscular mycorrhizal symbiosis contributes to the sustainability of soil-plant system. A field experiment was conducted to examine the effect of arbuscular mycorrhiza (AM) on quantitative and qualitative performance in forage maize (Zea mays L.). Within the project Sviluppo di modelli zootecnici ai fini della sostenibilità (SOS-ZOOT) a trial was conducted at the experimental farm of the Agricultural Research Council in Bella (PZ), located in Basilicata region (Southern Italy) at 360 m asl, characterised by an annual rainfall of approximately 650 mm. For spring sowing, two plots of 2500 m2 were used, one sown with seeds inoculated with AM (M), 1.0 kg/ha, and the other one with non-inoculated seeds (NM). After 120 days after sowing, when plants showed 30% dry matter, five replicates of 1 m2 per plot were used to estimate dry matter yield (DMY), while half plot was dedicated to the assessment of grain production. For each replicate, three representative plants were considered; each plant was measured for height and was divided into leaves, stem and ear. For each plot, the following constituents were determined: crude protein, ash, ether extract, crude fibre (CF), fractions of fibre [neutral detergent (NDF), acid detergent fibre (ADF) and sulphuric acid lignin] and phosphorus (P). Throughout the period of plants’ growth, no herbicides, organic or inorganic fertilisation, and irrigation water were distributed. The preliminary results revealed a significant effect of AM inoculation on forage maize DMY, P content in the whole plant, into the leaves and on the quality of steam. The M thesis showed a significant increase in terms of DMY in comparison with the NM thesis: 21.2 vs 17.9 t/ha (P<0.05). The mycorrhized whole plants [0.22 vs 0.17% dry matter (DM), P<0.05] and leaves (0.14 vs 0.09% DM, P<0.05) showed an increased P content. The stems of M plants showed a content of CF, NDF, ADF and Ash significantly lower compared with NM plants. No significant differences were observed for the other parameters. The preliminary study revealed a significant effect of AM seed inoculation on DMY and quality of forage maize cultivated within a low input system.

Effects on growth of persimmon (Diospyros virginiana) rootstock of arbuscular mycorrhizal fungi species

Persimmon (Diospyros kaki Thunb.) is grown in many parts of the world that display subtropical climate conditions, including Turkey. There are 2 common rootstocks used in its production: D. kaki and D. virginiana Thunb. Arbuscular mycorrhiza (AM), a symbiosis between plant roots and members of an ancient phylum of fungi, Glomeromycota, improves root development, water supply, and nutrients such as phosphate and zinc in the host plant. In this study, the effects of 5 AM fungi species (Glomus mosseae, G. clarium, G. etunicatum, G. caledonium, and G. intraradices) on plant growth, chlorophyll concentration, and chlorophyll fluorescence (Fv'/Fm') in D. virginiana were investigated under greenhouse conditions. We determined that mycorrhizal inoculations increased shoot and root dry weight compared to the noninoculated plants. Plants inoculated with G. etunicatum showed the highest total plant dry weight. Highest leaf chlorophyll concentration was measured in a plant inoculated with G. caledonium. The results of chlorophyll fluorescence were similar for all AM inoculations; however, they significantly differed from those of noninoculated plants. The results demonstrated the benefit potential of mycorrhizal inoculations for persimmon production.

Influence of Arbuscular Mycorrhiza and Phosphorus Levels on Dry Matter Production and Nutrients Uptake by Tomato Seedlings

To investigate the effects of arbuscular mycorrhiza (AM) and phosphorus (P) rates on the uptake of primary and secondary nutrients by tomato (Lycopersicon esculentum Milli) cv. BARI Tomato-2 seedlings, under P levels ranging from low to excessive, plants were grown in five levels of P (0, 7.5, 15.0, 22.5 and 30.0 mg P kg-1 soil) as TSP, either inoculated with AM or without AM. The total dry matter yield and uptake of N, P, K, S, Ca and Mg nutrients was significantly influenced by AM inoculation. Nutrient use efficiency in the AM-inoculated seedlings was also significantly higher than that in uninoculated seedlings. The application of different levels of P lonely increased different nutrients and its uptake positively up to certain level, but at higher level influenced negatively. The N, P, K, S, Ca and Mg content and uptake all were the highest when P applied @ 30 kg ha-1 and the lowest @ 0 kg P ha-1 but uptake found the lowest @ 60 kg P ha-1. There was a significant interaction effect of AM and P levels on nutrients content and their uptakes positively up to certain level, but at higher level of P combination influenced negatively. Among the treatment combinations, P30 x I showed the highest nutrient contents under study and their uptakes but dry matter yield gave the highest value when AM was applied with P @ 15 kg ha-1.DOI: http://dx.doi.org/10.3329/pa.v19i2.16932 Progress. Agric. 19(2): 75 - 84, 2008

THE EFFECT OF ARBUSCULAR MYCORRHIZAL FUNGI ON THE ESTABLISHMENT OF SOUR ORANGE (CITRUS AURANTIUM) UNDER DIFFERENT LEVELS OF PHOSPHORUS

Abstract The objective of this study was to evaluate the response of sour orange ( Citrus aurantium L.) seedlings to inoculation with arbuscular mycorrhiza (AM) fungi under different phosphorus (P) fertilizer levels during transplant production. Six months old seedlings of sour orange were obtained from a commercial nursery and inoculated or not inoculated (control) with a commercial AM inoculum (BioMycVital) in a pot trial in a plastic house. Three P fertilizer levels were applied [15 (low), 45 (medium) and 90 (high) mg kg-¹ soil)] as NPK (18:18:5 + TE) or/and KH 2 PO 4 . Ten months after transplanting, the AM inoculation stimulated growth of sour orange seedlings regardless of phosphorus level. Inoculation coupled with low and medium levels of P fertilizer enhanced the plant dry weight by 34.4 and 20.2% and stem diameter by 25.9 and 17.9% over the noninoculted plants, respectively. However, the enhancement effect for these two growth parameters was insignificant in treatment of inoculation with high P fertilizer in comparison to noninoculated plants. These results indicate that sour orange should be inoculated with AM fungi at nursery stage, with application of medium level of P.

Effects of arbuscular mycorrhiza inoculation on plant growth, biological and physiological parameters and mineral nutrition in pepper grown under different salinity and p levels

A study was conducted in a greenhouse, to investigate the effects of arbuscular mycorrhizal fungi (Glomus intraradices), soil salinity and P availability on growth (leaf area and dry weight), nutrient absorption and ion leakage, chlorophyll, soluble sugar and proline content and alkaline phosphatase activity of pepper plants (Capsicum annuum L.). Plants were grown at four levels of salinity (0, 50, 100 and 200 mM NaCl) and two P levels (10 and 40 mg kg -1 ). Colonisation was 80% to 51% in non-stressed and high salt-stressed plants, respectively. The mycorrhizal dependency was high and only reduced at the higher salinity level. Mycorrhizal plants maintained greater root and shoot biomass at all salinity levels compared to non-mycorrhizal plants, regardless the P level. Interactions between salinity, phosphorous and mycorrhizae were significant for leaf area, root and shoot dry mass. Non-mycorrhizal plants accumulated higher Na and lower K and P compared to mycorrhizal plants. The cell membrane integrity was greater in mycorrhizal plants than in non-mycorrhizal ones. The proline content increases with increasing salt stress and was significantly higher in leaves than in roots The results indicate that the mycorrhizal inoculation is capable of alleviating the damage caused by salt stress conditions on pepper plants, to maintaining the membranes stability and plant growth, and this could be related to P nutrition.

The role of Glomus mosseae on key physiological and biochemical parameters of pea plants grown in arsenic contaminated soil

Arbuscular mycorrhiza (AM) constitutes a key functional group of soil biota that can greatly contribute to ecosystem sustainability by playing a critical role in stress tolerance. The effects of arsenic (As) stress on physiological and biochemical mechanisms and the role of Glomus mosseae (AM) in reducing As accumulation was investigated in Pisum sativum L. (pea). As uptake and accumulation increased with an increase in external As concentration, increment being higher in roots than in shoots. Sodium arsenate significantly affected shoot and root dry matter yield, damaged chlorophyll pigments and induced oxidative stress by decreasing membrane stability and increasing H2O2 production in a concentration dependent manner. The phytotoxicity of arsenate (AsV) led to an increase in superoxide dismutase, catalase and peroxidase activities and synthesis of osmolytes such as soluble sugars, proline, glycine betaine and total proteins. Establishment of association with G. mosseae reduced As(V) uptake and increased N, P, K+ as well as plant growth. AM inoculations alleviated As(V) toxicity by reducing oxidative stress and modulating antioxidative mechanisms in pea plants.

Influence of Iron and Arbuscular Mycorrhiza Inoculation on Growth and Yield of Hybrid Maize in Calcareous Soil

Field experiment was conducted at the Department of Agronomy, Tamil Nadu Agricultural University, Coimbatore during Kharif 2010 to study the influence of iron and arbuscular mycorrhiza (AM) inoculation on growth and yield of hybrid maize in calcareous soil. The experiment was laid out in factorial randomized block design with three replications. The treatments included were inoculation of arbuscular mycorrhiza (M+) and control (without inoculation of mycorrhiza, M-) under factor A and T1 - 25 kg FeSO4 ha-1, T2 - 50 kg FeSO4 ha-1,T3 - 0.5% FeSO4 foliar spray, T4 - 25 kg FeSO4 ha-1 + 0.5 % FeSO4 foliar spray, T5 - 50 kg FeSO4 ha-1 + 0.5 % FeSO4 foliar spray and T6 – Control under factor B. The results revealed that among the iron treatments, 50 kg FeSO4 + 0.5% FeSO4 foliar spray showed the highest grain yield and it was comparable with 25 kg FeSO4 + 0.5% FeSO4 foliar spray. Regarding the mycorrhizal treatments, AM inoculated plants recorded the best results. Regarding the interaction, the treatment combination of 25 kg FeSO4 + 0.5% FeSO4 foliar spray along with AM recorded the highest grain yield. All the growth attributes showed the similar trend.

Influence of arbuscular mycorrhizae on root colonization, growth and productivity of two wheat cultivars under salt stress

Two pot experiments were conducted in the greenhouse of the National Research Center, Egypt during 2003/2004 and 2004/2005 to investigate the efficacy of arbuscular mycorrhizae (AM) on root colonization, growth and productivity in two wheat cultivars, Sakha 8 and Giza 167, under salt stress. The extent of the AM effect on wheat development varied with plant cultivar and salinity level. Maximum root colonization and spore production were observed with the Sakha 8 cultivar, which resulted in greater plant growth and productivity at all salinity levels. AM and plant development were adversely affected by increasing salinity. However, the presence of mycorrhizal fungi protected wheat against the detrimental effect of salinity, and stimulated growth, productivity, total crude protein concentration and nitrate reductase activity. The average enhancement in grain yield due to AM inoculation was 76 and 68% at 0.15 mS cm−1, 93 and 84% at 3.13 mS cm−1, 130 and 115% at 6.25 mS cm−1, and 154 and 120% at 9.38 mS cm−1 salinity for Sakha 8 and Giza 167, respectively. In general, mycorrhizal inoculation enhanced the ability of wheat to cope with saline conditions and using AM inoculants can help plants to thrive in degraded arid/semi-arid areas.

Growth and Nutrient Uptake Responses of Kinnow to Vesicular Arbuscular Mycorrhizae

In a field experiment, three-year-old Kinnow trees budded on Jatti Katti (C. jambhiri) rootstock were inoculated by three different arbuscular mycorrhiza (AM), Glomus manihotis (T1), Glomus mosseae (T2), and Gigaspora gigantia (T3), separately or in combination (T4). Microscopic assessment of AM colonization on Kinnow roots showed a relatively lower level of infection by different species when inoculated separately than when inoculaed together. Application of AM improved growth parameters like plant height, canopy volume, mean leaf area, and number of new shoots per plant but had no effect on trunk diameter, number of leaf per new shoot and new shoot diameter. Flowering phenology was also altered by AM infection. The infected plants produced more flowers which despite abscission caused an increase in the initial number of fruits. AM inoculation increased plant phosphorous in T3, potassium in T1, T2, T3, calcium in T2, T3, T4, and the AM-nutrient relationship did not reveal any generalized pattern. Inoculated plants, however, had higher concentration of different elements by the second year of the experiment indicating towards the continuous and cumulative effect of AM infection on plant nutrient accumulation. Further, the beneficial effects of AM on Kinnow were not related to the difference in the species of mycorrhiza.

Alleviation of salt-induced ionic, osmotic and oxidative stresses in Cajanus cajan nodules by AM inoculation

Legume-Rhizobium symbiotic nitrogen (N2) fixation plays a critical role in sustainable nitrogen management in agriculture. The nitrogen fixed by the root nodules not only affects the nitrogen cycle of nature, but is also of great economic importance. A number of physiological and biochemical processes in the nodules are affected by salt stress. The objective of this study was to evaluate the role of arbuscular mycorrhiza (AM) in moderating toxic effects of salt stress on nodular metabolism in Cajanus cajan (L.) Millspaugh (pigeonpea) cv. Manak. Exposure of plants to salinity stress (4, 6 and 8 dSm−1) caused ionic imbalance, which resulted in increased Na+ and reduced K+ and Ca2+ contents in the nodules. Salinity induced increased synthesis and accumulation of proline and glycine betaine. Salt stress significantly increased the antioxidant enzyme activities in the nodules of all plants. Nodular growth suffered remarkably and a marked decline in nodule biomass was observed under salt stress. Leghemoglobin content and acetylene reduction activity (ARA) also declined under saline conditions. AM could significantly improve nodule dry mass, leghemoglobin content and nitrogenase activity, and phosphorus content under salt stress. Activities of antioxidant enzymes increased markedly in nodules of mycorrhizal-stressed plants. This study suggested a correlation between improved functional efficiency of nodules and higher osmolyte accumulation and enhanced antioxidant enzyme activities of AM plants under stressed conditions relative to the nodules of uninoculated plants.

Growth and arsenic uptake by Chinese brake fern inoculated with an arbuscular mycorrhizal fungus

A split-root experiment investigated the effects of inoculation with the arbuscular mycorrhizal fungus Glomus mosseae and arsenic (As) addition on As uptake by Pteris vittata L. Either part or all of the root system was inoculated with G. mosseae or exposed to As addition (50 ml 1000 μmol L −1 As 1 week before harvest). Mycorrhizal colonization substantially increased frond and root dry weight and P and As contents irrespective of As addition. Frond As contents in mycorrhizal plants were highest when the whole root system was exposed to As. Frond As concentrations and contents were higher when inoculation and As addition were in the same parts of the root system than when spatially separate. There were positive effects of arbuscular mycorrhiza inoculation on plant growth and As uptake, and inoculation of part of the roots seemed to be as effective as inoculation of the whole root system.