The importance of phosphorus in the regulation of plant growth function is well studied. However, the role of the inorganic phosphate (Pi) molecule in the mitigation of abiotic stresses such as ...drought, salinity, heavy metal, heat, and acid stresses are poorly understood. We revisited peer-reviewed articles on plant growth characteristics that are phosphorus (P)-dependently regulated under the sufficient-P and low/no-P starvation alone or either combined with one of the mentioned stress. We found that the photosynthesis rate and stomatal conductance decreased under Pi-starved conditions. The total chlorophyll contents were increased in the P-deficient plants, owing to the lack of Pi molecules to sustain the photosynthesis functioning, particularly, the Rubisco and fructose-1,6-bisphosphatase function. The dry biomass of shoots, roots, and P concentrations were significantly reduced under Pi starvation with marketable effects in the cereal than in the legumes. To mitigate P stress, plants activate alternative regulatory pathways, the Pi-dependent glycolysis, and mitochondrial respiration in the cytoplasm. Plants grown under well-Pi supplementation of drought stress exhibited higher dry biomass of shoots than the no-P treated ones. The Pi supply to plants grown under heavy metals stress reduced the metal concentrations in the leaves for the cadmium (Cd) and lead (Pb), but could not prevent them from absorbing heavy metals from soils. To detoxify from heavy metal stress, plants enhance the catalase and ascorbate peroxidase activity that prevents lipid peroxidation in the leaves. The
HvPIP
and
PHO1
genes were over-expressed under both Pi starvation alone and Pi plus drought, or Pi plus salinity stress combination, implying their key roles to mediate the stress mitigations. Agronomy Pi-based interventions to increase Pi at the on-farm levels were discussed. Revisiting the roles of P in growth and its better management in agricultural lands or where P is supplemented as fertilizer could help the plants to survive under abiotic stresses.
Plant growth promoting rhizobacteria (PGPR) and arbuscular mycorrhizal fungi (AMF) are known for their beneficial effects. In recent years, more attention has been paid to their use as biofertilizers ...to reduce the use of chemical fertilizers causing significant damage to the environment. To have high plant yields, biofertilizers may not be able to sustain plant demands and could be used in combination with chemical fertilizers. However, the application of biofertilizers in the field such as rhizobacteria and AMF are understudied and powerfully needed. In this context, this study aims to evaluate the effect of inoculation with rhizobacteria and AMF and their potential to stimulate two of the most economically important crops in Mediterranean semi-arid areas (
L. and
L.). The effect of inoculation was studied in field experiment with six treatments: (i) the control without inoculation (C), (ii) PGPR alone (PG), (iii) rhizobia alone (R), (iv) the mixture of PGPR and rhizobia (PR), (v) AMF alone (M), and (vi) the mixture of PGPR, rhizobia and AMF (PRM). The inoculation with the consortium of PGPR-rhizobia-AMF (PRM) induced the greatest effect. This inoculation improved the growth parameters (dry weight of shoots and roots) of faba bean and wheat. An improvement of 130, 200, and 78% was observed in
shoot and root dry weight, and the number of leaves, respectively. Similarly, shoot and root dry weight and number of leaves of
were enhanced by 293, 258, and 87%, respectively. The inoculation improved the productivity of studied plants presented by the number and weight of bean pods (270 × 10
ha
and 30737.5 kg.ha
) and wheat spikes (440 × 10
ha
and 10560 kg.ha
). In addition, the mineral analyses showed that the inoculation with PGPR-rhizobia-mycorrhizae improved N, P, Ca, K, and Na shoots contents, as well as the contents of sugar and proteins. Finally, we revealed the positive impact of the tested biofertilizers and the interest of adoption of innovative practices improving crops productivity and soil fertility.
•Compost, phosphate sludge, marble waste allowed alfalfa growth in metal-contaminated soil.•Rhizobacteria and/or mycorrhizae inoculation with amendments promoted safe cultivation.•The organic and ...mineral amendments reduced CaCl2-soluble Zn, Cu, and Pb concentrations.•Mineral amendments stimulated plant proline production and improved soil properties.
Assisted natural remediation (ANR) has been highlighted as a promising, less expensive, and environmentally friendly solution to remediate soil contaminated with heavy metals. We tested the effects of three amendments (10% compost, C; 5 or 15% phosphate sludge, PS5 and PS15; and 5 or 15% marble waste, MW5 and MW15) in combination with microorganism inoculation (rhizobacteria consortium alone, mycorrhizae alone, and the two in-combination) on alfalfa in contaminated soil. Plant concentrations of Zn, Cu, and Pb were measured, along with proline and malondialdehyde production. The microbiological and physicochemical properties of the mining soil were evaluated. Application of the amendments allowed germination and promoted growth. Inoculation with the rhizobacteria consortium and/or mycorrhizae stimulated plant growth. PS and MW stimulated the production of proline. Inoculation of alfalfa with the rhizobacteria-mycorrhizae mixture and the application of MW allowed the safe cultivation of the legume, as shown by the low concentrations of metals in plant shoots. Zn and Pb concentrations were below the limits recommended for animal grazing and accumulated essentially in roots. Soil analyses showed the positive effect of the amendments on the soil physicochemical properties. All treatments increased soil pH (around 7), total organic carbon, and assimilable phosphorus content. Notably, an important decrease in soluble heavy metals concentrations was observed. Overall, our findings revealed that the applied treatments reduced the risk of metal-polluted soils limiting plant growth. The ANR has great potential for success in the restoration of polymetallic and acidic mining soils using the interaction between alfalfa, microorganisms, and organo-mineral amendments.
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Rainfall regimes are expected to shift on a regional scale as the water cycle intensifies in a warmer climate, resulting in greater extremes in dry versus wet conditions. Such changes are having a ...strong impact on the agro-physiological functioning of plants that scale up to influence interactions between plants and microorganisms and hence ecosystems. In (semi)-arid ecosystems, the date palm (
Phoenix dactylifera
L.) -an irreplaceable tree- plays important socio-economic roles. In the current study, we implemeted an adapted management program to improve date palm development and its tolerance to water deficit by using single or multiple combinations of exotic and native arbuscular mycorrhizal fungi (AMF1 and AMF2 respectively), and/or selected consortia of plant growth-promoting rhizobacteria (PGPR: B1 and B2), and/or composts from grasses and green waste (C1 and C2, respectively). We analyzed the potential for physiological functioning (photosynthesis, water status, osmolytes, mineral nutrition) to evolve in response to drought since this will be a key indicator of plant resilience in future environments. As result, under water deficit, the selected biofertilizers enhanced plant growth, leaf water potential, and electrical conductivity parameters. Further, the dual-inoculation of AMF/PGPR amended with composts alone or in combination boosted the biomass under water deficit conditions to a greater extent than in non-inoculated and/or non-amended plants. Both single and dual biofertilizers improved physiological parameters by elevating stomatal conductance, photosynthetic pigments (chlorophyll and carotenoids content), and photosynthetic efficiency. The dual inoculation and compost significantly enhanced, especially under drought stress, the concentrations of sugar and protein content, and antioxidant enzymes (polyphenoloxidase and peroxidase) activities as a defense strategy as compared with controls. Under water stress, we demonstrated that phosphorus was improved in the inoculated and amended plants alone or in combination in leaves (AMF2: 807%, AMF1+B2: 657%, AMF2+C1+B2: 500%, AMF2+C2: 478%, AMF1: 423%) and soil (AMF2: 397%, AMF1+B2: 322%, AMF2+C1+B2: 303%, AMF1: 190%, C1: 188%) in comparison with controls under severe water stress conditions. We summarize the extent to which the dual and multiple combinations of microorganisms can overcome challenges related to drought by enhancing plant physiological responses.
Rapid industrialization, mine tailings runoff, and agricultural activities are often detrimental to soil health and can distribute hazardous metal(loid)s into the soil environment, with harmful ...effects on human and ecosystem health. Plants and their associated microbes can be deployed to clean up and prevent environmental pollution. This green technology has emerged as one of the most attractive and acceptable practices for using natural processes to break down organic contaminants or accumulate and stabilize metal pollutants by acting as filters or traps. This review explores the interactions between plants, their associated microbiomes, and the environment, and discusses how they shape the assembly of plant-associated microbial communities and modulate metal(loid)s remediation. Here, we also overview microbe-heavy-metal(loid)s interactions and discuss microbial bioremediation and plants with advanced phytoremediation properties approaches that have been successfully used, as well as their associated biological processes. We conclude by providing insights into the underlying remediation strategies' mechanisms, key challenges, and future directions for the remediation of metal(loid)s-polluted agricultural soils with environmentally friendly techniques.
•Mycorrhizae stimulate plant growth and N acquisition in faba bean but not in wheat.•AM hyphal density is higher under intercropping than in sole cropping.•Mycorrhizal network enhances the transfer ...of fixed N from faba bean to wheat.•Transfer of fixed N is not correlated with proportion or total amount of fixed N.
In Morocco, the use of seed legumes is limited because significant water deficits and the low availability of soil phosphorus (P) limit nitrogen fixation. However, little is known about the ability of faba bean-rhizobium symbiosis to fix nitrogen in P-deficient soils and to transfer fixed nitrogen (N) to intercropped wheat. Arbuscular mycorrhizal fungi (AM) and their extraradical hyphae networks play an important role in the facilitation process by promoting interconnectivity and the transfer of nutrients, such as N and P, between associated plants. The aim of this study was to analyse the impact of AM inoculation on N2 fixation and the transfer of fixed N from faba bean to intercropped wheat. Germinated faba bean and wheat seeds were transferred into 1–l pots filled with a P-deficient soil that was collected from the Haouz valley near Marrakech (Morocco). Plants from the two species were grown in pots in either pure or mixed stands under greenhouse conditions, and each cropping system was subjected to three mycorrhizal inoculation treatments with a non-inoculated (AM0) and two concentrations of Rhizophagus irregularis inoculants containing 1000 (AM1) or 2000 (AM2) spores pot−1. The 15N isotope dilution method was used to determine the amount and proportion of atmospheric N fixed by faba bean (Ndfa%) and the fixed N that was transferred to wheat. Mycorrhizal inoculation had a significantly positive effect on the shoot dry weights and total shoot N in faba bean, but not in wheat. The cropping system had no significant effect on the plant growth and total shoot N in both faba bean and wheat. The Ndfa percentage was very high in all of the treatments, varying from 86 to 91%. The total N fixed by faba bean was 27% significantly higher in the AM2 treatment compared with the AM1 and AM0 treatments for both cropping systems combined. The estimated proportions of fixed N that were transferred from faba bean to wheat were far higher in AM1 (50%) and AM2 (32%) treatments than in AM0 (15%) treatment as well as for the total transferred fixed N. As corroborated by a parallel observation of root mycorrhizal colonization, these results suggest that the development of mycorrhizal networks stimulates the transfer of fixed N from faba bean to wheat, which could significantly contribute to the facilitation process under intercropping conditions.
Heavy metal (HM) pollution and the need to preserve the environment have gathered increasing scientific attention. The immobilization of HMs into less-soluble, less mobile, and less toxic forms in ...addition to the improvement of
Medicago sativa
L. growth and HMs accumulation were evaluated after the application of marble waste (MW) and/or beneficial PGP rhizobacteria and mycorrhizae to the mining soil compost. A greenhouse assay was conducted to elucidate the influence of both amendment and beneficial microorganisms. The application of marble waste to the soil-compost resulted in decreasing the bioavailability of metals (Cu, Zn, Pb, and Cd), thus ameliorating the installation of the vegetal cover for 6 months of culture. Cultivation of
M. sativa
under 5% MW-amended soil for 6 months increased the shoot dry weight by almost twofold, while the inoculation with rhizobacteria-mycorrhizae combined with the application of 15% MW resulted in an improvement of 3.5-fold in case of shoot dry weight. In addition, the application of marble waste amendment or their combination with metallo-resistant bacteria resulted in decreasing HM accumulation leading to HM content below the threshold recommended for animal grazing. Thus, the application of amendments and beneficial microorganisms appeared to guarantee the safe cultivation of alfalfa for 6 months of culture. The dual combination amendments and beneficial microorganisms showed the good potential to restore HM polluted soils and could stand as a novel approach for restoration of HM-contaminated soils.
Alfalfa (
Medicago sativa
L.) is one of the most important forages and legume crops in the Mediterranean region, where extensive soil exploitation and low soil fertility are among the factor ...limiting its production. In this study, a field experiment was carried out in the semi-arid area of Morocco, in order to assess the influence of the individual and combined application of autochthonous arbuscular mycorrhizal fungi (AMF), rhizobium strain and green compost supply on alfalfa. Vegetative yield, physiological and biochemical traits were evaluated together with the associated changes in the soil’s physico-chemical parameters. The results show that AMF and rhizobium inoculation combined with compost application induced the greatest effect. This treatment increased the dry matter yield, leaves and nodules number, and AMF infection rate. Moreover, the combined use of these biofertilizers further enhanced stomatal conductance, photosystem II efficiency, photosynthetic pigments (chlorophyll and carotenoids), protein and sugar content along with the nutrients uptake (Phosphorus (P), Nitrogen (N), Potassium (K) and Calcium (Ca)). When compared with the initial soil status, the compost (10 t/ha) combined with AMF and rhizobium significantly improved the organic matter, N and P content, decreased soil pH and increased electrical conductivity. This treatment is also efficient in increasing soil glomalin content. This study demonstrated that the interaction between green waste compost, AMF and rhizobium inoculation could have important implications in alfalfa sustainable agriculture.
Mycorrhizal symbiosis, the mutually beneficial association between plants and fungi, has gained significant attention in recent years due to its widespread significance in agricultural productivity. ...Specifically, arbuscular mycorrhizal fungi (AMF) provide a range of benefits to grain and oil crops, including improved nutrient uptake, growth, and resistance to (a)biotic stressors. Harnessing this symbiotic interaction using molecular and systems biology approaches presents promising opportunities for sustainable and economically-viable agricultural practices. Research in this area aims to identify and manipulate specific genes and pathways involved in the symbiotic interaction, leading to improved cereal and oilseed crop yields and nutrient acquisition. This review provides an overview of the research frontier on utilizing molecular and systems biology approaches for harnessing the symbiotic interaction in mycorrhizal symbiosis for grain and oil crop cultivation. Moreover, we address the mechanistic insights and molecular determinants underpinning this exchange. We conclude with an overview of current efforts to harness mycorrhizal diversity to improve cereal and oilseed health through systems biology.
Salinity is one of the devastating abiotic stresses that cause reductions in agricultural production. The increased salinization affects alfalfa growth, metabolism, and rhizobium capacity for ...symbiotic N
fixation negatively. This study was undertaken to investigate the efficiency of green compost (C; made from green waste), arbuscular mycorrhizal fungi (M; field-sourced native consortium), and/or rhizobium (R; a salt-tolerant rhizobium strain) individually or in combination as an effective strategy to improve alfalfa productivity under non-saline and high-saline (120 mM NaCl) conditions. In addition, we aimed to understand the agro-physiological and metabolic basis as well as glomalin content in the soil of biofertilizers-induced salt tolerance in alfalfa. Here, we show that mycorrhizal infection was enhanced after MR inoculation, while C application decreased it significantly. Salinity reduced growth, physiological functioning, and protein concentration, but the antioxidant system has been activated. Application of the selected biofertilizers, especially C alone or combined with M and/or R improved alfalfa tolerance. The tri-combination CMR mitigated the negative effects of high salinity by stimulating plant growth, roots and nodules dry matters, mineral uptake (P, N, and K), antioxidant system, synthesis of compatible solutes, and soil glomalin content, sustaining photosynthesis-related performance and decreasing Na
and Cl
accumulation, lipid peroxidation, H
O
content, and electrolyte leakage.
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