Increase Phosphate Availability Research Articles

Molecular Identification and Characterization of Indigenous Rhizobacteria from Haryana and Punjab and Their Inoculation Effect on Prosopis cineraria

India grapples with escalating soil salinity, projected to afflict 16.2 million hectares by 2050. Reforestation, vital in North India's sodic wastelands, counters severe degradation. Rhizobacteria that promote plant growth (PGPR) are essential for managing forests sustainably. These microbes help rhizosphere plants form symbiotic relationships that promote hormone production, nitrogen fixation, increased phosphate availability, iron sequestration, and defense against outside threats. The study aimed to isolate halo-tolerant microbial strains from salt-affected areas and studied their effect on tree species to alleviate their overall growth in Punjab and Haryana. We isolated 880 bacterial isolates from salt-affected areas in Punjab and Haryana; they have a variety of metabolic capabilities and are resistant to both salty and alkaline environments. Pot studies with a range of tree species verify the beneficial effects of particular bacterial strains, such as Pseudomonas mosselli and Klebsiella aerogenes, on soil &plant development metrics. Validation of these results by 16S rRNA gene sequencing highlights the potential of these isolates for soil remediation in salt-affected areas. The study highlighted the importance of microbial interventions in alleviating soil deterioration and fostering sustainable land use practices, and it suggests more field studies with different varieties of trees.

Utilization of Actinomycetes to increase phosphate availability at different soil moisture conditions in Andisols Namanteran, North Sumatera

The high phosphate retention in Andisols causes the availability of P to be low, can not be absorbed by plants. Actinomycetes are capable of solubilizing bound phosphates. This research aimed to identify Actinomycetes in Andisols Namanteran, assess their ability to increase phosphate availability, and understand how they work to increase phosphate availability in this soil. The research design used a factorial randomized block design with 2 factors; factor 1 was Actinomycetes isolate, consisting of A₀ = No Inoculant, A₁ = Inoculant A₁₃₂ (vegetable crops; 32 × 10⁸ CFU mL⁻¹), A₂ = A₄₆₈ (forest plants; 41 × 10⁸ CFU mL⁻¹), A₃ = A₄₅₈ (forest plant; 58 × 10⁸ CFUmL⁻¹), A₄ = A₄₇₁ (coffee plant; 35 × 10⁸ CFU mL⁻¹), A₅ = A₄₅₉ (forest plant; 63 × 10⁸ CFU mL⁻¹), A₆ = A₃₂₁ (hibiscus plant; 37 × 10⁸ CFU mL⁻¹), and A₇ = A₃₅₆ (vegetable plant; 33 × 10⁸ CFU mL⁻¹), and factor 2 was soil water content, consisting of K₁ = 50%, K₂ = 75% and K₃ = 100% of field capacity. The results showed that the availability of P in Andisols increased due to the application of Actinomycetes from 42.46 ppm to 159.20−266.60 ppm. The population of Actinomycetes in Actinomycetes treatment ranged from 27.33−31.58 × 10⁸ CFU mL⁻¹), with a soil pH of 4.41. Water content of 100% was the best in increasing soil pH and Actinomycetes population, but not having significant effects on the available P of the soil. The results of molecular identification of Actinomycetes that have the best potential in dissolving P include A₃>A₅>A₂>A₄>A₁.

The influence of flow, nutrient enrichment and aquatic macrophytes on benthic microalgal dynamics in a perched temporarily closed estuary

This study investigated the benthic microalgal dynamics in a temporarily closed microtidal estuary situated along a degraded stretch of coastline, where estuaries are impacted by development, flow modification, and nutrient pollution. The near natural, perched uMdlotane Estuary experienced regular high flow conditions that maintained the open mouth state for 40% of the study period. Increased nutrient input originated from agricultural-return flow derived from the extensive catchment sugarcane farming (55.9%). No notable temporal differences were recorded for the benthic microalgal biomass (range: 0–41.3 mg m−2). The benthic diatom diversity and evenness indices ranged between 0.6 and 3.1 H′ and 0.2–1 J′, respectively. Higher benthic microalgal biomass (14.9 ± 15.6 mg m−2) coincided with lower diatom diversity (1.3 H’) in the lower reaches. The habitat stability provided by the rooted Stuckenia pectinata facilitated benthic microalgal accumulation, while the absence of sediment disturbance contributed to the decrease in the benthic diatom diversity. The benthic diatom species Cocconeis lineata, Halamphora acutiuscula, and Hantzschia amphioxys largely dominated the community. Temporal differentiation in benthic diatom composition was driven by salinity, water temperature, phosphate, and photic depth changes. The pollution tolerant species Cyclotella atomus increased in abundance (sub-dominant RA = 5%) in response to increased phosphate availability. The presence of nutrient tolerant taxa serves as an early warning of impending environmental deterioration. Implementation of an adaptive management approach supported by monitoring is required to facilitate timely interventions to prevent the loss of ecosystem functionality induced by nutrient enrichment.

The Utilization of Serratia marcescens to Increase Phosphate-Availability and Production of Cucumber in Alfisols

Serratia marcescens is a bacterium that can dissolve phosphate (P) in soil, increasing phosphate availability and allowing plants to use it to support plant growth. P-available in the soil is generally low, including in Alfisols, due to the formation of bonds with Al, Fe, Ca, Mg, and other cations, which is influenced by soil pH or clay mineral adsorption. Cucumber plants require adequate nutrients, including P nutrients, for optimal growth and production. The study was carried out in a greenhouse using a completely randomized design (CRD) with four treatments and five replications. The treatments were S. marcescens bacterial solution concentrations of P0 (0 ml); P1 (20 ml); and P2 (20 ml); P3 (60 ml) bacterial colony density: 33x109 cfu/ml. According to the findings of the study, S. marcescens inoculation had a significant effect on increasing soil pH by 6,16, P-total concentration of 41,62 mg/100g, P-available concentration of 28,39 ppm, P-tissue concentration shoot and root were 0,30% and 0,78%, respectively, and P-root uptake of 2,27 g/pot. Similarly, S. marcescens inoculation significantly affected the plant height of 138,72 cm, root volume of 43 ml, and root length of 59,92 cm compared to the control treatment.

Increasing the Effectivity of Liquid Organic Fertilizer Enriched with Enterobacter cloacae to increase Phosphate Availability and Yield of Maize in Inceptisols

Inceptisols have problems of low availability of phosphorus. To improve soil phosphate and P fertilizer efficiency, it is necessary to develop fertilizer enriched with phosphate solubilizing bacteria (PSB). Liquid organic fertilizer enriched with PSB is expected to increase the efficiency in fertilization and improve the yield of sweet corn plants. This study was aimed to determine the effectiveness of liquid organic fertilizer enriched with Enterobacter cloacae on phosphate availability and increase the yield of maize (Zea mays L.) in Jatinangor Inceptisols. This experiment has been carried out at the Laboratory and Experimental Garden, Jatinangor, West Java, Indonesia with altitude of ±725 m above sea level. This experiment was conducted from March to September 2021. This experiment used Randomized Block Design (RBD) with three repetitions. The experiment showed the 10 L ha-1 of liquid organic fertilizer enriched with Enterobacter cloacae indigenous from Inceptisols enhanched the availability of phosphate (22,48 mg kg-1) and yield of maize (14,11 ton ha-1). Liquid organic fertilizer enriched with Enterobacter cloacae can reduced 50% of P fertilization and proposed as an alternative corn fertilizer and increased the yield of maize up to 55%, because Enterobacter cloacae to increase P solubility that caused soil available P increased.

UJI AKTIVITAS BAKTERI PELARUT FOSFAT TERHADAP KELARUTAN FOSFAT PADA TANAH SALIN

The high salt content in saline soils is the main cause of low salinity soil fertility, especially phosphorus nutrients. The application of phosphate-solubilizing bacteria in saline soil is one method to increase phosphate availability in saline soils. The study consisted of two tests, namely (1) qualitative and quantitative testing of phosphate-solubilizing bacteria in saline conditions and (2) testing of the activity of phosphate solubilizing bacteria in saline soil. This study used Pseudomonas sp. and Bacillus valezensis (Soil Biology Laboratory collection), Inceptisol saline soil from Banongan and Agel Situbondo. The study aimed to determine the activity of phosphate-solubilizing bacteria on the solubility of phosphate in saline soil. The results showed that: (1) Pseudomonas sp. and Bacillus valezensis have a solubility index of 1.25 to 2.68 on solid Pikovskaya medium with some NaCl concentration. Quantitatively test on liquid Pikovskaya medium, water-soluble phosphate concentration about 4.84 ppm to 14.18 ppm and soluble phosphate (extract Bray) between 15.91 ppm to 21.58 ppm. In addition, (2) on saline soil showed that Pseudomonas sp. and Bacillus valezensis could increase phosphate availability by 11.61% to 72,89%. Based on the study results, the genus Pseudomonas sp. and Bacillus valezensis have the potential to increase phosphate availability in saline soils.

Insight into the mechanisms of insoluble phosphate transformation driven by the interactions of compound microbes during composting.

Phosphate-solubilizing (PS) microbes are important to improve phosphorus availability and transformation of insoluble phosphate, e.g., rock phosphate (RP). The use of phosphate solubilizing bacteria (PSB) as inoculants have been proposed as an alternative to increase phosphate availability in RP and composting fertilizers. In this study, the effect of compound PSB coinoculation and single-strain inoculation on the transformation of insoluble phosphate were compared in a liquid medium incubation and RP-enriched composting. The goal of this study was to understand the possible mechanisms of insoluble phosphate transformation driven by the interactions of compound PS microbes during composting. The correlations between organic acids production, P-solubilization capacity and bacterial community with PSB inoculation were investigated in the RP-enriched composting by redundancy analysis (RDA) and structural equation models (SEM). Results showed that both single-strain and compound PSB inoculants had a high P-solubilization capacity in medium, but the proportion of Olsen P to total P in composts with inoculating compound PS microbes was 7% higher than that with single strain. PS inoculants could secrete different organic acids and lactic was the most abundant. However, RDA and SEM suggested that oxalic might play an important role on PS activity, inducing RP solubilization by changing pH during composting. Interaction between compound microbes could intensify the acidolysis process for insoluble P transformation compared to the single strain. Our findings help to understand the roles of complex microbial inoculants and regulate P availability of insoluble phosphate for the agricultural purposes.

Identification and characterization of an Arabidopsis phosphate starvation-induced secreted acid phosphatase as a vegetative storage protein

Induction and secretion of acid phosphatases is an adaptive response of plants to phosphate starvation. The secreted acid phosphatases are believed to scavenge phosphate from organophosphate compounds in the rhizosphere, thereby increasing phosphate availability for plant absorption. To date, however, all of the characterized phosphate starvation-induced secreted acid phosphatases in plants belong to a unique acid phosphatases subfamily, called purple acid phosphatase. In this work, we identified a phosphate starvation-induced secreted acid phosphatase in Arabidopsis as a vegetative storage protein, AtVSP3. AtVSP3 exists as a monomer with molecular weight of 29 kDa. The activity of recombinant AtVSP3 protein is activated by Mg2+, Co2+, and Ca2+. AtVSP3 has an optimal pH of 6.5 for its APase activity and is relatively thermostable. The transcription of AtVSP3 is induced in roots by phosphate starvation, and the accumulation of AtVSP3 protein is high in roots and siliques. Additional research is needed to determine the function of AtVSP3 in plant responses to stress conditions.

Determinants of bryophyte species composition and diversity on the Great Alvar of Öland, Sweden

Factors driving the species richness and distribution of bryophytes are poorly studied and not well understood, particularly in grasslands. We analysed the occurrence of bryophyte species and variation in species richness across 674 plots (0.5 m × 0.5 m) in alvar vegetation (grassland on limestone pavement with thin or no soil) on Öland (Sweden) in relation to substrate characteristics and chemistry, inundation frequency, grazing pressure and geographical variables. We found 148 taxa, including 11 nationally red-listed ones. Species richness per plot was significantly associated with substrate type, positively associated with pH and grazing intensity, but negatively associated with soil depth. However, richness of species typical of, or restricted to, alvar habitats responded differently to richness of species more common in other habitats. Typical alvar species were favoured by high pH, shallow soil and low phosphate availability, while generalists preferred relatively low pH, higher phosphate availability and organic or mull soil types. Distance from the alvar margin had only weak effects. Concerning the effects on individual species and community composition, inundation frequency and pH were found to have the largest effects, although other factors (substrate type, soil depth, bare soil, bare stone, phosphate availability and grazing pressure) were more important for some individual species, stressing the importance of microsite variability and variability in management for regional species richness. From a conservation perspective, it is concluded that grazing is generally positive whilst factors increasing phosphate availability may disadvantage the typical alvar species, and proximity to the alvar margin is not a major problem.

Phosphate-solubilizing fungi for efficient soil phosphorus management

Rhizosphere soil extracts obtained from eight cinnamon species and three pepper species cultivated organically were inoculated initially on Pikovskaya (PVK) medium. The twelve fungal isolates that solubilized the insoluble phosphates were further tested on the same medium added with both insoluble tricalcium phosphate and soluble dipotassium hydrogen phosphate to detect the expression of the trait in the presence of soluble phosphates in soil, for which all twelve qualified. The efficiencies of phosphate solubilization were investigated in two liquid media: PVK medium to represent soil phosphate pool and a rock phosphate (RP) medium, by determining the available phosphorus concentration in the liquid media at the end of the 24 h and 72 h incubation periods, respectively. The pH reduction in the medium was measured to ascertain the organic acid production by fungal isolates as a mechanism of solubilization. Three fungal isolates showing the highest efficiencies in phosphate solubilization were taxonomically identified based on the micromorphological characteristics and molecular techniques. Two isolates were identified as Penicillium oxalicum and Trichorderma virens and the other was belonging to the genus Aspergillus. A possible synergism between the three fungal species towards phosphate dissolution was detected using the broth culture procedure. Aspergillus sp. in combination with P. oxalicum dissolved both Ca3(PO4)2 and RP recording the highest significant dissolved phosphate levels of 893.43 (±56.768) mg P/L and 309.42 (±42.52) mg P/L, respectively, within 72 h post inoculation, making them prospective candidates for increased phosphate availability of soil phosphate pool and rock phosphates.

High serum phosphate concentration as the result of smoking might underlie the lower risk of Parkinson’s disease

Epidemiological studies have found a negative association between cigarette smoking and Parkinson’s disease (PD): PD patients are approximately 50% less likely to have smoked cigarettes than age- and sex-matched controls. In both women and men, the PD protection effect of smoking may be explained by higher levels of phosphate in serum (S-P) and triglycerides (S-TG) in smokers compared to non-smokers. That is, the protecting effect from smoking could be mediated by either a high S-P or high S-TG levels. I suggest that higher S-P as the result of smoking may be associated with intracellular depletion of Pi in skeletal muscle and that this depletion of Pi is associated with increased availability of phosphate for the brain. This increased phosphate availability would protect against PD, as oxidative phosphorylation in the mitochondria is a central and persistent phenomenon in the pathogenesis cascade of PD. Phosphate is necessary for energy production in the form of creatine phosphate (CP) and adenosine-tri-phosphate (ATP) in the brain and skeletal muscle. As such, hypophosphatemia increases risk of cell death. In some clinical instances, this energy depletion may pre-dispose to dopamine neuron death. Mitochondrial dysfunction is associated with the generation of oxidative stress and mediates the induction of apoptosis. Studies with NMR spectroscopy reveal that an energy deficit in brain cells is a strong mark for PD although this differed for men and women. Compared to women, men had lower serum phosphate and ATP levels in the brain (about 15% lower). In addition to sex differences, age, stress, and malnutrition may cause low serum phosphate levels, a situation that could contribute to the lack of energy available to the brain and the risk of PD. As hypophosphatemia is present in overnutrition and has an inverse relation with a high BMI, both obesity and malnutrition are considered to be presumptive risk factor for PD.

Polyphosphate accumulation is driven by transcriptome alterations that lead to near-synchronous and near-equivalent uptake of inorganic cations in an arbuscular mycorrhizal fungus.

Arbuscular mycorrhizal (AM) fungi accumulate a massive amount of phosphate as polyphosphate to deliver to the host, but the underlying physiological and molecular mechanisms have yet to be elucidated. In the present study, the dynamics of cationic components during polyphosphate accumulation were investigated in conjunction with transcriptome analysis. Rhizophagus sp. HR1 was grown with Lotus japonicus under phosphorus-deficient conditions, and extraradical mycelia were harvested after phosphate application at prescribed intervals. Levels of polyphosphate, inorganic cations and amino acids were measured, and RNA-Seq was performed on the Illumina platform. Phosphate application triggered not only polyphosphate accumulation but also near-synchronous and near-equivalent uptake of Na(+) , K(+) , Ca(2+) and Mg(2+) , whereas no distinct changes in the levels of amino acids were observed. During polyphosphate accumulation, the genes responsible for mineral uptake, phosphate and nitrogen metabolism and the maintenance of cellular homeostasis were up-regulated. The results suggest that inorganic cations play a major role in neutralizing the negative charge of polyphosphate, and these processes are achieved by the orchestrated regulation of gene expression. Our findings provide, for the first time, a global picture of the cellular response to increased phosphate availability, which is the initial process of nutrient delivery in the associations.

High phosphate availability as a possible cause for massive cyanobacterial production of oxygen in the Paleoproterozoic atmosphere

The deposition of major Precambrian phosphorites was restricted to times of global change and atmospheric oxygenation at both ends of the Proterozoic. Phosphorites formed after highly positive carbon isotope excursions in carbonates deposited during the Paleoproterozoic Lomagundi-Jatuli event and the Neoproterozoic Cryogenian and Ediacaran periods. The correlative step-wise rise in atmospheric oxygen over the Proterozoic has been linked to changes in the carbon cycle. However, the postulated relations between carbon isotope events, phosphorites, and atmospheric oxygenation remain unexplained. Paleoproterozoic carbonates of the Aravalli Supergroup, India, preserve evidence for cyanobacterial blooms in the form of tightly packed stromatolitic columns in the world's oldest significant sedimentary phosphate deposit. Restricted basins of the Lower Aravalli Group with stromatolitic phosphorites in Jhamarkotra, Udaipur, Jhabua, and Sallopat exhibit near-zero δ13Ccarb values and large ranges of δ13Corg values between −33.3‰ and −10.1‰, indicative of a complex carbon cycle. Because phosphate accumulates primarily in oxic sediments, these eutrophic microbial ecosystems likely developed within the photic zone of the shallow, oxygenated marine realm. This is consistent with deposition during the time of increasingly more oxidizing conditions, after the Great Oxidation Event (GOE). Approximately contemporaneous basins without phosphate deposits from Ghasiar, Karouli, Negadia, Umra, and Babarmal exhibit a range of positive δ13Ccarb excursions, some with values up to +11.2‰, that suggest high rates of organic carbon burial, and others with moderately high δ13Ccarb values around +6‰ or +3‰, that suggest smaller carbon cycle perturbations. The δ15N values of all these rocks vary between −0.7‰ and +3.4‰, and are consistent with the predominance of nitrogen fixation during cyanobacterial blooms in all basin types. Such low nitrogen isotope values are interpreted to have arisen from the biological response to high phosphate availability. We conclude that increased phosphate availability during and after the Paleoproterozoic Lomagundi-Jatuli event likely caused cyanobacterial blooms and was a key factor in the oxygenation of Earth's atmosphere. Increasing oxygenation of the shallow ocean seafloor favored the removal of excess phosphate as authigenic apatite, thus dampening effects of weathering increases on organic burial and marine δ13Ccarb after about 2.0Ga.

Roles of Ubiquitination in the Control of Phosphate Starvation Responses in PlantsF

Throughout evolution, plants have evolved sophisticated adaptive responses that allow them to grow with a limited supply of phosphate, the preferential form in which the essential macronutrient phosphorus is absorbed by plants. Most of these responses are aimed to increase phosphate availability and acquisition through the roots, to optimize its usage in metabolic processes, and to protect plants from the deleterious effects of phosphate deficiency stress. Regulation of these adaptive responses requires fine perception of the external and internal phosphate levels, and a complex signal transduction pathway that integrates information on the phosphate status at the whole-plant scale. The molecular mechanisms that participate in phosphate homeostasis include transcriptional control of gene expression, RNA silencing mediated by microRNAs, regulatory non-coding RNAs of miRNA activity, phosphate transporter trafficking, and post-translational modification of proteins, such as phosphorylation, sumoylation and ubiquitination. Such a varied regulatory repertoire reflects the complexity intrinsic to phosphate surveying and signaling pathways. Here, we describe these regulatory mechanisms, emphasizing the increasing importance of ubiquitination in the control of phosphate starvation responses.

Differential interaction between two Glomus intraradices strains and a phosphate solubilizing bacterium in maize rhizosphere

Abstract Arbuscular mycorrhizal (AM) fungi and phosphate solubilizing bacteria (PSB) have a positive effect on plant productivity primarily through increasing phosphate availability. In order to study the interaction between AM fungi and PSB, we used Bacillus megaterium, a PSB isolated from the sterilized surface of AM germinated spores, and two strains of the AM fungus Glomus intraradices with different mycelial architecture. A greenhouse experiment was designed with maize as host plant with the addition of tribasic calcium phosphate. We tested the hypothesis that PSB, intimately linked with AM fungi, could interact differentially with the two AM strains. We concluded that inoculation with the PSB positively affected maize mycorrhization. Insoluble phosphate alone did not influence the AM extraradical mycelium (ERM) length and maize mycorrhization when bacteria were not inoculated. The results provide evidence that the adverse effect on infectivity for some AM strains might be caused by solubilized phosphorus release to the rhizosphere by PSB. Differences related to the mycelium architecture of each AM strain were observed: the density of PSB in rhizosphere soil was significantly higher only with the GA8 strain coinciding with the highest values of maize biomass. The density of bacteria associated with GA8 mycelium could be the result of the transfer of photosynthates through the rhizosphere; this close contact would favor the persistence of the intimate relationship between PSB and AM hyphae. In the bacteria-free treatments, soil adherence was not significantly altered. Although the highest development of ERM occurred with GA5, plants inoculated with GA8 showed the highest values for soil adherence. This may be due to the AM mycelium which modifies bacterial persistence in the rhizosphere and consequently soil adherence. Our results show that for potential applications, some characteristics of the AM strains are key in the selection of the AM fungi–PSB combinations. These include the tolerance to soluble phosphorus, the rate of root colonization, and ERM development that favors the persistence of bacteria in rhizosphere soil.

Temporal and diel cycling of nutrients in a barrier–lagoon complex: Implications for phytoplankton abundance and composition

The cycling of nutrients (silicate, nitrate, ammonium and phosphate) in a quasi-pristine barrier–lagoon complex (Louro Lagoon, NW Iberian Peninsula) was studied both in a diel and temporal timescale covering different seasonal conditions. Hydrographical and meteorological conditions exert a major control on the nutrient cycling in the lagoon. From late autumn to early spring the lagoon is characterized by oxic conditions due to significant freshwater inputs and sporadic communication with the sea. In summer, elevated primary production coupled with water stagnancy leads to bottom waters hypoxia and marked diel variation of pH, oxygen and redox potentials. Diel variation of nutrients was only evident when mixing of surface and bottom waters during the night was observed.Temporal changes in nutrients concentrations and their relative abundance were found to induce a clear shift in the phytoplankton composition. In winter, during silicate and nitrate abundance and low phosphate, diatoms predominate. In summer, under hypoxic conditions, sediments take control on the supply of nutrients leading to increased phosphate availability relative to nitrate/ammonium or silicate. Diatoms are then replaced during the summer blooms – linked to low atomic N:P ratios (typically <2) – by flagellates and green algae with minor contributions of cyanophytes and dinoflagellates.

接种AM真菌对玉米和油菜种间竞争及土壤无机磷组分的影响

在温室盆栽条件下,分别模拟单作、间作和尼龙网分隔种植,比较接种丛枝菌根(arbuscular mycorrhizal, AM)真菌<em>Glomus intraradices</em>和<em>Glomus mosseae</em>对菌根植物玉米和非菌根植物油菜生长和磷吸收状况的影响,并分析土壤中各无机磷组分的变化。结果发现,接种AM真菌可以促进土壤中难溶性磷(Ca₁₀-P和O-P)向有效态磷转化,并显著降低总无机磷含量 (<em>P</em><0.05),显著提高菌根植物玉米的生物量和磷吸收量(<em>P</em><0.05),特别是在间作体系中使玉米的磷营养竞争比率显著提高了45.0%-104.1% (<em>P</em><0.05),显著降低了油菜的生物量和磷吸收量(<em>P</em><0.05),从而增强了了菌根植物的竞争优势,降低了非菌根植物与菌根植物的共存能力。揭示了石灰性土壤中AM真菌对植物物种多样性的影响,有助于更加全面地理解AM真菌在农业生态系统中的作用。;Arbuscular mycorrhizal fungi (AMF) form mutualistic associations with more than 85% of terrestrial plant species and play key roles in nutrient cycling and ecosystem functioning. Most plant individual stimulates nutrient availability through their fungal partner. Highly mycorrhizal-dependent plant species derive more benefits from AMF in comparison to low mycorrhizal dependency plant species. But the effects of AMF on the competition between mycorrhizal and non-mycorrhizal plants remained largely unclear, particularly in an environment with low phosphate bioavailability. The increased phosphate availability for host plants and enhanced plant phosphorus nutrition is a major outcome of the AM symbiosis and then AMF colonization could and consequently increase plant biomass. The larger plants are then expected to be successful competitors. <br> In our previous, AMF colonization significantly decreased phosphorus concentration and content of rape roots compared with non-inoculation treatments, while in contrast mycorrhizal association improved phosphorus nutrition of maize plants. The results clearly showed the beneficial effects of mycorrhizal associations on AMF host plants in competition with non-host plants. In this previous research, plants were cultivated in purple soil with higher phosphorus availability which is more important as this determined the effect of AMF inoculation on host plant P nutrition. Then in this research, calcareous fluvo-aquic soil with lower phosphorus availability was used and different form of inorganic phosphorus were measured to reveal the effect of AMF inoculation on competition between mycorrhizal plant and non-mycorrhizal plants species. Maize (<em>Zea mays </em>L.) and rape (<em>Brassica napus </em>L.) plants were cultivated in three different interaction patterns, namely intraspecific (monoculture), intespecific (intercropping) and no interaction (nylon net split). All plants were inoculated with <em>Glomus intraradices</em>, <em>Glomus mosseae</em> or remained uninoculated. The strength of competition was measured as the reduction in biomass caused by the presence of a competitor. The results showed that AMF inoculation decreased soil inorganic phosphate significantly and transformed more Ca₁₀-P and O-P into higher availability phosphorus form. In the intercropping treatment, the inoculation improved the plant growth and phosphorus uptake of maize, and meanwhile decreased the growth and phosphorus uptake of rape significantly. Our results clearly showed the strong competitive strength and phosphorus competitive strength of maize to rape., and the beneficial effects of mycorrhizal associations was due to the favorable growth of host plants over non-host plants. It reveals that AM fungus may play an important role in structuring plant community and needs a comprehensive insight to understand the effect of AM fungus on plant biodiversity in ecosystems.

Fire-mobilized nutrients from hydrophyte leaves favor differentially Typha domingensis seedling growth

In wetlands, altered disturbance regimes can change species composition and favor the expansion of invasive species. In Central Mexico, Typha domingensis expands after fires to colonize areas previously dominated by other natives, but the mechanisms are unknown. To explore if the invasion is facilitated by nutrient release after fire, we tested the effect of ash from Schoenoplectus americanus and T. domingensis plants on the growth of T. domingensis seedlings. Schoenoplectus ash had higher concentration of soluble phosphates (0.68±0.23mg/g) than Typha ash (0.36±0.08mg/g). At two months Typha seedlings were taller (48±8cm) in the treatment with Schoenoplectus ash added than in either the treatment with Typha ash (29±7cm) or in the control (25±6cm). Aboveground biomass (1.03±0.42g, 0.36±0.17g, 0.27±0.11g) and belowground biomass (0.65±0.24g, 0.32±0.11g, 0.27±0.11g) showed the same trends. Typha seedlings fertilized with Schoenoplectus ash had the lowest root:shoot ratios, but the largest rhizomes (dry weight 0.07±0.03g), followed by those fertilized with Typha ash (0.04±0.01g) and control plants (0.03±0.01g). These results show that T. domingensis responds to increased phosphate availability from ash of other species by growing larger and allocating more to storage tissues. We conclude that fire promotes the spread of Typha by facilitating seedling growth especially in areas dominated by S. americanus.

Composition of characteristic soils on the raised atoll Bellona, Solomon Islands

Knowledge is scarce about the composition of soils on Bellona and other Pacific atolls. Such knowledge is important as it is closely related to sustainable land use of these special soils formed on carbonatic/phosphatic materials. Therefore, the micromorphological, chemical and mineralogical composition of samples from genetic horizons in three dominant Bellonese soils (Malanga, Kenge Ungi and Kenge Toaha) and underlying rock (Tanahu) were investigated. Tanahu mainly consists of dolomite, but this mineral is absent in the three soils, which are dominated by phosphate-containing minerals. The Malanga soil is strongly dominated by Ca and P with minor amounts of Al, F and Fe present in fluorapatite, hydroxyapatite and crandallite. In contrast, Al, Fe and P dominate in the Kenge Ungi and Kenge Toaha soils in accordance with a mineralogy consisting of crandallite together with aluminum oxides (gibbsite/boehmite) and iron oxides, mainly goethite with minor contents of hematite. The observed carbonate for phosphate substitution in the apatites and crandallite is important as it indicates an increased phosphate availability in the soils. All three soil samples contain ≤1% Si and very little K and Mg. Total contents of essential microelements are considered adequate, but the rather high contents of Sr and U, especially in the Kenge Ungi soil may be problematic. Although the composition of the soils suggests substantial fertility and resilience, the lack of K-containing weatherable minerals (silicate minerals) is in line with a very low K (and low Mg) content and explains why fertilization may be needed to sustain future cultivation of these special soils. Due to a possible low bioavailability of Fe, Mn and maybe other micronutrients at the circumneutral pH of these carbonatic/phosphatic soils as well as the rather high contents of Sr and U, it may be recommended to test element availability using appropriate chemical soil tests supplemented by plant experiments to ensure safe and sustainable (optimal) soil use. However, according to the local farmers, the Malanga, Kenge Toaha and Kenge Ungi soils are considered well suited for production of the preferred crops.

Pyrroloquinoline Quinone Biosynthesis GenepqqC, a Novel Molecular Marker for Studying the Phylogeny and Diversity of Phosphate-Solubilizing Pseudomonads

Many root-colonizing pseudomonads are able to promote plant growth by increasing phosphate availability in soil through solubilization of poorly soluble rock phosphates. The major mechanism of phosphate solubilization by pseudomonads is the secretion of gluconic acid, which requires the enzyme glucose dehydrogenase and its cofactor pyrroloquinoline quinone (PQQ). The main aim of this study was to evaluate whether a PQQ biosynthetic gene is suitable to study the phylogeny of phosphate-solubilizing pseudomonads. To this end, two new primers, which specifically amplify the pqqC gene of the Pseudomonas genus, were designed. pqqC fragments were amplified and sequenced from a Pseudomonas strain collection and from a natural wheat rhizosphere population using cultivation-dependent and cultivation-independent approaches. Phylogenetic trees based on pqqC sequences were compared to trees obtained with the two concatenated housekeeping genes rpoD and gyrB. For both pqqC and rpoD-gyrB, similar main phylogenetic clusters were found. However, in the pqqC but not in the rpoD-gyrB tree, the group of fluorescent pseudomonads producing the antifungal compounds 2,4-diacetylphloroglucinol and pyoluteorin was located outside the Pseudomonas fluorescens group. pqqC sequences from isolated pseudomonads were differently distributed among the identified phylogenetic groups than pqqC sequences derived from the cultivation-independent approach. Comparing pqqC phylogeny and phosphate solubilization activity, we identified one phylogenetic group with high solubilization activity. In summary, we demonstrate that the gene pqqC is a novel molecular marker that can be used complementary to housekeeping genes for studying the diversity and evolution of plant-beneficial pseudomonads.