Bioenergy production combined with phytoremediation has been suggested to help in solving two critical world problems: the gradual reduction of fossil fuels and soil contamination. The aim of this ...research was to investigate the potential for the use of Ricinus communis L. (castor oil plant) as an energy crop and plant species to remediate metal-polluted sites. This study was performed in mine tailings containing high concentrations of Cu, Zn, Mn, Pb and Cd. Physico-chemical characterization, total, DTPA-extractable and water-soluble metals in rhizospheric tailings heap samples were carried. Metal concentrations in plant tissues and translocation factors (TFs) were also determined. The Ricinus seed-oil content was high between 41 and 64%, seeds from San Francisco site 6 had the highest oil content, while these from site 7 had the lowest. No trend between oil yield vs seed origin site was observed. Seed-oil content was negatively correlated with root concentration of Cu, Zn, Pb and Cd, but no correlation was observed with the extractable-metals. According to its shoot metal concentrations and TFs, castor bean is not a metal accumulator plant. This primary colonizing plant is well suited to cope with the local toxic conditions and can be useful for the stabilization of these residues, and for then decreasing metal bioavailability, dispersion and human health risks on these barren tailings heaps and in the surrounding area. Our work is the first report regarding combined oil production and a phytostabilization role for Ricinus plants in metal mine tailings and may give a new value to suitable metal-polluted areas.
► We evaluated metal uptake by Ricinus communis in tailing heaps. ► Oil content in R. communis seeds ranges from 41 to 64%. ► Castor bean plants phytostabilizate mine residues. ► Castor bean plants do not accumulate high concentrations of Ni, Zn nor Cd. ► R. communis could be used for soil remediation and oil production.
Metal(loid)s are contaminants of concern emitted as particulate matter (PM) from several pollution sources. The objective was to characterize potential exposure from local airborne metal(loid)s in a ...community in proximity to mine tailings. Air samples were collected weekly at five sites around the municipal mine tailings using two Hi-volume samplers for simultaneously collecting PM
10
and PM
2.5
. Total suspended particulates (TSP), concentrations, speciation, and bioaccessibility of metal(loid)s were quantified. The size and form of particles were determined by scanning electron microscopy. The concentration of TSP (μg m
−3
) in the airborne samples ranged from 21.2 to 64.6 for PM
2.5
and 23.6 to 80.1 for PM
10
. The profiles of analyzed quasi-total metal(loid) concentration from all sampling sites were similar between these aerosols PM sizes except at site 2 for Cd, at site 3 for Cu, and site 4 for Zn. The order of quasi-total metal(loid) concentration, in the airborne samples for both PM sizes, was As > Zn > Fe > Pb > Cu > Mn > Cd. As speciation included As-sulfite, As(III)-O, and As(V)-O with less concentration of As(III)-O in both PM sizes. Bioaccessible metal(loid) concentrations were very high and represented a great percentage from the quasi-total airborne concentrations, for instance, 10% and 37% for Pb and 8% and 6% for As in pulmonary and gastric bioaccessible concentrations, respectively. Knowing the toxic effects of these pollutants, there is an urgent need to establish environmental regulation of bioaccessible pollutant concentrations from PM dislodged from uncovered metal(loid) mine tailings affecting not only nearby human populations but also possible long-distance ecosystem transport.
Phosphate-solubilizing bacteria can release phosphorus (P) from insoluble minerals and benefit either soil fitness or plant growth. Bulk sized P compounds have been suggested but little is known ...about solubilization of nanosized materials such as hydroxyapatite nanoparticles (HANP). A screening of the initial 43 strains from vanilla rhizospheres for phosphate solubilization with bulk Ca
3
(PO
4
)
2
was carried out. Subsequently, 6 strains were selected on bulk rock phosphate (RP) and HANP. Two kinetics experiments were run out regarding evaluation at 5, 10 and 20 days after inoculation (dai). Bacterial biomass production was similar in both experiments; the lowest biomass was found at 20 dai. In all cases, bacteria reduced the original culture medium pH; which was related with phosphate solubilization from the production of organic acids. Citric acid was produced by all strains.
Enterobacter cloacae
CP 31 was the most interesting bacterium: produced the lowest culture pH at 20 dai (4) with both Ca
3
(PO
4
)
2
and RP, and 3.7 at 10 dai with HANP correlating with high soluble P concentration (536, 64 and 13 mg L
−1
with these P sources, respectively). This bacterium should be tested as an inoculant in plants to reveal its potential as plant promoter growth and HANP to suggest its role in the potential use of nano-P fertilizers.
In several countries, coffee is traditionally grown under the shade of large trees; however, the non-shade surface system has increased. Shade cultivation system benefits the soil, helps crops ...adaption to climate change, and reduces vulnerability. This study aimed to compare the physical, chemical, and biological soil features under coffee production systems: coffee-mango, coffee-banana, and full-sun coffee; to identify the nutritional variation of coffee plants in the three cultivation systems, and to establish recommendations for coffee production associated with other crops. Soil properties varied between the shaded and full-sun systems. The shade coffee systems had different pH, cation exchange capacity, potassium, and nitrogen concentrations, organic matter, carbon-, nitrogen-microbial biomass, and the number of earthworms from the full-sun coffee system. The coffee-mango association showed specific soil (exchangeable calcium, moisture, soil porosity, and aggregate stability index), foliar (calcium, potassium, nitrogen, iron, and chlorophyll a and b concentrations), and grain features (gold coffee yield, potassium, magnesium, and phosphorous concentrations) that make distinct from the other two coffee systems. The coffee-mango system positively influenced soil traits, nutrient concentration in leaves, production, yield, and nutritional status of the fruit. The production of coffee under full-sun adversely affects the soil and the coffee’s nutrition and yield. Therefore, the production of coffee should be in the traditional manner under shade trees. These results apply to coffee production under shade systems in other countries with similar agroecological conditions and to soil conservation as a pertinent vision under global climate change.
•Results may help producers for a sustainable coffee management.•The coffee-mango association improved soil characteristics that promote a higher yield.•The coffee-mango production system also increased nutrient concentration in leaves and fruit.•Immediate actions should be taken to preserve soil sustainability under shade coffee systems.
Vanilla planifolia is the source of the spice vanilla. This study is part of an international initiative to study the biology, including mycorrhizal fungi and cultivation practices of vanilla to ...improve its production in Mexico. The study focused on documenting mycorrhizal fungal diversity in vanilla. It also provided preliminary data on differences in mycorrhizal fungal communities associated with cultivation practices. A richer mycorrhizal community was observed in vanilla growing in a wild natural farm compared with those from a highly managed farm. Our research provides insights for sustainable vanilla production that can benefit Mexican farming communities.
Social Impact Statement
Vanilla planifolia is the source of the spice vanilla. This study is part of an international initiative to study the biology, including mycorrhizal fungi and cultivation practices of vanilla to improve its production in Mexico. The study focused on documenting mycorrhizal fungal diversity in vanilla. It also provided preliminary data on differences in mycorrhizal fungal communities associated with cultivation practices. A richer mycorrhizal community was observed in vanilla growing in a wild natural farm compared with those from a highly managed farm. Our research provides insights for sustainable vanilla production that can benefit Mexican farming communities.
Summary
Relatively little is known regarding differences in root symbionts (i.e., mycorrhizae) between epiphytic and terrestrial orchids. We characterized the mycorrhizal fungal communities of aerial and terrestrial roots of the orchid, Vanilla planifolia, from four Mexican farms representing different management systems.
Amplicon sequencing identified 40 putative mycorrhizal fungi based on ITS sequence data, these included traditional orchid mycorrhizal fungi such as Ceratobasidium, and Thanatephorus in the order Cantharellales as well as Serendipitaceae in the order Sebacinales, and species of several genera traditionally considered as ectomycorrhizal fungi. Mycorrhizal fungal communities were similar in aerial and terrestrial roots, but differed in read abundances.
Plants growing in wild‐natural conditions hosted a richer, but not statistically different, community of mycorrhizal fungi in comparison with plants in the highly managed farm. Soil characteristics including texture, organic matter, N, P, and K do not explain differences between fungal communities at these farms.
This is one of the first reports of a diverse community of fungi traditionally considered to form ectomycorrhizas in association with aerial orchid roots. Further research is needed to understand the functional role of these putative mycorrhizal fungi in the ecology of V. planifolia, and if ectomycorrhizal fungi commonly occur in other hemiepiphytic and epiphytic orchids.
Soil salinity is a limiting factor in crop productivity. Inoculating crops with microorganisms adapted to salt stress is an alternative to increasing plant salinity tolerance. Few studies have ...simultaneously propagated arbuscular mycorrhizal fungi (AMF) and dark septate fungi (DSF) using different sources of native inoculum from halophyte plants and evaluated their effectiveness. In alfalfa plants as trap culture, this study assessed the infectivity of 38 microbial consortia native from rhizosphere soil (19) or roots (19) from six halophyte plants, as well as their effectiveness in mitigating salinity stress. Inoculation with soil resulted in 26–56% colonization by AMF and 12–32% by DSF. Root inoculation produced 10–56% and 8–24% colonization by AMF and DSF, respectively. There was no difference in the number of spores of AMF produced with both inoculum types. The effective consortia were selected based on low Na but high P and K shoot concentrations that are variable and are relevant for plant nutrition and salt stress mitigation. This microbial consortia selection may be a novel and applicable model, which would allow the production of native microbial inoculants adapted to salinity to diminish the harmful effects of salinity stress in glycophyte plants in the context of sustainable agriculture.
Bacterial endophytes (120) were isolated from six halophytes (Distichlis spicata, Cynodon dactylon, Eragrostis obtusiflora, Suaeda torreyana, Kochia scoparia, and Baccharis salicifolia). These ...halophiles were molecularly identified and characterized with or without NaCl conditions. Characterization was based on tests such as indole acetic acid (IAA), exopolysaccharides (EPS), and siderophores (SID) production; solubilization of phosphate (P), potassium (K), zinc (Zn), and manganese (Mn); mineralization of phytate; enzymatic activity (acid and alkaline phosphatase, phytases, xylanases, and chitinases) and the mineralization/solubilization mechanisms involved (organic acids and sugars). Moreover, compatibility among bacteria was assessed. Eleven halophiles were characterized as highly tolerant to NaCl (2.5 M). The bacteria isolated were all different from each other. Two belonged to Bacillus velezensis and one to B. pumilus while the rest of bacteria were identified up to the genus level as belonging to Bacillus, Halobacillus, Halomonas, Pseudomonas, Nesterenkonia, and three strains of Oceanobacillus. The biochemical responses of nutrient solubilization and enzymatic activity were different between bacteria and were influenced by the presence of NaCl. Organic acids were involved in P mineralization and nutrient solubilization. Tartaric acid was common in the solubilization of P, Zn, and K. Maleic and vanillic acid were only detected in Zn and K solubilization, respectively. Furthermore, sugars appeared to be involved in the solubilization of nutrients; fructose was detected in the solubilization tests. Therefore, these biochemical bacterial characteristics should be corroborated in vivo and tested as a consortium to mitigate saline stress in glycophytes under a global climate change scheme that threatens to exacerbate soil salinity.
Plant surfaces are known as an important sink for various air pollutants, including particulate matter and its associated potentially toxic elements (PTE). Moreover, leaves surface or phylloplane is ...a habitat that harbors diverse bacterial communities (epiphytic). However, little is known about their possible functions during phytoremediation of air pollutants like PTE. The study of leaf epiphytic bacteria of plants colonizing mine residues (MR) containing PTE is thus a key to understand and exploit plant-epiphytic bacteria interactions for air phytoremediation purposes. In this research, we aimed (i) to characterize the functions of epiphytic bacteria isolated from the phylloplane of
,
,
sp., and
growing spontaneously on multi-PTE contaminated MR and (ii) to compare these against the same plant species in a non-polluted control site (NC). Concentrations (mg kg
) of PTE on MR leaf surfaces of
reached up to 232 for Pb, 13 for Cd, 2,728 for As, 52 for Sb, 123 for Cu in
, and 269 for Zn in
sp. In the four plant species, the amount of colony-forming units per cm
was superior in MR leaves than in NC ones, being
the plant species with the highest value. Moreover, the proportion of isolates tolerant to PTE (Zn, Cu, Cd, and Sb), UV light, and drought was higher in MR leaves than in those in NC. Strain BA15, isolated from MR
, tolerated 150 mg Zn L
, 30 mg Sb L
, 25 mg Cu L
; 80 mg Pb L
, and was able to grow after 12 h of continuous exposition to UV light and 8 weeks of drought. Plant growth promotion related traits N fixation, indole acetic acid (IAA) production, and phosphate solubilization of bacterial isolates varied among plant species isolates and between MR and NC sampling condition. The studied epiphytic isolates possess functions interesting for phytoremediation of air pollutants. The results of this research may contribute to the development of novel and more efficient inoculants for microbe-assisted phytoremediation applied to improve air quality in areas exposed to the dispersion of metal mine tailings.
Aims We investigated the possible transgenerational transfer of bacterial seed endophytes across three consecutive seed generations of Crotalaria pumila growing on a metal mining site in Mexico. ...Methods Seeds were collected during three successive years in the semi-arid region of Zimapan, Mexico. Total communities of seed endophytes were investigated using DNA extraction from surface sterilized seeds and 454 pyrosequencing of the V5-V7 hypervariable regions of the 16S rRNA gene. Results The communities consisted of an average of 75 operational taxonomic units (OTUs); richness and diversity did not change across years. Methylobacterium, Staphylococcus, Corynebacterium, Propionibacterium and eight other OTUs constituted >60% of the community in each generation The microbiome was dominated by Methylobacterium (present in >80% of samples). Functions associated with the microbiome were C and N fixation, oxidative phosphorylation and photosynthesis activity. Conclusions The bacterial endophytic communities were similar across three consecutive seed generations. Among the core microbiome Methylobacterium strains were the most abundant and they can contribute to nutrient acquisition, plant growth promotion and stress resilience to their host in metal contaminated mine residues. Identification of the seed microbiome of C. pumila may lead to novel and more efficient inoculants for microbe-assisted phytoremediation.
PDF
