A greenhouse pot experiment was conducted to evaluate the potential of three Brazilian leguminous woody species, Mimosa caesalpiniaefolia, Erythrina speciosa and Schizolobium parahyba, for the ...revegetation of lead- (Pb-) contaminated areas. The response of seedlings to increasing Pb concentrations (0, 250, 500 and 1000 mg kg−1) in the soil was studied. In addition to Pb accumulation and translocation, the following parameters were assessed: chlorophyll, nitrate, ammonia, lipid peroxidation (MDA) and free amino acid content; seedling growth; and nitrogenase activity. No differences were observed in the germination of woody species seeds sown in soils with or without Pb addition. M. caesalpiniaefolia did not show visual symptoms of Pb toxicity, while the other two species demonstrated stress symptoms, including reduced shoot biomass yield, leaf area and height. Biochemical analyses of plant tissues revealed markedly different responses to increasing Pb concentrations, such as changes in foliar soluble amino acid composition in S. parahyba; changes in ammonia and nitrate content in E. speciosa, M. caesalpiniaefolia and S. parahyba; and changes in MDA content in S. parahyba. The levels of chlorophyll a and b and carotenoid were affected in the species studied. For the Nitrogen-fixing (N2-fixing) species E. speciosa, an increase of Pb in the soil affected nodule formation and growth, which led to reduced nitrogenase activity in seedlings. The concentration of Pb in shoots and roots increased with the Pb concentration in soil. However, most of the Pb absorbed accumulated in the roots, and only a small fraction was translocated to aboveground parts. These findings were confirmed by the low bioconcentration factor (BCF) and translocation factor (TF) values for the three species. The tolerance index (TI) values suggested that M. caesalpiniaefolia, a N2-fixing tree, was the species that was most tolerant to high Pb concentrations in soil, while E. speciosa and S. parahyba showed moderate tolerance. Of the three Brazilian native woody species studied, M. caesalpiniaefolia was found to have the highest Pb tolerance and phytostabilisation potential in Pb-contaminated soils.
► Brazilian leguminous woody species were evaluated for the phytoremediation of Pb-contaminated soil. ► We analysed growth, mycorrhisation, biochemical and physiological biomarkers in addition to Pb uptake. ► The tolerance index, translocation factor and bioconcentration factor were determined. ► We found that Pb in the soil had different effects on the tree species studied. ► Mimosa caesalpiniaefolia showed the highest Pb tolerance and phytostabilisation potential.
Understanding the mechanisms that underlie the generation of beta‐diversity remains a challenge in ecology. Underground plant adaptations to environmental gradients have received relatively little ...attention.
We studied plant nutrient‐acquisition strategies and nutrient‐use efficiency at three stages of pedogenesis in infertile soils from campos rupestres and on less infertile soil from cerrado sensu stricto in Brazil. All soils support very high plant diversity with high species turnover between soil types at small spatial scales (metres). We expected that differences in nutrient‐acquisition and ‐use strategies would be associated with this high species turnover. With severely decreasing phosphorus (P) availability, we expected the effectiveness of arbuscular mycorrhizal (AM) symbioses for plant P acquisition to decrease, and reliance on nonmycorrhizal strategies (NM) to increase, while maintaining efficient nutrient use.
Concentrations of total soil P and nitrogen (N) were greater in soils in cerrado than in those from campos rupestres, and the more weathered soils from campos rupestres were severely P and N impoverished. The proportion of the root length colonized by AM fungi was 71% in the soils from the cerrado and <1% in the most P‐impoverished soil type from campos rupestres. Conversely, the proportion of species with nonmycorrhizal P‐acquisition strategies such as rhizosheaths was greater in the most P‐impoverished soils. Leaf P and N were very low and decreased with decreasing soil P and N. Leaf N:P ratios suggest P limitation of plant productivity in the campos rupestres but N‐P colimitation in the cerrado. Photosynthetic rates decreased with increasing P impoverishment, but photosynthetic P‐use efficiency was very high and photosynthetic N‐use efficiency moderately high on all soils. Most species had very high P‐remobilization efficiency during leaf senescence (>70%), but only moderate N‐remobilization efficiency (~50%).
Synthesis. We observed very high P‐use efficiency and moderately high N‐use efficiency in campos rupestres and cerrado species, consistent with plant productivity being more strongly limited by P than by N. Our findings demonstrate that different soil characteristics (nutrient availability and soil texture) select for species differing in nutrient‐acquisition and ‐use strategies (especially below‐ground traits) which is likely key for the very high species turnover at a very small scale between soil types (i.e., beta‐diversity) in campos rupestres and cerrado.
Our findings demonstrate that different soil characteristics (nutrient availability and soil texture, 1‐4) select for species differing in nutrient‐acquisition and ‐use strategies (a, b), which are likely key for the very high species turnover at a very small scale between soil types (i.e., beta‐diversity) in hyperdiverse campos rupestres and cerrado in Central Brazil.
Resumo
Compreender os mecanismos subjacentes à geração de diversidade beta continua sendo um desafio para a ecologia. As adaptações subterrâneas das plantas a gradientes ambientais, como a disponibilidade de nutrientes, têm sido pouco investigadas.
Nós estudamos as estratégias de aquisição e a eficiência no uso de nutrientes de plantas em solos inférteis. Conduzimos a pesquisa em três estágios diferentes de pedogênese em campos rupestres e, em um solo um pouco mais fértil de cerrado,no Brasil. Todos os solos comportam uma alta diversidade de plantas, com uma diferenciação na composição de espécies entre diferentes tipos de solo, em escalas espaciais muito pequenas (metros). Nós esperávamos que diferenças nas estratégias de aquisição e uso de nutrientes estivessem associadas à essa divergência na composição de espécies. Com a redução severa na disponibilidade de fósforo (P) nos solos de campos rupestres, nós esperávamos uma redução da efetividade de simbioses com fungos micorrízicos arbusculares para a obtenção de P; um aumento da dependência de estratégias não‐micorrízicas e, a manutenção da eficiência do uso de nutrientes nos diferentes tipos de solo.
As concentrações totais de P e nitrogênio (N) no solo foram maiores no cerrado do que nos campos rupestres. Os solos mais intemperizados dos campos rupestres foram os mais empobrecidos em N e P. A proporção do comprimento das raízes de plantas colonizadas por fungos micorrízicos arbusculares foi de 71% nas plantas de cerrado e <1% nas plantas dos solos mais pobres em P dos campos rupestres. Por outro lado, a proporção de espécies com estratégias para aquisição de P sem micorrizas, como as bainhas radiculares (rhizosheaths) foi maior nos solos mais pobres em P. As concentrações de P e N foliares foram muito baixas e diminuíram com a redução da disponibilidade de P e N no solo. As razões foliares de N: P sugerem que a produtividade vegetal nos campos rupestres é limitada por P, mas colimitada por P e N no cerrado. As taxas fotossintéticas das plantas foram menores nos solos mais pobres em P, no entanto, a eficiência fotossintética no uso de P foi muito alta e a eficiência fotossintética no uso de N foi moderada em todos os tipos de solo. A maioria das espécies apresentou uma eficiência muito alta na remobilização de P durante a senescência foliar (>70%), mas uma eficiência moderada na remobilização de N (~50%).
Síntese. Nossos resultados demonstram que diferentes atributos do solo (disponibilidade de nutrientes e textura) selecionam espécies com estratégias distintas de aquisição e uso de nutrientes, especialmente as estratégias subterrâneas. Essas estratégias são provavelmente a chave para entender a mudança na composição de espécies na pequena escala espacial (diversidade beta) em campos rupestres e cerrado.
This study is the first to investigate the speciation and spatial distribution patterns of manganese (Mn) accumulated at elevated concentrations in Eucalyptus leaves by X-ray fluorescence (µ-XRF) and ...absorption near-edge spectroscopy (µ-XANES). Eucalyptus tereticornis is a tree species with great economic value and potential to accumulate and tolerate high Mn despite not being considered a hyperaccumulator. Seedlings grown under glasshouse conditions were irrigated with two Mn treatments: control Mn (9 µM) and high Mn solution (1000 µM). Biomass and total nutrient concentrations were assessed in roots, stems and leaves. Manganese, calcium (Ca) and potassium (K) spatial patterns were imaged by µ-SXRF in different foliar structures, and Mn speciation was conducted in these compartments by µ-XANES. Under high supply, Mn was distributed across the leaf mesophyll suggesting vacuolar sequestration in these cells. High Mn decreased cytosolic Ca by almost 50% in mesophyll cells, but K remained unaltered. Speciation suggests that a majority of the Mn fraction was complexed by organic ligands modeled as Mn-bound malate and citrate, instead of as free aqueous Mn2+ or oxidised forms. These two detoxification mechanisms: effective vacuolar sequestration and organic acid complexation, may be responsible for the impressively high Mn tolerance found in eucalypts.
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•Leaf biomass was not affected by high Mn accumulation in E. tereticornis.•Synchrotron µ-XRF imaging showed Mn accumulation in mesophyll cells and leaf veins.•Deposition of excess Mn was not observed in Ca oxalate crystals.•High Mn supply decreased Ca inside mesophyll cells, but did not affect K levels.•A great fraction of Mn complexed by malate and citrate was indicated by µ-XANES.
Leptin is an adipocyte-secreted hormone that inhibits food intake and stimulates energy expenditure through interactions with neuronal pathways in the brain, particularly pathways involving the ...hypothalamus. Intact functioning of the leptin route is required for body weight and energy homeostasis. Given its function, the discovery of leptin increased expectations for the treatment of obesity. However, most obese individuals and subjects with a predisposition to regain weight after losing it have leptin concentrations than lean individuals, but despite the anorexigenic function of this hormone, appetite is not effectively suppressed in these individuals. This phenomenon has been deemed leptin resistance and could be the result of impairments at a number of levels in the leptin signalling pathway, including reduced access of the hormone to its receptor due to changes in receptor expression or changes in post-receptor signal transduction. Epigenetic regulation of the leptin signalling circuit could be a potential mechanism of leptin function disturbance. This review discusses the molecular mechanisms, particularly the epigenetic regulation mechanisms, involved in leptin resistance associated with obesity and the therapeutic potential of these molecular mechanisms in the battle against the obesity pandemic.
The influence of arbuscular mycorrhizal fungi (AMF) inoculation on
Canavalia ensiformis growth, nutrient and Zn uptake, and on some physiological parameters in response to increasing soil Zn ...concentrations was studied. Treatments were applied in seven replicates in a 2
×
4 factorial design, consisting of the inoculation or not with the AMF
Glomus etunicatum, and the addition of Zn to soil at the concentrations of 0, 100, 300 and 900
mg kg
−1. AMF inoculation enhanced the accumulation of Zn in tissues and promoted biomass yields and root nodulation. Mycorrhizal plants exhibited relative tolerance to Zn up to 300
mg
kg
−1 without exhibiting visual symptoms of toxicity, in contrast to non-mycorrhizal plants which exhibited a significant growth reduction at the same soil Zn concentration. The highest concentration of Zn added to soil was highly toxic to the plants. Leaves of plants grown in high Zn concentration exhibited a Zn-induced proline accumulation and also an increase in soluble amino acid contents; however proline contents were lower in mycorrhizal jack beans. Plants in association or not with the AMF exhibited marked differences in the foliar soluble amino acid profile and composition in response to Zn addition to soil. In general, Zn induced oxidative stress which could be verified by increased lipid peroxidation rates and changes in catalase, ascorbate peroxidase, glutathione reductase and superoxide dismutase activities. In summary,
G. etunicatum was able to maintain an efficient symbiosis with jack bean plants in moderately contaminated Zn-soils, improving plant performance under those conditions, which is likely to be due to a combination of physiological and nutritional changes caused by the intimate relation between fungus and plant. The enhanced Zn uptake by AMF inoculated jack bean plants might be of interest for phytoremediation purposes.
Background and aims
Tropical soils often present two issues that can hinder plant growth: low phosphorus (P) and high manganese (Mn) availability.
Eucalyptus tereticornis
is frequently cultivated in ...such soils. We investigated the effects of Mn in
E. tereticornis
under contrasting soil P availability and hypothesized that arbuscular mycorrhizal (AM) symbiosis could alleviate Mn toxicity by improving P nutrition and altering the expression of Mn transporter genes.
Methods
Inoculated (AM) and non-inoculated (NM) seedlings grew for seven months in a soil with low or sufficient P availability, under three Mn doses: control, 75 and 150 mg kg
−1
Mn. We assessed growth, AM colonization, nutrient concentrations, and the expression of eight genes related to Mn transport and homeostasis in roots. Mn distribution at one-leaf level was determined by μ-XRF.
Results
Low P exacerbated Mn toxicity and hindered plant growth. Mycorrhizal symbiosis did not influence Mn accumulation, but improved growth and Mn tolerance at low P, partly by improving P nutrition. At sufficient P, foliar Mn reached 3500 mg kg
−1
, and μ-XRF patterns suggest preferential accumulation in the leaf lamina compared to margins or midribs. In NM plants, the vacuolar transporters
EtVIT1
and
EtMTP8
and the Mn-nicotianamine influx transporter
EtYSL6
were the most responsive genes to Mn, while in AM roots most were downregulated.
Conclusion
Vacuolar sequestration and transport of complexed Mn are important mechanisms behind Mn tolerance in
E. tereticornis
. We propose that Mn is transported via the mycorrhizal pathway, explaining why it does not elicit the same molecular response observed in NM roots.
•AsV and AsIII were supplied to rice plants under AM symbiosis.•AsV and AsIII decreased photosynthetic rates and PSII efficiency.•AM promoted biomass accumulation, carbon assimilation and water use ...efficiency.•Maximum and actual quantum yields of photosystem II increased due to AM under As.
The metalloid arsenic (As) increases in agricultural soils because of anthropogenic activities and may have phytotoxic effects depending on the available concentrations. Plant performance can be improved by arbuscular mycorrhiza (AM) association under challenging conditions, such as those caused by excessive soil As levels. In this study, the influence of AM on CO2 assimilation, chlorophyll a fluorescence, SPAD-chlorophyll contents and plant growth was investigated in rice plants exposed to arsenate (AsV) or arsenite (AsIII) and inoculated or not with Rhizophagus irregularis. Under AsV and AsIII exposure, AM rice plants had greater biomass accumulation and relative chlorophyll content, increased water-use efficiency, higher carbon assimilation rate and higher stomatal conductance and transpiration rates than non-AM rice plants did. Chlorophyll a fluorescence analysis revealed significant differences in the response of AM-associated and -non-associated plants to As. Mycorrhization increased the maximum and actual quantum yields of photosystem II and the electron transport rate, maintaining higher values even under As exposure. Apart from the negative effects of AsV and AsIII on the photosynthetic rates and PSII efficiency in rice leaves, taken together, these results indicate that AM is able to sustain higher rice photosynthesis efficiency even under elevated As concentrations, especially when As is present as AsV.
The development and productivity of plants are governed by their genetic background, nutrient input, and the microbial communities they host, i.e. the holobiont. Accordingly, engineering beneficial ...root microbiomes has emerged as a novel and sustainable approach to crop production with reduced nutrient input. Here, we tested the effects of six bacterial strains isolated from sugarcane stalks on sugarcane growth and physiology as well as the dynamics of prokaryote community assembly in the rhizosphere and root endosphere under two N fertilization regimes. All six strains, Paraburkholderia caribensis IAC/BECa 88, Kosakonia oryzae IAC/BECa 90, Kosakonia radicincitans IAC/BECa 95, Paraburkholderia tropica IAC/BECa 135, Pseudomonas fluorescens IAC/BECa 141 and Herbaspirillum frisingense IAC/BECa 152, increased in shoot and root dry mass, and influenced the concentration and accumulation of important macro- and micronutrients. However, N input reduced the impact of inoculation by shifting the sugarcane microbiome (rhizosphere and root endosphere) and weakening the co-dependence between soil microbes and sugarcane biomass and nutrients. The results show that these beneficial microbes improved plant nutrient uptake conditioned to a reduced N nutrient input. Therefore, reduced fertilization is not only desirable consequence of bacterial inoculation but essential for higher impact of these beneficial bacteria on the sugarcane microbiome.
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•Inoculation shifted the sugarcane microbiome (rhizosphere and endosphere).•N input decreased the importance of plant growth promoting microbes.•Rhizosphere prokaryotes are associated with nutrient uptake in sugarcane.•N input reduced the co-dependence between soil microbes and plant nutrients.•Leifsonia abundance increased with N input as potential risk of ratoon stunting disease.
Key message
Eucalypt seedlings differently modulate root morphology in response to phosphorus availability, with changes in the length or density of root hairs being more common that changes in root ...length.
Phosphorus (P) is an essential nutrient for plant growth and development and thus can restrict biomass accumulation when it is at low levels in the soil. Eucalypts cover large areas of planted forests in the world, including regions with naturally low P availability. This study was conducted to evaluate the morphological changes in the roots of seedlings of five eucalypt species:
Eucalyptus acmenoides
,
E. globulus
,
E. grandis
,
E. tereticornis
and
Corymbia maculata
in response to low P concentration. Seedlings were grown in pots with vermiculite and received a nutrient solution of low (25 μM), and sufficient concentration (500 μM) of P. Root hair length and density were evaluated in secondary root segments, and the production of plant biomass and P concentration in the shoots were determined. The species modulated root morphology differently in response to P limitation.
E. tereticornis
showed the lowest plasticity of these morphological traits in response to P concentration. The total root length increased in some species, but changes in the length and/or density of root hairs were the commonest response to low P concentration. P concentrations in the shoots and biomass production were not related to increase of root length or root hair density and length.
Urochloa in Tropical Agroecosystems Baptistella, João Leonardo Corte; de Andrade, Sara Adrián López; Favarin, José Laércio ...
Frontiers in sustainable food systems,
08/2020, Letnik:
4
Journal Article
Recenzirano
Odprti dostop
Increasing biodiversity is an important issue in more secure and sustainable agriculture. Diversified systems are more resilient to climate change, environmental stresses and enhance soil health, ...nutrient cycling and nutrient use efficiency. In tropical agroecosystems, cover crops and intercrops are an alternative toward a more diverse and sustainable production. Urochloa spp. (syn. Brachiaria spp.) are perennial grasses, known for their high biomass production. They are commonly used as cover and companion crops in conservation agriculture in the tropics and the residues left in the field after cutting protect the soil and provide nutrient to the next crop cycle or intercropped culture. Urochloa species roots are vigorous, abundant and deep, as opposed to the more shallow and scarce roots of common crops. These traits contribute to carbon sequestration, soil organic matter stabilization and nutrient cycling. Urochloa roots also improve soil physical characteristics and influence soil nutrient dynamics, reducing nutrient losses and enhancing cycling, what is key to achieve greater nutrient use efficiency in agriculture. For instance, Urochloa root exudates can reduce nitrogen losses by denitrification and leaching through a process called biological nitrification inhibition; root exudates can mobilize recalcitrant phosphorus from soils and make it available for plant uptake; the deep roots of these grasses have the potential to recover nutrients that are virtually lost away from the root zone of other crops. This review compiles scientific progress regarding the introduction of Urochloa in agroecosystems, mainly on the aspects related to the contribution to more secure and sustainable agriculture.
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