RESUMO
RNA-Binding Protein 1 (RBP1) was first identified as a protein partner of the long noncoding RNA (lncRNA) ENOD40 in Medicagotruncatula, involved in symbiotic nodule development. RBP1 is localized in nuclear speckles and can be relocalized to the cytoplasm by the interaction with ENOD40. The two closest homologs to RBP1 in Arabidopsis thaliana were called Nuclear Speckle RNA-binding proteins (NSRs) and characterized as alternative splicing modulators of specific mRNAs. They can recognize in vivo the lncRNA ALTERNATIVE SPLICING COMPETITOR (ASCO) among other lncRNAs, regulating lateral root formation. Here, we performed a phylogenetic analysis of NSR/RBP proteins tracking the roots of the family to the Embryophytes. Strikingly, eudicots faced a reductive trend of NSR/RBP proteins in comparison with other groups of flowering plants. In Medicagotruncatula and Lotus japonicus, their expression profile during nodulation and in specific regions of the symbiotic nodule was compared to that of the lncRNA ENOD40, as well as to changes in alternative splicing. This hinted at distinct and specific roles of each member during nodulation, likely modulating the population of alternatively spliced transcripts. Our results establish the basis to guide future exploration of NSR/RBP function in alternative splicing regulation in different developmental contexts along the plant lineage.
Assuntos
Processamento Alternativo , Embriófitas/crescimento & desenvolvimento , Proteínas de Ligação a RNA/genética , Proteínas de Ligação a RNA/metabolismo , Núcleo Celular/metabolismo , Citoplasma/metabolismo , Embriófitas/genética , Evolução Molecular , Regulação da Expressão Gênica de Plantas , Lotus/genética , Lotus/crescimento & desenvolvimento , Medicago truncatula/genética , Medicago truncatula/crescimento & desenvolvimento , Filogenia , Proteínas de Plantas/genética , Proteínas de Plantas/metabolismo , Raízes de Plantas/genética , Raízes de Plantas/crescimento & desenvolvimento , RNA Longo não Codificante/genética , SimbioseRESUMO
Salinity is one of the most frequent limiting conditions in pasture production for grazing livestock. Legumes, such as Lotus spp. with high forage quality and capable of adapting to different environments, improves pasture performance in restrictive areas. In order to determine potential cultivars with better forage traits, the current study assess the response to salt stress of L. tenuis, L. corniculatus and a novel L. tenuis x L. corniculatus accession. For this purpose, chlorophyll fluorescence, biomass production, ion accumulation and anthocyanins and proanthocyanidins levels have been evaluated in control and salt-treated plants PSII activity was affected by salt in L. tenuis, but not in L. corniculatus or hybrid plants. Analyzed accessions showed similar values of biomass, Na+ and K+ levels after salt treatment. Increasing Cl- concentrations were observed in all accessions. However, hybrid plants accumulate Cl- in stems at higher levels than their parental. At the same time, the levels of anthocyanins considerably increased in L. tenuis x L. corniculatus stems. Chloride and anthocyanin accumulation in stems could explain the best performance of hybrid plants after a long saline treatment. Finally, as proanthocyanidins levels were no affected by salt, L. tenuis x L. corniculatus plants maintained adequate levels to be used as ruminant feed. In conclusion, these results suggest that hybrid plants have a high potential to be used as forage on salt-affected lands. High Cl- and anthocyanins accumulation in Lotus spp. stems seems to be a trait associated to salinity tolerance, with the possibility of being used in legume breeding programs.
Assuntos
Lotus/metabolismo , Antocianinas/metabolismo , Clorofila/metabolismo , Hibridização Genética , Lotus/crescimento & desenvolvimento , Lotus/fisiologia , Melhoramento Vegetal/métodos , Potássio/metabolismo , Estresse Salino , Plantas Tolerantes a Sal , Sódio/metabolismoRESUMO
Condensed tannins are formed by monomers of procyanidins and prodelfinidins, where the proportion and concentration of their monomers varies according to the plant species and environmental conditions. In Lotus spp., condensed tannins prevent tympanism in ruminants that feed on them. This study aimed to evaluate the concentration of procyanidins and their monomers, catechin and epicatechin in the genotypes of Lotus L. grown in soil with different saturations of aluminum. A two-factor (genotype × Al saturation) assay was performed, where the genotypes São Gabriel, Ganador, and UFRGS (Lotus corniculatus L.); Serrano (Lotus uliginosus); and El Rincón (Lotus subbiflorus) were cultivated in soil with an Al saturation of 0-20%. The procyanidins were evaluated using high-performance liquid chromatography, which was previously validated for catechin and epicatechin. The concentration of procyanidins and the proportion of epicatechin:catechin were affected by the genotype × environment interaction. In L. corniculatus and L. subbiflorus, the concentration of procyanidin was significantly higher when they were grown in the soil with an Al saturation of 20% compared to that when they were grown in the soil with 0% Al saturation, but the opposite effect was observed in L. uliginosus. The proportion of epicatechin:catechin decreased in plants grown in soil without Al, and only the UFRGS genotype maintained a similar proportion under both the soil acidity conditions. The predominant monomer was epicatechin, which varied from 57 % to 75 % according to the soil in which the plants were grown.(AU)
Os taninos condensados são formados por monômeros de procianidinas e prodelfinidinas, cuja proporção e concentração dos seus monômeros varia de acordo com a espécie vegetal e condições ambientais. Em Lotus spp., são essas substâncias que evitam o timpanismo em ruminantes que delas se alimentam. O objetivo deste trabalho foi avaliar a concentração de procianidinas e de seus monômeros, catequina e epicatequina, em genótipos de Lotus L. sob distintas saturações de alumínio no solo. O ensaio consistiu de um bifatorial (Genótipo x Saturação de Al), no qual os genótipos São Gabriel, Ganador e UFRGS (L. corniculatus L.), Serrano (L. uliginosus) e El Rincón (L. subbiflorus) foram cultivados em solo com 0% e 20% de saturação de Al. As procianidinas foram avaliadas por cromatografia líquida de alta eficiência, previamente validada para catequina e epicatequina. A concentração de procianidinas e a proporção epicatequina:catequina foram afetadas pela interação genótipo x ambiente. Em L. corniculatus e L. subbiflorus a concentração de procianidinas foi significativamente superior em solo com 20% de saturação de Al em relação ao solo com 0% de saturação de Al, mas o oposto foi observado em L. uliginosus. A proporção epicatequina:catequina reduziu nas plantas cultivadas em solo sem Al e apenas o genótipo UFRGS manteve proporção similar em ambas as condições de acidez do solo. A epicatequina foi o monômero preponderante, variando de 57 a 75 % de acordo com o solo em que as plantas foram cultivadas.(AU)
Assuntos
Lotus/crescimento & desenvolvimento , Lotus/genética , Proantocianidinas , Análise do Solo , AlumínioRESUMO
Condensed tannins are formed by monomers of procyanidins and prodelfinidins, where the proportion and concentration of their monomers varies according to the plant species and environmental conditions. In Lotus spp., condensed tannins prevent tympanism in ruminants that feed on them. This study aimed to evaluate the concentration of procyanidins and their monomers, catechin and epicatechin in the genotypes of Lotus L. grown in soil with different saturations of aluminum. A two-factor (genotype × Al saturation) assay was performed, where the genotypes São Gabriel, Ganador, and UFRGS (Lotus corniculatus L.); Serrano (Lotus uliginosus); and El Rincón (Lotus subbiflorus) were cultivated in soil with an Al saturation of 0-20%. The procyanidins were evaluated using high-performance liquid chromatography, which was previously validated for catechin and epicatechin. The concentration of procyanidins and the proportion of epicatechin:catechin were affected by the genotype × environment interaction. In L. corniculatus and L. subbiflorus, the concentration of procyanidin was significantly higher when they were grown in the soil with an Al saturation of 20% compared to that when they were grown in the soil with 0% Al saturation, but the opposite effect was observed in L. uliginosus. The proportion of epicatechin:catechin decreased in plants grown in soil without Al, and only the UFRGS genotype maintained a similar proportion under both the soil acidity conditions. The predominant monomer was epicatechin, which varied from 57 % to 75 % according to the soil in which the plants were grown.
Os taninos condensados são formados por monômeros de procianidinas e prodelfinidinas, cuja proporção e concentração dos seus monômeros varia de acordo com a espécie vegetal e condições ambientais. Em Lotus spp., são essas substâncias que evitam o timpanismo em ruminantes que delas se alimentam. O objetivo deste trabalho foi avaliar a concentração de procianidinas e de seus monômeros, catequina e epicatequina, em genótipos de Lotus L. sob distintas saturações de alumínio no solo. O ensaio consistiu de um bifatorial (Genótipo x Saturação de Al), no qual os genótipos São Gabriel, Ganador e UFRGS (L. corniculatus L.), Serrano (L. uliginosus) e El Rincón (L. subbiflorus) foram cultivados em solo com 0% e 20% de saturação de Al. As procianidinas foram avaliadas por cromatografia líquida de alta eficiência, previamente validada para catequina e epicatequina. A concentração de procianidinas e a proporção epicatequina:catequina foram afetadas pela interação genótipo x ambiente. Em L. corniculatus e L. subbiflorus a concentração de procianidinas foi significativamente superior em solo com 20% de saturação de Al em relação ao solo com 0% de saturação de Al, mas o oposto foi observado em L. uliginosus. A proporção epicatequina:catequina reduziu nas plantas cultivadas em solo sem Al e apenas o genótipo UFRGS manteve proporção similar em ambas as condições de acidez do solo. A epicatequina foi o monômero preponderante, variando de 57 a 75 % de acordo com o solo em que as plantas foram cultivadas.
Assuntos
Alumínio , Análise do Solo , Lotus/crescimento & desenvolvimento , Lotus/genética , ProantocianidinasRESUMO
Waterlogging imposes severe stress to the plant, and the interplay between root and aerial organs in the adjustment to this stress is poorly understood. A set of recombinant inbred lines (RILs) of Lotus japonicus (Gifu B-129 × Miyakojima MG-20) was subjected to control and waterlogging conditions for 21 d, and 12 traits related to leaf physiological functioning, root aerenchyma formation, shoot and root morphology, and dry mass accumulation were assessed to generate phenomic networks. The phenomic network became more complex under waterlogging as a result of the incorporation of root aerenchyma and dark-adapted Fv/Fm. Significant waterlogging-induced variation was found for stomatal conductance, dark-adapted Fv/Fm and aerenchyma. The RILs with stronger induction of aerenchyma in response to waterlogging tended to show reduced negative impact of this stress on root growth but suffered average impact on shoot growth. The RILs that retained higher stomatal conductance under waterlogging tended to retain higher dark-adapted Fv/Fm and shoot growth under waterlogging conditions but showed average impact on root traits. We propose a model where, although the stress experienced by the roots during waterlogging is transmitted to the shoot, shoots and roots deal with waterlogging in a less interdependent manner than often assumed.
Assuntos
Adaptação Fisiológica , Lotus/fisiologia , Oxigênio/metabolismo , Locos de Características Quantitativas/genética , Estresse Fisiológico , Água/fisiologia , Biomassa , Clorofila/metabolismo , Ligação Genética , Endogamia , Lotus/genética , Lotus/crescimento & desenvolvimento , Fenótipo , Raízes de Plantas/genética , Raízes de Plantas/crescimento & desenvolvimento , Raízes de Plantas/fisiologia , Brotos de Planta/genética , Brotos de Planta/crescimento & desenvolvimento , Brotos de Planta/fisiologia , Estômatos de Plantas , SoloRESUMO
The impact of different defoliation intensities on the ability of Lotus tenuis plants to regrowth, mobilise nutrients and to associate with native AM fungi and Rhizobium in a saline-sodic soil was investigated. After 70 days, plants were subjected to 0, 25, 50, 75 and 100% defoliation and shoot regrowth was assessed at the end of subsequent 35 days. Compared to non-defoliated plants, low or moderate defoliation up to 75% did not affect shoot regrowth. However, 100% treatment affected shoot regrowth and the clipped plants were not able to compensate the growth attained by non-defoliated plants. Root growth was more affected by defoliation than shoot growth. P and N concentrations in shoots and roots increased with increasing defoliation while Na(+) concentration in shoots of non-defoliated and moderately defoliated plants was similar. Non-defoliated and moderately defoliated plants prevented increases of Na(+) concentration in shoots through both reducing Na(+) uptake and Na(+) transport to shoots by accumulating Na(+) in roots. At high defoliation, the salinity tolerance mechanism is altered and Na(+) concentration in shoots was higher than in roots. Reduction in the photosynthetic capacity induced by defoliation neither changed the root length colonised by AM fungi nor arbuscular colonisation but decreased the vesicular colonisation. Spore density did not change, but hyphal density and Rhizobium nodules increased with defoliation. The strategy of the AM symbiont consists in investing most of the C resources to preferentially retain arbuscular colonisation as well as inoculum density in the soil.
Assuntos
Lotus/microbiologia , Micorrizas/crescimento & desenvolvimento , Microbiologia do Solo , Solo/química , Simbiose , Carbono/metabolismo , Clorofila/análise , Lotus/crescimento & desenvolvimento , Lotus/metabolismo , Micorrizas/metabolismo , Fósforo/metabolismo , Fotossíntese , Folhas de Planta/crescimento & desenvolvimento , Folhas de Planta/metabolismo , Nodulação , Raízes de Plantas/crescimento & desenvolvimento , Raízes de Plantas/metabolismo , Brotos de Planta/crescimento & desenvolvimento , Brotos de Planta/metabolismo , Rhizobium/crescimento & desenvolvimento , Salinidade , Plantas Tolerantes a Sal/crescimento & desenvolvimento , Plantas Tolerantes a Sal/metabolismo , Plantas Tolerantes a Sal/microbiologia , Sódio/metabolismo , Esporos Fúngicos/metabolismoRESUMO
Two main strategies allow plants to deal with submergence: (i) escape from below water by means of shoot elongation, or (ii) remaining quiescent under the water until water subsides and then resume growth. We investigated these strategies in seedlings of Lotus japonicus, L. corniculatus and L. tenuis subjected to control and submergence for 12 days, with a subsequent 30-day recovery period. All three species survived submergence but used different strategies. Submerged seedlings of L. japonicus exhibited an escape strategy (emerging from water) as a result of preferential carbon allocation towards shoot mass and lengthening, in detriment to root growth. In contrast, seedlings of L. corniculatus and L. tenuis became quiescent, with no biomass accumulation, no new unfolding of leaves and no shoot elongation. Upon de-submergence, seedlings of L. japonicus had the lowest recovery growth (a biomass and shoot height 58% and 40% less than controls, respectively), L. corniculatus was intermediate and L. tenuis showed the greatest recovery growth. Previously submerged seedlings of L. tenuis did not differ from their controls, either in final shoot biomass or shoot height. Thus, for the studied species, quiescence appears to be an adequate strategy for tolerance of short-term (i.e., 12 days) complete submergence, being consistent with field observations of L. tenuis colonisation of flood-prone environments.
Assuntos
Inundações , Lotus/crescimento & desenvolvimento , Água/fisiologia , Folhas de Planta/crescimento & desenvolvimento , Raízes de Plantas/crescimento & desenvolvimento , Brotos de Planta/crescimento & desenvolvimento , Plântula/crescimento & desenvolvimentoRESUMO
The genus Lotus comprises around 100 annual and perennial species with worldwide distribution. The relevance of Lotus japonicus as a model plant has been recently demonstrated in numerous studies. In addition, some of the Lotus species show a great potential for adaptation to a number of abiotic stresses. Therefore, they are relevant components of grassland ecosystems in environmentally constrained areas of several South American countries and Australia, where they are used for livestock production. Also, the fact that the roots of these species form rhizobial and mycorrhizal associations makes the annual L. japonicus a suitable model plant for legumes, particularly in studies directed to recognize the mechanisms intervening in the tolerance to abiotic factors in the field, where these interactions occur. These properties justify the increased utilization of some Lotus species as a strategy for dunes revegetation and reclamation of heavy metal-contaminated or burned soils in Europe.
Assuntos
Lotus/crescimento & desenvolvimento , Lotus/metabolismo , Poluentes do Solo/metabolismo , Adaptação Fisiológica , Austrália , Conservação dos Recursos Naturais , Ecossistema , Europa (Continente) , Metais Pesados/metabolismo , Raízes de Plantas/metabolismo , América do Sul , SimbioseRESUMO
AIMS: To isolate and characterize phosphate-solubilizing strains from a constrained environment such as the Salado River Basin and to assess their phosphate-solubilizing mechanisms, to further selection of the most promising strains to inoculate and improve the implantation and persistence of Lotus tenuis in the most important area devoted to meat-cow production in Argentina. METHODS AND RESULTS: Fifty isolates were obtained and through BOX-PCR analysis, 17 non-redundant strains were identified. Subsequently, they were found to be related to Pantoea, Erwinia, Pseudomonas, Rhizobium and Enterobacter genera, via 16S rRNA gene sequence analysis. This was in agreement with the clusters obtained by antibiotic resistance analysis. All isolates were tested for their phosphate-solubilizing activity and selected strains were inoculated onto L. tenuis plants. The most efficient isolate, was identified as Pantoea eucalypti, a novel species in terms of plant growth-promoting rhizobacteria. CONCLUSIONS: The isolates obtained in this study showed a significant in vitro plant-growth promoting activity onto Lotus tenuis and the best of them solubilizes phosphate mainly via induction of the metabolism through secretion and oxidation of gluconic acid. SIGNIFICANCE AND IMPACT OF THE STUDY: The use of these bacteria as bioinoculants, alone or in combination with nitrogen-fixing micro-organisms, could be a sustainable practice to facilitate the nutrient supply to Lotus tenuis plants and preventing negative side-effects such as eutrophication.
Assuntos
Lotus/crescimento & desenvolvimento , Lotus/microbiologia , Pantoea/fisiologia , Fosfatos/metabolismo , Rizosfera , Microbiologia do Solo , Argentina , Desidrogenases de Carboidrato/metabolismo , Enterobacter/genética , Erwinia/genética , Eucalyptus/metabolismo , Gluconatos/metabolismo , Glucose Desidrogenase/metabolismo , Oxirredução , Pantoea/genética , Pantoea/isolamento & purificação , Filogenia , Pseudomonas/genética , RNA Ribossômico 16S/genética , Rhizobium/genética , RiosRESUMO
Neste trabalho objetivou-se avaliar a sobrevivência das estacas e a produção de matéria seca na fase de cultivo de mudas das espécies forrageiras missioneira gigante (Axonopus catharinensis), amendoim forrageiro (Arachis pintoi) e maku (Lotus uliginosus cv. Maku). No sistema hidropônico de leito flutuante com solução nutritiva à base de biofertilizante ou adubo solúvel. O delineamento experimental adotado foi o de blocos ao acaso em esquema fatorial 3 x 2, sendo três espécies forrageiras e duas soluções nutritivas. As espécies não apresentaram diferença quanto à sobrevivência (p = 0,225), independentemente do tipo de fertilizante (p = 0,92). No entanto, quando se quantificou a produção de MS planta-1 proporcionada por cada uma dessas espécies, o maku (p = 0,001) obteve as maiores quantidades (47,18 g), enquanto o amendoim forrageiro (19,90 g) e a missioneira gigante (16,81 g) foram semelhantes entre si (p = 0,227), tendo o mesmo ocorrido entre os fertilizantes (p = 0,559). Deste modo, as três espécies possuem condições semelhantes de sobrevivência, independentemente da concentração de nutrientes da solução nutritiva, com o maku proporcionando a maior produção de MS planta-1.(AU)
The aim of this work was to evaluate the survival and dry matter production during the seedling culture phase of three forage species: Axonopus catharinensis, forage peanut (Arachis pintoi), and greater lotus (Lotus uliginosus cv. Maku), in a floating hydroponic system using biofertilizer or soluble fertilizer. The experimental design adopted was randomized blocks in a 3 x 2 factorial scheme, with three forage species and two fertilizers. There was no difference between species with regard to survival (p = 0.225), regardless of the fertilizer used (p = 0.92). However, when dry matter production was considered, Maku (P=0,001) showed greater weight (47.18 g), while there was no difference (p = 0.227) in weight between Arachis pintoi (19.90 g) and Axonopus catharinensis (16.81 g) or between fertilizers (p = 0.559). Thus, all three forage species have similar survival conditions, regardless of nutrient concentration of the fertilizer, and Maku had greater dry matter production.(AU)
Assuntos
Hidroponia , Poaceae/crescimento & desenvolvimento , Lotus/crescimento & desenvolvimento , Fertilizantes/análise , PastagensRESUMO
Neste trabalho objetivou-se avaliar a sobrevivência das estacas e a produção de matéria seca na fase de cultivo de mudas das espécies forrageiras missioneira gigante (Axonopus catharinensis), amendoim forrageiro (Arachis pintoi) e maku (Lotus uliginosus cv. Maku). No sistema hidropônico de leito flutuante com solução nutritiva à base de biofertilizante ou adubo solúvel. O delineamento experimental adotado foi o de blocos ao acaso em esquema fatorial 3 x 2, sendo três espécies forrageiras e duas soluções nutritivas. As espécies não apresentaram diferença quanto à sobrevivência (p = 0,225), independentemente do tipo de fertilizante (p = 0,92). No entanto, quando se quantificou a produção de MS planta-1 proporcionada por cada uma dessas espécies, o maku (p = 0,001) obteve as maiores quantidades (47,18 g), enquanto o amendoim forrageiro (19,90 g) e a missioneira gigante (16,81 g) foram semelhantes entre si (p = 0,227), tendo o mesmo ocorrido entre os fertilizantes (p = 0,559). Deste modo, as três espécies possuem condições semelhantes de sobrevivência, independentemente da concentração de nutrientes da solução nutritiva, com o maku proporcionando a maior produção de MS planta-1.
The aim of this work was to evaluate the survival and dry matter production during the seedling culture phase of three forage species: Axonopus catharinensis, forage peanut (Arachis pintoi), and greater lotus (Lotus uliginosus cv. Maku), in a floating hydroponic system using biofertilizer or soluble fertilizer. The experimental design adopted was randomized blocks in a 3 x 2 factorial scheme, with three forage species and two fertilizers. There was no difference between species with regard to survival (p = 0.225), regardless of the fertilizer used (p = 0.92). However, when dry matter production was considered, Maku (P=0,001) showed greater weight (47.18 g), while there was no difference (p = 0.227) in weight between Arachis pintoi (19.90 g) and Axonopus catharinensis (16.81 g) or between fertilizers (p = 0.559). Thus, all three forage species have similar survival conditions, regardless of nutrient concentration of the fertilizer, and Maku had greater dry matter production.
Assuntos
Hidroponia , Lotus/crescimento & desenvolvimento , Poaceae/crescimento & desenvolvimento , Fertilizantes/análise , PastagensRESUMO
Type III secretion systems (T3SS) have been found in several species of rhizobia. Proteins (termed effectors) secreted by this system are involved in host-range determination and influence nodulation efficiency. Mesorhizobium loti MAFF303099 possesses a functional T3SS in its symbiotic island whose expression is induced by flavonoids. As in other rhizobia, conserved cis-elements (tts box) were found in the promoter regions of genes or operons encoding T3SS components. Using a bioinformatics approach, we searched for other tts-box-controlled genes, and confirmed this transcriptional regulation for some of them using lacZ fusions to the predicted promoter regions. Translational fusions to a reporter peptide were created to demonstrate T3SS-mediated secretion of two new MAFF303099 effectors. Finally, we showed that mutation of the M. loti MAFF303099 T3SS affects its competitiveness on Lotus glaber and investigated, at the molecular level, responses of the model legume L. japonicus to the T3SS.
Assuntos
Alphaproteobacteria/genética , Proteínas de Bactérias/genética , Nódulos Radiculares de Plantas/genética , Simbiose/genética , Alphaproteobacteria/metabolismo , Alphaproteobacteria/fisiologia , Proteínas de Bactérias/análise , Proteínas de Bactérias/metabolismo , Biologia Computacional/métodos , Eletroforese em Gel de Poliacrilamida , Regulação da Expressão Gênica no Desenvolvimento , Regulação da Expressão Gênica de Plantas , Interações Hospedeiro-Patógeno , Lotus/genética , Lotus/crescimento & desenvolvimento , Lotus/microbiologia , Espectrometria de Massas , Mutação , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Nódulos Radiculares de Plantas/crescimento & desenvolvimento , Nódulos Radiculares de Plantas/microbiologiaRESUMO
Our hypothesis is that Lotus glaber (a glycophytic species, highly tolerant to saline-alkaline soils) displays a plastic root phenotypic response to soil salinity that may be influenced by mycorrhizal and rhizobial microorganisms. Uninoculated plants and plants colonised by Glomus intraradices or Mesorhizobium loti were exposed to either 150 or 0 mM NaCl. General plant growth and root architectural parameters (morphology and topology) were measured and phenotypic plasticity determined at the end of the salt treatment period. Two genotypes differing in their salt tolerance capacity were used in this study. G. intraradices and M. loti reduced the total biomass of non-salinised, sensitive plants, but they did not affect that of corresponding tolerant ones. Root morphology of sensitive plants was greatly affected by salinity, whereas mycorrhiza establishment counteracted salinity effects. Under both saline conditions, the external link length and the internal link length of mycorrhizal salt-sensitive plants were higher than those of uninoculated control and rhizobial treatments. The topological trend (TT) was strongly influenced by genotype x symbiosis interaction. Under non-saline conditions, nodulated root systems of the sensitive plant genotype had a more herringbone architecture than corresponding uninoculated ones. At 150 mM NaCl, nodulated root systems of tolerant plants were more dichotomous and those of the corresponding sensitive genotype more herringbone in architecture. Notwithstanding the absence of a link between TTs and variations in plant growth, it is possible to predict a dissimilar adaptation of plants with different TTs. Root colonisation by either symbiotic microorganisms reduced the level of root phenotypic plasticity in the sensitive plant genotype. We conclude that root plasticity could be part of the general mechanism of L. glaber salt tolerance only in the case of non-symbiotic plants.
Assuntos
Fungos/fisiologia , Lotus/fisiologia , Micorrizas/fisiologia , Raízes de Plantas/fisiologia , Rhizobium/fisiologia , Cloreto de Sódio/farmacologia , Resposta ao Choque Térmico , Lotus/crescimento & desenvolvimento , Lotus/microbiologia , Fenótipo , Raízes de Plantas/crescimento & desenvolvimento , Raízes de Plantas/microbiologia , Especificidade da Espécie , Simbiose/efeitos dos fármacosRESUMO
BACKGROUND AND AIMS: Flooding and grazing are major disturbances that simultaneously affect plant performance in many humid grassland ecosystems. The effects of flooding on plant recovery from defoliation were studied in two species: the grass Paspalum dilatatum, regrowing primarily from current assimilation; and the legume, Lotus tenuis, which can use crown reserves during regrowth. METHODS: Plants of both species were subjected to intense defoliation in combination with 15 d of flooding at 6 cm water depth. Plant recovery was evaluated during a subsequent 30-d growth period under well-watered conditions. Plant responses in tissue porosity, height, tiller or shoot number and biomass of the different organs were assessed. KEY RESULTS: Flooding increased porosity in both P. dilatatum and L. tenuis, as expected in flood-tolerant species. In P. dilatatum, defoliation of flooded plants induced a reduction in plant height, thus encouraging the prostrated-growth response typical of defoliated plants rather than the restoration of contact with atmospheric oxygen, and most tillers remained submerged until the end of the flooding period. In contrast, in L. tenuis, plant height was not reduced when defoliated and flooded, a high proportion of shoots being presented emerging above water (72 %). In consequence, flooding plus defoliation did not depress plant recovery from defoliation in the legume species, which showed high sprouting and use of crown biomass during regrowth, whereas in the grass species it negatively affected plant recovery, achieving 32 % lower biomass than plants subjected to flooding or defoliation as single treatments. CONCLUSIONS: The interactive effect of flooding and defoliation determines a reduction in the regrowth of P. dilatatum that was not detected in L. tenuis. In the legume, the use of crown reserves seems to be a key factor in plant recovery from defoliation under flooding conditions.
Assuntos
Desastres , Lotus/crescimento & desenvolvimento , Paspalum/crescimento & desenvolvimento , Folhas de Planta/crescimento & desenvolvimento , Adaptação Fisiológica , Análise de Variância , Argentina , Biomassa , Raízes de Plantas/crescimento & desenvolvimento , Brotos de Planta/crescimento & desenvolvimento , Porosidade , Fatores de TempoRESUMO
Temporal variations in the relationships among plant nutrient concentrations, soil properties and arbuscular-mycorrhizal (AM) fungal dynamics were studied along a topographic and saline gradient in a temperate grassland soil. Soil and plant (Lotus tenuis, Paspalum vaginatum, Stenotaphrum secundatum) samples were collected on four seasonally based occasions. The morphology of AM root colonization had a similar pattern in the plants studied. Maximum arbuscular colonization occurred at the beginning of the growing season in late winter and was minimal in late summer, but maximal vesicular colonization occurred in summer and was minimal in winter, suggesting a preferential production of these morphological phases by the fungus with respect to season. The greatest arbuscular colonization was associated with the highest N and P concentrations in plant tissue, suggesting a correspondence with increases in the rate of nutrient transfer between the symbiotic partners. Water content, salinity and sodicity in soil were positively associated with AM root colonization and arbuscule colonization in L. tenuis, but negatively so in the grasses. There were distinct seasonally related effects with respect to both spore density and AM colonization, which were independent of particular combinations of plant species and soil sites.
Assuntos
Lotus , Micorrizas , Poaceae , Solo/análise , Simbiose , Lotus/crescimento & desenvolvimento , Lotus/microbiologia , Micorrizas/crescimento & desenvolvimento , Micorrizas/fisiologia , Nitrogênio/análise , Paspalum , Fósforo/análise , Poaceae/crescimento & desenvolvimento , Poaceae/microbiologia , Poaceae/fisiologia , Estações do Ano , Cloreto de Sódio/análise , Água/análiseRESUMO
In this work we investigated the involvement of Glomus intraradices in the regulation of plant growth, polyamines and proline levels of two Lotus glaber genotypes differing in salt tolerance, after longterm exposure to saline stress. The experiment consisted of a randomized block design with three factors: (1) mycorrhizal treatments (with or without AM fungus); (2) two salinity levels of 0 and 200mM NaCl; and (3) L. glaber genotype. Experiments were performed using stem cuttings derived from L. glaber individuals representing a natural population from saline lowlands. One of the most relevant results was the higher content of total free polyamines in mycorrhized plants compared to non-AM ones. Since polyamines have been proposed as candidates for the regulation of root development under saline situations, it is possible that AM plants (which contained higher polyamine levels and showed improved root growth) were better shaped to cope with salt stress. Colonization by G. intraradices also increased (Spd+Spm)/Put ratio in L. glaber roots. Interestingly, such increment in salt stressed AM plants of the sensitive genotype, was even higher than that produced by salinization or AM symbiosis separately. On the other hand, salinity but not mycorrhizal colonization influenced proline levels in both L. glaber genotypes since high proline accumulation was observed in both genotypes under salt stress conditions. Our results suggest that modulation of polyamine pools can be one of the mechanisms used by AM fungi to improve L. glaber adaptation to saline soils. Proline accumulation in response to salt stress is a good indicator of stress perception and our results suggest that it could be used as such among L. glaber genotypes differing in salt stress tolerance.
Assuntos
Lotus/metabolismo , Lotus/microbiologia , Micorrizas/isolamento & purificação , Poliaminas/metabolismo , Cloreto de Sódio/farmacologia , Lotus/efeitos dos fármacos , Lotus/crescimento & desenvolvimento , Raízes de Plantas/crescimento & desenvolvimento , Raízes de Plantas/metabolismo , Brotos de Planta/crescimento & desenvolvimento , Brotos de Planta/metabolismoRESUMO
The seasonality of arbuscular mycorrhizal (AM) fungi-plant symbiosis in Lotus glaber Mill. and Stenotaphrum secundatum (Walt.) O.K. and the association with phosphorus (P) plant nutrition were studied in a saline-sodic soil at the four seasons during a year. Plant roots of both species were densely colonized by AM fungi (90 and 73%, respectively in L. glaber and S. secundatum) at high values of soil pH (9.2) and exchangeable sodium percentage (65%). The percentage of colonized root length differed between species and showed seasonality. The morphology of root colonization had a similar pattern in both species. The arbuscular colonization fraction increased at the beginning of the growing season and was positively associated with increased P concentration in both shoot and root tissue. The vesicular colonization fraction was high in summer when plants suffer from stress imposed by high temperatures and drought periods, and negatively associated with P in plant tissue. Spore and hyphal densities in soil were not associated with AM root colonization and did not show seasonality. Our results suggest that AM fungi can survive and colonize L. glaber and S. secundatum roots adapted to extreme saline-sodic soil condition. The symbiosis responds to seasonality and P uptake by the host altering the morphology of root colonization.