RESUMO
Arsenic in groundwater constitutes an agronomic problem due to its potential accumulation in the food chain. Among the agro-sustainable tools to reduce metal(oid)s toxicity, the use of plant growth-promoting bacteria (PGPB) becomes important. For that, and based on previous results in which significant differences of As translocation were observed when inoculating maize plants with Az39 or CD Azospirillum strains, we decided to decipher the redox metabolism changes and the antioxidant system response of maize plants inoculated when exposed to a realistic arsenate (AsV ) dose. Results showed that AsV caused morphological changes in the root exodermis. Photosynthetic pigments decreased only in CD inoculated plants, while oxidative stress evidence was detected throughout the plant, regardless of the assayed strain. The antioxidant response was strain-differential since only CD inoculated plants showed an increase in superoxide dismutase, glutathione S-transferase (GST), and glutathione reductase (GR) activities while other enzymes showed the same behavior irrespective of the inoculated strain. Gene expression assays reported that only GST23 transcript level was upregulated by arsenate, regardless of the inoculated strain. AsV diminished the glutathione (GSH) content of roots inoculated with the Az39 strain, and CD inoculated plants showed a decrease of oxidized GSH (GSSG) levels. We suggest a model in which the antioxidant response of the maize-diazotrophs system is modulated by the strain and that GSH plays a central role acting mainly as a substrate for GST. These findings generate knowledge for a suitable PGPB selection, and its scaling to an effective bioinoculant formulation for maize crops exposed to adverse environmental conditions.
Assuntos
Arsênio , Azospirillum brasilense , Água Subterrânea , Arsênio/toxicidade , Oxirredução , Raízes de Plantas , Zea maysRESUMO
Vicia villosa Roth is a legume species with a growing application in Argentina as a cover crop (CC), a practice that favors the sustainable development of agricultural systems. However, several areas where the use of this CC provides numerous advantages are affected by high concentrations of arsenic (As). Thus, in the present work we studied hairy vetch ability to cope with arsenate [As(V)], arsenite [As(III)], and the mixture of both along with oxidative stress indexes [chlorophyll content, malondialdehyde (MDA) equivalents] as well as anatomical and histological changes in the root structure. The results obtained suggested a different behavior of hairy vetch depending on its growth stage and on metal(oid) concentration. The roots treated with the contaminant showed less turgidity, thickening of the epidermal and subepidermal parenchymal outer layers, and the presence of dark deposits. The morpho-anatomic parameters (cortex length, vascular cylinder diameter, total diameter, and vascular cylinder area) were altered in plants treated with As(V) and As(V)/As(III) whereas the roots of plants treated with As(III) did not show significant differences respect to the control. Moreover V. villosa could tolerate and remove As from soil, thus the use of this legume species seems an attractive approach to remediate As while protecting contaminated soils.
Assuntos
Arsênio , Fabaceae , Vicia , Argentina , SoloRESUMO
Plant growth-promoting rhizobacteria (PGPR) generally exert their effects through enhancement of plant nutrient status and/or phytohormone production. The effects of PGPR on aromatic plant species are poorly known. We measured plant growth parameters, chlorophyll content, trichome density, stomatal density, and levels of secondary metabolites in peppermint (Mentha piperita) seedlings inoculated with PGPR strains Bacillus subtilis GB03, Pseudomonas fluorescens WCS417r, P. putida SJ04, or a combination of WCS417r + SJ04. The treated plants, in comparison with controls, showed increases in shoot biomass, root biomass, leaf area, node number, trichome density, and stomatal density, and marked qualitative and quantitative changes in monoterpene content. Improved knowledge of the factors that control or affect biosynthesis of secondary metabolites and monoterpene accumulation will lead to strategies for improved cultivation and productivity of aromatic plants and other agricultural crops without the use of chemical fertilizers or pesticides.
Assuntos
Bacillus subtilis/fisiologia , Mentha piperita/microbiologia , Pseudomonas fluorescens/fisiologia , Pseudomonas putida/fisiologia , Bacillus subtilis/genética , Mentha piperita/anatomia & histologia , Mentha piperita/química , Raízes de Plantas/microbiologia , Estômatos de Plantas/anatomia & histologia , Pseudomonas fluorescens/genética , Pseudomonas putida/genética , Tricomas/anatomia & histologiaRESUMO
Production of phytohormones is one of the main mechanisms to explain the beneficial effects of plant growth-promoting rhizobacteria (PGPR) such as Azospirillum sp. The PGPRs induce plant growth and development, and reduce stress susceptibility. However, little is known regarding the stress-related phytohormone abscisic acid (ABA) produced by bacteria. We investigated the effects of Azospirillum brasilense Sp 245 strain on Arabidopsis thaliana Col-0 and aba2-1 mutant plants, evaluating the morphophysiological and biochemical responses when watered and in drought. We used an in vitro-grown system to study changes in the root volume and architecture after inoculation with Azospirillum in Arabidopsis wild-type Col-0 and on the mutant aba2-1, during early growth. To examine Arabidopsis development and reproductive success as affected by the bacteria, ABA and drought, a pot experiment using Arabidopsis Col-0 plants was also carried out. Azospirillum brasilense augmented plant biomass, altered root architecture by increasing lateral roots number, stimulated photosynthetic and photoprotective pigments and retarded water loss in correlation with incremented ABA levels. As well, inoculation improved plants seed yield, plants survival, proline levels and relative leaf water content; it also decreased stomatal conductance, malondialdehyde and relative soil water content in plants submitted to drought. Arabidopsis inoculation with A. brasilense improved plants performance, especially in drought.
Assuntos
Ácido Abscísico/metabolismo , Arabidopsis/microbiologia , Azospirillum brasilense/fisiologia , Regulação da Expressão Gênica de Plantas , Reguladores de Crescimento de Plantas/metabolismo , Ácido Abscísico/análise , Arabidopsis/genética , Arabidopsis/fisiologia , Proteínas de Arabidopsis/genética , Proteínas de Arabidopsis/metabolismo , Biomassa , Clorofila/metabolismo , Secas , Flores/genética , Flores/microbiologia , Flores/fisiologia , Peroxidação de Lipídeos , Fotossíntese/fisiologia , Reguladores de Crescimento de Plantas/análise , Folhas de Planta/genética , Folhas de Planta/microbiologia , Folhas de Planta/fisiologia , Raízes de Plantas/genética , Raízes de Plantas/microbiologia , Raízes de Plantas/fisiologia , Transpiração Vegetal/fisiologia , Prolina/metabolismo , Plântula/genética , Plântula/microbiologia , Plântula/fisiologia , Sementes/genética , Sementes/microbiologia , Sementes/fisiologia , Água/fisiologiaRESUMO
Nowadays, soil salinity is the most unfavourable abiotic factors for plant growth, causing important yield loss of many crops. A partial solution to this situation is to establish crop varieties in these areas affected which are tolerant to stress. The aim of this study was to evaluate in a wheat variety, the morphophysiological plasticity to sodium chloride (NaCl) stress and the effect of exogenous Abscisic Acid (ABA) on physiological variables. This was carried out by using the BI3000 wheat variety, for regional adaptability experiments. The germination percentage, coleoptile and radicle growth and root anatomic were evaluated, both seedling irrigated with water or saline solution. On the other hand, ABA sprays were applied to wheat plants and their biomass, pigment, stomatal behaviour and cellular membrane injuries were determined after salt treatments. In this study, it was possible to determine that the BI3000 wheat variety can grow in high electrical conductivity, with good germination and seedling growth. This variety showed less radical anatomic variations under salinity, what allows a faster plasticity to adapt. ABA applications suggest a protective role in plants under salinity, due to an increase in chlorophyll and carotene content, stability of cell membranes and stomatal behavior. This study is a contribution to a better understanding of the morphophysiological responses of glycophytic plants to salt stress. This have been pointed out as a useful approach to show more tolerance to salt stress crops in the future and it suggests that ABA could help improve agriculture production in areas affected by this stress.