Using sentinel-2 satellite images and machine learning algorithms to predict tropical pasture forage mass, crude protein, and fiber content.

Grasslands cover approximately 24% of the Earth's surface and are the main feed source for cattle and other ruminants. Sustainable and efficient grazing systems require regular monitoring of the quantity and nutritive value of pastures. This study demonstrates the potential of estimating pasture leaf forage mass (FM), crude protein (CP) and fiber content of tropical pastures using Sentinel-2 satellite images and machine learning algorithms. Field datasets and satellite images were assessed from an experimental area of Marandu palisade grass (Urochloa brizantha sny. Brachiaria brizantha) pastures, with or without nitrogen fertilization, and managed under continuous stocking during the pasture growing season from 2016 to 2020. Models based on support vector regression (SVR) and random forest (RF) machine-learning algorithms were developed using meteorological data, spectral reflectance, and vegetation indices (VI) as input features. In general, SVR slightly outperformed the RF models. The best predictive models to estimate FM were those with VI combined with meteorological data. For CP and fiber content, the best predictions were achieved using a combination of spectral bands and meteorological data, resulting in R2 of 0.66 and 0.57, and RMSPE of 0.03 and 0.04 g/g dry matter. Our results have promising potential to improve precision feeding technologies and decision support tools for efficient grazing management.

Evaluation of metal accumulation in the forage grass Brachiaria decumbens Stapf grown in contaminated soils with iron tailings.

The biggest world tailing dam rupture occurred in Brazil in 2015, releasing approximately 32 million m3 of iron tailings in the Doce River watershed, along its 660 km trajectory, reaching the Atlantic Ocean. This disaster significantly altered water and soil properties, increasing the soil metal contents, mainly iron concentration. Little is known about the concentration of toxic elements in plants grown in these areas. Brachiaria decumbens stands out as the most cultivated grass in the affected areas and is widely used for cattle grazing. This study verified the metal contents in soils and in samples of B. decumbens grown in the initial pathway of the debris flow. It was noted that the tailing deposition altered the substrate chemically, increasing Fe by 181% and reducing Zn soil contents by 188%. However, the metal contents in the forage grass were below the toxic limit for cattle feed. In addition, the results suggest that the natural geological characteristics of the region also influenced the metal contents in plants since those plants grown in nonaffected areas also showed high metal concentrations. The impacted area soils had a slightly basic pH, which can reduce the metal availability. Considering that, in the future, these soils would return to their natural acid state, the metal contents in plants grown in the affected regions could probably increase. Thus, long-term studies are needed to ensure the food safety of the forage production in these areas. Integr Environ Assess Manag 2022;18:528-538. © 2021 SETAC.

AM fungi mediated bioaccumulation of hexavalent chromium in Brachiaria mutica-a mycorrhizal phytoremediation approach.

The experiment was designed to evaluate the roles of Rhizophagus irregularis on chlorophyll fluorescence and chromium bioaccumulation in a grass species (Brachiaria mutica) by supplementing Cr+6 at different concentrations. Arbuscular Mycorrhizal Fungi (AMF) association facilitated lessening of chromium level in contaminated soil and enhanced chromium bioavailability in Brachiaria mutica. The mycorrhizal inoculated increased the chlorophyll (0.925 mg/g), carotenoid (0.127 mg/g), protein (2.883 mg/g), proline (0.889 mg/g) contents and activities of antioxidant enzymes like catalase, ascorbate peroxidase and glutathione peroxidase. The mycorrhizal inoculated plants also showed enhanced overall photosynthetic performance (PIϕ = 2.473) and enhanced PS-II to PS-I electron transport as evident from yield parameter (0.712) and TR0/RC (2.419) for 60 mg/kg Cr+6 treatment. The observations suggest that AMF association could defend the plants from chromium stress by elevating the number of antioxidants in plants. Rhizophagus irregularis was found to maintain a successful symbiotic relationship with Brachiaria mutica in chromium contaminated soil. The observations recommended that Rhizophagus irregularis in association with Brachiaria mutica would be an innovative approach for decontamination of Cr+6.

Brachiaria species influence nitrate transport in soil by modifying soil structure with their root system.

Leaching of nitrate from fertilisers diminishes nitrogen use efficiency (the portion of nitrogen used by a plant) and is a major source of agricultural pollution. To improve nitrogen capture, grasses such as brachiaria are increasingly used, especially in South America and Africa, as a cover crop, either via intercropping or in rotation. However, the complex interactions between soil structure, nitrogen and the root systems of maize and different species of forage grasses remain poorly understood. This study explored how soil structure modification by the roots of maize (Zea maize), palisade grass (Brachiaria brizantha cv. Marandu) and ruzigrass (Brachiaria ruziziensis) affected nitrate leaching and retention, measured via chemical breakthrough curves. All plants were found to increase the rate of nitrate transport suggesting root systems increase the tendency for preferential flow. The greater density of fine roots produced by palisade grass, subtly decreased nitrate leaching potential through increased complexity of the soil pore network assessed with X-ray Computed Tomography. A dominance of larger roots in ruzigrass and maize increased nitrate loss through enhanced solute flow bypassing the soil matrix. These results suggest palisade grass could be a more efficient nitrate catch crop than ruzigrass (the most extensively used currently in countries such as Brazil) due to retardation in solute flow associated with the fine root system and the complex pore network.

Aluminum-induced toxicity in Urochloa brizantha genotypes: A first glance into root Al-apoplastic and -symplastic compartmentation, Al-translocation and antioxidant performance.

Previous studies have unraveled contrasting Al genotypic differences between Urochloa brizantha cv. Marandu (moderately tolerant) and Urochloa brizantha cv. Xaraés (more tolerant). Our objective was to evaluate differences in the response to Al-induced stress between these genotypes, focusing on Al compartmentation in the root apoplast and symplast, and antioxidant enzyme activities after Al exposure. Al-accumulation was 25% higher in the roots of cv. Xaraés than cv. Marandu, while in the shoot Al accumulation was 150% higher in cv. Marandu than cv. Xaraés. U. brizantha cv. Marandu accumulated 73% of the Al absorbed in the root symplast and 27% in the root apoplast, while cv. Xaraés accumulated 61% of the Al absorbed in symplast and 39% in apoplast. Furthermore, Al exposure leaded to physiological and developmental changes in root morphology, such as disorganization of vascular system, the collapse of cortical cells and absence of root hairs from the root tip, with more drastic effects detectable in cv. Marandu. Catalase (CAT) and guaiacol peroxidase (GPOX) activities in the roots of cv. Marandu were lower compared to cv. Xaraés. Our results pointed out that higher Al compartmentalization rates in the root apoplast, altogether with up-regulated metabolic activities of CAT and GPOX and also lower long distance transport of Al are seemingly at the base of the Al tolerance in cv. Xaraés. In conclusion, biochemical analysis of roots suggested that understanding of metabolic pathways is one of pressing approach to elucidate stress tolerance mechanisms in this genus.

Effective plant-endophyte interplay can improve the cadmium hyperaccumulation in Brachiaria mutica.

Soil contamination due to cadmium (Cd) is a ubiquitous environmental problem for which inexpensive remediation alternatives are required. Phytoaccumulation, the use of plants to extract and accumulate heavy metals from the contaminated environment, is such an alternative. In this study, we aimed at establishing effective plant-bacteria interplay between Brachiaria mutica and Cd-resistant endophytic bacteria eventually leading to improved phytoremediation. B. mutica was grown in a Cd-contaminated soil and inoculated with three Cd-tolerant endophytic bacteria individually as well as in combination. Plant physiological parameters, biomass production, bacterial colonization, and Cd-accumulation were observed at four different Cd exposures, i.e., 100, 200, 400 and 1000 mg kg-1 of soil. The combined application of endophytic bacteria was more effective as compared to their individual applications at all concentrations. Nevertheless, highest performance of consortium was seen at 100 mg Cd kg-1 of soil, i.e., root length was enhanced by 46%, shoot length by 62%, chlorophyll content by 40%, and dry biomass by 64%; which was reduced with the increase in Cd concentration. The bacterial population was highest in the root interior followed by rhizosphere and shoot interior. Concomitantly, plants inoculated with bacterial consortium displayed more Cd-accumulation in the roots (95%), shoots (55%), and leaves (44%). Higher values of BCFroot (> 1), and lower values for BCFshoot and TF (< 1) indicates capability of B. mutica to accumulate high amounts of Cd in the roots as compared to the aerial parts. The present study concludes that plant-endophyte interplay could be a sustainable and effective strategy for Cd removal from the contaminated soils.

Removal of phosphorous and nitrogen from wastewater in Brachiaria-based constructed wetland.

Considering the prevalence of eutrophication of water bodies, sustainable treatment technologies like constructed wetlands (CWs) have come up as a promising alternate for nutrient removal and wastewater treatment. The present study was undertaken to investigate the potential of Brachiaria-based constructed wetland for removal of phosphorus and nitrogen in different seasons of a sub-tropical region. The CW cell could efficiently remove phosphate and nitrogen under varying influent concentrations across different seasons. Average removal of total phosphate increased from 55.2% (winter) to 78.5% (spring), 80.7% (autumn), and 85.6% (summer), and maximum removal rate was 384.4 mg/m2-day during the summer season. The soluble/available phosphate was removed on priority owing to its easy bio-availability. The removal efficiency of Brachiaria increased with increasing influent phosphate concentration (5-20 mg/l), if supplemented with nitrogen maintaining the N:P ratio of 5:1. This highlighted the characteristic of Brachiaria to absorb chemical shocks w.r.t. phosphate. The neutral pH (6.2-8.3) and oxidising conditions in rhizosphere ruled out possibility of binding of phosphate with cations (Ca, Fe, and Al) in sediments. Ambient temperature and sunshine hours regulated evapotranspiration and hence nutrient removal. Simultaneous removal of nitrogen (75.6-84.6%) by Brachiaria indicated that it can serve dual purpose of nutrient removal and fodder-production for livestock, thus serving as a sustainable prototype for rural communities in sub-tropical regions.

Nitrate reductase activity in leaves as a plant physiological indicator of in vivo biological nitrification inhibition by Brachiaria humidicola.

The tropical forage grass Brachiaria humidicola (Bh) controls soil microbial nitrification via biological nitrification inhibition (BNI). The aim of our study was to verify if nitrate reductase activity (NRA) in Bh roots or leaves reflects in vivo performance of BNI in soils. NRA was measured in roots and leaves of contrasting accessions and apomictic hybrids of Bh grown under controlled greenhouse and natural field conditions. Nitrate (NO3-) contents were measured in soil solution and in Bh stem sap to validate NRA data. Potential soil nitrification rates (NRs) and leaf δ15N values were used to verify in vivo BNI by the NRA assay in the field study. NRA was detected in Bh leaves rather than roots, regardless of NO3- availability. NRA correlated with NO3- contents in soils and stem sap of contrasting Bh genotypes substantiating its reflectance of in vivo BNI performance. Additionally, leaf NRA data from the field study significantly correlated with simultaneously collected NRs and leaf δ15N data. The leaf NRA assay facilitated a rapid screening of contrasting Bh genotypes for their differences in in vivo performance of BNI under field and greenhouse conditions, but inconsistency of the BNI potential by Bh germplasm was observed. Among Bh genotypes tested, leaf NRA was closely linked with nitrification activity, and consequently with actual BNI performance. It was concluded that NRA in leaves of Bh can serve as an indicator of in vivo BNI activity when complemented with established BNI methodologies (δ15N, NRs) under greenhouse and field conditions.

Influence of water limitation on the competitive interaction between two Cerrado species and the invasive grass Brachiaria brizantha cv. Piatã.

Invasive grasses inhibit the growth of other plant species, and water deficit is one of the major competition problems for native vegetation. We evaluated whether the presence of Brachiaria brizantha cv. Piatã has a negative influence on the competition for water and nutrients between Anadenanthera macrocarpa and Anadenanthera colubrina (Angico species). The interspecific competition was evaluated using a randomized experimental design with the following treatments: 1) free competition (FC), in which the native species were cultivated without the grass presence and 2) under competition (UC), in which the native species grew together with the invasive grass for 120 days. We analysed the water relationships in the two species, the effect of water limitation on the antioxidant stress, the nutritional content of shoots and roots, the relative competition intensity (RCI) and growth. The presence of Piatã grass reduced the soil moisture causing a decrease of 21.9% and 29.5% in the relative water content (RWC) of leaves for A. macrocarpa and A. colubrina, respectively. For the two Angico species, the quantum efficiency of Photosystem II (ΦPSII) decreased with reduction of RWC leaf, resulting in the H2O2 increase (57.5% at day 30 for A. colubrina and 38.8% at day 120 for A. macrocarpa). The oxidative stress was evidenced by the increase in the superoxide dismutase (SOD), catalase (CAT) and ascorbate peroxidase (APX) activities in leaves and roots of both young native trees. In the UC treatment, reductions in water uptake also led to a decrease in root absorption of N, P, K, a Mg and low transport of these nutrients to the leaves of both Angico species. A. macrocarpa and A. colubrina showed less growth caused by limitation of water uptake, but the joint activity of the physiological and biochemical adjustments provided competitive ability.

Pleurotus spp. cultivation on Brachiaria sp. straw treatment with alkaline water: Oyster mushroom and substrate treatment.

The aim of this research was to evaluate the efficiency of aqueous alkali-treated Brachiaria straw for the cultivation of appropriate species of oyster mushroom. The substrate used in the cultivation of various Pleurotus spp. was soaked for 20min by using two different procedures: (i) 0.5-2.0% Ca(OH)2 in 100L water, and (ii) 50-250L water. As a result, 1% Ca(OH)2 dissolved in 100L water and 3.5kg of Brachiaria straw presented the best production. The most suitable species for the application of the present method were P. pulmonarius and P. sapidus. The success of this technique is directly related to the concentration of Ca(OH)2 and water, the species, and the origin and quality of raw material used as the substrate in the production of oyster mushroom.

Nutritional quality and organic matter degradability of Brachiaria spp. agronomically biofortified with selenium.

Selenium (Se) fertilisation in grazing systems can improve the quality of animal forage, but there are few studies addressing the influence of Se fertilisation on the chemical composition and ruminal degradability of forage fertilised with Se. The aim of this study was to evaluate the chemical composition and in vitro assays of truly degraded organic matter (TDOM), short-chain fatty acids (SCFA) total gas (GP) and methane (CH4 ) production of two harvests of Brachiaria brizantha cv. Marandu fertilised with urea coated with B, Cu and sodium selenate for 0, 10, 20, 40, 80 and 160 g/ha of Se. Selenium content in forage increased linearly with the different doses at 30 and 60 days after fertilisation. However, doses of 20 and 80 g/ha Se fertilisation yielded positive effects increasing Se content and truly degraded organic matter in vitro of Brachiaria brizantha cv. Marandu.

Pb-induced phytotoxicity in para grass (Brachiaria mutica) and Castorbean (Ricinus communis L.): Antioxidant and ultrastructural studies.

Hydroponics experiment was conducted to investigate the effects of different levels of Pb on Para Grass (Brachiaria mutica) and Castorbean (Ricinus communis L). Generally, Para Grass exhibited higher tolerance to excessive concentrations of Pb in nutrient solution, whereas a consistent decline was observed in growth of Castorbean plants exposed to similar Pb levels. Malondialdehyde (MDA) and H2O2 contents exhibited contrasting results with a general decrease in Para Grass and a linear increase in case of Castorbean. In both species a decrease was noticed in the activities of superoxide dismutase (SOD) and guaiacol peroxidase (G-POD) while catalase (CAT) activity was significantly increased. Ultrastructural studies revealed increased starch grains and adversely affected thylakoid membranes in chloroplasts of leaf cells of plants treated with 500 µM Pb. Photosynthetic parameters such as CO2 assimilation rate, stomatal conductance (gs) and transpiration rate (E) decreased in both plant species under different levels of Pb. Maximum concentrations of Pb in shoots of Para Grass and Castorbean were 1.29 and 0.352 g kg-1, respectively while in roots maximum values were 8.88 and 49.86 g kg-1, respectively. The high concentrations of Pb (about 5%) in the roots of Castorbean plants suggest its possible role in the phytoremediation/rhizofiltration of Pb contaminated water.

GID1 expression is associated with ovule development of sexual and apomictic plants.

KEY MESSAGE: BbrizGID1 is expressed in the nucellus of apomictic Brachiaria brizantha, previous to aposporous initial differentiation. AtGID1a overexpression triggers differentiation of Arabidopsis thaliana MMC-like cells, suggesting its involvement in ovule development. GIBBERELLIN-INSENSITIVE DWARF1 (GID1) is a gibberellin receptor previously identified in plants and associated with reproductive development, including ovule formation. In this work, we characterized the Brachiaria brizantha GID1 gene (BbrizGID1). BbrizGID1 showed up to 92% similarity to GID1-like gibberellin receptors of other plants of the Poaceae family and around 58% to GID1-like gibberellin receptors of Arabidopsis thaliana. BbrizGID1 was more expressed in ovaries at megasporogenesis than in ovaries at megagametogenesis of both sexual and apomictic plants. In ovules, BbrizGID1 transcripts were detected in the megaspore mother cell (MMC) of sexual and apomictic B. brizantha. Only in the apomictic plants, expression was also observed in the surrounding nucellar cells, a region in which aposporous initial cells differentiate to form the aposporic embryo sac. AtGID1a ectopic expression in Arabidopsis determines the formation of MMC-like cells in the nucellus, close to the MMC, that did not own MMC identity. Our results suggest that GID1 might be involved in the proper differentiation of a single MMC during ovule development and provide valuable information on the role of GID1 in sexual and apomictic reproduction.

Pleurotus spp. cultivation on Brachiaria sp. straw treatment with alkaline water

Abstract The aim of this research was to evaluate the efficiency of aqueous alkali-treated Brachiaria straw for the cultivation of appropriate species of oyster mushroom. The substrate used in the cultivation of various Pleurotus spp. was soaked for 20 min by using two different procedures: (i) 0.5-2.0% Ca(OH)2 in 100 L water, and (ii) 50-250 L water. As a result, 1% Ca(OH)2 dissolved in 100 L water and 3.5 kg of Brachiaria straw presented the best production. The most suitable species for the application of the present method were P. pulmonarius and P. sapidus. The success of this technique is directly related to the concentration of Ca(OH)2 and water, the species, and the origin and quality of raw material used as the substrate in the production of oyster mushroom.

Content of the Saponin Protodioscin in Brachiaria spp. from the Eastern Plains of Colombia.

Protodioscin is used as a marker of saponin content that could cause hepatotoxicity in ruminants. In Brachiaria spp. from two regions of the Colombian Eastern Plains (east mountain range of the Andean-"piedemonte" and Ariari River Valley) were determined this metabolite at 14 and 28 days post-cutting under different climatic conditions. No protodioscin was detected in B. dictyoneura or B. humidicola. In B. brizantha, B. decumbens and B. ruziziensis x B. decumbens x B. brizantha (hybrid), protodioscin content corresponded to an interaction between species, post-cutting time and season. Concentrations ≥1% (minimum toxic level) were recorded in B. decumbens and the hybrid, and to a lesser extent in B. brizantha. The concentration of protodioscin was higher at 28 days, when the pastures are suitable for consumption. B. brizantha accumulated the lowest saponin concentration, whereas the hybrid had the highest levels, particularly in the "piedemonte" and during drought (3.37%). Dry season favored the protodioscin concentration in B. decumbens (in river valley) and in the hybrid (in "piedemonte"). In the latter, there was a positive correlation with temperature and a negative with humidity, which are typical characteristics of dry periods. This is the first report of protodioscin content in the hybrid.

Intake and digestibility in sheep fed on marandu grass silages added with dehydrated barley / Ingestão e digestibilidade de ovinos alimentados com silagens de capim-marandu aditivadas com resíduo de cervejaria desidratado

The objective was to evaluate the intake and the apparent digestibility in sheep fed on marandu grass silages added with dehydrated barley. Twenty crossbred Santa Inês lambs were used, with a mean initial weight of 30±4.5 kg and mean age of 14±2 months. The experimental sheep were distributed into a completely randomized design and lining, with five treatments and four repetitions, with treatments levels of inclusion of 0, 10, 20, 30 and 40% natural matter of naturally dehydrated brewery residue for 36 hours to the marandu grass silage to feed the sheep. The evaluation period lasted 21 days, 15 for adaptation to the diets and 7 days for data collection. The data was submitted to analysis of variance, and when significant (P<0.05) the treatment means were analysed by regression. The inclusion of dehydrated barley to silage showed a linear increase in water intake (P<0.05), increased by 0.02% per unit of dehydrated barley. A quadratic effect was observed for the levels of dehydrated barley on the dry matter intake (DM), estimating a maximum consumption of 2.86% DM for silages containing 17.8% dehydrated barley. The crude protein intake (CP) behaved quadratically, with the maximum value estimated of 0.29% CP at a level of 22.5% dehydrated barley. Ether extract (EE) intake also exhibited quadratic behaviour (P<0.05), with the maximum value estimated of 0.2% EE at a level of 28.25% dehydrated barley. The regression study showed quadratic behaviour; with the maximum estimated value of neutral detergent fibre was 2.33% at a level of 34.58% dehydrated barley. No statistical significance was found for the intake of acid detergent fibre or organic matter (P>0.05). It was concluded that the addition of levels of 20 to 30% of dehydrated barley to silage resulted in a positive response for the dry matter intake, crude protein, Ether extract and neutral detergent fibre.(AU)

Objetivou-se avaliar o consumo e a digestibilidade aparente de ovinos alimentados com silagens de capim marandu aditivadas com resíduo de cervejaria desidratado. Foram utilizados 20 ovinos mestiços de Santa Inês machos inteiros, com peso médio inicial de 30±4.5 kg e média de 14±2meses de idade. O delineamento experimental foi o inteiramente casualizado, com cinco tratamentos e quatro repetições, sendo os tratamentos níveis de inclusão de 0, 10, 20, 30 e 40% da matéria natural de resíduo de cervejaria desidratado naturalmente por 36 horas à silagem de capim-marandu. O período de avaliação teve duração de 21 dias, sendo 15 para adaptação às dietas e seis para as coletas. Os dados foram submetidas à análise de variância, e quando significativo, as médias dos tratamentos à análise de regressão. A inclusão do resíduo de cervejaria desidratado promoveu aumento linear (P<0,05) no consumo de água, que aumentou em 0,02 ponto percentual a cada unidade de resíduo adicionada. Observou-se efeito quadrático (P<0,05) nos níveis de resíduo de cervejaria desidratado sobre o consumo de matéria seca, estimando-se consumo máximo de 2,86% peso vivo (PV) para silagens contendo 17,8% de resíduo de cervejaria. O consumo de proteína bruta apresentou comportamento quadrático, de modo que o valor máximo foi estimado em 0,29%PV de proteína bruta para o nível de 22,5% de resíduo de cervejaria desidratado. Para o consumo de extrato etéreo, houve comportamento quadrático (P<0,05), em que o valor máximo foi estimado em 0,2%PV de extrato etéreo para o nível de 28,25% de resíduo de cervejaria desidratado. O estudo de regressão mostrou comportamento quadrático (P<0,05) para o consumo de fibra em detergente neutro, em que o valor máximo foi estimado em 2,33% PV de fibra em detergente neutro para o nível de 34,58% de resíduo de cervejaria desidratado. Para os consumos de fibra em detergente ácido e matéria orgânica, não foi observada significância estatística (P>0,05). Conclui-se que silagens aditivada com níveis de 20 a 30% de resíduo de cervejaria desidratado, promoveram respostas positivas aos consumos de matéria seca, proteína bruta, extrato etéreo e fibra em detergente neutro.(AU)

Ultrahigh-Performance Liquid Chromatography-High-Resolution Quadrupole Time-of-Flight Mass Spectrometry Based Metabolomics Reveals Key Differences between Brachiaria decumbens and B. brizantha, Two Similar Pastures with Different Toxicities.

Several species of Brachiaria (Poaceae) currently cover extensive grazing areas in Brazil, providing valuable source of feed for a large cattle population. However, numerous cases of toxicity outbreaks in livestock have raised concerns on safety of using these plants, especially B. decumbens. In this study, chemometric analysis of ultrahigh-performance liquid chromatography-high-resolution quadrupole time-of-flight mass spectrometry (UHPLC-HR-QTOF-MS) data has for the first time uncovered qualitative and quantitative differences between metabolomes of toxic B. decumbens and nontoxic B. brizantha. The steroidal saponin protoneodioscin was established as the main biomarker for B. decumbens when compared to B. brizantha, and therefore the key explanation for their phytochemical differentiation. Quantification of protodioscin in both plants showed no significant differences; consequently, the idea that this compound is solely responsible for toxicity outbreaks must be discarded. Instead, we propose that the added occurrence of its stereoisomer, protoneodioscin, in B. decumbens, can be considered as the probable cause of these events. Interestingly, the greatest concentrations of saponins for both species were reached during winter (B. decumbens = 53.6 ± 5.1 mg·g(-1) dry weight (D.W.); B. brizantha = 25.0 ± 1.9 mg·g(-1) D.W.) and spring (B. decumbens = 49.4 ± 5.0 mg·g(-1) D.W.; B. brizantha = 27.9 ± 1.4 mg·g(-1) D.W.), although in the case of B. decumbens these values do not vary significantly among seasons.

Availability and toxicity of cadmium to forage grasses grown in contaminated soil.

It is important to know the mechanisms for forage development, especially those related to the tolerance of potentially toxic elements, when considering their use in phytoremediation in heavy metal contaminated areas. In this study, we evaluated plant growth, concentration, and the availability of cadmium (Cd) for forage grasses (Panicum maximum Jacq. cv. Aruana and cv. Tanzânia; Brachiaria decumbens cv. Basilisk; Brachiaria brizantha cv. Xaraés and cv. Marandu) cultivated in Cd contaminated soils. The experiments were performed under greenhouse conditions over a 90-day evaluation period, and the Cd rates were 2, 4, and 12 mg/kg of soil. The relative growth rate of the forage grasses decreased as Cd rates increased, and the following descending order of susceptibility was observed: Marandu > Xaraés > Aruana > Tanzânia > Basilisk, with regard to phytotoxicity in these plants. The forage Cd concentration increased in line with increases in the Cd rates. Cd contents extracted by Mehlich-1 and by diethylenetriaminepentaacetic acid presented high positive correlation with forage relative growth. The forage plants did not block Cd entry into the food chain because they were not capable of limiting Cd absorption.

The presence of Microlobius foetidus cause changes in the antioxidant defense of Urochloa decumbens?

Urochloa decumbens (Stapf) R. D. Webster (Poaceae) is an exotic species with has spread rapidly through the Cerrado area of Pantanal, Mato Grosso do Sul, Brazil. It has covered the soil aggressively turning it into cultivated pastures. Thus, it has become a challenge to protect native areas due its capacity of exclusion of native species. It has been observed that Microlobius foetidus (Jacq.) M.Sousa & G.Andrade species (Fabaceae) shows a dominant pattern over the development of U. decumbens. This work shows that M. foetidus interfere on the natural growth of U. decumbens within 10 m ratio. Between 15 and 20 m, it was observed an increase of Importance Value index (IVI) and Relative cover (RC) values. It was also observed a variation on the antioxidant defense system of U. decumbens within 10m ratio from M. foetidus. The enzymes superoxide dismutase, catalase and peroxidase present higher levels of activity then those found for glutathione reductase. This data indicates that M. foetidus may have an effect on U. decumbens, increase the activity of antioxidant enzymes. This effect probably happens as means to neutralize the toxic effects of the oxygen generated due to the presence of allelochemicals, which increases oxidative stress.

The presence of Microlobius foetidus cause changes in the antioxidant defense of Urochloa decumbens? / A presença de Microlobius foetidus causa alteraçõess na defesa antioxidante de Urochloa decumbens?

AbstractUrochloa decumbens (Stapf) R. D. Webster (Poaceae) is an exotic species with has spread rapidly through the Cerrado area of Pantanal, Mato Grosso do Sul, Brazil. It has covered the soil aggressively turning it into cultivated pastures. Thus, it has become a challenge to protect native areas due its capacity of exclusion of native species. It has been observed that Microlobius foetidus (Jacq.) M.Sousa & G.Andrade species (Fabaceae) shows a dominant pattern over the development of U. decumbens. This work shows that M. foetidusinterfere on the natural growth of U. decumbens within 10 m ratio. Between 15 and 20 m, it was observed an increase of Importance Value index (IVI) and Relative cover (RC) values. It was also observed a variation on the antioxidant defense system of U. decumbens within 10m ratio from M. foetidus. The enzymes superoxide dismutase, catalase and peroxidase present higher levels of activity then those found for glutathione reductase. This data indicates that M. foetidus may have an effect on U. decumbens, increase the activity of antioxidant enzymes. This effect probably happens as means to neutralize the toxic effects of the oxygen generated due to the presence of allelochemicals, which increases oxidative stress.

ResumoUrochloa decumbens (Stapf) R. D. Webster (Poaceae) é uma espécie exótica que se expandiu rapidamente no Cerrado do Pantanal de Mato Grosso do sul, e cobre o solo de maneira agressiva convertendo a vegetação natural em pastagens cultivadas e se tornando um desafio para o controle em áreas protegidas devido a sua capacidade de excluir espécies nativas. Observações demonstraram que a espécie Microlobius foetidus(Jacq.) M.Sousa & G.Andrade (Fabaceae) apresenta padrões de dominância, interferindo no desenvolvimento de U. decumbens e alterações na fitofisionomia e sistema de defesa antioxidante desta espécie foram investigados. Nossos estudos demonstraram que M. foetidus interfere no crescimento de U. decumbens nos primeiros 10 metros de distância, sendo que aos 15 e 20 metros, é verificado um aumento nos valores de IVI e CR. Alterações no sistema de defesa antioxidante de U. decumbens também foram verificados nos indivíduos amostrados até 10 metros de distância. Superóxido dismutase, catalase e peroxidase foram provavelmente as enzimas cruciais envolvidas na neutralização de espécies reativas de oxigênio, uma vez que apresentaram maiores níveis de atividade em comparação com outras enzimas, tais como glutationa redutase. Os dados indicam que a proximidade de U. decumbens as áreas onde se encontram populações de M. foetidus, aumentam a atividade das enzimas antioxidantes. Este efeito provavelmente ocorre como meio para neutralizar os efeitos tóxicos do oxigênio gerado, devido à presença de aleloquímicos, o que aumenta o estresse oxidativo.