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Sanchez-Pardo B.,Autonomous University of Madrid | Fernandez-Pascual M.,CSIC - Institute of Agricultural Sciences | Zornoza P.,Autonomous University of Madrid
Environmental and Experimental Botany | Year: 2012

Copper (Cu) is a heavy metal which, at high concentrations, is toxic to organisms. Some plants, however, possess systems for dealing with excess Cu, such as its cell localisation, and have antioxidant enzymes that help to reduce the oxidative stress. The present work examines the microlocalisation of Cu and the antioxidant enzyme activity present in the nodules of white lupin and soybean plants grown hydroponically for 35 days in the presence of 1.6μM (control) or 192μM (excess) Cu. The effect of these conditions on nodule (ultra)structure was also examined. Energy-dispersive X-ray microanalysis showed the cell walls to be the main area of Cu binding in the inner and outer cortex and infected zone of white lupin nodules grown under the excess Cu conditions, while in soybean a high Cu signal was detected inside cells (cytoplasm or vacuoles) both in the inner cortex and infected zone. At the tissue level, an increasing Cu gradient was seen from the outer towards the inner nodule cortex in white lupin nodules, while the opposite was seen in soybean. Cu excess also induced oxidative stress and promoted damage to the ultrastructure of nodules. In the white lupin infected cells, a breakdown of the peribacteroidal membrane was seen, along with an increased number of vesicles in the cytosol of these cells. In the infected cells of the soybean nodules, the bacteroidal membrane became degraded and precipitation was seen within the vacuoles of the infected and uninfected cells. Finally, the white lupin nodules seemed to be more sensitive to Cu excess than those of soybean, with the nodulation process, N 2 fixation, and the ultrastructure of bacteroids more strongly affected. A less effective antioxidative stress response against Cu was also seen in white lupin than in soybean nodules: the excess copper treatment induced a smaller increase in the total thiol content and ascorbate peroxidase activity in white lupin nodules than in soybean nodules, and promoted a greater reduction in catalase activity. © 2012 Elsevier B.V..

Badenes-Perez F.R.,CSIC - Institute of Agricultural Sciences
Acta Horticulturae | Year: 2013

Yellow rocket, Barbarea vulgaris R. Br. (Brassicaceae), is a biennial plant naturally occurring in temperate regions worldwide. This plant has been proposed as a trap crop for the diamondbaek moth, Plutella xylostella (L.) (Lepidoptera: Plutellidae). Since P. xylostella is the most damaging insect pest of cruciferous crops throughout the world and it can easily develop resistance to insecticides, trap cropping is a desirable technique for P. xylostella management as an alternative to insecticide use. Barbarea vulgaris has been used at a small scale as a vegetable and food medicine and it contains phytochemicals proven to be beneficial for human health, such as flavonoids, glucosinolates, and saponins. Here we study the capacity of vegetative regeneration of B. vulgaris after partial and full removal of its foliage, which would allow the use of B. vulgaris as a vegetable while also being used as a trap crop. The potential of B. vulgaris as a salad vegetable was assessed by a group of 30 inexperienced taste panelists. The capacity of vegetative regeneration combined with the positive evaluation of the plant as a salad vegetable indicates that the additional use of B. vulgaris as a marketable vegetable could improve its potential as trap crop because of economic reasons.

Plaza C.,CSIC - Institute of Agricultural Sciences | Courtier-Murias D.,University of Toronto | Fernandez J.M.,CSIC - Institute of Agricultural Sciences | Polo A.,CSIC - Institute of Agricultural Sciences | Simpson A.J.,University of Toronto
Soil Biology and Biochemistry | Year: 2013

Conservation tillage practices that entail no or reduced soil disturbance are known to help preserve or accumulate soil organic matter (OM). However, the underlying mechanisms especially at the molecular level are not well understood. In this study soil samples from 25-year-old experimental plots continuously cropped with barley (Hordeum vulgare L.) under no-tillage (NT) and chisel tillage (CT) were subjected to a new physical fractionation method to isolate dissolved OM, mineral-free particulate OM located outside aggregates (physically and chemically unprotected), OM occluded within both macroaggregates and microaggregates (weakly and strongly protected by physical mechanisms, respectively), and OM in intimate association with minerals (protected by chemical mechanisms). The whole soils and OM fractions were analyzed for organic C and N content and by modern nuclear magnetic resonance (NMR) techniques. The soil under NT stored 16% more organic C and 5% more N than the soil under CT. Compared to CT, NT increased free organic C content by 7%, intra-macroaggregate organic C content by 20%, intra-microaggregate organic C content by 63%, and mineral-associated organic C content by 16% and decreased dissolved organic C content by 11%. The mineral-associated OM pool accounted for 65% of the difference in total organic C content between NT and CT, whereas the intra-microaggregate OM only explained 18%, intra-macroaggregate OM 14%, and free OM 11%. The NMR experiments revealed that the free and intra-aggregate OM fractions were dominated by crop-derived materials at different stages of decomposition, whereas the mineral-associated OM pool was predominately of microbial origin. Overall, our results indicate that microbes and microbial by-products associated with mineral surfaces and likely physically protected by entrapment within very small microaggregates constitute the most important pool of OM stabilization and C sequestration in soils under NT. Most probably the slower macroaggregate turnover in NT relative to CT boosts not only the formation of microaggregates and thereby the physical protection of crop-derived particulate OM, but more importantly the interaction between mineral particles and microbial material that results in the formation of very stable organo-mineral complexes. © 2012 Elsevier Ltd.

del Monte J.P.,Technical University of Madrid | Dorado J.,CSIC - Institute of Agricultural Sciences
Weed Research | Year: 2011

Bromus diandrus is an emerging problem in barley crops in temperate climates, owing to its ability to adapt to certain farming techniques, as well as the absence of an efficient means of control. The aim of this study was to evaluate the germination of B. diandrus as a function of light conditions, time after ripening, temperature and water potential. Our results indicate that light conditions were the principal factor affecting germination and that seeds had negative photoblastism. Darkness modified the hydrotime parameters of the seeds somewhat, for example, by decreasing the values of Ψb and by favouring dormancy loss. The after-ripening time significantly modified the hydrotime parameters of the seeds, causing Ψb to drift towards more negative values (greater dormancy loss) as the after-ripening time increased. The combination of both variables explains the dormancy dynamics of this species in Mediterranean climates that are characterised by two distinct germination flushes, coinciding with two periods when soil humidity and temperature are not limiting. The first and main cohort of seedlings would emerge in autumn, originating from young buried seeds. A second cohort would emerge in the spring, from mature seeds on the surface of the soil. © 2011 The Authors. Weed Research © 2011 European Weed Research Society.

Garrido F.,CSIC - Institute of Agricultural Sciences | Helmhart M.,CSIC - Institute of Agricultural Sciences
Geoderma | Year: 2012

Preferential flow is the non-uniform movement of water and solutes through soils that bypasses a portion of the soil matrix. It limits the effective sorbing capacity of the soil and it has been related to a reduced solute residence time accounting for an increased risk of groundwater contamination. A dye tracer experiment and a subsequent soil sampling procedure in three adjacent soil profiles were performed in a moderately Pb contaminated roadside soil aiming to make visible different flow domains, to test whether preferential flow paths influence the metal content depth distribution, to study differences in selective soil properties resulting from flow domains and, lastly, to investigate whether preferential flow induces changes in the solid phase distribution of lead. Identified preferential flow domains showed greater lead concentration along with lower pH and greater amounts of both inorganic and organic C contents than unstained soil matrix domains. The ratio humic acids (HAs) to fulvic acids (FAs) contents was significantly lower in the preferential paths than in the matrix domains which might be related with sizable differences in the humification process. Lastly, based on the three-step BCR sequential extraction procedure, it has been shown that preferential flow phenomena induce differences in metal distribution between both identified flow domains. While lead content in the soluble and exchangeable (FI) as well as bound to organic matter fractions (FIII) were greater in the matrix than in the preferential flow domains, the amount of metal bound to Fe, Al and Mn (hydr)oxides (FII) was significantly greater in the preferential flow domain than in the matrix one. This indicates that more stable lead sorption mechanisms, thus leading to a lower metal mobility, might partially be responsible for the larger amount of total metal content found associated to the preferential flow paths. Overall, our results suggest that preferential flow domains may behave as metal storage compartments in the soils due to differences in soil properties promoted by means of the heterogeneous water flow distribution. © 2011 Elsevier B.V.

De La Pena T.C.,CSIC - Institute of Agricultural Sciences | Pueyo J.J.,CSIC - Institute of Agricultural Sciences
Agronomy for Sustainable Development | Year: 2012

Mineral nitrogen deficiency is a frequent characteristic of arid and semi-arid soils. Biological nitrogen fixation by legumes is a sustainable and environmentalfriendly alternative to chemical fertilization. Therefore, legumes have a high potential for the reclamation of marginal soils. Such issue is becoming more urgent due to the ever-rising requirement for food and feed, and the increasing extension of salinized and degraded lands, both as a consequence of global change and irrigation practices. This manuscript reviews current research on physiological and molecular mechanisms involved in the response and tolerance to environmental stresses of the Rhizobium- legume symbiosis. We report in particular recent advances on the isolation, characterization, and selection of tolerant rhizobial strains and legume varieties, both by traditional methods and through biotechnological approaches. The major points are the following. (1) Understanding mechanisms involved in stress tolerance is advancing fast, thus providing a solid basis for the selection and engineering of rhizobia and legumes with enhanced tolerance to environmental constraints. (2) The considerable efforts to select locally adapted legume varieties and rhizobial inocula that can fix nitrogen under conditions of drought or salinity are generating competitive crop yields in affected soils. (3) Biotechnological approaches are used to obtain improved legumes and rhizobia with enhanced tolerance to abiotic stresses, paying particular attention to the sensitive nitrogen-fixing activity. Those biotechnologies are yielding transgenic crops and inocula with unquestionable potential. In conclusion, the role of legumes in sustainable agriculture, and particularly, their use in the reclamation of marginal lands, certainly has a very promising future. © INRA and Springer Science+Business Media B.V. 2011.

Lopez-Fando C.,CSIC - Institute of Agricultural Sciences | Pardo M.T.,CSIC - Institute of Agricultural Sciences
Soil and Tillage Research | Year: 2011

Changes in the agricultural management can potentially increase the accumulation rate of soil organic carbon (SOC), thereby sequestering CO2 from the atmosphere. In a long-term experiment (1992-2008) we examined the effects of various tillage intensities: no-tillage (NT), minimum tillage with chisel plow (MT), and conventional tillage with mouldboard plow (CT), on the topsoil profile distribution (0-30cm) of SOC, on a semi-arid loamy soil from Central Spain. The crop sequence established was cheap pea (Cicer arietinun L.) cv. Inmaculada/barley (Hordeum vulgare L.) cv. Volley. Soil organic carbon in the various tillage treatments was expressed on a content bases and the equivalent soil mass approach. Measurements made at the end of 17 years showed that in the 0-30cm depth, stocks of SOC had increased under NT compared with MT and CT. Most dramatic changes occurred within the 0-5cm layer where plots under NT had 5.8 and 7.6Mgha-1 more SOC than under MT or CT respectively. No-tillage plots, however, exhibited strong vertical gradients of SOC with concentrations decreasing from 0-5 to 20-30cm. Stratification ratios of SOC in 1992 showed no significant differences between tillage systems. On the contrary, from 1993 onwards all stratification ratios were significantly higher in NT than in the other two tillage systems. In addition, since 2003 stratification ratios of SOC obtained under NT were systematically >2 and more than 2-fold those obtained under MT and CT. Stratification ratios >2 are uncommon under degraded conditions and could suggest that NT management system may have the most benefits to soil quality in semi arid regions with low native soil organic matter. © 2010 Elsevier B.V.

Hernandez D.,CSIC - Institute of Agricultural Sciences | Polo A.,CSIC - Institute of Agricultural Sciences | Plaza C.,CSIC - Institute of Agricultural Sciences
European Journal of Agronomy | Year: 2013

Intensive pig farming is a relevant economic activity in Mediterranean areas, which generates large amounts of pig slurry (PS) as a by-product. Pig slurry represents a valuable resource for low-fertility Mediterranean soils, capable of supplying organic matter and plant nutrients, particularly N. The cumulative and residual effects of PS on winter barley (Hordeum vulgare L.) yield and N use efficiency were investigated in a seven-year field experiment under semiarid Mediterranean conditions. Treatments included five rates of PS ranging from 30 to 150m 3ha -1 applied either every year or only once at the beginning of the experiment, an annual mineral N fertilization (traditional in the study area), and a control with no fertilization. Plant-available N content in soils after harvest increased with the annual application of PS with respect to the mineral fertilization and the control treatment, especially in dry years. Yearly variations in water availability also shaped the response of barley to PS fertilization. In general, the annual application of PS affected positively grain yield and biomass production. Residual effects were evident for the second and third barley crop. Cumulative N uptake by the barley crop increased with increasing the rate of PS (up to 120tha -1), while N use efficiency decreased, which suggested an increasing risk of leaching and contamination of ground water. As a whole, our data indicate that the annual application of 30m 3ha -1 of PS (equivalent to an average of 67kgNha -1) may result in barley yields similar to those obtained with the traditional mineral fertilization, while safely adhering to European regulations for the use of N in agriculture. The application of PS at rates higher than 60m 3ha -1 may result in better yields, but also in significantly lower N use efficiency and a higher potential environmental impact. © 2012 Elsevier B.V.

Badenes-Perez F.R.,Max Planck Institute for Chemical Ecology | Badenes-Perez F.R.,CSIC - Institute of Agricultural Sciences | Reichelt M.,Max Planck Institute for Chemical Ecology | Gershenzon J.,Max Planck Institute for Chemical Ecology | Heckel D.G.,Max Planck Institute for Chemical Ecology
New Phytologist | Year: 2011

Glucosinolates are plant secondary metabolites used in host plant recognition by insects specialized on Brassicaceae, such as the diamondback moth (DBM), Plutella xylostella. Their perception as oviposition cues by females would seem to require their occurrence on the leaf surface, yet previous studies have reached opposite conclusions about whether glucosinolates are actually present on the surface of crucifer leaves. DBM oviposits extensively on Barbarea vulgaris, despite its larvae not being able to survive on this plant because of its content of feeding-deterrent saponins. Glucosinolates and saponins in plant tissue and mechanically removed surface waxes from leaves of Barbarea spp. were analyzed with high-performance liquid chromatography (HPLC) and liquid chromatography-mass spectrometry (LC-MS). Surface waxes from leaves of Barbarea spp. contained glucosinolates, but not feeding-deterrent saponins. Our research is the first to show that glucosinolates are present on the leaf surface of Barbarea spp., but not in other crucifers investigated, resolving some conflicting results from previous studies. Our research is also the first to quantify glucosinolates on the leaf surface of a crucifer, and to show that the concentrations of glucosinolates found on the leaf surface of Barbarea spp. are sufficient to be perceived by ovipositing DBM. © The Authors (2010). Journal compilation © New Phytologist Trust (2010).

Lopez-Fando C.,CSIC - Institute of Agricultural Sciences | Pardo M.T.,CSIC - Institute of Agricultural Sciences
Soil and Tillage Research | Year: 2012

Tillage treatments had impact on total soil nitrogen (N) storage and consequently on soil carbon (C) sequestration. The objective of this study was to assess effects of long-term (1992-2010) tillage practices, including a partial-width tillage system (paraplow) on N concentration and stratification. The tillage treatments were: no-tillage (NT), minimum tillage (18-22cm depth) with chisel plow (MT), conventional tillage (25-30cm depth) with mouldboard plow (CT) and zone-tillage subsoiling (25-30cm) with a paraplow (ZT) applied in alternate years in rotation with NT. The soil was a Calcic Haploxeralf from Central Spain. The crop rotation was chick pea (Cicer arietinun L.) cv. Inmaculada/barley (Hordeum vulgare L.) cv. Volley. The equivalent mass approach was used to compare N stocks in the various tillage methods. Tillage treatments had significant effects on soil bulk density and no-till increased soil bulk density of the top layer. At the end of 19 years, the stocks of N had increased under NT compared with MT and CT. Most changes occurred within the 0-5cm layer, where plots under NT had 0.48MgNha -1 and 0.53MgNha -1 greater than in MT and CT, respectively. Zone tillage maintained most of the long-term benefit of NT in increasing N stocks in the top layer (0-5cm). At the end of the experiment, total N concentration in the 0-5cm depth under ZT was 42% and 53% higher that under MT and CT, respectively. Stratification ratios of N from 1992 to 2000 showed no significant differences between NT, MT and CT. In contrast, from 2001 onwards, all stratification ratios were significantly higher in NT than in the other two tillage systems. In addition, in 2010 the stratification ratio of N in NT was >2 and more than 2-fold those obtained in MT and CT. Values of stratification ratios under ZT followed the same trend than under NT and were significantly greater than under MT or CT. These greater stratification ratios of N observed under NT and ZT confirm, in the soil studied, not only the benefits associated with the long-term application of no-till in increasing total N in the top layer, but also the positive impact of the use of a paraplow as a rotational tillage system. © 2011 Elsevier B.V.

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