Underestimated role of legume roots for soil N fertility

Research ArticleNitrogen (N) is a major fertilizing element for plants. The distribution of N in legumes is influencing the efficiency of the next crop. Nitrogen storage in legumes is actually estimated by N fixation in shoots, whereas there is little knowledge on the contribution of roots and nodules to legume N and soil N. Here, we studied the contribution of roots and nodules of grain and pasture legumes to plant N and soil N in Mediterranean fields. Experiments were run under rainfed conditions for a 2-year period in three regions of Portugal. Entire plants including top plant and visible roots and nodules were sampled at the end of the growing seasons for grain legumes, sweet and yellow lupine, and over two harvests in case of pastures. N2 fixation was measured for grain legumes and pasture legumes using 15N tracing. Our results show that aboveground N concentration did not vary among legumes, but differed in the belowground tissues. Field studies show that 7–11%of total legume N was associated with roots and nodules. Data also show an allocation of 11– 14 kg N fixed t−1 belowground dry matter in indeterminate legumes, which represents half the amount of total aboveground plant. This finding demonstrates that investigation relying only on shoot Nunderestimates the role of legumes for soil N fertilityinfo:eu-repo/semantics/publishedVersio

Nitrogen fertilization on growth and productivity of young 'Rocha' pear trees

Pear trees (Pyrus communis L. ‘Rocha’) grafted on quince ‘BA29’ were planted in February of 2003 at “Pêro Moniz” (“Cadaval”, Portugal) and drip-fertigated for three years with four N levels (0, 10, 20 and 40 kg N/ha per year) using ammonium nitrate. At planting and at the end of each season, tree height (A), trunk cross sectional area (AST) and the number of shoots and shoot length (NL and CL) were determined. Leaves were collected 110 days after full bloom (DAPF) and at leaf fall and were chemically analysed for N. The onset of flowering was in 2005 and in that year the fruit set and the yield characteristics were evaluated. Moreover, in 2005 five extra trees were selected for each N level, and all flowers were collected and analysed. Most growthcharacteristics were irresponsive to N fertilization. In the third year the AST differed between N levels, whereas CL responded to N supply at the end of the first year of fertilization. The leaves N concentration varied in response to N supply. The control presented fewer flowers and the highest N level resulted in a greater flower production. Flower N concentration was lower at the intermediate N levels. Fruit set and yield were not significantly different between N treatments. Fruits from the highest N level presented lower pulp firmness and a bigger starch regression index, indicating a more advanced maturation stage than the fruits from other N levels

O cultivo do arroz e a resposta do agrossistema às alterações ambientais de temperatura e dióxido de carbono

A cultivar de arroz Ariete apresentou uma eficiência máxima de uso do N de 64% e uma produção de 8,5 t ha-1, após aplicação de 120 kg N ha-1, metade em fundo e metade ao afilhamento. Os fatores de emissão de GEEs medidos no campo foram de 136 kg CH4 ha-1 e 1,5% para o N2O. As emissões de COVs (especialmente na forma de terpenos) e NH3 foram reduzidas, mas atingiram 8 kg N-NH3 ha-1 dia-1 após a adubação de cobertura.FCT - projeto PTDC/AGR-AAM/102529/2008

High resolution human leukocyte antigen (HLA) class I and class II allele typing in Mexican mestizo women with sporadic breast cancer: case-control study

<p>Abstract</p> <p>Background</p> <p>The development of breast cancer is multifactorial. Hormonal, environmental factors and genetic predisposition, among others, could interact in the presentation of breast carcinoma. Human leukocyte antigen (HLA) alleles play an important role in immunity (cellular immunity) and may be important genetic traits. HLAAllele-specific interaction has not been well established. Recently, several studies had been conducted in order to do so, but the results are controversial and in some instances contradictory.</p> <p>Methods</p> <p>We designed a case-control study to quantify the association of HLA class I and II genes and breast cancer. HLA typing was performed by high resolution sequence-specific oligotyping after DNA amplification (PCR-SSOP) of 100 breast cancer Mexican mestizo patients and 99 matched healthy controls.</p> <p>Results</p> <p>HLA-A frequencies that we were able to observe that there was no difference between both groups from the statistical viewpoint. HLA-B*1501 was found three times more common in the case group (OR, 3.714; <it>p </it>= 0.031). HLA-Cw is not a marker neither for risk, nor protection for the disease, because we did not find significant statistical differences between the two groups. DRB1*1301, which is expressed in seven cases and in only one control, observing an risk increase of up to seven times and DRB1*1602, which behaves similarly in being present solely in the cases (OR, 16.701; 95% CI, 0.947 – 294.670). DQ*0301-allele expression, which is much more common in the control group and could be protective for the presentation of the disease (OR, 0.078; 95% CI, 0.027–0.223, <it>p </it>= 0.00001).</p> <p>Conclusion</p> <p>Our results reveal the role of the MHC genes in the pathophysiology of breast cancer, suggesting that in the development of breast cancer exists a disorder of immune regulation. The triggering factor seems to be restricted to certain ethnic groups and certain geographical regions since the relevant MHC alleles are highly diverse. This is the first study in Mexican population where high resolutions HLA typing has been performed in order to try to establish an association with malignancy.</p

Decomposição in situ de folhas senescentes de pereira (Pyrus communis L. cv. Rocha) In situ decomposition of pear (Pyrus communis L. cv. Rocha) senescent leaves

Estudou-se a variação da perda de peso e a contribuição das folhas senescentes de pereira (cv. Rocha) para a restituição de azoto (N) ao solo através da técnica dos sacos de decomposição in situ, colocados em Outubro de 2003 à superfície do solo dum pomar situado no Cadaval (Oeste de Portugal). Os sacos contendo folhas senescentes colhidas em pereiras com um ano de plantação e fertilizadas com três níveis de N (0, 10 e 40 kg N/ha), foram recolhidos em Dezembro de 2003, Janeiro, Fevereiro, Maio, Julho e Outubro de 2004 e Março de 2005. No mesmo pomar enterraram-se, em Outubro de 2003, 12 cilindros de PVC, contendo à superfície folhas senescentes de pereiras com três anos de plantação e fertilizadas com 40 kg N/ha de adubo enriquecido com 10% de átomos de 15N. Os cilindros foram recolhidos em Janeiro, Março, Junho e Novembro de 2004. Determinouse a variação do peso e os teores de N total e enriquecimento em 15N nos resíduos, e nas amostras de terra avaliaram-se os teores de N “total”, N-inorgânico e carbono (C) orgânico, bem como os nitratos potencialmente lixiviados e adsorvidos em resinas de troca aniónica, em cada data. A decomposição in situ das folhas senescentes das pereiras ‘Rocha’ jovens variou significativamente com a fertilização azotada após 506 dias. As folhas provenientes da modalidade 0 kg N/ha apresentaram menor peso residual (21% do inicial) e menor teor de N (44% do teor inicial de N) comparativamente com as folhas resultantes das modalidades adubadas com N, no final do período em estudo. Padrão idêntico de comportamento verificou-se na decomposição in situ das folhas das árvores com três anos, colocada à superfície do solo dos cilindros de PVC enterrados. A mineralização do N destas folhas levou à disponibilização do N para as árvores no início do abrolhamento e a partir de Junho, não se tendo observado lixiviação do N mineral produzido.The weight loss of one year-old ‘Rocha’ pear senescent leaves and their contribution to nitrogen (N) cycling in the soil, were studied using litter bags. The leaves were collected from trees fertilized with ammonium nitrate, using three N rates (0, 10 and 40 kg N/ha). The litter bags were installed in October 2003, at the surface of the soil, in an orchard located in Cadaval (Western Portugal). Litter bags were removed from the soil in December 2003, January, February, May, July and October 2004, and March 2005. Leaves were also collected from three-year old ‘Rocha’ pear trees fertilized with 40 kg N/ha using ammonium nitrate, double enriched with 10 atom% 15N. These were placed at the surface of non-disturbed soil cores, from cylinders buried in the same orchard in October 2003. The soil cores were removed from the soil in January, March, June and November 2004, and were analysed for the evolution of leaf weight, leaf N and 15N enrichment. Inorganic and “total” soil N, 15N enrichment, and organic carbon (C) in the soil and leached N captured in anion- -exchange resins were also determined at each sampling time. The decomposition of one-year old ‘Rocha’ pear senescent leaves was affected by N applied to the trees, after 506 days of decomposition in the field. The leaves from the 0 kg N/ha plots had less final weight (21% of the initial) and leaf N content (44% of leaf initial N content) at the end of the studied period, when compared to the leaves from the plots fertilized with N. Decomposition of senescent leaves from three-years-old trees at the soil surface in PVC cylinders showed a similar pattern. N mineralization in these leaves showed the potential availability of inorganic N at the beginning of trees bud break and after June, without nitrate leaching in the soil

Impact of agricultural practices, elevated temperature and atmospheric carbon dioxide concentration on nitrogen and pH dynamics in soil and floodwater during the seasonal rice growth in Portugal

Data on the movements of available N and non-exchangeable NH4 + in the soil are of crucial importance in designing an efficient plant N nutrition management scheme in paddy rice fields. To investigate the processes affecting the dynamics of N and pH under Mediterranean conditions, rice (Oryza sativa L. cv. Ariete) was cultivated in 2011 and 2012 in Salvaterra de Magos (central Portugal) under the following climate scenarios: (i) ambienttemperature and ambient [CO2] in the open-field, (ii) elevated temperature (+3 C) and ambient [CO2] in open-top chambers, and (iii) elevated temperature (+3 C) and elevated [CO2] (+175mmol mol1 ) in open-top chambers. Plants were grown under an intermittent flooding regime. Soil and water samples were taken at eight different stages of plant growth, including before and after N basal and topdressing. Our study indicated that the processes underlying N changes in response to the timing of N fertilization were different depending on the N form. After basal dressing under aerobic conditions, both available and non-exchangeable NH4 + contents were increased. Following the topdressing under flooded conditions, the available content of soil N increased, whereas the non-exchangeable NH4 + content decreased. A negative relationship was found between soil pH and NH4 + “fixation” when roots were active, and vice-versa. Elevated temperature alone or in combination with elevated [CO2] had no effect on the total available N content in the soil and floodwater. Under elevated temperature, however, the non-exchangeable NH4 + content was significantly reduced (11%), with the same magnitude of change (10%) observed under co-elevation of temperature and [CO2]. These results suggested that non-exchangeable NH4 + in paddy fields might be insensitive to [CO2] elevation under Mediterranean conditions, while reductions observed under co-elevation of [CO2] and temperature might be associated with temperature alone. This information could be used to alter rice management practices and to adjust N application under climate change

A alteração climática na “fixação” do amónio em solos cultivados com arroz (Oryza sativa) por alagamento

O arroz, é essencialmente produzido como monocultura, em canteiros alagados, nas regiões do centro e sul do País (Vales do Mondego, Tejo e Sado). O ião NH4 + é a forma de N mineral mais abundante e preferencialmente absorvida pelo arroz, em condições de alagamento. O alagamento potencia a mineralização, por acção dos microrganismos aeróbios facultativos, aumentando a sua concentração na solução do solo. No solo, este catião pode ser adsorvido nos colóides ou "fixado" nos minerais argilosos do tipo 2:1, tornando-se temporariamente indisponível para a cultura. A taxa de "fixação" e posterior libertação para a solução depende da textura do solo, do teor e mineralogia da argila, pH, potencial redox, temperatura e presença de outros catiões. Não se conhecem os efeitos do aumento simultâneo da concentração de CO2 na atmosfera e da temperatura na "fixação" do NH4 + , sabendo-se que, isoladamente, o aumento da temperatura potencia a "fixação". Neste estudo, avaliou-se o teor de NH4 + em dois solos (areno-franco e argilo-limoso) alagados e cultivados com arroz, em 2012, como resposta à fertilização mineral e ao alagamento. Compararam-se esses teores com os medidos no solo argilo-limoso, em condições controladas de aumento da [CO2] e temperatura. O teor de NH4 + "fixado" em ambos os solos (ar livre) foi superior ao da concentração de NH4 + disponível no respectivo solo. A concentração de NH4 + "fixada" no solo argilo-limoso manteve-se superior à do solo arenofranco, variando com os tratamentos (ar livre > CO2+temperatura = temperatura), com as datas de amostragem e com a fertilização azotada.Rice is produced as monoculture under flooding, in the central and southern Portugal (Mondego, Tejo and Sado Valleys). Ammonium (NH4 + ) is the most abundant and the preferential N form for rice uptake under flooding. Flooding enhances mineralization by the action of facultative microorganisms, increasing the concentration of NH4 + in the soil solution. This cation can be adsorbed by colloids or "fixed" in 2:1 type clay minerals, becoming temporary unavailable for crops and losses. The rate of "fixation" and subsequent release to the solution depends mostly on soil texture, clay content and composition, soil pH, redox potential, temperature, and the competition for other cations. The effects of simultaneous increase of atmospheric CO2 and air temperature on NH4 + "fixation" are unknown. This research evaluated the concentration of "fixed" NH4 + in two flooded soils (sandy loam and silt clay) cultivated in 2012 with rice, in response to mineral fertilization and flooding. These levels were compared with those measured in the silt clay soil under controlled conditions (CO2 and temperature increase). The "fixed" NH4 + in both soils (openfield) was significantly higher than the available NH4 + in the respective soil. The amount of "fixed" NH4 + in the silt clay soil was higher than the sandy loam soil, varying significantly with the treatments (open-field>CO2+temperature=temperature) and sampling dates