Open Access
Biological and synthetic approaches to inhibiting nitrification in non-tilled Mediterranean soils
(SpringerOpen, 2021) Bozal-Leorri, Adrián; Corrochano Monsalve, Mario; Arregui Odériz, Luis Miguel; Aparicio Tejo, Pedro María; González Murua, Carmen; Agronomía, Biotecnología y Alimentación; Agronomia, Bioteknologia eta Elikadura; Ciencias; Zientziak
Background: The increasing demand for food production has led to a tenfold increase in nitrogen (N) fertilizer use since the Green Revolution. Nowadays, agricultural soils have been turned into high-nitrifying environments that increase N pollution. To decrease N losses, synthetic nitrification inhibitors (SNIs) such as 3,4-dimethylpyrazole phosphate (DMPP) have been developed. However, SNIs are not widely adopted by farmers due to their biologically limited stability and soil mobility. On the other hand, allelopathic substances from root exudates from crops such as sorghum are known for their activity as biological nitrification inhibitors (BNIs). These substances are released directly into the rhizosphere. Nevertheless, BNI exudation could be modified or even suppressed if crop development is affected. In this work, we compare the performance of biological (sorghum crop) and synthetic (DMPP) nitrification inhibitors in field conditions. Results: Sorghum crop BNIs and DMPP prevented an increase in the abundance of ammonia-oxidizing bacteria (AOB) without affecting the total bacterial abundance. Both nitrification inhibitors maintained similar soil NH4+ content, but at 30 days post-fertilization (DPF), the sorghum BNIs resulted in higher soil NO3− content than DMPP. Even so, these inhibitors managed to reduce 64% and 96%, respectively, of the NO3−-N/NH4+-N ratio compared to the control treatment. Similar to soil mineral N, there were no differences in leaf δ15N values between the two nitrification inhibitors, yet at 30 DPF, δ15N values from sorghum BNI were more positive than those of DMPP. N2O emissions from DMPP-treated soil were low throughout the experiment. Nevertheless, while sorghum BNIs also maintained low N2O emissions, they were associated with a substantial N2O emission peak at 3 DPF that lasted until 7 DPF. Conclusions: Our results indicate that while sorghum root exudates can reduce nitrification in field soil, even at the same efficiency as DMPP for a certain amount of time, they are not able to prevent the N pollution derived from N fertilization as DMPP does during the entire experiment.
Open Access
Overexpression of a pine Dof transcription factor in hybrid poplars: A comparative study in trees growing under controlled and natural conditions
(Public Library of Science, 2017) Rueda López, Marina; Pascual, María Belén; Pallero, Mercedes; Henao, Luisa María; Lasa Larrea, Berta; Jáuregui Mosquera, Iván; Aparicio Tejo, Pedro María; Cánovas, Francisco M.; Ávila, Concepción; Ciencias del Medio Natural; Natura Ingurunearen Zientziak
In this work, the role of the pine transcriptional regulator Dof 5 in carbon and nitrogen metabolism has been examined in poplar trees. The overexpression of the gene and potential effects on growth and biomass production were compared between trees growing in a growth chamber under controlled conditions and trees growing in a field trial during two growth seasons. Ten-week-old transgenic poplars exhibited higher growth than untransformed controls and exhibited enhanced capacity for inorganic nitrogen uptake in the form of nitrate. Furthermore, the transgenic trees accumulated significantly more carbohydrates such as glucose, fructose, sucrose and starch. Lignin content increased in the basal part of the stem likely due to the thicker stem of the transformed plants. The enhanced levels of lignin were correlated with higher expression of the PAL1 and GS1.3 genes, which encode key enzymes involved in the phenylalanine deamination required for lignin biosynthesis. However, the results in the field trial experiment diverged from those observed in the chamber system. The lines overexpressing PpDof5 showed attenuated growth during the two growing seasons and no modification of carbon or nitrogen metabolism. These results were not associated with a decrease in the expression of the transgene, but they can be ascribed to the nitrogen available in the field soil compared to that available for growth under controlled conditions. This work highlights the paramount importance of testing transgenic lines in field trials.
Open Access
Leaves play a central role in the adaptation of nitrogen and sulfur metabolism to ammonium nutrition in oilseed rape (Brassica napus)
(BioMed Central, 2017) Coleto, Inmaculada; Peña, Marlon de la; Rodríguez Escalante, Jon; Bejarano, Iraide; Glauser, Gaëtan; Aparicio Tejo, Pedro María; González Moro, María Begoña; Marino Bilbao, Daniel; Ciencias del Medio Natural; Natura Ingurunearen Zientziak
Background: The coordination between nitrogen (N) and sulfur (S) assimilation is required to suitably provide plants with organic compounds essential for their development and growth. The N source induces the adaptation of many metabolic processes in plants; however, there is scarce information about the influence that it may exert on the functioning of S metabolism. The aim of this work was to provide an overview of N and S metabolism in oilseed rape (Brassica napus) when exposed to different N sources. To do so, plants were grown in hydroponic conditions with nitrate or ammonium as N source at two concentrations (0.5 and 1 mM). Results: Metabolic changes mainly occurred in leaves, where ammonium caused the up-regulation of enzymes involved in the primary assimilation of N and a general increase in the concentration of N-compounds (NH4 +, amino acids and proteins). Similarly, the activity of key enzymes of primary S assimilation and the content of S-compounds (glutathione and glucosinolates) were also higher in leaves of ammonium-fed plants. Interestingly, sulfate level was lower in leaves of ammonium-fed plants, which was accompanied by the down-regulation of SULTR1 transporters gene expression. Conclusions: The results highlight the impact of the N source on different steps of N and S metabolism in oilseed rape, notably inducing N and S assimilation in leaves, and put forward the potential of N source management to modulate the synthesis of compounds with biotechnological interest, such as glucosinolates.
Open Access
Improving the short‑term efficiency of rock phosphate‑based fertilizers in pastures by using edaphic biostimulants
(Springer, 2016) Fernández, L.; Baigorri, R.; Urrutia Vera, Olaia; Erro, J.; Aparicio Tejo, Pedro María; Yvin, J. C.; García Mina, José M.; IdAB. Instituto de Agrobiotecnología / Agrobioteknologiako Institutua; Gobierno de Navarra / Nafarroako Gobernua
Background: The use of reactive rock phosphate (RP) in acidic soils as a phosphate (P) source for pastures and crops presents attractive economic advantages with respect to soluble phosphate. However, some studies have demonstrated that the short-term (1-year) efficiency of RP, compared with that of water-soluble P, is relatively poor. This fact penalizes not only the yield and quality of the earlier harvests, but even the whole final yield when the crop is affected by some abiotic or biotic stress at the beginning of the cycle. In the present study, we investigated the ability of new edaphic biostimulants to increase the short-term efficiency of RP-based fertilizer as a P source for pastures cultivated in acid soils. To this end, we have granulated rock phosphate with two edaphic biostimulants: tryptophan and a heteromolecular organic complex formed by humic acid and tryptophan through iron bridges, and compared their short-term P fertilizer efficacy with that of single superphosphate and rock phosphate. Results: Soil incubation studies showed that the heteromolecular complex humic acid–tryptophan and Tryptophan were able to increase soil CO2 production compared with native soil, rock phosphate, and superphosphate. Likewise, the presence of humic acid–tryptophan complex and Trp significantly increases plant-available phosphate compared with rock phosphate, up to levels similar to those of superphosphate. Plant (ray grass)–soil–pot studies showed that rock phosphate/(humic acid–tryptophan) formulation yielded values for both ray grass dry matter production and shoot P concentration, clearly higher than those of rock phosphate and rock phosphate/tryptophan. In addition, the results associated with rock phosphate/(humic acid–tryptophan) were similar to those for superphosphate, after 3 months of cultivation. Conclusions: Taken together, these results showed the suitability of the use of specific humic acid-based edaphic biostimulants to improve the short-term effect of rock phosphate fertilizers as a phosphate source for pastures cultivated in acid soils.
Open Access
Meat waste as feedstock for home composting: effects on the process and quality of compost
(Elsevier, 2016) Storino, Francesco; Sánchez Arizmendiarrieta, Joseba; Irigoyen Iriarte, Ignacio; Muro Erreguerena, Julio; Aparicio Tejo, Pedro María; Ciencias del Medio Natural; Natura Ingurunearen Zientziak; Producción Agraria; Nekazaritza Ekoizpena
Home composting is a powerful tool, which is spreading in different parts of the world, to reduce the generation of municipal waste. However, there is debate concerning the appropriateness, in terms of domestic hygiene and safety, of keeping a composter bin in the household deputed to kitchen waste of animal origin, such as meat or fish scraps and pet droppings. The purpose of our work was to study how the addition of meat scraps to household waste influences the composting process and the quality of the final compost obtained. We compared four raw material mixtures, characterized by a different combination of vegetable and meat waste and different ratios of woody bulking agent. Changes in temperature, mass and volume, phenotypic microbial diversity (by Biolog TM) and organic matter humification were determined during the process. At the end of the experiment, the four composts were weighed and characterized by physicochemical analysis. In addition, the presence of viable weed seeds was investigated and a germination bioassay was carried out to determine the level of phytotoxicity. Finally, the levels of pathogens (E. coli and Salmonella spp.) were also determined in the final compost. Here we show that the presence of meat waste as raw feedstock for composting in bins can improve the activity of the process, the physicochemical characteristics and maturity of the compost obtained, without significantly affecting its salinity, pH and phytotoxicity. Pathogen levels were low, showing that they can be controlled by an intensive management and proper handling of the composter bins.
Open Access
Quantitative proteomics reveals the importance of nitrogen source to control glucosinolate metabolism in Arabidopsis thaliana and Brassica oleracea
(Oxford University Press, 2016) Marino Bilbao, Daniel; Ariz Arnedo, Idoia; Lasa Larrea, Berta; Santamaría Martínez, Enrique; Aparicio Tejo, Pedro María; Ciencias del Medio Natural; Natura Ingurunearen Zientziak
Accessing different nitrogen (N) sources involves a profound adaptation of plant metabolism. In this study, a quantitative proteomic approach was used to further understand how the model plant Arabidopsis thaliana adjusts to different N sources when grown exclusively under nitrate or ammonium nutrition. Proteome data evidenced that glucosinolate metabolism was differentially regulated by the N source and that both TGG1 and TGG2 myrosinases were more abundant under ammonium nutrition, which is generally considered to be a stressful situation. Moreover, Arabidopsis plants displayed glucosinolate accumulation and induced myrosinase activity under ammonium nutrition. Interestingly, these results were also confirmed in the economically important crop broccoli (Brassica oleracea var. italica). Moreover, these metabolic changes were correlated in Arabidopsis with the differential expression of genes from the aliphatic glucosinolate metabolic pathway. This study underlines the importance of nitrogen nutrition and the potential of using ammonium as the N source in order to stimulate glucosinolate metabolism, which may have important applications not only in terms of reducing pesticide use, but also for increasing plants’ nutritional value.
Open Access
Compost de FORM con restos de alimentos cárnicos como componente de sustratos de cultivo
(Sociedad Española de Ciencias Hortícolas, 2014) Storino, Francesco; Irigoyen Iriarte, Ignacio; Ollo Alcasena, María Arantzazu; Aparicio Tejo, Pedro María; Muro Erreguerena, Julio; Producción Agraria; Ciencias del Medio Natural; Nekazaritza Ekoizpena; Natura Ingurunearen Zientziak
La utilización de compost de FORM como fertilizante es una práctica inocua y segura ampliamente implantada en la unión europea y que presenta gran cantidad de ventajas desde un punto de vista agronómico y medioambiental. La utilización de este tipo de compost como materia prima para la elaboración de sustratos de cultivo genera ciertas dudas por sus características, especialmente cuando provienen de sistemas de compostaje descentralizado en los que se han compostado restos de alimentos entre los que se incluyen alimentos de origen animal (carne y/o pescado). El objetivo del este trabajo es evaluar compost domésticos como componente de sustratos para cultivo de ornamentales que incluyen distintas proporciones de restos de alimentos cárnicos. Para este fin se compararon 3 compost domésticos (uno vegetal y dos con 15% carne) y uno comercial. Los compost fueron caracterizados mediante análisis de su composición elemental, pH y CE. Cada compost fue mezclado al 25 y 75 % v/v con sustrato a base de turba (utilizado puro como control). Además las dos mezclas con mayor CE fueron sometidas a lavados sucesivos, monitorizando el descenso de salinidad tras cada lavado y la composición elemental del líquido drenado. Plantas de pensamientos fueron cultivadas en macetas de 2 L con cada uno de los 11 sustratos indicados. Durante seis semanas de cultivo se midió la biomasa vegetal, la altura y el número de tallos, el número de flores y el contenido en clorofila mediante índice colorimétrico SPAD. Las diferencias entre los distintos tratamientos fueron pequeñas. El lavado previo de los sustratos no modifico significativamente la respuesta del cultivo. Se concluyen que los sustratos con compost de FORM que contiene hasta un 15% de restos de alimentos de origen animal no afectan negativamente al cultivo de pensamientos bajo las condiciones del presente ensayo.
Open Access
Plant ammonium sensitivity is associated with external pH adaptation, repertoire of nitrogen transporters, and nitrogen requirement
(Oxford University Press, 2024-03-11) Rivero Marcos, Mikel; Lasa Larrea, Berta; Neves, Tomé; Zamarreño, Ángel M.; García Mina, José M.; García Olaverri, Carmen; Aparicio Tejo, Pedro María; Cruz, Cristina; Ariz Arnedo, Idoia; Ciencias; Zientziak; Estadística, Informática y Matemáticas; Estatistika, Informatika eta Matematika; Institute for Multidisciplinary Research in Applied Biology - IMAB; Institute for Advanced Research in Business and Economics - INARBE; Universidad Publica de Navarra / Nafarroako Unibertsitate Publikoa; Gobierno de Navarra / Nafarroako Gobernua
Modern crops exhibit diverse sensitivities to ammonium as the primary nitrogen source, influenced by environmental factors such as external pH and nutrient availability. Despite its significance, there is currently no systematic classification of plant species based on their ammonium sensitivity. We conducted a meta-analysis of 50 plant species and present a new classification method based on the comparison of fresh biomass obtained under ammonium and nitrate nutrition. The classification uses the natural logarithm of the biomass ratio as the size effect indicator of ammonium sensitivity. This numerical parameter is associated with critical factors for nitrogen demand and form preference, such as Ellenberg indicators and the repertoire of nitrogen transporters for ammonium and nitrate uptake. Finally, a comparative analysis of the developmental and metabolic responses, including hormonal balance, is conducted in two species with divergent ammonium sensitivity values in the classification. Results indicate that nitrate has a key role in counteracting ammonium toxicity in species with a higher abundance of genes encoding NRT2-type proteins and fewer of those encoding the AMT2-type proteins. Additionally, the study demonstrates the reliability of the phytohormone balance and methylglyoxal content as indicators for anticipating ammonium toxicity. This study emphasizes the importance of ecophysiological requirements and the repertoire of nitrogen transporters in understanding plant sensitivity to ammonium, and enhances our knowledge of plant nitrogen nutrition.
Open Access
Leaf δ15N as a physiological indicator of the responsiveness of N2-fixing alfalfa plants to elevated CO2, temperature and low water availability
(Frontiers Media, 2015) Ariz Arnedo, Idoia; Cruz, Cristina; Neves, Tomé; Irigoyen, Juan J.; García Olaverri, Carmen; Nogués, Salvador; Aparicio Tejo, Pedro María; Aranjuelo Michelena, Iker; Estatistika eta Ikerketa Operatiboa; Natura Ingurunearen Zientziak; Estadística e Investigación Operativa; Ciencias del Medio Natural; IdAB. Instituto de Agrobiotecnología / Agrobioteknologiako Institutua; Gobierno de Navarra / Nafarroako Gobernua
The natural 15N/14N isotope composition (δ15N) of a tissue is a consequence of its N source and N physiological mechanisms in response to the environment. It could potentially be used as a tracer of N metabolism in plants under changing environmental conditions, where primary N metabolism may be complex, and losses and gains of N fluctuate over time. In order to test the utility of δ15N as an indicator of plant N status in N2-fixing plants grown under various environmental conditions, alfalfa (Medicago sativa L.) plants were subjected to distinct conditions of [CO2] (400 vs. 700 μmol mol−1), temperature (ambient vs. ambient +4°C) and water availability (fully watered vs. water deficiency—WD). As expected, increased [CO2] and temperature stimulated photosynthetic rates and plant growth, whereas these parameters were negatively affected by WD. The determination of δ15N in leaves, stems, roots, and nodules showed that leaves were the most representative organs of the plant response to increased [CO2] and WD. Depletion of heavier N isotopes in plants grown under higher [CO2] and WD conditions reflected decreased transpiration rates, but could also be related to a higher N demand in leaves, as suggested by the decreased leaf N and total soluble protein (TSP) contents detected at 700 μmol mol−1 [CO2] and WD conditions. In summary, leaf δ15N provides relevant information integrating parameters which condition plant responsiveness (e.g., photosynthesis, TSP, N demand, and water transpiration) to environmental conditions.
Open Access
Soil moisture modulates biological nitrification inhibitors release in sorghum plants
(Springer, 2023) Bozal-Leorri, Adrián; Arregui Odériz, Luis Miguel; Torralbo, Fernando; González Moro, María Begoña; González Murua, Carmen; Aparicio Tejo, Pedro María; Institute on Innovation and Sustainable Development in Food Chain - ISFOOD; Institute for Multidisciplinary Research in Applied Biology - IMAB
Background and aims: Sorghum (Sorghum bicolor) is able to exude allelochemicals with biological nitrifcation inhibition (BNI) capacity. Therefore, sorghum might be an option as cover crop since its BNI ability may reduce N pollution in the following crop due to a decreased nitrifcation. However, BNI exudation is related to the physiological state and development of the plant, so abiotic stresses such as drought might modify the rate of BNI exudation. Hence, the objective was to determine the efect of drought stress on sorghum plants’ BNI release. Methods: The residual efects of sorghum crops over ammonia-oxidizing bacteria (AOB) were monitored in a 3-year feld experiment. In a controlled-conditions experiment, sorghum plants were grown under Watered (60% WFPS) or Moderate drought (30% WFPS) conditions, and fertilized with ammonium sulphate (A), ammonium sulphate+DMPP (A+D), or potassium nitrate (KNO3 −). Soil mineral N was determined, and AOB populations were quantifed. Additionally, plant biomass, isotopic discrimination of N and C, and photosynthetic parameters were measured in sorghum plants. Results: In the driest year, sorghum was able to reduce the AOB relative abundance by 50% at feld conditions. In the plant-soil microcosm, drought stress reduced leaf photosynthetic parameters, which had an impact on plant biomass. Under these conditions, sorghum plants exposed to Moderate drought reduced the AOB abundance of A treatment by 25% compared to Watered treatment. Conclusion: The release of BNI by sorghum under limited water conditions might ensure high soil NH4 +-N pool for crop uptake due to a reduction of nitrifying microorganisms.