Root ABA and H+-ATPase are key players in the root and shoot growth-promoting action of humic acids

Although the ability of humic (HA) and fulvic acids (FA) to improve plant growth has been demonstrated, knowledge about the mechanisms responsible for the direct effects of HA and FA on the promotion of plant growth is scarce and fragmentary. Our study investigated the causal role of both root PM H+-ATPase activity and ABA in the SHA-promoting action on both root and shoot growth. The involvement of these processes in the regulation of shoot cytokinin concentration and activity was also studied. Our aim was to integrate such plant responses for providing new insights to the current model on the mode of action of HA for promoting root and shoot growth. Experiments employing specific inhibitors and using Cucumis sativus L. plants show that both the root PM H+-ATPase activity and root ABA play a crucial role in the root growth-promoting action of SHA. With regard to the HA-promoting effects on shoot growth, two pathways of events triggered by the interaction of SHA with plant roots are essential for the increase in root PM H+-ATPase activity-which also mediates an increase in cytokinin concentration and action in the shoot-and the ABA-mediated increase in hydraulic conductivity (Lp(r))

Quality and quantity of organic fractions as affected by soil depth in an Argiudoll under Till and No-till systems

Aims: The aim of this study was to evaluate the long-term effect of tillage systems on the quantity and quality of organic carbon fractions at different soil layers. Study Design: The experimental design was a split plot with three blocks. The long-term effects (25 years) of conventional- (CT) and no-tillage (NT) systems on a Tipic Argiudoll was sampled at 0-5, 5-10, 10-15 and 15-20 cm soil depth. Place and Duration of Study: The field experiment was carried out at Tornquist (38° 07' 06'' S - 62°02' 17'' O) and soil sampling was performed during wheat seeding (June 2011). Methodology: Total soil organic carbon (SOC) content and the following fractions were determined: Coarse particulate (POCc, 105-2000 µm), fine particulate (POCf, 53-105 µm) and mineral-associated (MOC, 0-53 µm) carbon fractions; humic (HA) and fulvic (FA) acids; and total (CHt) and soluble (CHs) carbohydrates. The main physico-chemical properties of HA and FA were analyzed using both FT-IR and fluorescence spectroscopies. Results: After 25 years, total SOC at the 0-20 cm depth was 9% higher in no-tilled than in tilled soils. The POCf was the SOM fraction that turned out to be the most sensitive to tillage effects. The POCc:POCf:MOC ratio at 0-20 cm was similar for NT (3:14:82) and CT (5:10:84); however, differences were found across soil depths. Tilled soils showed higher aromaticity, starting by CH-degradation, in more superficial soil layers

Alternative polyadenylation and salicylic acid modulate root responses to low nitrogen availability

Nitrogen (N) is probably the most important macronutrient and its scarcity limits plant growth, development and fitness. N starvation response has been largely studied by transcriptomic analyses, but little is known about the role of alternative polyadenylation (APA) in such response. In this work, we show that N starvation modifies poly(A) usage in a large number of transcripts, some of them mediated by FIP1, a component of the polyadenylation machinery. Interestingly, the number of mRNAs isoforms with poly(A) tags located in protein-coding regions or 5 '-UTRs significantly increases in response to N starvation. The set of genes affected by APA in response to N deficiency is enriched in N-metabolism, oxidation-reduction processes, response to stresses, and hormone responses, among others. A hormone profile analysis shows that the levels of salicylic acid (SA), a phytohormone that reduces nitrate accumulation and root growth, increase significantly upon N starvation. Meta-analyses of APA-affected and fip1-2-deregulated genes indicate a connection between the nitrogen starvation response and salicylic acid (SA) signaling. Genetic analyses show that SA may be important for preventing the overgrowth of the root system in low N environments. This work provides new insights on how plants interconnect different pathways, such as defense-related hormonal signaling and the regulation of genomic information by APA, to fine-tune the response to low N availability

Shoot iron status and auxin are involved in iron deficiency-induced phytosiderophores release in wheat

Background: The release of phytosiderephores (PS) to the rhizosphere is the main root response to iron (Fe) deficiency in graminaceous plants. We have investigated the role of the Fe status in the shoot as well as of the signaling pathways controlled by three relevant phytoregulators-indolacetic acid (IAA), ethylene and nitric oxide (NO) - in the regulation of this root response in Fe-starved wheat plants. To this end, the PS accumulation in the nutrient solution and the root expression of the genes encoding the nicotianamine aminotransferase (TaNAAT) and ferritin (TaFER) have been evaluated in plants subjected to different treatments. Results: The application of Fe to leaves of Fe-deficient plants prevented the increase in both PS root release and TaNAAT gene expression thus showing the relevant role of the shoot to root communication in the regulation of PS root release and some steps of PS biosynthesis. Experiments with specific hormone inhibitors showed that while ethylene and NO did not positively regulate Fe deficiency induced PS root release, auxin plays an essential role in the regulation of this process. Moreover, the application of IM to Fe-sufficient plants promoted both PS root release and TaNAAT gene expression thus indicating that auxin might be involved in the shoot to root signaling network regulating Fe-deficiency root responses in wheat Conclusions: These results therefore indicate that PS root release in Fe-deficient wheat plants is directly modulated by the shoot Fe status through signaling pathways involving, among other possible effectors, auxin

VISTA Variables in the <i>Vía Láctea</i> (VVV): Halfway Status and Results

The VISTA Variables in the Vía Láctea (VVV) survey is one of six near-infrared ESO public surveys, and is now in its fourth year of observing. Although far from being complete, the VVV survey has already delivered many results, some directly connected to the intended science goals (detection of variable stars, microlensing events, new star clusters), others concerning more exotic objects, e.g., novae. Now, at the end of the fourth observing period, and comprising roughly 50% of the proposed observations, the status of the survey, as well some of results based on the VVV data, are presented.Facultad de Ciencias Astronómicas y Geofísica

VISTA Variables in the <i>Vía Láctea</i> (VVV): Halfway Status and Results

The VISTA Variables in the Vía Láctea (VVV) survey is one of six near-infrared ESO public surveys, and is now in its fourth year of observing. Although far from being complete, the VVV survey has already delivered many results, some directly connected to the intended science goals (detection of variable stars, microlensing events, new star clusters), others concerning more exotic objects, e.g., novae. Now, at the end of the fourth observing period, and comprising roughly 50% of the proposed observations, the status of the survey, as well some of results based on the VVV data, are presented.Facultad de Ciencias Astronómicas y Geofísica

VISTA Variables in the Via Lactea (VVV): The public ESO near-IR variability survey of the Milky Way

We describe the public ESO near-IR variability survey (VVV) scanning the Milky Way bulge and an adjacent section of the mid-plane where star formation activity is high. The survey will take 1929 h of observations with the 4-m VISTA telescope during 5 years (2010–2014), covering ∼109 point sources across an area of 520 deg2, including 33 known globular clusters and ∼350 open clusters. The final product will be a deep near-IR atlas in five passbands (0.9–2.5 μm) and a catalogue of more than 106 variable point sources. Unlike single-epoch surveys that, in most cases, only produce 2-D maps, the VVV variable star survey will enable the construction of a 3-D map of the surveyed region using well-understood distance indicators such as RR Lyrae stars, and Cepheids. It will yield important information on the ages of the populations. The observations will be combined with data from MACHO, OGLE, EROS, VST, Spitzer, HST, Chandra, INTEGRAL, WISE, Fermi LAT, XMM-Newton, GAIA and ALMA for a complete understanding of the variable sources in the inner Milky Way. This public survey will provide data available to the whole community and therefore will enable further studies of the history of the Milky Way, its globular cluster evolution, and the population census of the Galactic Bulge and center, as well as the investigations of the star forming regions in the disk. The combined variable star catalogues will have important implications for theoretical investigations of pulsation properties of stars.Facultad de Ciencias Astronómicas y Geofísica

Effects of a sedimentary humic acid on plant growth: study of the general mechanisms of action upon root application in cucumber plants (Cucumis Sativus l. Cv Ashley).

HS (humic substances) constitute one of the most abundant forms of organic matter in the biosphere. Many studies reported the ability of humic acids (HAs) isolated from HS to affect plant the plant development of diverse plant species. However, the mechanism of action that is behind these events is scarcely understood and it is not integrated into a holistic view. To this end, the aim of this work was to study the mechanism of action of an specific sedimentary humic acid (SHA) under roots application in cucumber plants (Cucumis sativus L. cv Ashley) in detail. More specifically, the potential role of hydraulic conductivity (Lpr) linked to root abscisic acid (ABA) concentration and some of water relations such us stomatal conductance (Gs) and leave ABA concentration in the SHA shoot growth promotion activity. Indeed, the functional relationship between Lpr with root-ABA biosynthesis and root plasma membrane aquaporins (CsPIPs) molecular regulation was also investigated. With the aim to integrate the studied SHA root mechanism into previously SHA enhanced potential response, the relative role of SHA mediated PM-H+-ATPase activity and Lpr on shoot and/or root growth promotion of cucumber plants was also assessed. Indeed, the SHA-mediated regulation of root genes associated with root growth was also studied in Arabidopsis thaliana seedlings. Finally, with the purpose of studying the relationship between the chemical structure of SHA and the biological activity exerted in plants, a sequential fractionation process named “humeomics” was applied to SHA, and the behavior of some of the obtained fractions was assessed in cucumber plant biological activity. The results showed that the beneficial effect of SHA on shoot growth was associated with a significant increase of Lpr and Gs. The SHA mediated increase in Lpr was root-ABA dependent and regulated by some of the root aquaporin homologues. Regarding the discriminating role of SHA enhancing Lpr activation or PM-H+-ATPase activity in both shoot and/or root growth, results showed that the SHA-mediated enhancement of root PM-H+-ATPase activity might play a secondary role in the improvement of shoot growth caused by SHA, Lpr activity being more relevant. Furthermore, our results indicated that probably the stimulation of root PM-H+-ATPase activity plays a more relevant role than the increase of Lpr in the mechanism of action of SHA on plant root growth. In relation to the structure-activity relationship using humeomic fractionation approach in cucumber, results showed that 62.5% of the extracted material corresponded to the unbound fraction (ORG 1). In the determination of biological activity, two fractions were studied: the mentioned ORG 1 fraction and the remained residue (RES 1). The main structural difference between both samples was that RES 1 fraction showed higher aromatic character than ORG 1, which was more aliphatic. RES 1 fraction increased Lpr, root and shoot growth compared to control and bulk SHA treated plants. ORG 1 fraction, instead, did not show significant differences on Lpr or shoot growth compared to control or SHA treated plants. The response in root growth was similar to SHA bulk treatment. As for the SHA regulated root gene expression in Arabidopsis thaliana, results showed that there were several up-regulated genes encoding root promotion ability functions, such us AT3G15370.1 gene function, identified as a member of an Alpha-Expansin Gene Family or AT2G14960.1 gene that encodes a protein similar to IAA-amino synthetase, which maintains the auxin homeostasis. Moreover, some other up-regulated genes that could be related with SHA responses that other authors previously reported were also identified.Las sustancias húmicas (SH) constituyen una de las formas más abundantes de materia orgánica de la biosfera. Muchos estudios anteriormente publicados describen que los ácidos húmicos (AH) extraídos previamente de las SH poseen la capacidad de afectar al desarrollo de plantas de diversas especies. Sin embargo, la comprensión del mecanismo de acción que subyace a este efecto es escasa y no está integrada en una visión holística sobre el tema. Con este fin, el objetivo principal de este trabajo fue estudiar en detalle el mecanismo de acción de un ácido húmico específico de origen sedimentario (AHS) aplicado radicularmente en plantas de pepino (Cucumis sativus L. cv Ashley). Concretamente se estudió la participación potencial de la conductividad hidráulica (Lpr) unido a la síntesis de ácido abscísico (ABA) en raíz junto a otras relaciones hídricas tales como la conductancia estomática (Gs) o la síntesis de ABA en hoja sobre la actividad promotora del AHS en el desarrollo vegetal de la parte aérea. Además, se investigó la relación funcional entre Lpr y ABA en raíz con la regulación molecular de las acuaporinas de la membrana plasmática en raíz (CsPIPs). Con la intención de integrar el citado mecanismo radicular del AHS en respuestas activadas por AHS y descritas anteriormente, se estudió la implicación relativa de la activación de la ATPasa de la membrana plasmática (PM-H+-ATPase) y de la Lpr sobre la estimulación del desarrollo de la raíz y parte aérea en plantas de pepino. También se estudió la regulación de los genes de la raíz por acción del AHS, en plántulas de Arabidopsis thaliana. Finalmente, con el objetivo de estudiar la relación estructura química de AHS- actividad biológica ejercida en planta, se llevó a cabo un fraccionamiento secuencial del AHS denominado “humeómica” y se estudió la actividad biológica derivada de la aplicación de ciertas fracciones en plantas de pepino. Los resultados mostraron que el efecto beneficioso mostrado por AHS en el crecimiento de la parte aérea estaba unido a un incremento significativo de Lpr y Gs. Este aumento de Lpr mostró ser dependiente de ABA-radicular y estar regulado por ciertos hómologos de las acuaporinas de la membrana plasmática de células radiculares. En relación al estudio de la relevancia ejercida por AHS en la activación de PM-H+-ATPase o Lpr como respuesta al crecimiento de la raíz y/o parte aérea, los resultados mostraron que la activación de la PM-H+-ATPase mediada por AHS jugaría un papel secundario en el beneficio del desarrollo de la parte aérea, siendo más relevante la activación de Lpr. Además, nuestros resultados también indicaron que probablemente la estimulación de PM-H+-ATPase sería un factor más relevante que el incremento de Lpr sobre el crecimiento de la raíz. En relación al estudio de estructura-actividad biológica realizada aplicando el fraccionamiento “humeómico”, los resultados mostraron que el 62.5% del material extraído correspondía a la fracción no enlazada (ORG 1). Para la determinación de la actividad biológica, se estudiaron dos fracciones: la mencionada fracción ORG 1, y el remanente del fraccionamiento (RES 1). La principal diferencia estructural entre las dos fracciones fue que la fracción RES 1 presentaba un carácter más aromático que la fracción ORG 1, cuyo carácter fue más alifático. La aplicación de la fracción RES 1 en planta incrementó Lpr, el crecimiento de la raíz y parte aérea en comparación al control y al AHS integral. Sin embargo, la fracción ORG 1, no presentó diferencias significativas en Lpr o crecimiento de la parte aérea en comparación al control o al AHS integral. La respuesta de la aplicación de ORG 1 en el crecimiento radicular fue similar al mostrado por el AHS integral. Con respecto a la regulación de genes radiculares ejercida por la aplicación de AHS en Arabidopsis thaliana, los resultados mostraron que entre los genes sobre-expresados, algunos codificaban para respuestas relacionadas con la estimulación del desarrollo radicular, como el gen AT3G15370.1, identificado como un miembro de la familia de los genes de Alpha-Expansinas, o el gen AT2G14960.1, que codifica para una proteína similar a IAA-amino synthetase, el cual mantiene la homeostasis de auxinas. Además, también fueron identificados otros genes sobre-expresados que relacionaban respuestas previamente descritas por AHS en planta por otros autores

Effects of a sedimentary humic acid on plant growth: study of the general mechanisms of action upon root application in cucumber plants (Cucumis Sativus l. Cv Ashley).

HS (humic substances) constitute one of the most abundant forms of organic matter in the biosphere. Many studies reported the ability of humic acids (HAs) isolated from HS to affect plant the plant development of diverse plant species. However, the mechanism of action that is behind these events is scarcely understood and it is not integrated into a holistic view. To this end, the aim of this work was to study the mechanism of action of an specific sedimentary humic acid (SHA) under roots application in cucumber plants (Cucumis sativus L. cv Ashley) in detail. More specifically, the potential role of hydraulic conductivity (Lpr) linked to root abscisic acid (ABA) concentration and some of water relations such us stomatal conductance (Gs) and leave ABA concentration in the SHA shoot growth promotion activity. Indeed, the functional relationship between Lpr with root-ABA biosynthesis and root plasma membrane aquaporins (CsPIPs) molecular regulation was also investigated. With the aim to integrate the studied SHA root mechanism into previously SHA enhanced potential response, the relative role of SHA mediated PM-H+-ATPase activity and Lpr on shoot and/or root growth promotion of cucumber plants was also assessed. Indeed, the SHA-mediated regulation of root genes associated with root growth was also studied in Arabidopsis thaliana seedlings. Finally, with the purpose of studying the relationship between the chemical structure of SHA and the biological activity exerted in plants, a sequential fractionation process named “humeomics” was applied to SHA, and the behavior of some of the obtained fractions was assessed in cucumber plant biological activity. The results showed that the beneficial effect of SHA on shoot growth was associated with a significant increase of Lpr and Gs. The SHA mediated increase in Lpr was root-ABA dependent and regulated by some of the root aquaporin homologues. Regarding the discriminating role of SHA enhancing Lpr activation or PM-H+-ATPase activity in both shoot and/or root growth, results showed that the SHA-mediated enhancement of root PM-H+-ATPase activity might play a secondary role in the improvement of shoot growth caused by SHA, Lpr activity being more relevant. Furthermore, our results indicated that probably the stimulation of root PM-H+-ATPase activity plays a more relevant role than the increase of Lpr in the mechanism of action of SHA on plant root growth. In relation to the structure-activity relationship using humeomic fractionation approach in cucumber, results showed that 62.5% of the extracted material corresponded to the unbound fraction (ORG 1). In the determination of biological activity, two fractions were studied: the mentioned ORG 1 fraction and the remained residue (RES 1). The main structural difference between both samples was that RES 1 fraction showed higher aromatic character than ORG 1, which was more aliphatic. RES 1 fraction increased Lpr, root and shoot growth compared to control and bulk SHA treated plants. ORG 1 fraction, instead, did not show significant differences on Lpr or shoot growth compared to control or SHA treated plants. The response in root growth was similar to SHA bulk treatment. As for the SHA regulated root gene expression in Arabidopsis thaliana, results showed that there were several up-regulated genes encoding root promotion ability functions, such us AT3G15370.1 gene function, identified as a member of an Alpha-Expansin Gene Family or AT2G14960.1 gene that encodes a protein similar to IAA-amino synthetase, which maintains the auxin homeostasis. Moreover, some other up-regulated genes that could be related with SHA responses that other authors previously reported were also identified.Las sustancias húmicas (SH) constituyen una de las formas más abundantes de materia orgánica de la biosfera. Muchos estudios anteriormente publicados describen que los ácidos húmicos (AH) extraídos previamente de las SH poseen la capacidad de afectar al desarrollo de plantas de diversas especies. Sin embargo, la comprensión del mecanismo de acción que subyace a este efecto es escasa y no está integrada en una visión holística sobre el tema. Con este fin, el objetivo principal de este trabajo fue estudiar en detalle el mecanismo de acción de un ácido húmico específico de origen sedimentario (AHS) aplicado radicularmente en plantas de pepino (Cucumis sativus L. cv Ashley). Concretamente se estudió la participación potencial de la conductividad hidráulica (Lpr) unido a la síntesis de ácido abscísico (ABA) en raíz junto a otras relaciones hídricas tales como la conductancia estomática (Gs) o la síntesis de ABA en hoja sobre la actividad promotora del AHS en el desarrollo vegetal de la parte aérea. Además, se investigó la relación funcional entre Lpr y ABA en raíz con la regulación molecular de las acuaporinas de la membrana plasmática en raíz (CsPIPs). Con la intención de integrar el citado mecanismo radicular del AHS en respuestas activadas por AHS y descritas anteriormente, se estudió la implicación relativa de la activación de la ATPasa de la membrana plasmática (PM-H+-ATPase) y de la Lpr sobre la estimulación del desarrollo de la raíz y parte aérea en plantas de pepino. También se estudió la regulación de los genes de la raíz por acción del AHS, en plántulas de Arabidopsis thaliana. Finalmente, con el objetivo de estudiar la relación estructura química de AHS- actividad biológica ejercida en planta, se llevó a cabo un fraccionamiento secuencial del AHS denominado “humeómica” y se estudió la actividad biológica derivada de la aplicación de ciertas fracciones en plantas de pepino. Los resultados mostraron que el efecto beneficioso mostrado por AHS en el crecimiento de la parte aérea estaba unido a un incremento significativo de Lpr y Gs. Este aumento de Lpr mostró ser dependiente de ABA-radicular y estar regulado por ciertos hómologos de las acuaporinas de la membrana plasmática de células radiculares. En relación al estudio de la relevancia ejercida por AHS en la activación de PM-H+-ATPase o Lpr como respuesta al crecimiento de la raíz y/o parte aérea, los resultados mostraron que la activación de la PM-H+-ATPase mediada por AHS jugaría un papel secundario en el beneficio del desarrollo de la parte aérea, siendo más relevante la activación de Lpr. Además, nuestros resultados también indicaron que probablemente la estimulación de PM-H+-ATPase sería un factor más relevante que el incremento de Lpr sobre el crecimiento de la raíz. En relación al estudio de estructura-actividad biológica realizada aplicando el fraccionamiento “humeómico”, los resultados mostraron que el 62.5% del material extraído correspondía a la fracción no enlazada (ORG 1). Para la determinación de la actividad biológica, se estudiaron dos fracciones: la mencionada fracción ORG 1, y el remanente del fraccionamiento (RES 1). La principal diferencia estructural entre las dos fracciones fue que la fracción RES 1 presentaba un carácter más aromático que la fracción ORG 1, cuyo carácter fue más alifático. La aplicación de la fracción RES 1 en planta incrementó Lpr, el crecimiento de la raíz y parte aérea en comparación al control y al AHS integral. Sin embargo, la fracción ORG 1, no presentó diferencias significativas en Lpr o crecimiento de la parte aérea en comparación al control o al AHS integral. La respuesta de la aplicación de ORG 1 en el crecimiento radicular fue similar al mostrado por el AHS integral. Con respecto a la regulación de genes radiculares ejercida por la aplicación de AHS en Arabidopsis thaliana, los resultados mostraron que entre los genes sobre-expresados, algunos codificaban para respuestas relacionadas con la estimulación del desarrollo radicular, como el gen AT3G15370.1, identificado como un miembro de la familia de los genes de Alpha-Expansinas, o el gen AT2G14960.1, que codifica para una proteína similar a IAA-amino synthetase, el cual mantiene la homeostasis de auxinas. Además, también fueron identificados otros genes sobre-expresados que relacionaban respuestas previamente descritas por AHS en planta por otros autores

Biochar-Ca and Biochar-Al/-Fe-mediated phosphate exchange capacity are main drivers of the different biochar effects on plants in acidic and alkaline soils

Because of the low consistency of the results obtained in the field, the use of biochar as a soil amendment is controversial. Thus, in general, in acidic soils, results are positive, while in alkaline soils, they are non-significant or even negative. The results regarding biochar action in acidic soils have been related to a lime-like effect due to its alkaline pH and the high doses normally used. However, the causes of biochar effects in alkaline soils remain unknown. Our objective was to explore the chemical mechanism of biochar interaction in acidic and alkaline soils. We used well-characterized biochar as a component of two complex N and PK granulated fertilizers at two different doses (1% and 5%). These fertilizers were applied to wheat cultivated in pots containing an alkaline soil and grown for 60 days. No effect was shown for the N-biochar fertilizer application. However, the PK-biochar fertilizer application caused a decrease in crop yield. In addition, the adsorption isotherms of Al, Fe, Mo, Mn, and Phosphate (Pi) in biochar were also studied. The results showed that Fe and Al were rapidly adsorbed in biochar, while Pi was only adsorbed on the Fe-, Al-biochar complex. Desorption experiments showed that P and Fe/Al were not desorbed from the P-Fe/Al-biochar complex by water or the Olsen reagent, while partial desorption was observed when HCl 0.1 M was used