Transcriptional Landscape of Ectomycorrhizal Fungi and Their Host Provides Insight into N Uptake from Forest Soil

Although EMF are well known for their role in supporting tree N nutrition, the molecular mechanisms underlying N flux from the soil solution into the host through the ectomycorrhizal pathway remain widely unknown. Furthermore, ammonium and nitrate availability in the soil solution is subject to frequent oscillations that create a dynamic environment for the tree roots and associated microbes during N acquisition.

Improving Nitrogen Status Estimation in Malting Barley Based on Hyperspectral Reflectance and Artificial Neural Networks

Malting barley requires sensitive methods for N status estimation during the vegetation period, as inadequate N nutrition can significantly limit yield formation, while overfertilization often leads to an increase in grain protein content above the limit for malting barley and also to excessive lodging. We hypothesized that the use of N nutrition index and N uptake combined with red-edge or green reflectance would provide extended linearity and higher accuracy in estimating N status across different years, genotypes, and densities, and the accuracy of N status estimation will be further improved by using artificial neural network based on multiple spectral reflectance wavelengths. Multifactorial field experiments on interactive effects of N nutrition, sowing density, and genotype were conducted in 2011–2013 to develop methods for estimation of N status and to reduce dependency on changing environmental conditions, genotype, or barley management. N nutrition index (NNI) and total N uptake were used to correct the effect of biomass accumulation and N dilution during plant development. We employed an artificial neural network to integrate data from multiple reflectance wavelengths and thereby eliminate the effects of such interfering factors as genotype, sowing density, and year. NNI and N uptake significantly reduced the interannual variation in relationships to vegetation indices documented for N content. The vegetation indices showing the best performance across years were mainly based on red-edge and carotenoid absorption bands. The use of an artificial neural network also significantly improved the estimation of all N status indicators, including N content. The critical reflectance wavelengths for neural network training were in spectral bands 400–490, 530–570, and 710–720 nm. In summary, combining NNI or N uptake and neural network increased the accuracy of N status estimation to up 94%, compared to less than 60% for N concentration.

Canopy Fluorescence Sensing for in-Season Maize Nitrogen Status Diagnosis

Accurate assessment of crop nitrogen (N) status and understanding the N demand are considered essential in precision N management. Chlorophyll fluorescence is unsusceptible to confounding signals from underlying bare soil and is closely related to plant photosynthetic activity. Therefore, fluorescence sensing is considered a promising technology for monitoring crop N status, even at an early growth stage. The objectives of this study were to evaluate the potential of using Multiplex® 3, a proximal canopy fluorescence sensor, to detect N status variability and to quantitatively estimate N status indicators at four key growth stages of maize. The sensor measurements were performed at different growth stages, and three different regression methods were compared to estimate plant N concentration (PNC), plant N uptake (PNU), and N nutrition index (NNI). The results indicated that the induced differences in maize plant N status were detectable as early as the V6 growth stage. The first method based on simple regression (SR) and the Multiplex sensor indices normalized by growing degree days (GDD) or N sufficiency index (NSI) achieved acceptable estimation accuracy (R2 = 0.73–0.87), showing a good potential of canopy fluorescence sensing for N status estimation. The second method using multiple linear regression (MLR), fluorescence indices and GDDs had the lowest modeling accuracy (R2 = 0.46–0.79). The third tested method used a non-linear regression approach in the form of random forest regression (RFR) based on multiple sensor indices and GDDs. This approach achieved the best estimation accuracy (R2 = 0.84–0.93) and the most accurate diagnostic result.

Mycorrhizal symbiosis changes host nitrogen source use

Purpose The ecological importance of arbuscular mycorrhizal fungi (AMF) in plant acquisition of inorganic and organic sources of nitrogen (N) is not clear. To improve understanding of the plant N nutrition ecology, we tested the effect of intraspecific competition and AMF in plant N source use in growth and N acquisition. Methods Solidago virgaurea was grown in microcosms in a fully factorial experiment under greenhouse conditions. The factors tested were intraspecific competition between seedlings and adult plants (yes, no), N source (NH4, glycine) and AMF (inoculated with Glomus hoi, not inoculated). Results When grown separately, non-mycorrhizal seedling growth was highest when grown with ammonium, but non-mycorrhizal adults grew best with glycine as the sole N source. Mycorrhizal symbiosis with Glomus hoi evened out this initial niche partitioning in terms of differences in N source use and all mycorrhizal plants grew best with ammonium. Competition shaped plant benefit from mycorrhizal symbiosis depending on the N source. Competition reduced mycorrhizal growth benefit in glycine-grown seedlings, but not in adults. Plant performance did not show uniform relationship with δ15N, but δ15N was affected by life stage, competition and mycorrhiza. Conclusions Plant competition and AMF shape plant N source use. Plant and AMF benefit of the symbiosis depend on the N source.

Interaction Effects of Nitrogen Rates and Forms Combined With and Without Zinc Supply on Plant Growth and Nutrient Uptake in Maize Seedlings

Previous studies have shown that zinc (Zn) accumulation in shoot and grain increased as applied nitrogen (N) rate increased only when Zn supply was not limiting, suggesting a synergistic effect of N on plant Zn accumulation. However, little information is available about the effects of different mineral N sources combined with the presence or absence of Zn on the growth of both shoot and root and nutrient uptake. Maize plants were grown under sand-cultured conditions at three N forms as follows: NO3– nutrition alone, mixture of NO3–/NH4+ with molar ratio of 1:1 (recorded as mixed-N), and NH4+ nutrition alone including zero N supply as the control. These treatments were applied together without or with Zn supply. Results showed that N forms, Zn supply, and their interactions exerted a significant effect on the growth of maize seedlings. Under Zn-sufficient conditions, the dry weight (DW) of shoot, root, and whole plant tended to increase in the order of NH4+ < NO3– < mixed-N nutrition. Compared with NH4+ nutrition alone, mixed-N supply resulted in a 27.4 and 28.1% increase in leaf photosynthetic rate and stomatal conductance, which further resulted in 35.7 and 33.5% of increase in shoot carbon (C) accumulation and shoot DW, respectively. Furthermore, mixed-N supply resulted in a 19.7% of higher shoot C/N ratio vs. NH4+ nutrition alone, which means a higher shoot biomass accumulation, because of a significant positive correlation between shoot C/N ratio and shoot DW (R2 = 0.682***). Additionally, mixed-N supply promoted the greatest root DW, total root length, and total root surface area and synchronously improved the root absorption capacity of N, iron, copper, manganese, magnesium, and calcium. However, the above nutrient uptake and the growth of maize seedlings supplied with NH4+ were superior to either NO3– or mixed-N nutrition under Zn-deficient conditions. These results suggested that combined applications of mixed-N nutrition and Zn fertilizer can maximize plant growth. This information may be useful for enabling integrated N management of Zn-deficient and Zn-sufficient soils and increasing plant and grain production in the future.

Legume-Based Mobile Green Manure Can Increase Soil Nitrogen Availability and Yield of Organic Greenhouse Tomatoes

Information about the availability of soil mineral nitrogen (N) in organic greenhouse tomatoes after the application of mobile green manure (MGM), and its impact on plant nutrient status and yield is scarce. Considering this knowledge gap, the effects of legume biomass from faba beans that are cultivated outdoors (FAB), or from feed-grade alfalfa pellets at two different doses (AAL = 330 g m−2; AAH = 660 g m−2) that were applied as MGM on the nutrition and yield of an organic greenhouse crop of tomatoes were evaluated. All of the MGM treatments increased the mineral N concentrations in the soil throughout the cropping period, and the total N concentration in tomato leaves when compared to the untreated control. FAB and AAH treatments had a stronger impact than AAL in all of the measured parameters. In addition, AAL, AAH, and FAB treatments increased the yield compared to the control by 19%, 33%, and 36%, respectively. The application of MGM, either as faba bean fresh biomass or as alfalfa dry pellets, in organic greenhouse tomatoes significantly increased the plant available soil N, improved N nutrition, and enhanced the fruit yield. However, the N mineralization rates after the MGM application were excessive during the initial cropping stages, followed by a marked decrease thereafter. This may impose an N deficiency during the late cropping period.

Nitrogen Source Preference and Growth Carbon Costs of Leucaena leucocephala (Lam.) de Wit Saplings in South African Grassland Soils

Leucaena leucocephala (Fabaceae) is native to Central America and has invaded many climatic regions of the tropics. In South Africa, the species is categorized as an emerging or incipient weed used as fodder, timber, firewood and in erosion control on degraded habitats. The species is common along the eastern subtropical regions of KwaZulu-Natal (KZN) Province, where it invades grasslands, savannas and edges of forests. Soils of these ecosystems are characterized as nutrient deficient and acidic. Using a pot trial, we determined the effects of the nutrient addition treatments on microbial symbiosis, N nutrition and biomass accumulation of L. leucocephala under greenhouse conditions. After 180 days of growth, plants were harvested, and their utilization of N derived from the atmosphere and from the soil was quantified through determination of δ15N values. L. leucocephala maintained growth and N nutrition by relying on both atmospheric- and soil-derived N across all soil treatments. The NDFA was significantly higher in high P (N1 + P, N2 + P and N3 + P) soils. L. leucocephala was able to nodulate with intermediate and fast-growing strains from the Mesorhizobium and Rhizobium genus in N2 + P grown plants. This shows that L. leucocephala possesses traits that are successful in acquiring nutrients, especially in nutrient limited conditions, by establishing plant symbiosis with multiple bacteria and relying on extracting N from the soil and from the atmosphere through the symbiosis.

Ameliorative Effects of Nitrogen Application on Vegetative Growth and Productivity in Genotypes of Ragi (Eleusine coracana Gaertn.) under Saline Conditions

Background: Salinity and low soil nitrogen availability are important growth limiting factors for most crops. The proper use of N fertilizer is not only important for growth but it may also alter the salinity tolerance of plants depending on the level of salinity. Methods: The present study was undertaken to determine the interactive effects of N nutrition and saline irrigations (3, 6, 7.2, 10, 12 and 14 dSm-1) on growth and grain productivity in two varieties of finger millet viz. VL-315 and Local Hills. Different growth and productivity parameters (like plant height, dry weight of shoot, root and leaves, dry weight of panicle/plant, no. of grains, grain yield/plant etc.) adversely affected by saline irrigations, however, nitrogen nutrition minimized at different levels of salinity. Result: The positive response of nitrogen was comparatively higher at lower salinity levels (3-7.2 dSm-1) as well as at control than higher salinity (10-14 dSm-1). The effect of salinity was lower in cv. VL- 315 than Local Hills, but the interactive effects of N nutrition and salinity also enhanced the dry weight of shoot, root, leaves, dry weight of panicles and grains/plant. It is probable that N nutrition had enhanced assimilation of NO3-1-N, through the activity of NRA which further increased total nitrogen and protein content in leaves, hence, enhanced growth, biological and grain yield in both cultivars.

Diagnosis and Treatment of Acute Pancreatitis: Bibliographic Review

Introduction: Acute pancreatitis (AP) is a sudden, reversible inflammatory process of the pancreas, caused by self-digestion. In Ecuador in 2016, 4715 cases were presented, with a mortality of 2.99%. The etiology includes gallstones, alcoholism, hypertriglyceridemia. It presents with upper abdominal pain, nausea and vomiting, it is hospital management. Methodology: It is a descriptive review of the literature on the diagnosis and treatment of BP, based on 31 articles in English and Spanish. Discussion and Results: AP is diagnosed by the clinic and by the serum measurement of lipase and pancreatic amylase. You can also perform other studies such as C-reactive protein, alanine aminotransferase, aspartate aminotransferase, ultrasonography, computed tomography, magnetic resonance imaging, among others. The management of the intake as the main points of perfusion, analgesia, nutrition, clinical, radiology, retrograde endoscopic cholangiopancreatography, antibiotic and surgery. Conclusion: Although the diagnosis is generally clinical and laboratory, for atypical cases, imaging studies are very useful to confirm or exclude the diagnosis. The treatment of PA is summarized in the PANCREAS nemotechnics. (P perfusion, A analgesia, N nutrition, C clinical, R radiology, E endoscopic retrograde cholangiopancreatography, A antibiotic, S surgery). Keywords: pancreatitis, inflammation, diagnosis, treatment. RESUMEN Introducción: La pancreatitis aguda (PA) es un proceso inflamatorio repentino, reversible del páncreas, causado por autodigestión. En Ecuador en el 2016 se presentaron 4 715 casos, con una mortalidad del 2,99%. En la etiología constan: Cálculos biliares, alcoholismo, hipertrigliceridemia. Se presenta con dolor abdominal superior, náuseas y vómito, es de manejo hospitalario. Metodología: Es una revisión bibliográfica descriptiva, sobre el diagnóstico y tratamiento de la PA, en base a 31 artículos en inglés y español. Discusión y Resultados: La PA se diagnostica mediante la clínica y por la medición sérica de lipasa y amilasa pancreática; también se pueden realizar otros estudios como proteína C reactiva, alanina aminotranferasa, aspartato aminotransferasa, ultrasonografía, tomografía computarizada, imagen por resonancia magnética, entre otros. El tratamiento apunta a brindar una adecuada perfusión de tejidos, buena analgesia y principalmente evitar complicaciones. El manejo toma como como principales puntos perfusión, analgesia, nutrición, clínica, radiología, colangiopancreatografia retrograda endoscópica, antibiótico y cirugía. Conclusiones: A pesar de que el diagnóstico es generalmente clínico y de laboratorio, para casos atípicos son de gran utilidad los estudios de imagen para confirmar o excluir el diagnóstico. El tratamiento de PA se resume en la nemotecnia PANCREAS. (P perfusión, A analgesia, N nutrición, C clínica, R radiología, E colangiopancreatografía retrógrada endoscópica, A antibiótico, S cirugía). Palabras clave: pancreatitis, inflamación, diagnóstico, tratamiento.