Shining Light on Photosynthesis in the Harmful Dinoflagellate Karenia mikimotoi–Responses to Short-Term Changes in Temperature, Nitrogen Form, and Availability

Karenia mikimotoi is a toxic bloom-forming dinoflagellate that sometimes co-blooms with Karenia brevis in the Gulf of Mexico, especially on the West Florida Shelf where strong vertical temperature gradients and rapid changes in nitrogen (N) can be found. Here, the short-term interactions of temperature, N form, and availability on photosynthesis–irradiance responses were examined using rapid light curves and PAM fluorometry in order to understand their interactions, and how they may affect photosynthetic yields. Cultures of K. mikimotoi were enriched with either nitrate (NO3−), ammonium (NH4+), or urea with varying amounts (1, 5, 10, 20, 50 µM-N) and then incubated at temperatures of 15, 20, 25, 30 °C for 1 h. At 15–25 °C, fluorescence parameters (Fv/Fm, rETR) when averaged for all N treatments were comparable. Within a given light intensity, increasing all forms of N concentrations generally led to higher photosynthetic yields. Cells appeared to dynamically balance the “push” due to photon flux pressure and reductant generation, with consumption in overall metabolism (“pull” due to demand). However, at 30 °C, all fluorescence parameters declined precipitously, but differential responses were observed depending on N form. Cells enriched with urea at 30 °C showed a smaller decline in fluorescence parameters than cells treated with NO3− or NH4+, implying that urea might induce a photoprotective mechanism by increasing metabolic “pull”.

Connecting Homomorphism and Separating Cycles

We discuss the construction of a long semi-exact Mayer–Vietoris sequence for the homology of any finite union of open subspaces. This sequence is used to obtain topological conditions of representation of the integral of a meromorphic n-form on an n-dimensional complex manifold in terms of Grothendieck residues. For such a representation of the integral to exist, it is necessary that the cycle of integration separates the set of polar hypersurfaces of the form. The separation condition in a number of cases turns out to be a sufficient condition for representing the integral as a sum of residues. Earlier, when describing such cases (in the works of Tsikh, Yuzhakov, Ulvert, etc.), the key was the condition that the manifold be Stein. The main result of this article is the relaxation of this condition

For a Better Understanding of the Effect of N Form on Growth and Chemical Composition of C3 Vascular Plants under Elevated CO2—A Case Study with the Leafy Vegetable Eruca sativa

Plant responses to elevated atmospheric CO2 (eCO2) are well studied, but the interactions of the carbon and nitrogen metabolism in the process are still not fully revealed. This is especially true for the role of nitrogen forms and their assimilation by plants under eCO2. This study investigated the interacting metabolic processes of atmospheric CO2 levels and N form in the short-term crop arugula. The effects on physiological processes and their consequences for crop growth, yield and nutritional value were elucidated. Two varieties of arugula were grown in climate cabinets under 400 or 800 ppm CO2, respectively. The plants were fertilized with either pure nitrate or ammonium-dominated-N. Photosynthetic CO2 assimilation increased in response to eCO2 regardless of the N form. This did not affect the assimilation of nitrate and consequently had no impact on the biomass of the plants. The extra photosynthates were not invested into the antioxidative compounds but were probably diverted towards the leaf structural compounds, thereby increasing dry mass and “diluting” several mineral elements. The fertilization of arugula with ammonium-dominated N had little benefits in terms of crop yield and nutritional quality. It is therefore not recommended to use ammonium-dominated N for arugula production under future elevated CO2 levels.

Increasing nitrogen supply to phosphorus-deficient Medicago sativa decreases shoot growth and enhances root exudation of tartrate to discharge surplus carbon dependent on nitrogen form

Aims Carboxylate release by roots has been considered a strategy for mobilization and acquisition of phosphorus (P). However, recently, it was argued that carboxylate release may be a way to discharge surplus carbon produced under conditions that limit plant growth. Plant P status may not be the main factor driving carboxylate release by roots. Instead, plant nitrogen (N) status and/or N:P ratio of the soil or plant may play a more important role in enhancing carboxylate release. Methods A greenhouse pot experiment was performed to grow alfalfa in a P-deficient soil, supplied with two rates of P (0 and 20 mg kg− 1) in combination with four forms of nitrogen (N) at five rates (0, 25, 50, 75, and 100 mg kg− 1), to explore the effects of P rate, N form, N rate, and their interactions on plant growth, P and N status, and carboxylate release, and to determine the factors driving carboxylate release. Results Nitrogen addition weakened the positive effect of P addition on plant growth, and increased plant N ([N]) and P concentrations ([P]); P addition increased plant [P], but weakened the effect of N addition on plant [N]. The amount of tartrate increased dramatically with increasing N rate, which decreased shoot growth, depending on N form. At high P supply, tartrate exudation correlated negatively with shoot biomass. Conclusions Nitrogen addition to P-deficient alfalfa decreased shoot growth and enhanced the release of tartrate, likely to discharge surplus carbon; and the effects varied with N form.

Asymptotic factorization of n-particle SU(N) form factors

We investigate the high energy behavior of the SU(N) chiral Gross-Neveu model in 1 + 1 dimensions. The model is integrable and matrix elements of several local operators (form factors) are known exactly. The form factors show rapidity space clustering, which means factorization, if a group of rapidities is shifted to infinity. We analyze this phenomenon for the SU(N) model. For several operators the factorization formulas are presented explicitly.

Energieeinsatz und Energieeffizienz von Winterweizen bei unterschiedlicher mineralischer Stickstoffdüngung im Marchfeld

ZusammenfassungDie Korn- und Stroherträge, der Energie-Input (Kraftstoff, Mineraldünger, Pflanzenschutzmittel, Maschinen) und die Kennzahlen zur Energieeffizienz (Energie-Output, Netto-Energie-Output, Energieintensität, Energienutzungseffizienz) in Abhängigkeit der mineralischen Stickstoffdüngermenge (0 kg, 60 kg, 120 kg und 180 kg N ha−1) und der Düngerstrategie (unterschiedliche Mineraldüngerformen und Gabenteilungen) wurden auf zwei Standorten im Marchfeld (Engelhartstetten und Groß-Enzersdorf) auf Basis von zwei zweijährigen Feldversuchen analysiert. Dabei sollte die Frage beantwortet werden, welche mineralische N-Düngung (N-Form, N-Menge und Splittung der N-Menge) die höchste Energieeffizienz aufweist. Mit zunehmender mineralischer N-Menge (60 kg, 120 kg bzw. 180 kg N ha−1) nahm der energetische Anteil des Mineraldüngers am Gesamtenergie-Input um 24 %, 38 % bzw. 48 % zu. Durch das Gesetz des abnehmenden Ertragszuwachses wurde in Engelhartstetten bei einer N-Düngermenge von 180 kg N ha−1 eine signifikant verringerte Energieeffizienz im Vergleich zu 60 kg N ha−1 und 120 kg N ha−1 festgestellt. Eine Aufteilung der N-Düngermenge auf drei Gaben erhöhte den Kraftstoffverbrauch um 4 % gegenüber einer einmaligen Applikation der gesamten Düngermenge. Die Kennzahlen der Energieeffizienz wurden durch die Gabenteilung kaum beeinflusst. Die N-Düngung mit Kalkammonsalpeter war energieeffizienter als die Harnstoffdüngung (rein, stabilisiert, eingearbeitet). Die Energieeffizienzanalyse kann somit einen wertvollen Beitrag leisten, um pflanzenbauliche Maßnahmen hinsichtlich ihren Umweltauswirkungen zu bewerten.

Natural Formulation Based on Diatomaceous Earth and Botanicals against Stored Product Insects

Diatomaceous earth (DE) has long been known as a potential protectant for stored cereals against various stored product insects. Despite favorable effect for the environment and human health, DE has some negative side effects on the treated commodity. In order to minimize negative response and to improve its efficacy, this paper represents a study of developed natural formulation based on DE SilicoSec® enhanced with botanicals (essential oil lavender, corn oil, and bay leaves dust) and silica gel. The activity of formulation (labeled as N Form) was tested against Sitophilus oryzae (L.), Rhyzopertha dominica (F.), and Tribolium castaneum (Herbst) in seed wheat and barley under controlled conditions. As a reference comparative value, DE SilicoSec® was used. N Form showed higher efficacy than DE, especially in barley at the lowest concentration, inducing higher mortality of all three insect species. The highest average progeny inhibition was recorded in R. dominica population both in seed wheat and barley with 94.9% and 96.3% of inhibition, respectively, followed with S. oryzae and T. castaneum inhibition of 90.6% and 86.1%, respectively, in wheat and 94.9% and 89.7%, respectively, in barley. Results indicate that the developed natural formulation N Form enhanced the activity of DE SilicoSec® using lower amount of DE dust and that it could be successfully implemented for storage of cereals as alternatives to chemical pesticides for stored product insect control.

Interactive Effects of N Form and P Concentration on Growth and Tissue Composition of Hybrid Napier Grass (Pennisetum purpureum × Pennisetum americanum)

This study aimed to assess effect of nitrogen (N) form and phosphorus (P) level on the growth and mineral composition of hybrid Napier grass. Experimental plants were grown with different N forms (NO3−, NH4NO3, and NH4+; 500 µM) and P concentrations (100 and 500 µM) under greenhouse conditions for 42 days. Growth rate, morphology, pigments, and mineral nutrients in the plant tissue were analysed. At the low P concentration, the better growth was found in the plants supplied with NH4+ (relative growth rate (RGR) = 0.05 g·g−1·d−1), but at the high P concentration, the NH4+-fed plants had 37% lower growth rates and shorter roots and stems. At the high P level, the NH4NO3−-fed plants had the highest RGR (0.04 g·g−1·d−1). The mineral nutrient concentrations in the plant tissues were only slightly affected by N form and P concentration, although the P concentrations in the plant tissue of the NO3−-fed plants supplied with the high P concentration was 26% higher compared to the low P concentration plants. The N concentrations in the plant tissues did not vary between treatments. The results showed that the optimum N form for the plant growth and biomass productivity of hybrid Napier grass depends on P level. Hybrid Napier grass may be irrigated by treated wastewater containing high concentrations of N and P, but future studies are needed to evaluate biomass production and composition when irrigating with real wastewater from animal farms.

Extreme precipitation increases plant biomass through altering nitrogen acquisition by grasses and soil microorganisms

<p>Extreme precipitation events resulting from climate change have strong impact on structure and functions of grassland ecosystems. The extreme climate events may shift plant productivity and nutrient acquisition preferences by roots and microorganisms.We conducted an extreme precipitation simulation experiment and used in-situ <sup>15</sup>N labeling of the three N forms to investigate N acquisition (N uptake rate, <sup>15</sup>N recovery and preference for N form) by the dominant plant species Stipa grandis and soil microorganisms.Increased rain frequency raised the growth and N acquisition of S. grandis, while microbial N uptake remains unaffected. Microorganisms strongly outcompeted S. grandis for total <sup>15</sup>N acquisition, however such superiority decreased in higher extreme precipitation frequency. Plant and microorganisms converged their N demands from distinct to similar preferences for N forms with high precipitation frequency. Such chemical niche partitioning by extreme precipitation effectively reduced root and microbial competition for each N form. Overall, important mechanistical insights into chemical niche differentiation by the effects of extreme climate events and their effects on structure, functions and plant-microbial interactions in temperate grasslands were explained.</p>