Nitrogen Concentration Levels Research Articles

Optimization of continuous astaxanthin production by Haematococcus pluvialis in nitrogen-limited photobioreactor

The industrial production of astaxanthin from Haematococcus pluvialis is mainly operated following a two-stage cultivation strategy in photobioreactors (PBRs) operating in batch mode. This study provides a strategy for optimizing continuous astaxanthin production in a one-stage approach, by optimizing both astaxanthin accumulation and biomass productivity of H. pluvialis under nitrogen-limited condition. To achieve the good balance in culture conditions to maintain growth under nitrogen-limited conditions, while triggering significant astaxanthin accumulation in reddish vegetative cells, the role of light absorption, as represented by the mean rate of photon absorption (MRPA), and nitrate concentration was especially investigated. For that purpose, H. pluvialis cultures were grown in a flat-panel PBR with constant dilution rate D of 0.015 h−1, different photon flux densities PFDs ranging from 75 to 750 μmolhν·m−2·s−1 and different nitrogen concentration levels in the feeding medium [NO3−] of 1, 3 and 8.8 mM. A parabolic relationship between MRPA and astaxanthin production rate was obtained. This indicated that astaxanthin synthesis was limited by the MRPA, opening further optimization by adjusting incident light intensity, nitrogen concentration in the feeding medium or culture dilution rate. After optimization of operating conditions, we demonstrated that a large quantity of astaxanthin can be produced in continuous mode, following then a one-stage strategy which may be advantageous for industrial use. A maximum astaxanthin productivity of 1.27 ± 0.03 g·m−2·d−1 with an astaxanthin accumulation of 3.9 ± 0.2 % DW was reached for the culture featuring MRPA of 9000 μmolhν·kgx−1·s−1. The process was also proved reversible, allowing to tailor the biomass composition and physiological state (from green to red cells enriched in astaxanthin) by adjusting operating conditions, opening perspectives from an optimized coupling with downstream processing steps.

The specifics of the content of chemical elements and ash in the leaves of ornamental plants in an urban environment

The content of sulfur, nitrogen, phosphorus, ash content in the leaves of annual and perennial species and varieties grown in urban conditions near highways and industrial enterprises of the cities of the Novosibirsk region: Iskitim, Berdsk, Koltsovo, Evsino, Sovetsky district of Novosibirsk was studied. Indications of these substances were determined in the leaves of Hemerocallis hybrida, Iris hybrida, Hosta lancifolia, H. decorata, Salvia splendens, Tagetis patula, Senecio cineraria Malva hybrida, Gatsania hybrida, Alyssum hybrida. The individual features of the accumulation of nutrients and ash in aboveground vegetative organs have been revealed. It was noted that the level of nitrogen concentration and ash content in the leaves of floral and ornamental plants exceeded the values of phosphorus and sulfur by 6–11 times. An increase in the concentration of chemicals and ash in plant leaves in an urban environment has been established.

Impact of trimethoprim on serum creatinine, sodium, and potassium concentrations in patients taking trimethoprim-sulfamethoxazole without changes in glomerular filtration rate.

Trimethoprim (TMP) inhibits the Na+ /K+ -ATPase present in the basement membrane of distal tubular epithelial cells. However, hyponatremia and hyperkalemia may develop in patients taking TMP-sulfamethoxazole (SMX). In addition, because TMP inhibits drug transporters, such as organic cation transporter 2 and multidrug and toxin extrusion protein 2-K in proximal tubules, reversible increases in the concentration of serum creatinine (SCr), the substrate of these transporters, may occur. Here, we investigated variability in SCr, serum sodium (Na+ ), and serum potassium (K+ ) concentrations after initiation of TMP-SMX treatment and evaluated the risk of hyponatremia and hyperkalemia in patients with increased SCr concentrations without changes in the glomerular filtration rate (GFR). In this retrospective study, all patients aged 20 years or older who received oral TMP-SMX during hospitalization were enrolled. The patients with estimated creatinine (Cr) clearance (eCCr) lower than 30 mL/min were excluded, as were patients taking drugs that were likely to induce renal dysfunction, drugs other than glucocorticoids that were likely to induce electrolyte imbalances, or drugs other than TMP that inhibit tubular Cr secretion. Additionally, those with SCr concentrations elevated more than 30% from baseline or serum blood urea nitrogen concentration levels above 20 mg/dL during follow-up were also excluded. In total, 111 patients were enrolled in the study. The common independent variable affecting the change rate in SCr, Na+ , and K+ concentrations (ΔSCr, ΔNa+ , and ΔK+ ) from baseline to the highest value during the follow-up period (14 days after initiation of TMP-SMX treatment) was the daily dose of TMP. There were significant correlations between ΔSCr and ΔNa+ or ΔK+ (ρ=-0.199, p=0.036 and ρ=0.244, p=0.010, respectively). Kaplan-Meier curves for hyponatremia and hyperkalemia with greater than or equal to grade 1 severity showed different profiles when the TMP dose varied (≤ 160 vs. > 160 mg/day; p=0.005 and 0.008). The cumulative incidences of both adverse effects were 64.7% (median: 7 days) and 29.4% in patients taking more than 160 mg/day TMP and 35.2% and 6.7% in patients taking 160 mg/day TMP or less. Thus, TMP may affect the kinetics of Cr, Na+ , and K+ in the proximal and distal tubules in a dose-dependent without changing the GFR. This study is the first report to demonstrate the degree of changes in SCr, Na+ , and K+ concentrations after initiation of TMP-SMX treatment. If SCr is elevated after initiation of TMP-SMX treatment, clinicians should be aware of decreased Na+ and increased K+ concentrations. TMP may increase the risks of hyponatremia and hyperkalemia in a dose-dependent manner without altering GFR.

Response of forage plants to alteration of temperature and spring thaw date: implications for geese in a warming Arctic

AbstractChanges in summer temperatures in Arctic Alaska have led to longer and warmer growing seasons over the last three decades. Corresponding with these changes in climate, the abundance and distributions of geese have increased and expanded over the same period. We used an experimental approach to assess the response of goose forage plants to simulated environmental change. We subjected Carex subspathacea, a preferred goose forage growing on the Arctic Coastal Plain (ACP) of Alaska, to manipulations of temperature and timing of spring thaw to measure potential effects in terms of plant nitrogen concentration, aboveground biomass, and total nitrogen availability. Carex subspathacea responded to warming in a dynamic fashion. Increases in temperature led to decreases in leaf nitrogen concentration but increases in aboveground biomass. The increase in biomass was stronger than the decline in nitrogen concentration such that total nitrogen availability was increased with temperature for the first 35–40 d of the season. Grazing removal accounted for only minimal offtake of biomass, and we found no indication that grazing maintained elevated levels of nitrogen concentration longer in the season as reported in other studies. Based on demonstrated relationships in the literature between forage nitrogen concentrations and gosling growth rates, we conclude that there is currently abundant high‐quality forage available across the ACP. This finding fits with recent evidence of high gosling growth rates and increasing trends in goose abundance on the ACP. Our results suggest that with climate warming of a few degrees, nitrogen concentration of forage may decrease, but forage biomass and total nitrogen availability will increase. Our data suggest that nitrogen concentration will not fall below the minimum threshold required by geese in the near future. As such, we suggest that there is currently no bottom‐up limitation to goose numbers on the ACP.

Early Root Development of Eucalyptus pellita F. Muell. Seedlings from Seed and Stem Cutting Propagation Methods at Nursery Stage

Macropropagation using cutting for larger multiplying seedlings is cheaper and efficient instead of clonal seeds for uniform plant material seedling production. However, information on root growth of Eucalyptus pellita at early development from seed and stem cutting of E. pellita seedlings is still lacking. With such information, it is useful for forest plantation company management in enhancing the understanding of strategies to optimize yield production with the appropriate agronomic or silvicultural approach in the field of planting. Therefore, the objectives of this study were to compare the root development of two different types of propagation seedlings of E. pellita and to study the effect of various nitrogen concentration levels on two different types of propagation of E. pellita seedlings. The study was conducted using E. pellita seedlings from two different types of propagation, namely, seed and stem cuttings, along with three different nitrogen concentrations (0, 50, and 200 kg N ha−1). Shoot biomass, root intensity (RI), total root intensity (TRI), root biomass, root length density (RLD), and specific root length (SRL) were recorded. Dried shoot biomass, RLD, and SRL of E. pellita seedlings using stem cutting were significantly higher ( P < 0.05 ) compared to seed, whereas there were no significant differences ( P > 0.05 ) for root biomass, TRI, and RI between the propagation types of E. pellita seedlings. In conclusion, E. pellita seedlings from stem cutting were greater in terms of root distribution compared to propagation by seeds at the nursery stage, and 50 kg N ha−1 was the optimal nitrogen concentration level from the considered levels to be applied to the E. pellita seedlings.

Bottom-up Effects on Tri-trophic Interactions: Plant Fertilization Enhances the Fitness of a Primary Parasitoid Mediated by Its Herbivore Host.

Plants play a pivotal role in interactions involving herbivores and their natural enemies. Variation in plant primary and secondary metabolites not only affects herbivores but, directly and indirectly, also their natural enemies. Here, we used a commercial NPK fertilizer to test the impact of three fertilizer, namely 50, 100, and 200 ppm nitrogen, and one control (i.e., water) treatments, on the weight of the nymphs of the whitefly Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae). Subsequently, the whitefly parasitoid Eretmocerus mundus Mercet (Hymenoptera: Aphelinidae) was reared on the different groups of whitefly nymphs and upon parasitoid emergence, the number of oocytes was determined as a measure of reproductive capacity. Trials were done on tomato and tobacco plants. The level of nitrogen concentration in tobacco leaves was directly correlated with the fertilizer applications, thus confirming the effect of our fertilizer treatments. Both in tomato and tobacco plants, healthy as well as parasitized whitefly nymphs, were heaviest in the 200 ppm nitrogen treatment. The highest number of oocytes per female parasitoid was recorded in the 200 ppm nitrogen treatment in tomato (31% more oocytes as compared with the control) and in the 100 and 200 ppm nitrogen treatments in tobacco (200% more oocytes). We suggest that the increase in oocytes was the result of the enhanced size (food quantity) and/or nutritional quality of the whitefly host. The practical implications of these results for the mass rearing of whitefly parasitoids and for biological pest control are discussed.

Ammonia Removal Using Biotrickling Filters: Part B: Determination of the Nitrogen Accumulation in the Scrubbing Liquid at a Livestock Facility Using Electrical Conductivity Measurement

It was demonstrated that the daily monitoring of electrical conductivity (EC) of scrubbing water can easily be used to determine the performance of biotrickling filters treating ammonia (NH3) emissions, generated by livestock facilities. Two different measurement campaigns were carried out on a pilot-scale biotrickling filter installed at a pig facility. Different phases of the operation were observed for each campaign, in accordance with EC values. For EC ranges of between 5 and 40 mS cm−1, performance was similar for both campaigns, indicating that the nitrogen accumulated in water (φ) was controlled by the operating conditions and biotrickling filter design (φ = 205 gN day−1 corresponding to 1.71 mS cm−1 day−1). Due to the correlation established in Part A of this study, the performance of the biotrickling filter can be directly expressed as gN h−1 m−3packing material without gas-phase monitoring. Thus, for an Empty Bed Residence Time of 1 s, the nitrogen accumulation capacity of the biotrickling filter was 24 gN h−1 m−3packing material. For higher EC values, the ammonia mass transfer slowed down and stopped with EC at around 50–60 mS cm−1 (campaign #1) and 70 mS cm−1 (campaign #2). It was evidenced that the mass transfer stopped due to ammonia mass transfer limitation controlled by the driving force, although biomass inhibition can occur at these levels of nitrogen concentration in the scrubbing liquid. EC monitoring can also be used to assess the ratio of nitrogen accumulated in water φ and amount of ammonia entering the system φmax. Thus φ/φmax ratios of 41% and 27% were recorded for campaign #1 and #2 respectively.

Biogas-driven complete nitrogen removal from wastewater generated in side-stream partial nitritation

Anaerobic digestion is an attractive process in wastewater treatment plants (WWTPs) to achieve simultaneous sludge reduction and energy recovery. While converting the majority of organic carbon to biogas (mainly consisting 60%CH4 + 40%CO2), the high-strength anaerobic digestion liquor consists of a high level of nitrogen concentration. The feasibility of utilizing biogas produced in-situ to achieve satisfactory nitrogen removal performance from partially nitrified anaerobic digestion liquor was examined in this study. To this end, a membrane biofilm reactor (MBfR) was used to couple nitrite- or nitrate-dependent anaerobic methane oxidation (n-DAMO) and anammox microorganisms, which was supplied with synthetic biogas and partially nitrified anaerobic digestion liquor (470 mg NH4+-N/L + 560 mg NO2−-N/L). The MBfR achieved not only nearly complete nitrogen removal (~99%), but also a practically useful nitrogen removal rate above 1 kg N/m3/d. Due to the acidification caused by excessive CO2 supply from biogas, pH dropping was observed. Two corresponding strategies, i.e., intermittent alkali dosing and intermittent nitrogen gas flushing, were developed to control the pH at neutral. Mass balance based on batch tests and microbial community analysis by 16S rRNA gene amplicon sequencing both showed the joint contribution of anammox bacteria and anaerobic methane oxidizers to the nitrogen removal. This study proved the potential and capacity of MBfR to access complete nitrogen removal from high-strength wastewater by using biogas produced in-situ, thus leading to a significant reduction of external carbon addition in practice.

An optimization model of light intensity and nitrogen concentration coupled with yield and quality

The nitrogen content of nutrient solution and light intensity are two crucial factors affecting the yield and quality of controlled environment hydroponic vegetables. In this study, Purple Bok Choy (Brassica rapa var. Chinensis) was evaluated in a two-factor experiment with five levels of light intensity and five levels of nitrogen concentration. The plants were harvested on the 35th day after planting and different parameters such as shoot fresh weight, root fresh weight, anthocyanin, and soluble sugar were measured as representatives of yield and quality. This paper investigated the effects of different light/nitrogen combinations on the yield and quality of Purple Bok Choy, and established an optimal model coupled with yield and quality indicators. The result reveals that the light intensity and nitrogen concentration have a strong synergistic interaction on shoot fresh weight, root fresh weight, anthocyanin, and soluble sugar of Purple Bok Choy. A combination of light/nitrogen could be found to achieve the common improvement for the indicators with a similar change trend. This work gives valuable insights into the combinational regulation of nitrogen concentration and light intensity and provides a new idea for the comprehensive improvement of production yield and quality.

Use of Biofuel Industry Wastes as Alternative Nutrient Sources for DHA-Yielding Schizochytrium limacinum Production

The simultaneous use of crude glycerol and effluent from anaerobic digestate, both wastes derived from the biofuel industry, were tested in the frame of circular economy concept, as potential low-cost nutrient sources for the cultivation of rich in docosahexaenoic acid (DHA) oil microalgae strain Schizochytrium limacinum SR21. Initially, the optimal carbon and nitrogen concentration levels for high S. limacinum biomass and lipids production were determined, in a culture media containing conventional, high cost, organic nitrogen sources (yeast extract and peptone), micronutrients and crude glycerol at varying concentrations. Then, the effect of a culture media composed of crude glycerol (as carbon source) and effluent digestate at varying proportions on biomass productivity, lipid accumulation, proximate composition, carbon assimilation and fatty acid content were determined. It was shown that the biomass and total lipid content increased considerably with varying effluent concentrations reaching 49.2 g L−1 at 48% (v/v) of effluent concentration, while the lipid yield at the same effluent concentration reached 10.15 g L−1, compared to 17.0 g L−1 dry biomass and 10.2 g L−1 lipid yield when yeast extract and peptone medium with micronutrients was used. Compared to the control treatment, the above production was obtained with 48% less inorganic salts, which are needed for the preparation of the artificial sea water. It was shown that Schizochytrium limacinum SR21 was able to remediate 40% of the total organic carbon content of the biofuel wastes, while DHA productivity remained at low levels with saturated fatty acids comprising the main fraction of total fatty acid content. The results of the present study suggest that the simultaneous use of two waste streams from the biofuel industry can serve as potential nutrient sources for the growth of Schizochytrium limacinum SR21, replacing the high cost organic nutrients and up to one half the required artificial sea water salts, but upregulation of DHA productivity through optimization of the abiotic environment is necessary for industrial application, including aqua feed production.

Effect of sulfate anions on nitrates accumulation and total Kjeldahl nitrogen content in lettuce plants cultivated in peat-perlite mixture

Intensive agriculture is characterized by increased use of synthetic nitrogen fertilizers. If the supplied nitrogen fertilizers are excessive, many vegetables, particularly leafy vegetables, accumulate high levels of nitrates. Increased vegetable nitrate content is related to possible implications for health, as nitrate metabolites can cause carcinogenesis, infantile methaemoglobinaemia and possibly even teratogenesis. The aim of the present study was to investigate the effect of sulfate ions on nitrate accumulation and total Kjeldahl nitrogen (TKN) content in lettuce (Lactuca sativa var. crispa ‘Lollo Bionda’), as an attempt to suggest possible ways to reduce nitrate levels. Plants were grown in peat-perlite mixture and fertilized by nutrient solutions under glasshouse conditions. Three levels of nitrogen concentrations (100, 200 and 400 mg L(‑1) N) have been applied in combination with three levels of sulfate anions (15, 150 and 300 mg L(‑1) S as SO(4)2-). At harvest stage, the fresh weight of leaves, nitrate accumulation, total sulfur concentration and TKN tissue content were determined. As expected, foliar biomass, nitrate accumulation and TKN content were enhanced when nitrogen concentration was increased. However, the increased levels of sulfates (150 and 300 mg L(‑1) S) had no effect on plant weight whereas a decline of nitrate accumulation was observed when sulfate fertilization increased. Moreover, a concentration of 150 mg L(‑1) S caused TKN increase while the reverse was the case for the concentration of 300 mg L(‑1) S. The results of the present study indicate that the enhanced concentrations of sulfates resulted in decreased nitrate accumulation in lettuce leaves. This may be due to interference in the uptake of nitrates by sulfates ions and may be proposed as a possible way to decrease nitrate content in lettuce, resulting in consumer safety.

Crop reflectance measurements for nitrogen deficiency detection in a soilless tomato crop

Early detection of nitrogen deficit stress is essential to effectively and precisely manage crop production under greenhouse conditions. This article demonstrates the use of hyperspectral machine vision as a non-contact technique for detecting crop nitrogen deficit in a soilless tomato crop. Three different levels of nitrogen concentration were applied in tomato plants grown in a growth chamber under controlled environment conditions. The results demonstrate that crop reflectance increased due to nitrogen deficiency, mostly in the wavelength bands between 775 nm–850 nm and 910 nm–960 nm. Based on the reflectance measurements several reflectance indices were calculated and correlated with the tomato leaf chlorophyll or nitrogen content and with the leaf photosynthesis rate (As). The results showed that when the As and the chlorophyll content values changed more than 0.5 μmol m−2 s−1 and 2.8 μg cm−2, respectively, the photochemical reflectance index (PRI) and the transformed chlorophyll absorption in reflectance index (TCARI) values varied more than 0.05 and 2.8, respectively. In addition, the results showed that for N changes higher than 0.20%, the optimised soil adjusted vegetation index (OSAVI) and the modified soil adjusted vegetation index (MSAVI) values varied more than 0.05 and 0.25, respectively. A new spectral index (background adjustment nitrogen index – BANI) was developed and validated under experimental conditions for the estimation of tomato plant nitrogen concentration.

Kinetic Characterization of Red Pigment of Monascus Purpureus at Different Level of Nitrogen Concentration.

Natural and synthetics colors are the two types of food coloring existed in the industries. Over time, most of synthetic colors were banned due to the clearly evident side effects and their possible carcinogenic effects. Pigment produced by Monascus purpureus is microbial origin and safe to use as food grade coloring. The aim of this research is to study the kinetic characterization of red pigment production throughout the solid state fermentation process at different level of nitrogen (peptone) concentration. The concentrations of nitrogen used are in between 1 to 5% of peptone. The highest (0.1182 ), ( 119.7 g ), ( 92.53), (1.35), and (0.016) are obtained at day 5 of fermentation period with the addition of 2% peptone. However, no further increase of the kinetic values with the increasing of peptone concentration from 2% to 5% was observed, except on where the value was high with higher concentration. This indicates that with higher concentration the conversion of biomass to red pigment is enhanced.

Exploring constant substrate temperature and constant high pressure SCD growth using variable pocket holder depths

SCD substrates were successfully synthesized using an optimized pocket holder design. The pocket holder design creates an appropriate thermal environment to shield the diamond substrate from the intense microwave discharge. This substrate configuration allows for a polycrystalline diamond (PCD) rimless, uniform single crystal diamond (SCD) growth process. Square shaped pocket holders with a constant width but with varying depths were used. The SCD growth procedures were carried out via microwave plasma assisted chemical vapor deposition (MPACVD) in a 2.45GHz microwave cavity plasma reactor C at a constant pressure of 240Torr and high power density of ~500W/cm3. By continuously adjusting incident microwave power (Pinc), the substrate temperature (Ts) was held at 1020°C±5°C throughout the entire process cycle. Under these growth conditions, the crystal morphologies exhibited a smooth and flat surface. The average growth rate of the SCDs varied between 30 and 24μm/h as the pocket depth increased from 2.0 to 2.9mm. The PCD rim was eliminated for all pocket depths and the shape of the final, as grown, top SCD surface varied from a square to a circular shape as the pocket holder depth increased. When using the 2.0mm and 2.3mm pockets, the final top SCD surface area increased to almost twice the original HPHT diamond seed area and the lateral growth rate was slightly larger than the vertical growth rate. Birefringence imaging of the grown CVD diamond indicated low stress and SIMS analysis indicated nitrogen concentration levels in the freestanding, CVD diamond plates were in the range of 50ppb to 140ppb. Prime novelty statementSingle crystal diamond is grown by high power density, microwave plasma assisted chemical vapor deposition in a pocket holder held at a constant temperature of 1020°C, a constant pressure of 240Torr and with 5% CH4/H2. Experimental variables were pocket depth and deposition time. Thick, PCD rimless growth was achieved, and for shallow holders, top growth surface area gains of 1. 4–1.9 were demonstrated.

Impact of Carbon Dioxide and Increasing Nitrogen Levels on Growth, Photosynthetic Capacity, Carbohydrates and Secondary Metabolites in Kacip Fatimah (Labisia pumila)

Aims: This study was designed to investigate how CO2 and nitrogen availability alters growth, leaf gas exchange, primary and secondary metabolites production (total phenolics and flavonoid) in three varieties of L. pumila. namely var alata, var pumila and var lanceolata. under CO2 enrichment (1200 µmol mol-1) combined with four levels of nitrogen fertilization (0, 90, 180 and 270 kg N ha-1) for 15 weeks. Study Design: Three-month old L. pumila seedlings of var. alata, var. pumila and var. lanceolata were left for a month to acclimatize in a nursery until ready for the treatments. Carbon dioxide enrichment treatment started when the seedlings reached 4 months old where plants were exposed to 1200 µmol-1 mol-1 CO2 and fertilized with four levels of nitrogen concentrations viz. 0, 90, 180 and 270 kg N Ha-1. The fertilization with nitrogen levels were split into three applications. A control at ambient CO2 (400 µmol-1 mol-1) with standard N fertilization (180 kg N ha-1) was included to compare plant responses to high CO2 combined with different levels of N. Place and Duration of Study: Faculty of Agriculture Glasshouse Complex, Universiti Putra Malaysia from February to May 2011. Methodology: The seedlings were raised in specially constructed growth houses receiving 12-h photoperiod and average photosynthetic photon flux density of 300 µmol m-2 s-1. Carbon dioxide at 99.8% purity was supplied from a high–pressure CO2 cylinder and injected through a pressure regulator into fully sealed 2 m x 3 m growth houses at 2-h daily and applied continuous from 800 to 1000. Total plant biomass was taken by calculating the dry weight of root, stem and leaf per seedling. Total leaf area per plant was measured using a leaf area meter (LI-3100, Lincoln Inc, USA). The measurement of photosynthesis was obtained from a closed system of infra-red gas analyzer LICOR 6400 Portable Photosynthesis System. The response of net CO2 exchange (A) to changing intercellular CO2 concentration (Ci) was conducted at 27°C, 50% relative humidity and at light saturating conditions of 800 µmol m-2s-1. Anthrone method was used to determine the content of total available carbohydrate. Follin–Ciocalteau reagent was used to determine total phenolics and flavonoid using spectrophotometer. Results: In all parameters measured there were no significant was observed in the three varieties. As the levels of nitrogen increased from 0 to 270 kg N ha-1, plant growth, photosynthesis and total chlorophyll content was enhanced. However, carbohydrate, total phenolics and flavonoid was reduced with the increase in nitrogen fertilization. It was found that the high application of nitrogen can increased the photosynthetic capacity of L. pumila by having high Vcmax (RuBisCO CO2 fixation capacity), A sat (CO2 saturation point) and low dark respiration rate in the analysis of A/Ci curves. The production of secondary metabolites was related to increased total non-structural carbohydrate (TNC) under low nitrogen condition. Photosynthesis, displayed a significant negative relationship with secondary metabolites production. Total chlorophyll content exhibited very significant negative relationships with total soluble sugar, starch and total non-structural carbohydrate. Conclusion: This study demonstrated that enrichment with high levels of CO2 is able to enhance the production of plant secondary metabolites. However, increased nitrogen fertilization can reduce the production of these plant secondary metabolites under CO2 enrichment. When there were accumulation of TNC in plant leaves and reduction in photosynthesis, the production of plant secondary metabolites might be up-regulated. The increase in the production of plant secondary metabolites was indicated by reduction in chlorophyll contents.

Spectroscopic Determination of Leaf Nitrogen Concentration and Mass Per Area in Sweet Corn and Snap Bean

Rapid nondestructive measurements at leaf level of nitrogen concentration (%N) and leaf mass per area (LMA) are needed to improve crop simulation model development and calibration, and better understanding of in‐season N management. Many contact reflectance‐based techniques for %N and LMA estimations require calibration across species, cultivars, growing stages, and cultural practices. Narrowband (hyperspectral) reflectance spectroscopy, in combination with partial least square regression (PLSR) models, offers improved performance over vegetation indices derived from standard linear regression analysis with simple ratios or combined formulas. Little research on the application of contact spectroscopy data and PLSR techniques has been conducted for sweet corn (Zea mays L.) and snap bean (Phaseolus vulgaris L.). In this study, we sought to determine the optimum wavelength ranges for %N and LMA estimations and to develop and evaluate spectroscopic models in estimating %N and LMA in the two species. Best PLSR predictions utilized 1500 to 2400 nm for %N estimations and 450 to 2400 nm for LMA estimations in both species, with high averaged coefficient of determination (R2) values (0.90–0.95 for cross‐validation, 0.52–0.71 for external validation) and low root mean square error (RMSE, reported as percentage of sample data range) (4.59–5.67% for cross‐validation, 9.50–18.46% for external validation). The results indicate that narrowband reflectance spectroscopy (450–2500 nm) combined with PLSR analysis is a promising method for rapid and nondestructive estimates of %N and LMA at leaf level in sweet corn and snap bean across growth stages, N management, and years.Core Ideas Spectroscopy combined with partial least square regression models is useful for estimates of leaf nitrogen concentration and leaf mass per area. The optimum spectra for nitrogen concentration and leaf mass per area estimations were 1500 to 2400 and 450 to 2400 nm. Spectroscopy appears appropriate for routine agronomic research field experiments.

Nitrogen starvation for lipid accumulation in the microalga species Desmodesmus sp.

Recently, to obtain lipids from microalgae has been the object of extensive research, since it is viewed as a promising feedstock for biodiesel production, especially when compared with crops such as soybean and sunflower, in terms of theoretical performance. The reduction of nutrient availability in culture media, especially nitrogen, stresses the microorganisms and affects cell growth, thus inducing lipid accumulation. This is an interesting step in biodiesel feedstock obtention from microalgae and should be better understood. In this study, four levels of nitrogen concentration in the BG-11 culture medium were evaluated in the growth of the chlorophycean microalga Desmodesmus sp. Both cell growth and lipid content were monitored over 7 days of cultivation, which yielded a final cell density of 33 × 10(6) cells mL(-1) with an initial NaNO3 concentration of 750 mg L(-1) in the medium and a maximum lipid content of 23 % with total nitrogen starvation. It was observed that the microalgae presented high lipid accumulation in the fourth day of cultivation with nitrogen starvation, although with moderate cell growth.

Effect of nitrogen fertilisation on biology, life table parameters and population abundance of greenbug; Schizaphis graminum (Rondani) (Hemiptera: Aphididae)

Understanding the relationship between fertilisation and pest’s reproductive potential is an essential knowledge for fertilisation and pest management in modern agroecosystems. Hence, the influence of wheat nitrogen nutrition on biology and life table of greenbug, Schizaphis graminum (Rondani) was studied under laboratory conditions (25 ± 1 °C, 70 ± 10% RH and 16:8 L:D). Plants are treated with four nitrogen concentration levels of 0, 50, 100 and 150% of the normal nitrogen complement. The increase in nitrogen fertilisation resulted in increasing in the percentage of soluble nitrogen concentration in plants. Nitrogen had no effect on pre- and post-reproductive periods but significant effects were observed on reproduction period, adult longevity and fecundity. Statistical analysis demonstrated aphid’s feeding on plants treated with higher fertilisation significantly had higher R0 , DT, T, and r m. Greenhouse experiments showed number of wingless aphids on treated wheat plants significantly increased with increase in fertilisation level while the number of winged aphids produced decreased.

Herbaceous production in South India—limiting factors and implications for large herbivores

This study’s goal was to better understand the growth pattern and limitations of the herbaceous production that supports South India’s rich large herbivore grazer assemblage. We conducted a fully factorial nitrogen and water (three levels each) treatment field experiment in the herbivore rich South Indian Western Ghats region to determine the seasonal pattern and the extent to which nitrogen and water availability limit herbaceous production. Graminoid production was found to be nitrogen limited. Despite low rainfall, additional water did not significantly increase overall biomass production nor extend growth in the dry season. Accumulated standing biomass was highest in the late wet season (November) and lowest in the dry season (May). Leaf nitrogen was highest in the early wet season (June) and lowest in the late dry season (March). Grazing had a positive effect on grass production by extending the growing season. Biomass production and graminoid leaf nitrogen concentration levels in the study area were similar to other tropical areas in the world. Also similar to other tropical large herbivore areas, the dry season poses an annual challenge for large herbivores in the study area —particularly the smaller bodied species—to satisfy their nutrient requirements.

Nutrient loading of Norway spruce seedlings hastens bud burst and enhances root growth after outplanting

We studied the effects of late season nutrient loading (NLOAD) on the timing of bud burst, growth and changes in nitrogen (N) concentrations in the first growing season after seedlings were outplanted. Two-year-old Norway spruce (Picea abies (L.) Karst.) seedlings with three foliar nitrogen concentration levels (NLOAD levels 11.3, 22.5 and 27.5 g N kg for L, M- and H-seedlings, respectively) were examined in the following three experiments: root growth capacity test (RGC), rooting experiment in the field and soil fertility experiment (‘rich’ or ‘poor’ soil) in the field. Bud burst in RGC was monitored daily and foliar N concentration (field experiments), height and root growth (rooting experiment) at monthly intervals. With respect to the RGC test, no differences in root growth were observed among the three NLOAD levels, but buds of H-seedlings burst 2–6 days earlier than others. In the rooting experiment, nutrient loading increased height and root growth but did not affect the timing of height growth. In the soil fertility experiment, foliar N of H- and M-seedlings decreased rapidly, but the decline was slower in rich soil. Current-year needles had more N in seedlings growing in rich soil and the N concentration declined until height growth ceased whereafter it increased until autumn. Improved growth from nutrient loading seems to last only for the first season after planting and the greatest benefits are enjoyed by seedlings planted in poor soils.-1