Maximum Rate Of Accumulation Research Articles

Effects of nitrogen regulation and strip intercropping on faba bean biomass, nitrogen accumulation and distribution, and interspecific interactions

AbstractEffects of nitrogen fertilization on the accumulation and distribution of biomass and plant nitrogen content in intercropped faba beans, together with its impact on the interspecific interactions between faba bean and wheat has not been well studied. Here, we have used a logistic model to analyze the cropping systems (i.e., monocropped faba bean, monocropped wheat, and faba bean intercropped with wheat) by evaluating the effects of different levels of nitrogen application on the dynamic changes in biomass and nitrogen accumulation, along with the interspecific interaction. Using monocropped and intercropped faba beans in field experiments spanning two years, we found that nitrogen application increased both monocropped and intercropped faba bean yields. The yield of intercropped faba beans was greatest at the lower nitrogen input for two consecutive years. Nitrogen application increased the biomass and nitrogen accumulation in both monocropped and intercropped faba beans. The simulation parameters that increased were maximum nitrogen accumulation (A') and maximum accumulation rate (R'max) while the initial cumulative rate (r') decreased. Compared with monocropping, intercropped faba bean–wheat showed increased yield and biomass accumulation, along with a significantly increased initial growth rate (r) and a maximum instantaneous growth rate (Rmax). Intercropping reduced stem and leaf biomass and the nitrogen distribution ratio while increasing the pod content. In the early intercropped faba bean growth stage, there was no competition for nutrients or any kind of yield advantage, while in the later stages, the nutrient competitiveness of intercropping was stronger than the intraspecific competition, showing the advantages of intercropping on biomass and yield (i.e., relative crowding coefficient [K] >1, relative interspecific competitiveness [RC] >0, and relative competition intensity [RCI] <0). In summary, nitrogen application of 45 kg ha–1 could be the desired amount that maximizes the nutrient competition and interspecific advantages in the middle and late stages of faba bean growth when intercropped, thus contributing to the yield.

Applicability of two-stage anoxic/oxic shortcut nitrogen removal via partial nitrification and partial denitrification for municipal wastewater by adding sludge fermentation products continuously

Partial nitrification and partial denitrification combined with anammox is a promising process for sewage treatment. In this study, real municipal wastewater was treated in a continuous two-stage anoxic/oxic (A/O) reactor. External mixed sludge fermentation products were added in the anoxic zone, simultaneously achieving partial nitrification and partial denitrification and achieving a high and relatively stable accumulation of nitrite. The maximum accumulation rates of NO2−-N in A1.2 and A2.1-A2.4 zones of the reactor reached 70% and 61%–37%, respectively, which improved denitrification efficiency and created conditions that supported the coupling of subsequent anammox. The influent nitrogen load of the system was 0.078 kg/(m3•d), and the mean influent and effluent total nitrogen were 51 and 12 mg/L, respectively. The mean total nitrogen removal rate reached 76%. Further analysis revealed that Hyphomicrobium (incomplete denitrifiers) and Nitrosomonas (ammonia oxidizing bacteria) were enriched, which may have facilitated the high nitrite accumulation. Moreover, the batch test showed that adding sludge fermentation during denitrification significantly suppressed nitrite reduction, resulting in the nitrite accumulation.

Reductive potential from cathode electrode as an option for the achievement of short-cut nitrification in bioelectrochemical systems

Nitrogen removal based on short-cut nitrification (SCN) have attract more attentions, in which stable nitrite accumulation is prerequisite. In this study, different reductive potential was applied to inhibit nitrite oxidizing bacteria for achievement of SCN in aerobic cathode chamber of bioelectrochemical systems with dissolved oxygen concentration of 3.5 mg/L. The results demonstrated that the applied potential facilitated nitrite accumulation with high ammonia oxidation rates. The maximum nitrate accumulation rate of 87.61% was obtained at −800 mV. The abundance of Nitrosomonas and Thauera increased while Nitrospira abundance declined with more negative reductive potentials. The activity of nitric oxide reductase was also evidently inhibited. The above-mentioned three genera were the keystone taxa in co-occurrence network with high degree and closeness centrality. Interestingly, total nitrogen (TN) removal was enhanced simultaneously in the absence of external organic carbon. Reductive potential would be a promising approach for achieving SCN and simultaneously TN removal.

Electrogeneration of hydrogen peroxide by oxygen reduction using anodized graphite felt

BackgroundElectrocatalytic synthesis of H2O2 by oxygen reduction is regarded as the most promising alternative to AO process, and thus, design of a cost-effective and highly active cathode of vital significance. MethodsThis work modified graphite felts via anodic oxidation process in NH4HCO3 aqueous, and demonstrated the electrogeneration of H2O2 by using modified graphite felt cathode. The surface properties of different modified graphite felt were investigated. Various conditions of the process, including potential, reaction pH, and O2 flux, were optimized. Significant findingsThrough the modification, the beneficial functional groups COO and C=O has considerable increased, which lead the kinetics of ORR enhanced and H2O2 electrochemical production increased. The maximum accumulation rate of H2O2 achieved 2.00 mg/h/cm2 at the conditions of -0.60 V (vs.SCE), 0.4 L/min oxygen flow rate and pH 3. The modified cathode kept a stable performance for H2O2 electrochemical synthesis during 5 cycles.

Quantifying the effect of low-temperature events on the grain quality formation of wheat

Protein and starch are the main components of nutritional quality in wheat grain, which are influenced by temperature. Since few studies have been aimed at quantifying the effect of low temperature on protein and starch formation in wheat, this study was undertaken to employ logistic functions for describing the dynamics of protein and starch accumulation in wheat grain, based on the datasets from two-year temperature-controlled experiments involving different low-temperature intensity, frequency and occurrence time with two genotypes. In general, low temperature had a substantial effect on the grain protein and starch concentrations of wheat and the obvious effect was detected when low temperatures applied at the booting stage. The accumulation of protein and starch decreased with the decreasing temperature and low-temperature duration extension for both Yangmai16 and Xumai30. In addition, the dynamics of protein and starch accumulation under different low-temperature conditions could be described well by logistic functions. The characteristic parameters of maximum accumulation per grain (K), maximum accumulation rate (Rmax) and average accumulation rate (Rmean) in the logistic functions decreased with decreasing temperature and increasing low-temperature duration, and then the active accumulation duration (D) was shortened. Moreover, the sensitivity of the parameters to low temperatures was different. The most sensitive parameters of protein and starch accumulation were K and Rmax for both Yangmai16 and Xumai30, while the least sensitive parameter was D, which indicates that the decreases in protein and starch accumulation under low-temperature treatment were mainly attributed to the maximum protein and starch accumulation per grain and the maximum accumulation rate.

Realization of nitrite accumulation in a sulfide-driven autotrophic denitrification process: Simultaneous nitrate and sulfur removal

The study was based on the removal of nitrate and sulfide, and aimed to nitrite accumulation. The process of autotrophic denitrification driven by sulfide as an electron donor was investigated in a sequencing batch reactor. The research showed that autotrophic denitrification successfully started on day 22, and the removal rates of NO3−-N and S2--S were 95.8% and 100%, respectively, when the S/N molar ratio was 1.45. When the S/N ratio was reduced to 0.94, the phenomenon of NO2−-N accumulation was observed. NO2−-N continuously accumulated, and the maximum accumulation rate was 55.3% when the S/N ratio was 0.8. In the batch test, the study showed that NO2−-N accumulation was optimal when the S/N ratio was 0.8, and the NO2−-N concentration increased with increasing NO3−-N concentration at the same S/N ratio. Microbial communities also changed based on the high-throughput analysis, and Proteobacteria (59.5%–84%) was the main phylum. Arenimonas (11.4%–28.2%) and uncultured_f_ Chromatiaceae (5.7%–27.5%) were the dominant bacteria, which complete denitrification and desulfurization throughout the operating system. Therefore, this study provided a theoretical basis for the simultaneous removal of NO3−-N and S2--S, as well as the accumulation of nitrite, and provided material support for anaerobic ammonia oxidation technology.

Weed Interference on Growth and Leaf Nutrient Accumulation in Two Cassava Varieties

The development of cassava varieties with more efficient nutrient absorption can prevent losses caused by weed competition. The objective of this study was to evaluate dry matter accumulation and leaf nutrient content in traditional and improved cassava varieties, with and without coexistence with weeds throughout the cycle. A randomized complete block design was used in a 2 x 2 x 11 factorial scheme with four replications. The first factor consisted of two varieties (Baianinha and Clone 56-03); the second factor was composed of the conditions with and without coexistence with weeds, and the third factor was 11 harvest periods. Coexistence with weeds reduced leaf contents of N (20.8% and 24.8%), P (26.7% and 4.6%) and K (27.1% and 12.6%) for 'Baianinha' and 'Clone 56-03', respectively. For coexistence with 'Baianinha', the period up to the maximum daily nutrient accumulation rate (N, P and K) ranged from 82 to 99 days after planting (DAP), while for 'Clone 56-03', coexistence in this period ranged from 80 to 88 DAP. The plants from the variety 'Clone 56-03' presented higher total dry mass and root dry mass accumulation, as well as higher leaf contents of N, P and K than the traditional cassava variety 'Baianinha', especially when in coexistence with weeds during the whole cycle.

Effect of the co‐digestion of agricultural lignocellulosic residues with manure from South American camelids

AbstractThis study aims to evaluate the effects of the co‐digestion of agricultural residues with manure from camelids from the Andean zone. Different combinations of llama manure (LM) and vicuñas (VM) were made with amaranth (AS), quinoa (QS), and wheat (WS) residues. They were fermented using sewage sludge as inoculum. The co‐digestion was evaluated under mesophilic conditions for 40 days. The ratios of volatile substances of substrate / co‐substrate evaluated were 0:100; 25:75; 50:50, 75:25, and 100:0. Two substrate / inoculum ratios (SIR 1:1 and SIR1:2) were also evaluated. The results indicate that the maximum methane accumulation rate is obtained in SIR 1:1 for a VM‐AS ratio (25:75) with 540 mL/g volatile solid (VS). In general, the results did not increase with the increase in inoculum; rather, the tendency to improve methane yield is associated with an increase in the amount of agricultural residues, mainly AS. Regarding the kinetic modeling, the transfer model is the one that best adjusted the predicted values to those observed with an r2 between 0.991 and 0.999, and an RMSE value between 2.06 and 13.62 mL/g (volatile solid) VS. Finally, all the trials presented synergistic effects in their co‐digestion except the digesters formed by LM‐AS, LM‐QS and LM‐WS of SIR 1:2. These presented antagonistic effects in which the addition of the co‐substrate generated competition with the substrates, reducing methane production. © 2021 Society of Chemical Industry and John Wiley & Sons, Ltd

Can sampling for vegetation characterisation surrogate for species richness? Case studies from the wet–dry tropics of northern Australia

Understanding the distribution of plant species and vegetation communities is important for effective conservation planning and ecosystem management, but many parts of the world remain under-surveyed. The Top End of Australia’s Northern Territory is vast, remote, and sparsely populated; knowledge of the flora, in many areas, is limited to common or dominant species. Here, we describe and contrast the benefits and trade-offs between two approaches to botanical survey – vegetation sampling (assessment of structural attributes and species composition, fundamentally for mapping purposes) and hybrid floristic survey (an intensive, inventory approach considering seasonality) – as applied in each of four remote areas of the Australian wet–dry monsoonal tropics. Hybrid floristic survey effectively doubled the species richness recorded within each study area, largely due to improved detections of forbs and sedges. Species-sampling effort relationships predicted hybrid floristic survey to consistently out-perform vegetation sampling in maximum species richness and rate of species accumulation. Although vegetation sampling offers an efficient means of circumscribing vegetation communities over large areas, hybrid floristic survey improved detection of seasonal species and, potentially, those of conservation concern. Strategic, proactive investment in hybrid floristic surveys may offer improved conservation outcomes and potential efficiency dividends in biodiversity conservation planning.

Defoliation intensity and leaf area index recovery in defoliated swards: implications for forage accumulation

This study evaluated the leaf area index (LAI) recovery mechanisms and forage accumulation rates on the regrowth of different grass species subjected to different defoliation intensities. For that purpose, plots of Pennisetum clandestinum (kikuyugrass), Lolium multiflorum (annual ryegrass), and Avena strigosa (black oats) were defoliated from 20 to 80 % of their initial heights (25, 20, and 25 cm, respectively). At different increments in height, forage samples were collected to ground level and used to estimate tiller population density (TPD), leaf area per tiller (LA), and forage mass. From these data, we calculated the leaf area index (LAI), average leaf area index (aLAI), and average and instantaneous forage accumulation rate (FAR and IFAR, respectively). Data were plotted over time (days) to describe LAI recovery and forage accumulation rates. As the defoliation intensity increased, greater canopy heights were needed for pastures to achieve their maximum forage accumulation rates, which required longer regrowth intervals. The need for high tiller recruitment after defoliation, which delayed canopy LAI recovery, seemed to be one of the main cause. Thus, grazing management strategies that involve costly tiller recruitment could decrease both overall forage production and sward persistence over time. However, the plant ability to recover LAI after successive intense defoliations seems to be species-dependent and related to their phenotypic plasticity.

Effect of controlled-release fertilizers on leaf characteristics, grain yield, and nitrogen use efficiency of machine-transplanted rice in southwest China

ABSTRACT Controlled-release fertilizers (CRFs) are known to improve grain yield and N-use efficiency (NUE) without intensive labor input in crop production. Here, we report field experiments conducted to investigate the effects of different CRFs [polymer coated complex fertilizer (PCCF), polymer-coated urea (PCU), and sulfur-coated urea (SCU)] on leaf characteristics, biomass, N uptake, grain yield, and NUE of machine-transplanted rice in Sichuan, China, from 2016 to 2017. Grain yield, N recovery efficiency (NRE), N agronomic efficiency (NAE), and N partial factor productivity (PFP) were positively correlated with improved leaf characteristics, dry matter accumulation, and N uptake. Total leaf area, leaf area, chlorophyll content, and net photosynthetic rate of the top three leaves, maximum accumulation rate of dry matter, and N accumulation, as well as panicles per m2 and spikelets per panicle were increased by CRFs, thereby increasing both grain yield and NUE. Furthermore, compared to PCCF and SCU, PCU promoted relatively higher leaf photosynthetic potential of the top three leaves, which is closely related to increased biomass and N uptake. These effects ultimately improved grain yield, NRE, NAE, and PFP under the PCU treatment. Thus, PCU is effective in enhancing grain yield and NUE in machine-transplanted rice.

Characteristics of microbial denitrification under different aeration intensities: Performance, mechanism, and co-occurrence network

This study aimed to explore how dissolved oxygen (DO) affected the characteristics and mechanisms of denitrification in mixed bacterial consortia. We analyzed denitrification efficiency, intracellular nicotinamide adenine dinucleotide (NADH), relative expression of functional genes, and potential co-occurrence network of microorganisms. Results showed that the total nitrogen (TN) removal rates at different aeration intensities (0.00, 0.25, 0.63, and 1.25 L/(L·min)) were 0.93, 1.45, 0.86, and 0.53 mg/(L·min), respectively, which were higher than previously reported values for pure culture. The optimal aeration intensity was 0.25 L/(L·min), at which the maximum NADH accumulation rate and highest relative abundance of napA, nirK, and nosZ were achieved. With increased aeration intensity, the amount of electron flux to nitrate decreased and nitrate assimilation increased. On one hand, nitrate reduction was primarily inhibited by oxygen through competition for electron donors of a certain single strain. On the other hand, oxygen was consumed rapidly by bacteria by stimulating carbon metabolism to create an optimal denitrification niche for denitrifying microorganisms. Denitrification was performed via inter-genus cooperation (competitive interactions and symbiotic relationships) between keystone taxa (Azoarcus, Paracoccus, Thauera, Stappia, and Pseudomonas) and other heterotrophic bacteria (OHB) in aeration reactors. However, in the non-aeration case, which was primarily carried out based on intra-genus syntrophy within genus Propionivibrio, the co-occurrence network constructed the optimal niche contributing to the high TN removal efficiency. Overall, this study enhanced our knowledge about the molecular ecological mechanisms of aerobic denitrification in mixed bacterial consortia and has theoretical guiding significance for further practical application.

3D Anatomy of a 60-year-old siliceous hot spring deposit at Hipaua-Waihi-Tokaanu geothermal field, Taupo Volcanic Zone, New Zealand

In 1941, a 72-m-deep bore (Healy's Bore 2; HB2) at the Hipaua-Waihi-Tokaanu geothermal field, Taupo Volcanic Zone, New Zealand, tapped alkali chloride water of 145 °C at the bottom of the well. Since then, thermal fluid (<100 °C) has intermittently flowed from the HB2 wellhead, resulting in formation of a 20 m wide by 50 m long sinter terrace. The discharging fluid at the vent was previously recorded to have a measured pH range of 7.5–8 and silica concentration of 263–287 mg/kg. The sinter terrace is dominated by low rimstone dams forming terracettes, where colorful brown, orange and pink microbial mats occur on surfaces bathed by the discharging fluid. In 2002, 11 shallow cores (up to 0.5 m deep, 3 cm diameter) were collected from the HB2 sinter terrace. Petrography, X-ray Powder Diffraction, X-Ray Fluorescence and Scanning Electron Microscopy were used to evaluate the stratigraphic, sedimentological and mineralogical character of the sinter. Surface and core samples allowed identification of six mid-temperature (<60 °C) sinter facies (conical peak, bubble mat, finely laminated, tufted peak, network, oncoidal), one low-temperature (<40 °C) sinter facies (palisade), and four tepid to dried (once wet) sinter facies (plant-rich, peloidal, clotted marsh). Sinter breccia also was common in the cores. The sinter is interbedded with sand, mud, detrital material and andesite fragments. Presence of kaolinite clay indicates localized secondary overprinting via acidic steam condensate. All sinter cores comprise opal-A silica. Based on the 1941 onset of spring flow with intermittent discharge from HB2 to 2002, and measured core thicknesses, we estimate a maximum sinter accumulation rate of 10 mm/yr close to the vent (core H9, 5 m S directly downslope from vent) and 3.5 mm/yr farthest from the discharge point (core H4, 22 m S directly downslope from vent). Yellow and pink stained horizons in the core indicate localized acidic steam overprinting of detrital sediments and sinter. Our sedimentological facies model illuminates the history of development of an immature, 60-year-old sinter terrace, providing insights into the complexity of sinter formation processes, depositional conditions, varying fluid flow regimes, channel migration pathways, biotic preservation and the effects of hydrothermal alteration in a rare 3D example of siliceous hot-spring build up over a known period of time. Such features are useful analogs in studies of hydrothermal settings associated with early life on Earth and possibly Mars.

Heavy Metal Contents in Animal Manure in China and the Related Soil Accumulation Risks

The environmental risks posed by heavy metals (HMs) in animal manure are increasing because of the use of trace metals as additives in feedstuffs. Manure samples were collected, and published literature was reviewed in this study to systematically analyze the HMs content in animal manure and compare the results to different sources of animal manures. Results show that the distribution of HMs content in animal manure was skewed. The ranges were between not detected (ND)-147 mg·kg-1 for Cd, ND-1919 mg·kg-1 for Pb, 0.003-2278 mg·kg-1 for Cr, ND-978 mg·kg-1 for As, ND-103 mg·kg-1 for Hg, ND-1747 mg·kg-1 for Cu, ND-11547 mg·kg-1 for Zn, and 1.22-1140 mg·kg-1 for Ni. The means (medians) of those elements were 2.31(0.72) mg·kg-1, 13.5(8.96) mg·kg-1, 36.3(12.0) mg·kg-1, 14.0(3.52) mg·kg-1, 0.97(0.07) mg·kg-1, 282(115) mg·kg-1, 656(366) mg·kg-1, and 21.8 (13.1) mg·kg-1 for Cd, Pb, Cr, As, Hg, Cu, Zn, and Ni, respectively. Means were significantly higher (1-13 times) than the medians. According to maximum limits of Cd, Pb, Cr, As, and Hg for organic fertilizers NY 525-2012, about 12.3% (for Cd), 2.58% (for Pb), 2.76% (for Cr), 20.6% (for As), and 3.69% (for Hg) of the data were above the limits. According to the composting regulations of Germany, about 53.9% (for Cu), 45.7% (for Zn), and 0.59% (for Ni) exceeded the maximum limits. The heavy metal contents in animal manure of different regions differs significantly. As and Cd contents in animal manure in the Shandong Province tend to be higher with their average values at 1.7 times and 10.1 times of the mean contents for national scale, respectively; the heavy metal contents in eastern China tend to be higher. Cd and As contents in animal manure tend to be higher in Northeast and Eastern China, while Cu and Zn contents were higher in Eastern and South China. After comparing HMs content in different sources of manures, we found that Cd, As, Hg, Cu, Zn, and Ni mean contents in pig manure were 1.0-3.0 times, 1.8-6.8 times, 1.1-15.8 times, 4.9-17.5 times, 2.7-12.0 times, and 1.7-2.1 times that of cattle manure, sheep manure, and poultry manure. The Pb content in poultry manure was the highest, with the mean being 2.8, 2.5, and 2.2 times higher than pig manure, cattle manure, and sheep manure, respectively. When recycling animal manure into the crop field, the accumulation rates for Cd were under 0.02 mg·(kg·a)-1 in over 90% of the circumstances and the accumulation rates for Pb were all below 0.15 mg·(kg·a)-1. When applying poultry manure, Cr in soil is easily accumulated with the maximum accumulation rate of 0.28 mg·(kg·a)-1.

The role of temperature in phenanthrene transfer and accumulation in crop leaves

Polycyclic aromatic hydrocarbons (PAHs) pollution has become a worldwide environmental problem, and the spread of PAHs can cause carcinogenicity, mutagenicity, and toxicity to humans. However, the transfer and accumulation of PAHs in crop leaves has not been clearly understood. In this study, we first reported that the environmental temperature could induce phenanthrene transfer and accumulation in hydrocultured wheat, corn and soybean leaves via vacuum-infiltration-centrifugation method. Phenanthrene accumulation rises significantly (p < 0.05) in the first 8 h and reaches the maximum accumulation rate at the 4th h. Then the accumulation turns stable in both apoplast and sympalst of wheat, soybean and corn leaves. Temperature is positively correlated with phenanthrene accumulation in apoplast and sympalst of soybean and corn leaves, and phenanthrene accumulation increases under lower temperature in apoplast and sympalst of wheat leaves. Temperature also displays a positive correlation with the phenanthrene accumulation under gradient phenanthrene treatments in both apoplast and sympalst. In addition, the wheat, corn and soybean leaves have the same phenanthrene accumulation pathways and symplast pathway is major for phenanthrene accumulation with the contribution over 55% in total phenanthrene accumulation. Meanwhile, based on the Elovich equation, the symplast and apoplast processes of phenanthrene accumulation are endothermic. In the end, our findings will offer a new understanding for phenanthrene transfer and accumulation pathway in plant leaves and put forward a new biological reference of PAHs transfer in environmental science.

Integrated soil-cotton management system enhances nitrogen use efficiency under different soil fertility levels

ABSTRACT An integrated soil-cotton management system integrated with optimal management practices is projected to replace the conventional management system for enhancing nitrogen use efficiency. Field experiment was conducted in the more and less fertile soil with two treatments. Results showed that compared with conventional management system, integrated soil-cotton management system increased 9.5–21.2% soil-available nitrogen during the middle and later growth stages, in addition, improved average and maximum accumulation rate of nitrogen by 30.4–36.2% and 39.9–45.1%, and postponed the start time of the fast nitrogen accumulation phase by 3–6d, resulting in 32.5–38.3% higher final nitrogen accumulation. Furthermore, the increased nitrogen accumulation improved leaf area index, leaf area duration and boll number, finally enhanced agronomic nitrogen use efficiency and recovery nitrogen use efficiency. We suggest the nitrogen-based fertilizer of integrated soil-cotton management system could be omitted completely in the more fertile soil to enhance physiological nitrogen use efficiency ultimately by optimizing leaf area index. In addition, the decrement of nitrogen use efficiency was diminished under integrated soil-cotton management system. These results demonstrate ISMS might be a more profitable pattern for nitrogen use efficiency of cotton, especially to meet the challenge of soil degradation in future.

Quantifying accumulation characteristics of glutelin and prolamin in rice grains.

Glutelin and prolamin are the two major proteins in rice grains. Grain content of glutelin is considerably higher than that of prolamin in rice, but there is limited information on the factors determining the different grain contents of glutelin and prolamin. To address this knowledge gap, the present study compared final weight per grain and accumulation characteristics of glutelin and prolamin in four rice cultivars. Results showed that final glutelin weight per grain was 3.24–3.95 times higher than final prolamin weight per grain. Glutelin and prolamin accumulation processes were well fitted by the logistic equation. The initial, maximum, and mean accumulation rates of glutelin were 1.69–4.67 times higher than those of prolamin. The active accumulation duration of glutelin was 2.9–5.1 d longer than that of prolamin. These results indicate that both higher accumulation rate and longer active accumulation duration are responsible for the higher final weight per grain of glutelin compared to prolamin in rice.

GROWTH AND NUTRIENT ACCUMULATION AND EXPORT IN A SHORT-DAY ONION

ABSTRACT New hybrid onions that are more productive are currently being cultivated. Information on growth and nutrient accumulation must thus be updated to assist in the refinement of existing recommendations, enabling the better exploitation of the productive potential of these new genotypes. We determined the growth of plants and the accumulation and export of nutrients of the short-day onion ‘Soberana’ established by direct seeding. The experimental design was a randomized block with four replicates and the treatments were evaluation times. Leaf number, tissue dry weight, nutrient accumulation, and the maximum daily rate of accumulation were evaluated throughout the growing cycle. The order of nutrient accumulation was (g plant-1) K (0.72) &gt; Ca (0.38) &gt; N (0.32) &gt; S (0.14) &gt; P (0.08) &gt; Mg (0.06) and (mg plant-1) Fe (2.26) &gt; Mn (1.43) &gt; Cu (0.93) &gt; Zn (0.91) &gt; B (0.85). Macronutrient demand was highest between 61 and 148 days after sowing (DAS), and micronutrient demand was highest between 70 and 148 DAS.

Mg ∕ Ca and &amp;lt;i xmlns=&amp;quot;&amp;quot;&amp;gt;δ&amp;lt;/i&amp;gt;&amp;lt;sup&amp;gt;18&amp;lt;/sup&amp;gt;O in living planktic foraminifers from the Caribbean, Gulf of Mexico and Florida Straits

Abstract. Past ocean temperatures and salinities can be approximated from combined stable oxygen isotopes (δ18O) and Mg ∕ Ca measurements in fossil foraminiferal tests with varying success. To further refine this approach, we collected living planktic foraminifers by net sampling and pumping of sea surface water from the Caribbean Sea, the eastern Gulf of Mexico and the Florida Straits. Analyses of δ18O and Mg ∕ Ca in eight living planktic species (Globigerinoides sacculifer, Orbulina universa, Neogloboquadrina dutertrei, Pulleniatina obliquiloculata, Globorotalia menardii, Globorotalia ungulata, Globorotalia truncatulinoides and Globorotalia tumida) were compared to measured in situ properties of the ambient seawater (temperature, salinity and δ18Oseawater) and fossil tests of underlying surface sediments. “Vital effects” such as symbiont activity and test growth cause δ18O disequilibria with respect to the ambient seawater and a large scatter in foraminiferal Mg ∕ Ca. Overall, ocean temperature is the most prominent environmental influence on δ18Ocalcite and Mg ∕ Ca. Enrichment of the heavier 18O isotope in living specimens below the mixed layer and in fossil tests is clearly related to lowered in situ temperatures and gametogenic calcification. Mg ∕ Ca-based temperature estimates of G. sacculifer indicate seasonal maximum accumulation rates on the seafloor in early spring (March) at Caribbean stations and later in the year (May) in the Florida Straits, related to the respective mixed layer temperatures of ∼26 ∘C. Notably, G. sacculifer reveals a weak positive linear relationship between foraminiferal derived δ18Oseawater estimates and both measured in situ δ18Oseawater and salinity. Our results affirm the applicability of existing δ18O and Mg ∕ Ca calibrations for the reconstruction of past ocean temperatures and δ18Oseawater reflecting salinity due to the convincing accordance of proxy data in both living and fossil foraminifers, and in situ environmental parameters. Large vital effects and seasonally varying proxy signals, however, need to be taken into account.

Transient responses of Wickerhamia sp. yeast continuous cultures to qualitative changes in carbon source supply: induction and catabolite repression of α-amylase synthesis

The purpose of this study was to evaluate the inductive effect of starch and maltose, and the repressive/inhibitory effect of glucose, on amy-1 gene expression and α-amylase production by Wickerhamia sp., using continuous culture under transient-state conditions at a dilution rate (D) of 0.083 h−1. Induction and repression kinetics of α-amylase were studied by changing the medium feed from glucose to maltose or starch in the induction experiments and vice versa in the repression experiments. Expression levels of amy-1 gene were measured by RT-qPCR. Results showed that starch was a more efficient inducer of α-amylase synthesis compared to maltose, with maximum accumulation rate constants of 0.424 and 0.191 h−1, respectively. In contrast, α-amylase synthesis in starch and maltose cultures was partially repressed by glucose as indicated by a specific activity close to basal levels and a decay constant rate (− 0.065 and − 0.069 h−1, respectively) higher than − D. A linear dependence of the specific rate of α-amylase production on mRNA relative abundance of amy-1 gene was observed. An inhibitory effect of glucose was not observed even at a concentration of 30 g L−1. In conclusion, the transient continuous culture is a useful tool to determine the qualitative and quantitative effects of maltose and starch on α-amylase induction and of glucose on enzyme repression, as well as to obtain a detailed understanding of the dynamic behavior of the yeast culture. Furthermore, results showed that amylaceous substrates can be very effective carbon sources for the production of α-amylase without being inhibited by glucose.