Fertilization Events Research Articles

The effect of nitrification inhibitors on NH3 and N2O emissions in highly N fertilized irrigated Mediterranean cropping systems

There is an increasing concern about the negative impacts associated to the release of reactive nitrogen (N) from highly fertilized agro-ecosystems. Ammonia (NH3) and nitrous oxide (N2O) are harmful N pollutants that may contribute both directly and indirectly to global warming. Surface applied manure, urea and ammonium (NH4+) based fertilizers are important anthropogenic sources of these emissions. Nitrification inhibitors (NIs) have been proposed as a useful technological approach to reduce N2O emission although they can lead to large NH3 losses due to increasing NH4+ pool in soils. In this context, a field experiment was carried out in a maize field with aiming to simultaneously quantify NH3 volatilization and N2O emission, assessing the effect of two NIs 3,4‑dimethilpyrazol phosphate (DMPP) and 3,4‑dimethylpyrazole succinic acid (DMPSA). The first treatment was pig slurry (PS) before seeding (50 kg N ha−1) and calcium ammonium nitrate (CAN) at top-dressing (150 kg N ha−1), and the second was DMPP diluted in PS (PS + DMPP) (50 kg N ha−1) and CAN + DMPSA (150 kg N ha−1) also before seeding and at top-dressing, respectively. Ammonia emissions were quantified by a micrometeorological method during 20 days after fertilization and N2O emissions were assessed using manual static chambers during all crop period. The treatment with NIs was effective in reducing c. 30% cumulative N2O losses. However, considering only direct N2O emissions after second fertilization event, a significant reduction was not observed using CAN+DMPSA, probably because high WFPS of soil, driven by irrigation, favored denitrification. Cumulative NH3 losses were not significantly affected by NIs. Indeed, NH3 volatilization accounted 14% and 10% of N applied in PS + DMPP and PS plots, respectively and c. 2% of total N applied in CAN+DMPSA and CAN plots. Since important NH3 losses still exist even although abating strategies are implemented, structural and political initiatives are needed to face this issue.

How shallow water table conditions affect N2O emissions and associated microbial abundances under different nitrogen fertilisations

Globally, agriculture is the largest source of nitrous oxide (N2O), a potent greenhouse gas (GHG). A recognised tool to prevent its loss from agricultural soils is the presence of a shallow water table. A four-year lysimeter experiment (2011–2014) was conducted in northeast Italy to investigate how water table levels affect N2O emissions after different N fertilisation techniques. Soil surface flux and groundwater-dissolved N2O were studied under free drainage and at two shallow water table levels (60 cm and 120 cm) and at two levels of N input (250 and 368 kg N ha−1 y−1), using dry manure in 2011 and 2012 and fresh manure in 2013 and 2014. DNA was extracted from soils and quantitative PCR (qPCR) was used to assess the size of nitrifying, denitrifying and N2-fixing bacterial communities. at three soil depths. The day after pre-seeding fertiliser incorporation, N2O emission started to be detected and continued for two-three weeks; brief measurable emissions also followed top–dressing fertilisation events. Cumulative N2O emission measured between 0.97 and 2.33 kg N2O-N ha−1 y−1, corresponding to emission factors from 0.4% to 1.1%. Manure fertilisation significantly affected the N dose only when applied as fresh manure. Water-filled pore space (WFPS) affected daily N2O emissions with a significant interaction with fertilisation level. The two N input levels showed differences only when WFPS was >40%, which revealed N availability as key to increased N2O emissions at high water content, supposedly by fostering anaerobic denitrification. No significant relationships were observed between peak N2O emissions and the values of the temperature or irrigation variables recorded during the experimental observation period. Groundwater dissolved N2O-N concentrations measured about 1.7 μg L−1 with some peak variability from nitrate leaching. Quantitative PCR assays demonstrated that shifts in microbial population that can be involved in oxidation processes and heterotrophic denitrification occurred in the soil, even though the contributions of the different N pathways on N2O emissions were indistinguishable. Indeed, both nitrifying and denitrifying genes were simultaneously promoted by the high fertilisation input and hindered by the high water table level. Shallow groundwater conditions appeared to reduce N2O emissions probably by favouring complete denitrification. These results suggest that in the Po Plain, regulated by the Nitrate Directive, shallow groundwater conditions, with a balanced N input, may mitigate air and water pollution.

Cordilleran ice-sheet growth fueled primary productivity in the Gulf of Alaska, northeast Pacific Ocean

Fertilization of the ocean by eolian dust and icebergs is an effective mechanism to enhance primary productivity. In particular, high-nutrient, low-chlorophyll (HNLC) areas where phytoplankton growth is critically iron-limited, such as the subarctic Pacific Ocean and the Southern Ocean, are proposed to respond to increases in bioavailable Fe supply with enhanced phytoplankton productivity and carbon export to the seafloor. While Fe-fertilization from dust is widely acknowledged to explain a higher export production during glacial periods in the Southern Ocean, paleoceanographic records supporting links between productivity and eolian dust and/or icebergs in the North Pacific are scarce. By combining independent proxies indicative of ice-sheet dynamics and ocean productivity from a single marine sedimentary record (Integrated Ocean Drilling Program [IODP] Site U1417), we present a comprehensive data set of phytoplankton response to different fertilization mechanisms in the subarctic northeast Pacific between 1.5 and 0.5 Ma, including the Mid Pleistocene Transition. Importantly, the timing of the fertilization events is more strongly controlled by local ice-sheet extent than by glacial-interglacial climate variability. Our findings indicate that fertilization by glacigenic debris results in productivity events in HNLC areas adjacent to ice sheets, and that this mechanism may represent an important, yet rarely considered, driver of phytoplankton growth.

Acrosomal alkalization triggers Ca2+ release and acrosome reaction in mammalian spermatozoa.

The sperm acrosome reaction (AR), an essential event for mammalian fertilization, involves Ca2+ permeability changes leading to exocytosis of the acrosomal vesicle. The acrosome, an intracellular Ca2+ store whose luminal pH is acidic, contains hydrolytic enzymes. It is known that acrosomal pH (pHacr ) increases during capacitation and this correlates with spontaneous AR. Some AR inducers increase intracellular Ca2+ concentration ([Ca2+ ]i ) through Ca2+ release from internal stores, mainly the acrosome. Catsper, a sperm specific Ca2+ channel, has been suggested to participate in the AR. Curiously, Mibefradil and NNC55-0396, two CatSper blockers, themselves elevate [Ca2+ ]i by unknown mechanisms. Here we show that these compounds, as other weak bases, can elevate pHacr , trigger Ca2+ release from the acrosome, and induce the AR in both mouse and human sperm. To our surprise, μM concentrations of NNC55-0396 induced AR even in nominally Ca2+ free media. Our findings suggest that alkalization of the acrosome is critical step for Ca2+ release from the acrosome that leads to the acrosome reaction.

Porcine Cell-Free System to Study Mammalian Sperm Mitophagy.

A cell-free system using oocyte extracts is a valuable tool to study early events of animal fertilization and examine protein-protein interactions difficult to observe in whole cells. The process of postfertilization sperm mitophagy assures timely elimination of paternal, sperm-contributed mitochondria carrying potentially corrupted mitochondrial DNA (mtDNA). Cell-free systems would be especially advantageous for studying postfertilization sperm mitophagy as large amounts of oocyte extracts can be incubated with hundreds to thousands of spermatozoa in a single trial, while only one spermatozoon per zygote can be examined by whole-cell approaches. Since sperm mitophagy is species-specific, the abundantly available frog egg extracts commonly used for cell-free systems have to be replaced with isospecific mammalian oocyte extracts, which are difficult to obtain. Here we describe the protocol for a mammalian, porcine cell-free system consisting of permeabilized domestic boar spermatozoa co-incubated with cell extracts from porcine oocytes, suitable for studying the interactions of maternal, oocyte-derived mitophagy factors with paternal, sperm mitochondria.

Toxicity of marine pollutants on the ascidian oocyte physiology: an electrophysiological approach.

In marine animals with external fertilization, gametes are released into seawater where fertilization and embryo development occur. Consequently, pollutants introduced into the marine environment by human activities may affect gametes and embryos. These xenobiotics can alter cell physiology with consequent reduction of fertilization success. Here the adverse effects on the reproductive processes of the marine invertebrate Ciona intestinalis (ascidian) of different xenobiotics: lead, zinc, an organic tin compound and a phenylurea herbicide were evaluated. By using the electrophysiological technique of whole-cell voltage clamping, the effects of these compounds on the mature oocyte plasma membrane electrical properties and the electrical events of fertilization were tested by calculating the concentration that induced 50% normal larval formation (EC50). The results demonstrated that sodium currents in mature oocytes were reduced in a concentration-dependent manner by all tested xenobiotics, with the lowest EC50 value for lead. In contrast, fertilization current frequencies were differently affected by zinc and organic tin compound. Toxicity tests on gametes demonstrated that sperm fertilizing capability and fertilization oocyte competence were not altered by xenobiotics, whereas fertilization was inhibited in zinc solution and underwent a reduction in organic tin compound solution (EC50 value of 1.7 µM). Furthermore, fertilized oocytes resulted in a low percentage of normal larvae with an EC50 value of 0.90 µM. This study shows that reproductive processes of ascidians are highly sensitive to xenobiotics suggesting that they may be considered a reliable biomarker and that ascidians are suitable model organisms to assess marine environmental quality.

Conversion of grazed pastures to energy cane as a biofuel feedstock alters the emission of GHGs from soils in Southeastern United States

The cultivation of energy cane throughout the Southeastern United States may displace grazed pastures on organic soil (Histosols) to meet growing demands for biofuels. We combined results from a field experiment with a biogeochemical model to improve our understanding of how the conversion of pasture to energy cane during early crop establishment affected soil GHG (CO2, CH4, and N2O) exchange with the atmosphere. GHG fluxes were measured under both land uses during wet, hot and cool, dry times of year, and following a fertilization event. We also simulated the impact of changes in precipitation on GHG exchange. Higher fertilization of cane contributed to greater emission of N2O than pasture during warmer and wetter times of the year. The model predicted that energy cane emitted more nitrogen than pasture during simulated wetter than drier years. The modeled emission factor for N2O was 20 to 30-fold higher than the default value from IPCC (1%), suggesting that the default IPCC value could dramatically underestimate the consequences of this land conversion on the climate system. Predicted soil CH4 and CO2 fluxes were higher in pasture than energy cane, and this difference was not affected by increasing precipitation. Model simulations predicted that soils under first year cane emit more GHGs than pasture, particularly during wet years, but this difference disappeared two years after energy cane establishment. Our results suggest that management practices may be important in determining soil GHG emissions from energy cane on organic soils particularly during the first year of cane establishment.

Focused time-lapse analysis reveals novel aspects of human fertilization and suggests new parameters of embryo viability.

Can focused application of time-lapse microscopy (TLM) lead to a more detailed map of the morphokinetics of human fertilization, revealing novel or neglected aspects of this process? Intensive harnessing of TLM reveals novel or previously poorly characterised phenomena of fertilization, such as a cytoplasmic wave (CW) preceding pronuclear formation and kinetics of pronuclear chromatin polarization, thereby suggesting novel non-invasive biomarkers of embryo quality. In recent years, human preimplantation development has been the object of TLM studies with the intent to develop morphokinetic algorithms able to predict blastocyst formation and implantation. Regardless, our appreciation of the morphokinetics of fertilization remains rather scarce, currently including only times of polar body II (PBII) emission, pronuclear appearance and fading, and first cleavage. This is not consistent with the complexity and importance of this process, calling for further TLM studies aimed at describing previously unrecognized or undetected morphokinetic events and identifying novel developmental biomarkers. The study involved a retrospective observation by TLM of the fertilization process in 500 oocytes utilized in consecutive ICSI cycles carried out in 2016. A maximum of five fertilized oocytes per patients were included in the analysis to reduce possible patient-specific biases. Oocytes of patients with different diagnoses of infertility where included in the analysis, while cases involving cryopreserved gametes or surgically retrieved sperm were excluded. Microinjected oocytes where assessed by a combined TLM-culture system (Embryoscope). Oocytes that were not amenable to TLM assessment, due to excess of residual corona cells or inadequate orientation for the observation of PBII emission, were not analysed. We identified and monitored 28 parameters relevant to meiotic resumption, pronuclear dynamics, chromatin organization, and cytoplasmic/cortical modifications. Times (T) were expressed as mean ± SD hours post-insemination (p.i.) and analysed, where appropriate, by Paired T Student or Fisher's exact tests. PBII emission was occasionally followed (4.3% of cases) by the transient appearance of a protrusion of the cell surface, the fertilization cone (FC), probably resulting from interaction of the male chromatin with the oocyte cortex. Pronuclear formation was always preceded by a radial CW originating from the initial position of the male pronucleus (PN) and extending towards the oocyte periphery. The appearance of the CW followed a precise sequence, occurring always 2-3 h after PBII emission and shortly before PN appearance. Male and female PN appeared virtually simultaneously at approximately 6.2 h p.i. However, while the female PN always formed cortically and near the site of emission of the PBII, the initial position of the male PN was cortical, intermediate, or central (15.2%, 31.2% and 53.6%, respectively). PN juxtaposition involved rapid and straight movement of the female PN towards the male PN. In addition, the initial position of male PN formation was predictive of the position of PN juxtaposition. It was also observed that nucleolar precursor bodies (NPBs) aligned along the juxtaposition area and this happened considerably earlier for the female PN (8.2 ± 2.6 vs.11.2 ± 4.1 h, P = 0.0001). Although it occurred rarely, displacement of juxtaposed PN to the cortex was strongly associated (P < 0.0001) with direct cleavage into three blastomeres at the first cell division. The times of PN breakdown and first cleavage showed a very consistent trend, occurring earlier or progressively later depending on whether initial male PN positioning was central, intermediate or cortical, respectively. Finally, time intervals between discrete fertilization events were strongly associated with embryo quality on Day 3. For example, longer intervals between disappearance of the cytoplasmic halo and PN breakdown were highly predictive of reduced blastomere number and increased fragmentation (P = 0.0001). N/A. Some of the morphokinetic parameters assessed in this study may require better definition to reduce inter-operator annotation variability. To our knowledge, overall, these data represent the most detailed morphokinetic description of human fertilization. Many of the illustrated parameters are novel and may be amenable to further elaboration into algorithms able to predict embryo quality, as suggested by the findings presented in this study. None.

Yield, Fruit Quality Traits, and Leaf Nutrient Concentration of ‘Prolific’ Sapodilla Grafted onto Seedlings of 16 Sapodilla Rootstocks in Puerto Rico

Research on sapodilla (Manilkara zapota) has been very limited. A field study was conducted to determine the yield potential, fruit quality traits, leaf nutrient composition, and scion/rootstock compatibility of ‘Prolific’ sapodilla grafted onto 16 sapodilla rootstock seedlings. For this purpose, seedlings (maternal half-sibs) of cultivars Adelaide, Arcilago, Aruz, Blackwood, Blocksberg, Guilbe, Hanna, Jamaica-1, Larsen, Mendigo-1, Gallera, Morning Star, Russel, Prolific, Timothe, and Vasallo-1 were used as rootstock seedlings and evaluated during 7 years of production at Isabela, PR. Year showed a significant effect on the number of fruit per hectare, yield, individual fruit weight, fruit length and diameter, and total soluble solids. Rootstock seedlings had a significant effect on the number of fruit per hectare, yield, and individual fruit weight but had no effect on other fruit traits. The year × rootstock interaction was not significant for any of the variables measured in the study. Rootstock seedlings ‘Timothe’, ‘Vasallo-1’, ‘Larsen’, and ‘Aruz’ had the highest 7-year mean for number and the yield of fruit averaging 4479 fruit/ha and 1245 kg·ha−1, respectively. ‘Timothe’ and ‘Vasallo-1’ significantly out yielded the ‘Prolific’ rootstock seedling. The number of fruit per hectare and corresponding yield obtained in this study were very low probably as the result of wind exposure, the presence of the fungus Pestalotia causing floral necrosis, or both. Scion/rootstock incompatibility was not the cause of the low yield performance of grafted trees. The average individual weight of fruit was 282 g and ranged from 264 to 303 g. Averaged over rootstock seedlings, leaf tissue nutrient concentration did not vary greatly over time. Moreover, tissue nutrient concentration was similar before and after fertilization events.

Genetic-genealogy approach reveals low rate of extrapair paternity in historical Dutch populations.

Evolutionary theory has shown that seeking out extrapair paternity (EPP) can be a viable reproductive strategy for both sexes in pair-bonded species, also in humans. As yet, estimates of the contemporary or historical EPP rate in human population are still rare. In the present study, we estimated the historical EPP rate in the Dutch population over the last 400 years and compared the rate with those obtained for other human populations to determine the evolutionary, cultural, and socio-demographic factors that influence human cuckoldry behavior. We estimated the historical EPP rate for the Dutch population via the "genealogical pair method", in which the EPP rate is derived from Y-chromosome mismatches between pairs of individuals that, based on genealogical evidence, share a common paternal ancestor. Based on the analysis of 68 representative genealogical pairs, separated by a total of 1013 fertilization events, we estimated that the historical EPP rate for the Dutch population over the last 400 years was 0.96% per generation (95% confidence interval 0.46%-1.76%). The Dutch EPP rate fits perfectly within the range reported for other contemporary and historical populations in Western Europe and was highly congruent with that estimated for neighboring Flanders, despite the socio-economic and religious differences between both populations. The estimated low EPP rate challenges the "dual mating strategy hypothesis" that states that women could obtain fitness benefits by securing investment from one man while cuckolding him to obtain good genes from an affair partner.

Long term farming systems affect soils potential for N2O production and reduction processes under denitrifying conditions

N2O is a potent greenhouse gas with an atmospheric lifetime of 114 years which also contributes to ozone layer destruction. Mitigating N2O emissions is especially challenging to the agricultural sector that is responsible for the majority of anthropogenic N2O release. In order to develop effective mitigation strategies, a detailed understanding of drivers for N2O production and reduction in agriculturally managed soils is needed. Denitrification is recognized as one of the most important source processes for N2O emissions from soils. However, the last step in denitrification, the reduction of N2O to N2 is the only known sink for N2O in soil. Although the impact of single parameters on denitrification is quite well documented, there is still a knowledge gap when it comes to the impact of complex farming systems on N2O production and reduction. In this experiment, we incubated soil samples from the DOK long term field trial in Therwil/Switzerland comparing organic (BIOORG) and conventional (CONMIN) farming systems with an a non-fertilized control (NOFERT). Soil samples were incubated under 90% WFPS after fertilization with NH415NO3 equivalent to a moderate fertilization event in the field with 40 kg N ha−1. In order to assess soil's potential for N2O production and reduction, we combined direct measurements of denitrification end products N2O and N2 with molecular analysis of functional denitrifying communities involved in NO2− and N2O reduction on DNA and mRNA levels. In order to monitor N cycling processes under the chosen conditions, stable isotope tracing was employed to quantify nitrification and NO3− consumption rates. Results revealed increased NO3− consumption and greatest potential for N2O emissions in BIOORG as a result of increased soil organic carbon contents. Production of N2 was similar in BIOORG and CONMIN and significantly lower in NOFERT, most likely due to significantly decreased pH inhibiting N2O reduction. This caused the greatest N2O/(N2O + N2) ratios in NOFERT (0.88 ± 0.02) followed by BIOORG (0.79 ± 0.01) and CONMIN (0.68 ± 0.02) (p < 0.001). Lowest N2O/(N2O + N2) ratios in CONMIN were reflected by lowest N2O emissions and coincided with elevated nosZ transcript copies in the beginning of incubation. Although highest N2O emissions in BIOORG were detected, the incubation setup cannot directly be translated to field conditions. Nevertheless, our results emphasize that farming system induced changes on soil geochemical parameters like soil pH and soil organic carbon affect microbial N2O production and reduction processes during denitrification.

Nitrogen oxides and ozone fluxes from an oilseed-rape management cycle: the influence of cattle slurry application

Abstract. This study reports NO, NO2 and O3 mixing ratios and flux measurements using the eddy covariance method during a 7-month period over an oilseed-rape field, spanning an organic and a mineral fertilisation event. Cumulated NO emissions during the whole period were in agreement with previous studies and showed quite low emissions of 0.26 kg N ha−1 with an emission factor of 0.27 %, estimated as the ratio between total N emitted in the form of NO and total N input. The NO emissions were higher following organic fertilisation in August due to conditions favouring nitrification (soil water content around 20 % and high temperatures), while mineral fertilisation in February did not result in high emissions. The ozone deposition velocity increased significantly after organic fertilisation. The analysis of the chemical and turbulent transport times showed that reactions between NO, NO2 and O3 below the measurement height occurred constantly throughout the 7-month period. Following organic fertilisation, the NO ground fluxes were 30 % larger than the NO fluxes at the measurement height (3.2 m), while the NO2 fluxes switched from deposition to emission during certain periods, being negative at the surface and positive at the measurement height. This phenomenon of apparent NO2 emissions appears to be significant during strong NO emissions and high O3 ambient mixing ratios, even on a bare soil during August.

Assessment of pollen viability of some sweet cherry cultivars used in plant breeding in Extremadura, Spain

Pollen performance depends on several factors, one of which is pollen germination capacity. Pollen germination on stigma is an essential event for proper fertilization in seed producing plants. In the context of plant breeding, it is of great importance to assess pollen viability of the different cultivars involved in breeding in the first stages of the program, and thus optimize resources. In this work we have analyzed the pollen viability of pollen from sweet cherry cultivars intended to be used in obtaining new cultivars to secure a suitable positioning of cherry in the coming decades in Extremadura. Through in vitro culture, staining, and microscopy methods we assessed the pollen viability of 16 cherry cultivars from two different collections. At the same time, we attempted to identy differences in the pollen viability of the same cultivars from both locations (a traditional cherry cultivation place and a much warmer and dryer field) and tried to link them to an eventual global warming scenario. Different germination percentages were found among both approaches, in different cultivars located in the same place and the same cultivars from two different locations. The cultivars '7-91-C', 'Celeste', 'Sweetheart' and 'Van' reached the higuest pollen germination levels in both locations, being therefore suitable cultivars to use in a regional breeding program.

Effect of nitrification inhibitors on mitigating N2O and NO emissions from an agricultural field under drip fertigation in the North China Plain

N2O and NO emissions from a winter wheat-summer maize rotation field with five different treatments in the North China Plain (NCP) were comparably investigated from 8 October 2014 to 11 October 2015. Compared with the treatments with only flood or drip irrigation, evident emission peaks of N2O and NO from the fertilization treatments with flood irrigation (A-Flood) and with drip fertigation (A-Drip) were observed after each fertilization event, whereas their emissions from the fertilization treatments with nitrification inhibitors under drip fertigation (A+DCD-Drip and A+Nitrapyrin-Drip) were greatly suppressed. The reduction effect of the nitrification inhibitors on N2O and NO emissions was found to be more conspicuous during the maize season than during the wheat season, implying that the soil temperature could play an important role in the reduction effect. Compared with the A-Flood treatment, the annual cumulative emission from the A-Drip treatment reduced by 22% for N2O and increased by 18% for NO, whereas the reductions of N2O and NO from the treatments with nitrification inhibitors could achieve as high as 66% and 95%, respectively. The yields of the maize were significantly greater from the A-Drip and A+Nitrapyrin-Drip treatments than from the A-Flood treatment, and the yields of the wheat were almost same among the treatments of A-Flood, A-Drip and A+DCD-Drip. Considering the yields, the water saving and the reduction of N2O and NO emissions, the application of nitrification inhibitor combined with drip fertigation is recommended in the NCP.

Genetic diversity within and among aecia of the wheat rust fungus Puccinia striiformis on the alternate host Berberis vulgaris

An isolate of the fungus Puccinia striiformis, causing yellow (stripe) rust on cereals and grasses, was selfed on the alternate (sexual) host, Berberis vulgaris. This enabled us to investigate genetic variability of progeny isolates within and among aecia. Nine aecial clusters each consisting of an aecium (single aecial cup) and nine clusters containing multiple aecial cups were selected from 18 B. vulgaris leaves. Aeciospores from each cluster were inoculated on susceptible wheat seedlings and 64 progeny isolates were recovered. Molecular genotyping using 37 simple sequence repeat markers confirmed the parental origin of all progeny isolates. Thirteen molecular markers, which were heterozygous in the parental isolate, were used to analyse genetic diversity within and among aecial cups. The 64 progeny isolates resulted in 22 unique recombinant multilocus genotypes and none of them were resampled in different aecial clusters. Isolates derived from a single cup were always of the same genotype whereas isolates originating from clusters containing up to nine aecial cups revealed one to three genotypes per cluster. These results implied that each aecium was the result of a successful fertilization in a corresponding pycnium and that an aecium consisted of genetically identical aeciospores probably multiplied via repetitive mitotic divisions. Furthermore, the results suggested that aecia within a cluster were the result of independent fertilization events often involving genetically different pycniospores. The application of molecular markers represented a major advance in comparison to previous studies depending on phenotypic responses on host plants. The study allowed significant conclusions about fundamental aspects of the biology and genetics of an important cereal rust fungus.

Environmental and biological cues for spawning in the crown-of-thorns starfish.

Sporadic outbreaks of the coral-eating crown-of-thorns starfish are likely to be due, at least in part, to spatial and temporal variation in reproductive and settlement success. For gonochoric and broadcast spawning species such as crown-of-thorns starfish, spawning synchrony is fundamental for achieving high rates of fertilization. Highly synchronized gamete release within and among distinct populations is typically the result of the entrainment of neurohormonal endogenous rhythms by cues from the environment. In this study, we conducted multiple spawning assays to test the effects of temperature change, reduced salinity and nutrient enrichment of seawater, phytoplankton, gametes (sperm and eggs), and the combined effect of sperm and phytoplankton on the likelihood of spawning in male and female crown-of-thorns starfish. We also investigated sex-specific responses to each of these potential spawning cues. We found that (1) abrupt temperature change (an increase of 4°C) induced spawning in males, but less so in females; (2) males often spawned in response to the presence of phytoplankton, but none of the females spawned in response to these cues; (3) the presence of sperm in the water column induced males and females to spawn, although additive and synergistic effects of sperm and phytoplankton were not significant; and (4) males are more sensitive to the spawning cues tested and most likely spawn prior to females. We propose that environmental cues act as spawning ‘inducers’ by causing the release of hormones (gonad stimulating substance) in sensitive males, while biological cues (pheromones) from released sperm, in turn, act as spawning ‘synchronizers’ by triggering a hormonal cascade resulting in gamete shedding by conspecifics. Given the immediate temporal linkage between the timing of spawning and fertilization events, variability in the extent and synchronicity of gamete release will significantly influence reproductive success and may account for fluctuations in the abundance of crown-of-thorns starfish.

Planned conventional fertilization compared to intracytoplasmic sperm injection improves pregnancy rates in patients with unexpalined infertilty

While intracytoplasic sperm injection (ICSI) reduces the rare event of failed fertilization among couples with unexplained infertility, it is unclear as to whether it improves fertilization and pregnancy rates compared to conventional fertilization. To compare the fertilization, implantation, and pregnancy rates following ICSI versus conventional insemination in couples with unexplained infertility. This was a retrospective cohort study of women with a diagnosis of unexplained infertility undergoing autologous in vitro fertilization (IVF) with an antagonist. The cohort included 3,281 fresh antagonist IVF cycles performed between January 1, 2013 and December 31, 2015 at 14 clinics in the IntegraMed Fertility Network. Fertilization method was determined from the treatment plan. Fertilization, implantation, and pregnancy rates were compared using Student T-test an Chi-square analysis where appropriate Subsequent binomial regression models were constructed to determine the probability of ultrasound confirmed pregnancy adjusting for age, nulligravidity, history of prior IVF, race (White: yes/no), and using a cluster term for each clinic. Women prescribed ICSI (N=1879) tended to be older (34.8 ± 3.85 years versus 34.3 ± 3.78), were more likely to be white (68% versus 61%), were less likely to be nulligravid (46% versus 50%), and more likely to have done a prior IVF cycle (39% versus 26%) compared to women prescribed conventional fertilization. The fertilization, implantation and pregnancy rates for ICSI fertilization was significantly lower when compared to conventional fertilization (Table 1). Compared to conventional insemination, ICSI reduced the probability of pregnancy by 10% (relative risk [RR] 0.90 [95% CI 0.82 – 0.99]) in unadjusted and adjusted models (RR 0.91 [95% CI 0.83 – 0.99]). For patients with unexplained Infertility undergoing an antagonist IVF cycle, ICSI significantly reduces fertilization, pregnancy, and implantation rates compared to conventional fertilization.

Linkage between N2O emission and functional gene abundance in an intensively managed calcareous fluvo-aquic soil

The linkage between N2O emissions and the abundance of nitrifier and denitrifier genes is unclear in the intensively managed calcareous fluvo-aquic soils of the North China Plain. We investigated the abundance of bacterial amoA for nitrification and narG, nirS, nirK, and nosZ for denitrification by in situ soil sampling to determine how the abundance of these genes changes instantly during N fertilization events and is related to high N2O emission peaks. We also investigated how long-term incorporated straw and/or manure affect(s) the abundance of these genes based on a seven-year field experiment. The overall results demonstrate that the long-term application of urea-based fertilizer and/or manure significantly enhanced the number of bacterial amoA gene copies leading to high N2O emission peaks after N fertilizer applications. These peaks contributed greatly to the annual N2O emissions in the crop rotation. A significant correlation between annual N2O emissions and narG, nirS, and nirK gene numbers indicates that the abundance of these genes is related to N2O emission under conditions for denitrification, thus partly contributing to the annual N2O emissions. These findings will help to draw up appropriate measures for mitigation of N2O emissions in this ‘hotspot’ region.

Emissions of Fe(II) and its kinetic of oxidation at Tagoro submarine volcano, El Hierro

Abstract The eruptive process that took place in October 2011 in the submarine volcano Tagoro off the Island of El Hierro and the subsequent degasification stage, five months later, have increased the concentration of TdFe(II) (Total dissolved iron(II)) in the waters nearest to the volcanic edifice. In order to detect any variation in concentrations of TdFe(II) due to hydrothermal emissions, three cruises were carried out two years after the eruptive process in October 2013, March 2014 and May 2015. The results from these cruises confirmed important positive anomalies in TdFe(II), which coincided with negatives anomalies in pHF,is (pH in free scale, at in situ conditions) located in the proximity of the main cone. Maximum values in TdFe(II) both at the surface, associated to chlorophyll a maximum, and at the sea bottom, were also observed, showing the important influence of organic complexation and particle re-suspension processes. Temporal variability studies were carried out over periods ranging from hours to days in the stations located over the main and two secondary cones in the volcanic edifice with positive anomalies in TdFe(II) concentrations and negative anomalies in pHF,is values. Observations showed an important variability in both pHF,is and TdFe(II) concentrations, which indicated the volcanic area was affected by a degasification process that remained in the volcano after the eruptive phase had ceased. Fe(II) oxidation kinetic studies were also undertaken in order to analyze the effects of the seawater properties in the proximities of the volcano on the oxidation rate constants and t1/2 (half-life time) of ferrous iron. The increased TdFe(II) concentrations and the low associated pHF,is values acted as an important fertilization event in the seawater around the Tagoro volcano at the Island of El Hierro providing optimal conditions for the regeneration of the area.

Measurement and modeling of nitrous and nitric oxide emissions from a tea field in subtropical central China

Tea fields represent an important source of nitrous oxide (N2O) and nitric oxide (NO) emissions due to high nitrogen (N) fertilizer applications and very low soil pH. To investigate the temporal characteristics of N2O and NO emissions, daily emissions were measured over 2½ years period using static closed-chamber/gas chromatograph and chemiluminescent measurement system in a tea field of subtropical central China. Our results revealed that N2O and NO fluxes showed similar temporal trends, which were generally driven by temporal variations in soil temperature and soil moisture content and were also affected by fertilization events. The measured average annual N2O and NO emissions were 10.9 and 3.3 kg N ha−1 year−1, respectively, highlighting the high N2O and NO emissions from tea fields. To improve our understanding of N-cycling processes in tea ecosystems, we developed a new nitrogenous gas emission module for the water and nitrogen management model (WNMM, V2) that simulated daily N2O and NO fluxes, in which the NO was simulated as being emitted from both nitrification and nitrite chemical decomposition. The results demonstrated that the WNMM captured the general temporal dynamics of N2O (NSE = 0.40; R2 = 0.52, RMSE = 0.03 kg N ha−1 day−1, P < 0.001) and NO (NSE = 0.41; R2 = 0.44, RMSE = 0.01 kg N ha−1 day−1, P < 0.001) emissions. According to the simulation, denitrification was identified as the dominant process contributing 76.5% of the total N2O emissions, while nitrification and nitrite chemical decomposition accounted for 52.3 and 47.7% of the total NO emissions, respectively.