Effects Of Nutrient Availability Research Articles

Fertilization benefits the facultative parasitic plant Rhamphicarpa fistulosa while gains by the infected host Oryza sativa are marginalized.

Rhamphicarpa fistulosa (Hochst.) Benth. is an annual facultative parasitic plant adapted to hydromorphic soils. In sub-Saharan Africa it causes high crop losses as a weed in rainfed lowland rice (Oryza sativa L.). Fertilizers are often proposed as a control measure against hemiparasitic weeds, but an understanding of the nutrient effects on R. fistulosa is currently still elusive. In two greenhouse pot experiments, conducted in 2016 in the Netherlands and in 2019 in the UK, host plants (O. sativa, cv IR64) and parasitic plants (R. fistulosa) were grown alone or combined and were subjected to different levels of nutrient availability. Biomass measurements were used to assess whether and how effects of nutrient availability are expressed in the host and parasite. Compared with parasite-free host plants, the biomass of parasite-infested plants was severely reduced, and nutrient effects on host plant biomass were less pronounced. Conversely, increased nutrient availability did not have an effect on parasitic plants when grown alone, but when grown with a host the parasitic plant biomass increased proportionally. Grown together, the combined biomass of host plant and parasite was substantially lower than that of the host plant grown alone. The ratio of biomass between host plant and parasite was unaffected by nutrient availability. Fertilization benefits to rice plants are severely reduced but not completely nullified by R. fistulosa infection. The benefits to production and reproduction accrued by the parasite from increased nutrient availability are restricted to conditions in the presence of a host plant. Host presence and nutrient effects are thus observed to be synergetic; R. fistulosa plants parasitizing a suitable host respond strongly to increasing levels of nutrients. This is associated with an increased root biomass of the parasitic plant itself, but is more likely to result from exploitation of the nutrient uptake capacity of the host plant it parasitizes.

Multiscale Modeling of Spheroid Tumors: Effect of Nutrient Availability on Tumor Evolution.

Recent years have revealed a large number of complex mechanisms and interactions that drive the development of malignant tumors. Tumor evolution is a framework that explains tumor development as a process driven by survival of the fittest, with tumor cells of different properties competing for limited available resources. To predict the evolutionary trajectory of a tumor, knowledge of how cellular properties influence the fitness of a subpopulation in the context of the microenvironment is required and is often inaccessible. Computational multiscale-modeling of tissues enables the observation of the full trajectory of each cell within the tumor environment. Here, we model a 3D spheroid tumor with subcellular resolution. The fitness of individual cells and the evolutionary behavior of the tumor are quantified and linked to cellular and environmental parameters. The fitness of cells is solely influenced by their position in the tumor, which in turn is influenced by the two variable parameters of our model: cell-cell adhesion and cell motility. We observe the influence of nutrient independence and static and dynamically changing nutrient availability on the evolutionary trajectories of heterogeneous tumors in a high-resolution computational model. Regardless of nutrient availability, we find a fitness advantage of low-adhesion cells, which are favorable for tumor invasion. We find that the introduction of nutrient-dependent cell division and death accelerates the evolutionary speed. The evolutionary speed can be increased by fluctuations in nutrients. We identify a distinct frequency domain in which the evolutionary speed increases significantly over a tumor with constant nutrient supply. The findings suggest that an unstable supply of nutrients can accelerate tumor evolution and, thus, the transition to malignancy.

Cutting Edge: l-Arginine Transfer from Antigen-Presenting Cells Sustains CD4+ T Cell Viability and Proliferation.

Metabolomics analyses suggest changes in amino acid abundance, particularly l-arginine (L-ARG), occur in patients with tuberculosis. Immune cells require L-ARG to fuel effector functions following infection. We have previously described an L-ARG synthesis pathway in immune cells; however, its role in APCs has yet to be uncovered. Using a coculture system with mycobacterial-specific CD4+ T cells, we show APC L-ARG synthesis supported T cell viability and proliferation, and activated T cells contained APC-derived L-ARG. We hypothesize that APCs supply L-ARG to support T cell activation under nutrient-limiting conditions. This work expands the current model of APC-T cell interactions and provides insight into the effects of nutrient availability in immune cells.

Spatiotemporal distribution of chemical signatures exhibited by Myxococcus xanthus in response to metabolic conditions.

Myxococcus xanthus is a common soil bacterium with a complex life cycle, which is known for production of secondary metabolites. However, little is known about the effects of nutrient availability on M. xanthus metabolite production. In this study, we utilize confocal Raman microscopy (CRM) to examine the spatiotemporal distribution of chemical signatures secreted by M. xanthus and their response to varied nutrient availability. Ten distinct spectral features are observed by CRM from M. xanthus grown on nutrient-rich medium. However, when M. xanthus is constrained to grow under nutrient-limited conditions, by starving it of casitone, it develops fruiting bodies, and the accompanying Raman microspectra are dramatically altered. The reduced metabolic state engendered by the absence of casitone in the medium is associated with reduced, or completely eliminated, features at 1140cm-1, 1560cm-1, and 1648cm-1. In their place, a feature at 1537cm-1 is observed, this feature being tentatively assigned to a transitional phase important for cellular adaptation to varying environmental conditions. In addition, correlating principal component analysis heat maps with optical images illustrates how fruiting bodies in the center co-exist with motile cells at the colony edge. While the metabolites responsible for these Raman features are not completely identified, three M. xanthus peaks at 1004, 1151, and 1510cm-1 are consistent with the production of lycopene. Thus, a combination of CRM imaging and PCA enables the spatial mapping of spectral signatures of secreted factors from M. xanthus and their correlation with metabolic conditions.

Long-term ecosystem nitrogen limitation from foliar δ15 N data and a land surface model.

The effect of nutrient availability on plant growth and the terrestrial carbon sink under climate change and elevated CO2 remains one of the main uncertainties of the terrestrial carbon cycle. This is partially due to the difficulty of assessing nutrient limitation at large scales over long periods of time. Consistent declines in leaf nitrogen (N) content and leaf δ15 N have been used to suggest that nitrogen limitation has increased in recent decades, most likely due to the concurrent increase in atmospheric CO2 . However, such data sets are often not straightforward to interpret due to the complex factors that contribute to the spatial and temporal variation in leaf N and isotope concentration. We use the land surface model (LSM) QUINCY, which has the unique capacity to represent N isotopic processes, in conjunction with two large data sets of foliar N and N isotope content. We run the model with different scenarios to test whether foliar δ15 N isotopic data can be used to infer large-scale N limitation and if the observed trends are caused by increasing atmospheric CO2 , changes in climate or changes in sources and magnitude of anthropogenic N deposition. We show that while the model can capture the observed change in leaf N content and predict widespread increases in N limitation, it does not capture the pronounced, but very spatially heterogeneous, decrease in foliar δ15 N observed in the data across the globe. The addition of an observation-based temporal trend in isotopic composition of N deposition leads to a more pronounced decrease in simulated leaf δ15 N. Our results show that leaf δ15 N observations cannot, on their own, be used to assess global-scale N limitation and that using such a data set in conjunction with an LSM can reveal the drivers behind the observed patterns.

High cytokinin concentration and nutrient starvation trigger DNA methylation changes in somaclonal variants of Agave angustifolia Haw

Somaclonal variation (SV) is observed during micropropagation, especially in organogenic processes when differentiated somatic cells are induced into a pluripotent state. However, the clones obtained show differences in phenotype from each other and from the mother plants, which could be an agricultural problem or an ornamental advantage. Few of the mechanisms associated with how a somatic cell generates phenotypic variation have been elucidated. Recently, our group demonstrated that an albino phenotype produced in Agave in in vitro culture was linked to changes in DNA methylation through the micropropagation process, suggesting a new way to investigate the mechanism. Therefore, here we evaluate the effect of stressful conditions in the culture media on three different phenotypes (green, variegated and albino) of Agaveangustifolia Haw. to determine the changes in DNA methylation linked to SV in the new formed shoots. The effects of nutrient availability and exogen cytokinin concentration in the culture media were evaluated for five months in each phenotype. We observed that a reduction of 25 % in the nutrients in the culture media affected the coloration of green plantlets. On the other hand, a high 6-benzyladenine (BA) concentration exposure (88.8 μM) in the variegated phenotype enhanced organogenic capability, increased phenotypic variation, and changed DNA methylation levels. We have demonstrated that long periods of time under nutrient-limited conditions or high cytokinin concentration provoke changes in DNA methylation levels that increase SV frequency in the newly formed shoots. Epigenetic changes may thus be an overlooked factor in SV induced by culture media stress.

Dendritic Cells Supply CD4+ T Cells With L-arginine

Abstract Tuberculosis (TB), caused by Mycobacterium tuberculosis, is responsible for over 1 million deaths each year. Mycobacteria-infected dendritic cells (DCs) migrate to the lymph node to initiate adaptive immune priming, which is vital to antimycobacterial immunity. This response is intimately tied to nutrient availability – especially the amino acid L-arginine (L-ARG), metabolism of which is altered in TB patients. We have characterized a pathway utilized by immune cells to synthesize L-ARG. Loss of L-ARG synthesis in CD11c+ cells, which includes DCs, results in increased mycobacterial burden following infection in mice. To characterize the role of this pathway in DCs, we developed a co-culture system with mycobacterial-specific CD4+ T cells and bone marrow derived DCs. Using CD4+ T cells and DCs with differing capabilities of L-ARG synthesis, we found 1) DC L-ARG synthesis supports CD4+ T cell proliferation and 2) activated T cells contain DC-derived L-ARG. We hypothesize DCs “share” synthesized L-ARG to support CD4+ T cell activation when L-ARG is limiting. Our data suggest nutrient availability as a 4th signal – following antigen presentation, co-stimulation, and cytokine receptor ligation – required for T cell activation. This work expands the current model of DC-T cell interactions and provides insight into the effects of nutrient availability in immune cells.

Effects of nutrient availability and light intensity on the sterol content of Saccharina latissima (Laminariales, Phaeophyceae)

Seaweed phytosterols are associated with potential health benefits, affording them and the seaweeds that produce them commercial interest. However, little is known about how their production is affected by the cultivation environment, limiting the efficiency with which these compounds can be exploited. Therefore, we performed a pilot study on the effect of nutrient availability and light stress on the sterol content of Saccharina latissima, a rapid growing brown alga of increasing interest in western mariculture. Individuals of S. latissima were subjected to a nutrient-replete and nutrient-depleted regime for 5 weeks, followed by the introduction of light-limited and light-saturated conditions in the sixth week; sampling occurred each week. No significant inter-treatment differences were found in the sterol content in week 1–5. However, significant intra-treatment differences were found in weeks 3–5 regardless of nutrient treatment, wherein the fucosterol, 24-methylenecholesterol, and squalene contents of both treatment groups were found to correlate inversely with photosynthetic performance. Factorial treatment of differential nutrient availability and light stress resulted in marked differences between the sterol content of all groups in week 6. Here, squalene and cycloartenol increased in concentration with increasing irradiance regardless of nutrient treatment. Concentrations of all other sterolic components increased with increasing irradiance and low nutrient conditions while decreasing or remaining unchanged with increasing irradiance and high nutrient conditions. Our data shows that within our cultivation conditions and time frame, the sterol content of S. latissima is unaffected by nutrient availability alone but changes with combined alterations in irradiance and nutrient availability.Graphical abstract

The Effect of Nutrient Availability and Light Conditions on the Growth and Intracellular Nitrogen Components of Land-Based Cultivated Saccharina latissima (Phaeophyta)

With the increasing interest and activities regarding seaweed cultivation in Europe, it is becoming crucial to utilize the opportunities that lies within environmental resources, such as light and nutrients, to produce biomass of a high yield and quality. The chemical composition of seaweed varies between seasons and depths as an effect of resource supply and environmental conditions. These factors are particularly important to assess for economically feasible species like the kelp Saccharina latissima. This paper examines how differences in light conditions and nutrient availability affect the growth and intracellular nitrogen in S. latissima. This was done through cultivating sporophytes in land-based tanks with four different combinations of high/low light and high/low nutrient supply over an experimental period of 20 days, with measurements of growth rate and subsequent analysis of tissue nitrogen metabolites. The results revealed that the mean growth rate and the intracellular nitrogen components of the sporophytes were positively related to the external nitrate concentration during the experimental period, indicating that S. latissima requires high nutrient concentration to maintain a rapid growth.

Effect of nutrient availability on lipid productivity of Botryococcus sp. (Botryococcaceae, Chlorophyta), a newly isolated tropical microalgae strain from Puerto Rico

Microalgae are promising sources of biofuels due to the high lipid content of some species. However, growing microalgae at large scales involves high production costs, mainly associated with nutrient inputs and harvesting processes. Therefore, to be cost competitive, species to be used as a source of fuels should be capable of accumulating lipids and biomass at lower fertilizer inputs. In the present study, we isolated and identified a native microalgal strain of Botryococcus sp. which was cultured under varying nitrogen, phosphorus and carbon dioxide regimes. The effects of nutrient availability on biomass, lipid production and fatty acid profiles were examined. We observed an increase in the relative lipid content from 25.5% under nitrogen non-limiting conditions to 41.8% under nitrogen deprivation. The lipid profile induced by nitrogen limitation was found to be dominated by saturated and monounsaturated lipid classes, meeting the European Standards for biodiesel and oil suitable for biofuel production. Thus, this Botryococcus sp. has the potential to be used at large scale cultures with the purpose of producing biofuels with lower fertilizer costs.

Computer-Assisted Tracking of Chlamydomonas Species.

The green algae Chlamydomonas reinhardtii is a model system for motility in unicellular organisms. Photo-, gravi-, and chemotaxis have previously been associated with C. reinhardtii, and observing the extent of these responses within a population of cells is crucial for refining our understanding of how this organism responds to changing environmental conditions. However, manually tracking and modeling a statistically viable number of samples of these microorganisms is an unreasonable task. We hypothesized that automated particle tracking systems are now sufficiently advanced to effectively characterize such populations. Here, we present an automated method to observe C. reinhardtii motility that allows us to identify individual cells as well as global information on direction, speed, and size. Nutrient availability effects on wild-type C. reinhardtii swimming speeds, as well as changes in speed and directionality in response to light, were characterized using this method. We also provide for the first time the swimming speeds of several motility-deficient mutant lines. While our present effort is focused around the unicellular green algae, C. reinhardtii, we confirm the general utility of this approach using Chlamydomonas moewusii, another member of this genus which contains over 300 species. Our work provides new tools for evaluating and modeling motility in this model organism and establishes the methodology for conducting similar experiments on other unicellular microorganisms.

Imbalanced stoichiometric patterns in foliar nutrient resorption response to N and P addition in grazing alpine grassland

Although the effect of nutrient availability on plant nutrient resorption has been extensively studied, the influence of nutrient addition on the coupled biogeochemical cycling of N and phosphorus (P) remains unclear. Studies on how increased nutrient addition affects the imbalance between N and P resorption are limited. We investigated the influence of a wide nutrient addition gradient on the foliar nutrient resorption of dominant grass, Stipa capillata, in grazing alpine grassland. We applied seven addition levels for N (0.5–24 g N ∙ m−2 yr−1) and P (0.05–3.2 g P ∙ m−2 yr−1), collected plant and soil samples, and calculated plant foliar nutrient resorption. Results showed that N and P resorption efficiencies decreased with increasing N addition and N:P resorption ratios. However, N and P resorption efficiencies significantly decreased but N:P resorption ratios increased with the P addition gradient. Moreover, the N:P resorption ratios were negatively correlated with senesced foliar N:P ratios. Our findings suggest that N and P responses to nutrient fertilization are tightly coupled at the intraspecific level. Hence, plants show different tendencies of resorbing nutrient with N and P addition, leading to imbalance between N and P. Plant stoichiometric patterns were regulated by the nutrient status of senesced foliar. This study reveals that nutrient additions accelerate ecosystem N and P cycling, N and P cycles are coupled, but their resorptions are imbalanced. The imbalanced stoichiometric patterns in foliar nutrient resorption response to nutrient enrichment provide insights into N and P cycling under human-driven nutrient imbalance scenarios.

Nitrogen enrichment leads to changing fatty acid composition of phytoplankton and negatively affects zooplankton in a natural lake community

Secondary production in freshwater zooplankton is frequently limited by the food quality of phytoplankton. One important parameter of phytoplankton food quality are essential polyunsaturated fatty acids (PUFAs). Since the fatty acid composition of phytoplankton is variable and depends on the algae’s nutrient supply status, inorganic nutrient supply may affect the algal PUFA composition. Therefore, an indirect transfer of the effects of nutrient availability on zooplankton by changes in algal PUFA composition is conceivable. While the phosphorus (P) supply in lakes is largely decreasing, nitrogen (N) inputs continue to increase. This paper presents data from a mesocosm field experiment in which we exposed phytoplankton communities to increasing N enrichment. As a consequence, the PUFA composition of the phytoplankton community changed. With increasing nitrogen fertilisation, we observed lower quantities of essential PUFAs, together with a decrease in the abundances of the dominant herbivorous zooplankton Daphnia sp. Their biomass was significantly correlated with phytoplankton PUFA content (C18:3 ω3, C20:5 ω3, C18:2 ω6). Our data therefore indicate that changes in nitrogen supply, together with the resultant changes in phytoplankton food quality, can negatively affect the secondary production of herbivorous zooplankton by reducing the availability of essential polyunsaturated fatty acids.

Nutrient restriction causes reversible G2 arrest in Xenopus neural progenitors.

Nutrient status affects brain development; however, the effects of nutrient availability on neural progenitor cell proliferation in vivo are poorly understood. Without food, Xenopus laevis tadpoles enter a period of stasis during which neural progenitor proliferation is drastically reduced, but resumes when food becomes available. Here, we investigate how neural progenitors halt cell division in response to nutrient restriction and subsequently re-enter the cell cycle upon feeding. We demonstrate that nutrient restriction causes neural progenitors to arrest in G2 of the cell cycle with increased DNA content, and that nutrient availability triggers progenitors to re-enter the cell cycle at M phase. Initiation of the nutrient restriction-induced G2 arrest is rapamycin insensitive, but cell cycle re-entry requires mTOR. Finally, we show that activation of insulin receptor signaling is sufficient to increase neural progenitor cell proliferation in the absence of food. A G2 arrest mechanism provides an adaptive strategy to control brain development in response to nutrient availability by triggering a synchronous burst of cell proliferation when nutrients become available. This may be a general cellular mechanism that allows developmental flexibility during times of limited resources.

Plant-soil feedback is shut down when nutrients come to town

Background and aimsThe concept of plant-soil feedback is increasingly used to explain plant community assembly processes. Soil nutrient availability can be expected to play a critical role on these processes. However, little is known about the effects of nutrient availability on feedback direction and strength.MethodsA plant-soil feedback experiment was performed with the grasses Anthoxanthum odoratum and Festuca rubra, and the forbs Leontodon hispidus and Plantago lanceolata, on soil with either low or high nutrient availability. Additionally, we tested if plant-soil feedback of the two forbs under these conditions changed by inoculation of the soil with spores of an arbuscular mycorrhizal fungus.ResultsIncreased nutrient availability neutralised plant-soil feedback based on shoot biomass independent of its negative or positive direction, whereas the effects on root biomass were either not altered or turned negative. Mycorrhizal fungi spore addition decreased negative feedback and increased positive feedback.ConclusionsOur results suggest that negative plant-soil feedback on low nutrient soil can be overcome with nutrient addition, and that positive soil biota associations on low nutrient soil may become superfluous with nutrient increase. We hypothesize that species-specific, microbial mediated plant community assembly processes occur in low rather than high nutrient environments.

Pet Food Factory Isolates of Salmonella Serotypes Do Not Demonstrate Enhanced Biofilm Formation Compared to Serotype-Matched Clinical and Veterinary Isolates.

Environmentally persistent Salmonella in the pet food factory environment has been described, with biofilm formation suggested as a candidate mechanism contributing to their persistence. In this study the ability of a panel of Salmonella isolates from factory, clinical, and veterinary sources was investigated for their ability to form biofilms at 24 and 48 hours. The effect of nutrient availability and incubation time on biofilm formation was investigated using full strength and diluted 1/20 TSB media at 37°C, 25°C, 15°C, and 10°C. Results highlighted that all the Salmonella isolates were able to form biofilms in both nutrient conditions and this was highly correlated with temperature. At 25°C, biofilm formation was enhanced in diluted 1/20 TSB and increased incubation time (48h) (p= <0.001). However, this was not observed at 10°C, 15°C, or 37°C. None of the factory isolates demonstrated enhanced biofilm formation in comparison to serotype-matched isolates from veterinary and clinical sources. Salmonella enterica Senftenberg 775W was the strongest biofilm former at 15°C, 25°C, and 37°C in all the conditions tested (p=<0.05). Biofilm formation is an important mechanism of environmental persistence in the food manufacturing environment; however, there is no evidence of an enhanced biofilm-producing phenotype in factory persistent strains.

Yeast Genome-Scale Metabolic Models for Simulating Genotype-Phenotype Relations.

Understanding genotype-phenotype dependency is a universal aim for all life sciences. While the complete genotype-phenotype relations remain challenging to resolve, metabolic phenotypes are moving within the reach through genome-scale metabolic model simulations. Genome-scale metabolic models are available for commonly investigated yeasts, such as model eukaryote and domesticated fermentation species Saccharomyces cerevisiae, and automatic reconstruction methods facilitate obtaining models for any sequenced species. The models allow for investigating genotype-phenotype relations through simulations simultaneously considering the effects of nutrient availability, and redox and energy homeostasis in cells. Genome-scale models also offer frameworks for omics data integration to help to uncover how the translation of genotypes to the apparent phenotypes is regulated at different levels. In this chapter, we provide an overview of the yeast genome-scale metabolic models and the simulation approaches for using these models to interrogate genotype-phenotype relations. We review the methodological approaches according to the underlying biological reasoning in order to inspire formulating novel questions and applications that the genome-scale metabolic models could contribute to. Finally, we discuss current challenges and opportunities in the genome-scale metabolic model simulations.

Bacterial culturability and the viable but non-culturable (VBNC) state studied by a proteomic approach using an artificial soil

Gram-negative bacteria in soil rapidly adapt to various stresses, including nutrient limitation and desiccation, by adopting the viable but non-culturable (VBNC) state as a survival strategy. Due to the physico-chemical and microbiological complexity of soils, little is understood on the effects of nutrient availability and moisture level on the transition from the VBNC state to culturability in soil. We evaluated the effects of gluconate or water on the transition of the soil borne bacterium C. metallidurans strain CH34 from the VBNC state to culturability by experiments of inoculation into artificial soils and bacterial metaproteomic analysis. Incubation without water or nutrients reduced the bacterial culturability to zero in 12 d, and addition of both water or gluconate restored the bacterial culturability to high levels within 24 h. The proteomic analysis showed that under water and nutrient limitation, proteins related to the cell shape and protein synthesis were rapidly down-regulated and stress-related proteins were quickly up-regulated during the transition from culturability to VBNC state. Reversion from the VBNC state to a culturable state with water or gluconate led to highly different bacterial proteomic profiles of C. metallidurans. Gluconate availability restored main protein biosynthesis and energy metabolic pathways, whereas water addition led to up-regulation of only six proteins, one of which degrade sigma factors involved in expression of genes controlling bacterial resistance under nutrient limitation. Proteins regulated during the transition between culturable and VBNC states could also be involved in the phenotypic VBNC for other soil bacteria, and can highlight some of the microbial genetic mechanisms allowing the entering and exiting from the VBNC state. Implications of the VBNC in microbial diversity and soil functionality are discussed.

Interactive effects of nutrient availability and temperature on growth and survival of different size classes of Saccharina japonica (Laminariales, Phaeophyceae)

:In northern Japan, the production of Saccharina japonica exhibits marked annual fluctuation due to changes in seawater temperature and nutrient availability during winter and spring. To better understand this phenomenon, we examined the combined effects of temperature (5°C, 10°C, 15°C and 20°C) and nutrient availability (seawater enriched with 25% Provasoli's enriched seawater vs nonenriched seawater) on photosynthesis, growth and survival and nitrogen and chlorophyll a contents of juvenile sporophytes (2–3 cm) and larger size class sporophytes (100–150 cm) from southern Hokkaido. Both juvenile sporophytes and discs from 100–150-cm-class sporophytes cultured in enriched seawater showed significantly higher growth rates and photosynthetic activities than those cultured in nonenriched seawater. This difference likely was due to the significantly higher nitrogen and chlorophyll a contents of thalli grown in enriched seawater. Significant effects of temperature on growth and photosynthesis were also detected. A significant interaction between temperature and nutrient availability for relative growth rate (RGR) was detected. The positive effect of elevated nutrient availability on RGRs was magnified by an increase in temperature from 5°C to 15°C for juvenile sporophytes and from 5°C to 10°C for 100–150-cm-class sporophytes; whereas, the negative effect of elevated temperature from 10°C to 15°C on RGRs of 100–150-cm-class sporophytes was antagonised by a reduction in nutrient availability. In contrast to the 100% survival rate in enriched seawater, dead juvenile sporophytes and discs from 100–150-cm-class sporophytes were found at 15°C and 20°C in nonenriched seawater, and the survival rates decreased with increasing temperature. Therefore, the growth and survival of sporophytes of S. japonica are significantly affected by nutrient availability and temperature, which may lead to marked fluctuations in annual production.

Masting synchrony in northern hardwood forests: super‐producers govern population fruit production

Summary Trees commonly reproduce via masting cycles, which involves synchronized inter‐annual variability in fruit crop size. A few individuals in a population will commonly produce much more fruit than others. If these trees produce fruit more frequently, as indicated by a lower inter‐annual variability in fruit production, they may dominate fruit production over time. By measuring fruit production of 1635 individuals of 10 temperate tree species across 4 years in northern lower Michigan, we estimated the inter‐annual variability and synchrony in each species. We compared fruit production estimates with measurements of tree size, soil nutrient availability and neighbourhood crowding to investigate the source of inter‐individual variation in number of fruit produced. We found that trees’ fruit production increased with tree size. The trees that accounted for the largest proportion of total fruit production had lower inter‐annual variability and higher synchrony in fruit production. These ‘super‐producer’ trees tended to have high nutrient availability and few neighbouring trees, but there were no effects of nutrient availability or neighbourhood crowding on fruit production in the population as a whole. Synthesis. Masting is a population‐level phenomenon, and is typically studied at this level. However, when we apply individual tree observations of fruit production to this phenomenon, it reveals super‐producers which produce fruit more consistently than the rest of the population. By reducing inter‐annual variability in fruit production, but increasing synchrony and making large numbers of fruit, super‐producers may be able to reap the benefits of masting while governing population fruit production over time.