Allometric biomass partitioning under nitrogen enrichment: Evidence from manipulative experiments around the world.
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ABSTRACT:
SUBMITTER: Peng Y
PROVIDER: S-EPMC4923945 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:Biomass allocation affects the ability of plants to acquire resources and nutrients; a limited allocation of nutrients, such as nitrogen and phosphorus, affects ecological processes. However, little research has been conducted on how plant allocation patterns change and on the trade-offs involved in allocation strategies when microhabitat gradients exist. We selected a 3.6 km transect in the Ebinur Lake Wetland Natural Reserve of Xinjiang, China, to investigate the relationships between plant traits (biomass and N and P concentrations) of herbaceous plants and environmental factors (soil moisture, salinity and nutrient content), and to determine the allometric scaling of biomass and stoichiometric traits between the above- and below-ground plant parts. The results show that the biomass and stoichiometric traits of plants reflected both the change of micro-environment and the natural characteristics of plants. With a decrease of the soil water availability and salinity, above- and below-ground N and P concentrations decrease gradually; scaling relationships exist between above- and below-ground plant parts, for biomass and N and P concentrations. Biomass allocation is influenced by soil nutrient ratios, and the allocation strategy tended to be conserved for N and variable for P. Second, the scaling relationships also show interspecific differences; all scaling exponents of Suaeda prostrata are larger than for other species and indicate a 'tolerance' strategy, while other species tend to increase the below-ground biomass and N and P concentrations, i.e. a 'capture' strategy.
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Project description:Nitrogen (N) is an important macronutrient needed for grain yield, grain N and grain protein content in rice. Grain yield and quality are significantly determined by N availability. In this study, to understand the mechanisms associated with reproductive stage N remobilization and N partitioning to grain 2 years of field experiments were conducted with 30 diverse rice genotypes during 2019-Kharif and 2020-Kharif seasons. The experiments were conducted with two different N treatments; N deficient (N0-no external N application, available soil N; 2019-234.15 kgha-1, 2020-225.79 kgha-1) and N sufficient (N120-120 kgha-1 external N application, available soil N; 2019-363.77 kgha-1, 2020-367.95 kgha-1). N application increased the NDVI value, biomass accumulation, grain yield, harvest index and grain N accumulation. Post-anthesis N uptake and N remobilization from vegetative tissues to grain are critical for grain yield and N harvest index. Rice genotypes, Kalinga-1, BAM-4234, IR-8384-B-B102-3, Sahbhagi Dhan, BVD-109 and Nerica-L-42 showed a higher rate of N remobilization under N sufficient conditions. But, under N deficiency, rice genotypes-83929-B-B-291-3-1-1, BVD-109, IR-8384-B-B102-3 and BAM-4234 performed well showing higher N remobilization efficiency. The total amount of N remobilization was recorded to be high in the N120 treatment. The harvest index was higher in N120 during both the cropping seasons. RANBIR BASMATI, BAM-832, APO, BAM-247, IR-64, Vandana, and Nerica-L-44 were more efficient in N grain production efficiency under N deficient conditions. From this study, it is evident that higher grain N accumulation is not always associated with higher yield. IR-83929-B-B-291-3-1-1, Kalinga-1, APO, Pusa Basmati-1, and Nerica-L-44 performed well for different N use efficiency component traits under both N deficient (N0) and N sufficient (N120) conditions. Identifying genotypes/donors for N use efficiency-component traits is crucial in improving the fertilizer N recovery rate and site specific N management.
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Project description:Marine diazotrophs are a diverse group with key roles in biogeochemical fluxes linked to primary productivity. The unicellular, diazotrophic cyanobacterium Cyanothece is widely found in coastal, subtropical oceans. We analyze the consequences of diazotrophy on growth efficiency, compared to NO3 --supported growth in Cyanothece, to understand how cells cope with N2-fixation when they also have to face carbon limitation, which may transiently affect populations in coastal environments or during blooms of phytoplankton communities. When grown in obligate diazotrophy, cells face the double burden of a more ATP-demanding N-acquisition mode and additional metabolic losses imposed by the transient storage of reducing potential as carbohydrate, compared to a hypothetical N2 assimilation directly driven by photosynthetic electron transport. Further, this energetic burden imposed by N2-fixation could not be alleviated, despite the high irradiance level within the cultures, because photosynthesis was limited by the availability of dissolved inorganic carbon (DIC), and possibly by a constrained capacity for carbon storage. DIC limitation exacerbates the costs on growth imposed by nitrogen fixation. Therefore, the competitive efficiency of diazotrophs could be hindered in areas with insufficient renewal of dissolved gases and/or with intense phytoplankton biomass that both decrease available light energy and draw the DIC level down.
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Project description:Angiosperm genome sizes (GS) range c. 2400-fold, and as nucleic acids are amongst the most phosphorus- (P) and nitrogen (N)-demanding cellular biomolecules, we test the hypothesis that a key influence on plant biomass and species composition is the interaction between N and P availability and plant GS. We analysed the impact of different nutrient regimes on above-ground biomass of angiosperm species with different GS, ploidy level and Grime's C-S-R (competitive, stress-tolerant, ruderal) plant strategies growing at the Park Grass Experiment (Rothamsted, UK), established in 1856. The biomass-weighted mean GS of species growing on plots with the addition of both N and P fertilizer were significantly higher than that of plants growing on control plots and plots with either N or P. The plants on these N + P plots are dominated by polyploids with large GS and a competitive plant strategy. The results are consistent with our hypothesis that large genomes are costly to build and maintain under N and P limitation. Hence GS and ploidy are significant traits affecting biomass growth under different nutrient regimes, influencing plant community composition and ecosystem dynamics. We propose that GS is a critical factor needed in models that bridge the knowledge gap between biodiversity and ecosystem functioning.
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Project description:BACKGROUND:The belowground component of the trees is still poorly known because it needs labour- and time-intensive in situ measurements. However, belowground biomass (BGB) constitutes a significant share of the total forest biomass. I analysed the BGB allocation patterns, fitted models for estimating root components and root system biomasses, and called attention for its possible use in predicting anchoring functions of the different root components. RESULTS:More than half and almost one third of BGB is allocated to the lateral roots and to the root collar, respectively. More than 80% of the BGB is found at a depth range of 9.6-61.2 cm. As the tree size increased, the proportion of BGB allocated to taproots decreased and that allocated to lateral roots increased. All independent models performed almost equally, with the predictors explaining, on average, 98% of the variation in the BGB. CONCLUSIONS:It was hypothesised that BGB allocation patterns are a response of the anchoring functions of the tap and lateral roots and therefore, root component biomass models can be used as a methodology to predict anchoring functions of the different root components. Based on the fact that all models performed almost equally, the models using either diameter at breast height (DBH) exclusively as a predictor should be preferred, as tree height is difficult to measure. Models using the root collar diameter (RCD) only should be preferred when the tree is found cut down, as sometimes the RCD is affected by root buttress. Given the large sample size, the validation results, and the coverage of a wide geographical, soil and climatic range, the models fitted can be applied in all A. johnsonii stands in Mozambique.
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Project description:In this paper, we present a new method for detecting overlapping communities in networks with a predefined number of clusters called LPAM (Link Partitioning Around Medoids). The overlapping communities in the graph are obtained by detecting the disjoint communities in the associated line graph employing link partitioning and partitioning around medoids which are done through the use of a distance function defined on the set of nodes. We consider both the commute distance and amplified commute distance as distance functions. The performance of the LPAM method is evaluated with computational experiments on real life instances, as well as synthetic network benchmarks. For small and medium-size networks, the exact solution was found, while for large networks we found solutions with a heuristic version of the LPAM method.
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Project description:ObjectivesThe first and second demographic transitions have led to profound changes in family networks. However, the timing and extent of these transitions vary widely across contexts. We examine how common it is for contemporary older adults to lack living kin and whether such individuals are uniformly disadvantaged around the world.MethodsUsing surveys from 34 countries that together contain 69.6% of the world's population over age 50 and come from all regions of the world, we describe the prevalence and correlates of lacking immediate kin. We examine macro-level demographic indicators associated with the prevalence of kinlessness as well as micro-level associations between kinlessness and sociodemographic and health indicators.ResultsThere is great variation in levels of kinlessness, from over 10% with neither a spouse nor a biological child in Canada, Ireland, the Netherlands, and Switzerland to levels below 2% in China and the Republic of Korea. There are strong macro-level relationships between kinlessness and lagged or contemporaneous fertility, mortality, and nuptiality measures and more marginal relationships with other demographic forces. Micro-level associations between kinlessness and respondent attributes are varied. The kinless are more likely to live alone than those with kin in all countries. In most countries, they have equivalent or worse self-rated health and lower education, although there are notable exceptions. There is substantial variation in the gender composition of the kinless population.DiscussionAs demographic changes affecting kinlessness continue, we expect the scale of the kinless population to grow around the world.
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Project description:Maize (Zea mays) plants exhibit altered carbon partitioning under nitrogen (N) deficiency, but the mechanisms by which N availability affects sugar export out of leaves and transport into developing ears remain unclear. Maize was grown under field conditions with different N supply. Plant growth, sugar movement, and starch turnover in source or sink tissues were investigated at silking and 20 or 21 days after silking. Nitrogen deficiency stunted plant growth and grain yield compared with N-sufficient plants, and resulted in greater starch concentrations in leaves due to more as well as larger starch granules in bundle sheath cells. Transmission electron microscopy revealed an open symplastic pathway for sucrose movement in N-deficient leaves, while the expression levels of transporters responsible for sucrose efflux and phloem loading were lower than in N-sufficient leaves. Nonetheless, greater starch concentrations in the apical cob portion of N-deficient plants implied sufficient carbon supply relative to the diminished sink strength (decreased kernel number and weight). Together with the high sugar concentrations in the developing kernels, the results indicated that reduced sink capacity and sugar utilization during grain filling may limit the yield in N-deficient plants, which in turn imposes a feedback inhibition on sugar export from leaves.
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Project description:The use of autologous cells harvested and subsequently transplanted in an intraoperative environment constitutes a new approach to promote regeneration. Usually cells are isolated by selection methods such as fluorescence- or magnetic- activated cell sorting with residual binding of the antibodies or beads. Thus, cell-based therapies would benefit from the development of new devices for cell isolation that minimally manipulate the target cell population. In the clinic, 5 to 10 percent of fractures do not heal properly and CD31+ cells have been identified as promising candidates to support bone regeneration. The aim of this project was to develop and prototype a simple system to facilitate the enrichment of CD31+ cells from whole blood. After validating the specificity of a commercially available aptamer for CD31, we combined this aptamer with traditional magnetic bead strategies, which led to enrichment of CD31+ cells with a purity of 91±10%. Subsequently, the aptamer was attached to agarose beads (Ø = 100-165 um) that were incorporated into a column-based system to enable capture and subsequent release of the CD31+ enriched cells. Different parameters were investigated to allow a biophysical-based cell release from beads, and a simple mixing was found sufficient to release initially bound cells from the optimized column without the need for any chemicals that promote disassociation. The system led to a significant enrichment of CD31+ cells (initial population: 63±9%, released: 87±3%) with excellent cell viability (released: 97±1%). The composition of the released CD31+ fraction indicated an enrichment of the monocyte population. The angiogenic and osteogenic potential of the released cell population were confirmed in vitro. These results and the simplicity of this system highlight the potential of such approach to enable cell enrichment strategies in intraoperative settings.
| S-EPMC5493423 | biostudies-literature
Project description:Nitrogen (N) deposition poses a serious threat to terrestrial biodiversity and alters plant and soil microbial community composition. Species turnover and nestedness reflect the underlying mechanisms of variations in community composition. However, it remains unclear how species turnover and nestedness contribute to different responses of taxonomic groups (plants and soil microbes) to N enrichment. Here, based on a 13-year consecutive multi-level N addition experiment in a semiarid steppe, we partitioned community β-diversity into species turnover and nestedness components and explored how and why plant and microbial communities reorganize via these two processes following N enrichment. We found that plant, soil bacterial, and fungal β-diversity increased, but their two components showed different patterns with increasing N input. Plant β-diversity was mainly driven by species turnover under lower N input but by nestedness under higher N input, which may be due to a reduction in forb species, with low tolerance to soil Mn2+, with increasing N input. However, turnover was the main contributor to differences in soil bacterial and fungal communities with increasing N input, indicating the phenomenon of microbial taxa replacement. The turnover of bacteria increased greatly whereas that of fungi remained within a narrow range with increasing N input. We further found that the increased soil Mn2+ concentration was the best predictor for increasing nestedness of plant communities under higher N input, whereas increasing N availability and acidification together contributed to the turnover of bacterial communities. However, environmental factors could explain neither fungal turnover nor nestedness. Our findings reflect two different pathways of community changes in plants, soil bacteria, and fungi, as well as their distinct community assembly in response to N enrichment. Disentangling the turnover and nestedness of plant and microbial β-diversity would have important implications for understanding plant-soil microbe interactions and seeking conservation strategies for maintaining regional diversity.
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