Open Access Publications

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Open access publications by faculty, postdocs, and graduate students in the Department of Plant and Soil Sciences.

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Phloem unloading in Arabidopsis roots is convective and regulated by the phloem- pole pericycle
(eLIFE Sciences Publications, 2017-02-23) Ross-Elliott, Timothy J.; Jensen, Kaare H.; Haaning, Katrine S.; Wager, Brittney M.; Knoblauch, Jan; Howell, Alexander H.; Mullendore, Daniel L.; Monteith, Alexander G.; Paultre, Danae; Yan, Dawei; Otero, Sofia; Bourdon, Matthieu; Sager, Ross; Lee, Jung-Youn; Helariutta, Yka¨; Knoblauch, Michael; Oparka, Karl J.; Timothy J Ross-Elliott, Kaare H Jensen, Katrine S Haaning, Brittney M Wager, Jan Knoblauch, Alexander H Howell, Daniel L Mullendore, Alexander G Monteith, Danae Paultre, Dawei Yan, Sofia Otero, Matthieu Bourdon, Ross Sager, Jung-Youn Lee, Yka¨ Helariutta, Michael Knoblauch, Karl J Oparka; Sager, Ross; Lee, Jung-Youn
In plants, a complex mixture of solutes and macromolecules is transported by the phloem. Here, we examined how solutes and macromolecules are separated when they exit the phloem during the unloading process. We used a combination of approaches (non-invasive imaging, 3D-electron microscopy, and mathematical modelling) to show that phloem unloading of solutes in Arabidopsis roots occurs through plasmodesmata by a combination of mass flow and diffusion (convective phloem unloading). During unloading, solutes and proteins are diverted into the phloem-pole pericycle, a tissue connected to the protophloem by a unique class of ‘funnel plasmodesmata’. While solutes are unloaded without restriction, large proteins are released through funnel plasmodesmata in discrete pulses, a phenomenon we refer to as ‘batch unloading’. Unlike solutes, these proteins remain restricted to the phloem-pole pericycle. Our data demonstrate a major role for the phloem-pole pericycle in regulating phloem unloading in roots.
Distribution of urban green spaces: Comparative analysis between cities in different countries
(Ornamental Horticulture, 2020-11-04) Garcia, Cecília Souza Gontijo; Paiva, Patrícia Duarte de Oliveira; Bruck, Jules; Sousa, Rafael de Brito
The presence of urban green spaces (UGS) increases the human’s contact with nature and provides numerous benefits to the society and the local environment. In this way, analyzing, planning and stimulating the implementation of UGS in cities is a fundamental action to improve the life quality of urban society. In this context, the aim was to analyze the situation and distribution of the green spaces of the universities cities of Lavras, Minas Gerais State (Brazil) and Newark, Delaware (USA). For data collection, researches performed field visits and used aerial photography to survey and analysis before calculating indicators including green area index (GAI) and green space ratio (GSR). The city of Lavras has a GAI of 0.54 m2 inh-1. The GSR value was 0.29%, not meeting the minimum of 5% required by local municipal law. Furthermore, there is a bad distribution of UGSs in the urban framework. However, in Newark, the distribution of UGSs is homogeneous and covers all regions of the city. The calculated GAI was 50.2 m² inh-1 and the GSR has met the 7% minimum required by its Newark Municipal Law. When comparing the two cities, in different countries and conditions it is concluded that Newark (DE) presents UGS indicators, GAI (m² inh-1) and GSR (%), higher than the values obtained in Lavras (MG), indicating the need for Government actions to increase these values. Resumo As áreas verdes públicas urbanas (AVPs) concebem um importante tema, pois sua presença nas cidades, ampliando o contato do homem com a natureza, além dos efeitos ambientais geram inúmeros benefícios. Dessa maneira, analisar, planejar e estimular a implantação das AVPs nas cidades é ação fundamental para a melhoria da qualidade de vida da sociedade urbana. Nesse contexto objetivou-se analisar a situação e distribuição das áreas verdes das cidades universitárias de Lavras, estado de Minas Gerais, Brasil e Newark, estado de Delaware, EUA. Para a coleta de dados foram realizadas visitas a campo e o levantamento de áreas das AVPs por meio da análise de imagens de satélite utilizando o software ArcGIS e calculados os indicadores, índice de áreas verdes (IAV) e percentual de áreas verdes (PAV). A cidade de Lavras possui um IAV de 0,54m² hab-1. O valor de PAV foi de 0,29%, não cumprindo o mínimo de 5% exigido pela lei municipal local. Além disto, existe uma má distribuição das AVPs na malha urbana. Já em Newark, a distribuição das AVPs é homogênea abrangendo todas as regiões da cidade. O IAV calculado foi de 50,2m² hab-1 e o PAV cumpriu o mínimo de 7% exigido pela sua Lei municipal de Newark. Ao comparar as duas cidades, conclui-se que Newark (DE) apresenta indicadores sobre as áreas verdes públicas, IAV (m² hab-1) e PAV (%) superiores em comparação aos valores obtidos em Lavras (MG), indicando a necessidade de ações governamentais para ampliar esses valores.
Substantial hysteresis in emergent temperature sensitivity of global wetland CH4 emissions
(Nature Communications, 2021-04-15) Chang, Kuang-Yu; Riley, William J.; Knox, Sara H.; Jackson, Robert B.; McNicol, Gavin; Poulter, Benjamin; Aurela, Mika; Baldocchi, Dennis; Bansal, Sheel; Bohrer, Gil; Campbell, David I.; Cescatti, Alessandro; Chu, Housen; Delwiche, Kyle B.; Desai, Ankur R.; Euskirchen, Eugenie; Friborg, Thomas; Goeckede, Mathias; Helbig, Manuel; Hemes, Kyle S.; Hirano, Takashi; Iwata, Hiroki; Kang, Minseok; Keenan, Trevor; Krauss, Ken W.; Lohila, Annalea; Mammarella, Ivan; Mitra, Bhaskar; Miyata, Akira; Nilsson, Mats B.; Noormets, Asko; Oechel, Walter C.; Papale, Dario; Peichl, Matthias; Reba, Michele L.; Rinne, Janne; Runkle, Benjamin R. K.; Ryu, Youngryel; Sachs, Torsten; Schäfer, Karina V. R.; Schmid, Hans Peter; Shurpali, Narasinha; Sonnentag, Oliver; Tang, Angela C. I.; Torn, Margaret S.; Trotta, Carlo; Tuittila, Eeva-Stiina; Ueyama, Masahito; Vargas, Rodrigo; Vesala, Timo; Windham-Myers, Lisamarie; Zhang, Zhen; Zona, Donatella
Wetland methane (CH4) emissions (FCH4) are important in global carbon budgets and climate change assessments. Currently, FCH4 projections rely on prescribed static temperature sensitivity that varies among biogeochemical models. Meta-analyses have proposed a consistent FCH4 temperature dependence across spatial scales for use in models; however, site-level studies demonstrate that FCH4 are often controlled by factors beyond temperature. Here, we evaluate the relationship between FCH4 and temperature using observations from the FLUXNET-CH4 database. Measurements collected across the globe show substantial seasonal hysteresis between FCH4 and temperature, suggesting larger FCH4 sensitivity to temperature later in the frost-free season (about 77% of site-years). Results derived from a machine-learning model and several regression models highlight the importance of representing the large spatial and temporal variability within site-years and ecosystem types. Mechanistic advancements in biogeochemical model parameterization and detailed measurements in factors modulating CH4 production are thus needed to improve global CH4 budget assessments.
Spatial biases of information influence global estimates of soil respiration: How can we improve global predictions?
(Global Change Biology, 2021-05-01) Stell, Emma; Warner, Daniel; Jian, Jinshi; Bond-Lamberty, Ben; Vargas, Rodrigo
Soil respiration (Rs), the efflux of CO2 from soils to the atmosphere, is a major component of the terrestrial carbon cycle, but is poorly constrained from regional to global scales. The global soil respiration database (SRDB) is a compilation of in situ Rs observations from around the globe that has been consistently updated with new measurements over the past decade. It is unclear whether the addition of data to new versions has produced better-constrained global Rs estimates. We compared two versions of the SRDB (v3.0 n = 5173 and v5.0 n = 10,366) to determine how additional data influenced global Rs annual sum, spatial patterns and associated uncertainty (1 km spatial resolution) using a machine learning approach. A quantile regression forest model parameterized using SRDBv3 yielded a global Rs sum of 88.6 Pg C year−1, and associated uncertainty of 29.9 (mean absolute error) and 57.9 (standard deviation) Pg C year−1, whereas parameterization using SRDBv5 yielded 96.5 Pg C year−1 and associated uncertainty of 30.2 (mean average error) and 73.4 (standard deviation) Pg C year−1. Empirically estimated global heterotrophic respiration (Rh) from v3 and v5 were 49.9–50.2 (mean 50.1) and 53.3–53.5 (mean 53.4) Pg C year−1, respectively. SRDBv5’s inclusion of new data from underrepresented regions (e.g., Asia, Africa, South America) resulted in overall higher model uncertainty. The largest differences between models parameterized with different SRDVB versions were in arid/semi-arid regions. The SRDBv5 is still biased toward northern latitudes and temperate zones, so we tested an optimized global distribution of Rs measurements, which resulted in a global sum of 96.4 ± 21.4 Pg C year−1 with an overall lower model uncertainty. These results support current global estimates of Rs but highlight spatial biases that influence model parameterization and interpretation and provide insights for design of environmental networks to improve global-scale Rs estimates.
Spatiotemporal variability and origin of CO2 and CH4 tree stem fluxes in an upland forest
(Global Change Biology, 2021-07-02) Barba, Josep; Poyatos, Rafael; Capooci, Margaret; Vargas, Rodrigo
The exchange of multiple greenhouse gases (i.e., CO2 and CH4) between tree stems and the atmosphere represents a knowledge gap in the global carbon cycle. Stem CO2 and CH4 fluxes vary across time and space and are unclear, which are their individual or shared drivers. Here we measured CO2 and CH4 fluxes at different stem heights combining manual (biweekly; n = 678) and automated (hourly; n > 38,000) measurements in a temperate upland forest. All trees showed CO2 and CH4 emissions despite 20% of measurements showing net CH4 uptake. Stem CO2 fluxes presented clear seasonal trends from manual and automated measurements. Only automated measurements captured the high temporal variability of stem CH4 fluxes revealing clear seasonal trends. Despite that temporal integration, the limited number of automated chambers made stand-level mean CH4 fluxes sensitive to “hot spots,” resulting in mean fluxes with high uncertainty. Manual measurements provided better integration of spatial variability, but their lack of temporal variability integration hindered the detection of temporal trends and stand-level mean fluxes. These results highlight the potential bias of previous studies of stem CH4 fluxes solely based on manual or automated measurements. Stem height, temperature, and soil moisture only explained 7% and 11% of the stem CH4 flux variability compared to 42% and 81% for CO2 (manual and automated measurements, respectively). This large unexplained variability, in combination with high CH4 concentrations in the trees' heartwood, suggests that stem CH4 fluxes might be more influenced by gas transport and diffusivity through the wood than by drivers of respiratory CO2 flux, which has crucial implications for developing process-based ecosystem models. We postulate that CH4 is likely originated within tree stems because of lack of a consistent vertical pattern in CH4 fluxes, evidence of CH4 production in wood incubations, and low CH4 concentration in the soil profile but high concentrations within the trees' heartwood.
FLUXNET-CH4: a global, multi-ecosystem dataset and analysis of methane seasonality from freshwater wetlands
(Earth System Science Data, 2021-07-29) Delwiche, Kyle B.; Knox, Sara Helen; Malhotra, Avni; Fluet-Chouinard, Etienne; et al.
Methane (CH4) emissions from natural landscapes constitute roughly half of global CH4 contributions to the atmosphere, yet large uncertainties remain in the absolute magnitude and the seasonality of emission quantities and drivers. Eddy covariance (EC) measurements of CH4 flux are ideal for constraining ecosystem-scale CH4 emissions due to quasi-continuous and high-temporal-resolution CH4 flux measurements, coincident carbon dioxide, water, and energy flux measurements, lack of ecosystem disturbance, and increased availability of datasets over the last decade. Here, we (1) describe the newly published dataset, FLUXNET-CH4 Version 1.0, the first open-source global dataset of CH4 EC measurements (available at https://fluxnet.org/data/fluxnet-ch4-community-product/, last access: 7 April 2021). FLUXNET-CH4 includes half-hourly and daily gap-filled and non-gap-filled aggregated CH4 fluxes and meteorological data from 79 sites globally: 42 freshwater wetlands, 6 brackish and saline wetlands, 7 formerly drained ecosystems, 7 rice paddy sites, 2 lakes, and 15 uplands. Then, we (2) evaluate FLUXNET-CH4 representativeness for freshwater wetland coverage globally because the majority of sites in FLUXNET-CH4 Version 1.0 are freshwater wetlands which are a substantial source of total atmospheric CH4 emissions; and (3) we provide the first global estimates of the seasonal variability and seasonality predictors of freshwater wetland CH4 fluxes. Our representativeness analysis suggests that the freshwater wetland sites in the dataset cover global wetland bioclimatic attributes (encompassing energy, moisture, and vegetation-related parameters) in arctic, boreal, and temperate regions but only sparsely cover humid tropical regions. Seasonality metrics of wetland CH4 emissions vary considerably across latitudinal bands. In freshwater wetlands (except those between 20∘ S to 20∘ N) the spring onset of elevated CH4 emissions starts 3 d earlier, and the CH4 emission season lasts 4 d longer, for each degree Celsius increase in mean annual air temperature. On average, the spring onset of increasing CH4 emissions lags behind soil warming by 1 month, with very few sites experiencing increased CH4 emissions prior to the onset of soil warming. In contrast, roughly half of these sites experience the spring onset of rising CH4 emissions prior to the spring increase in gross primary productivity (GPP). The timing of peak summer CH4 emissions does not correlate with the timing for either peak summer temperature or peak GPP. Our results provide seasonality parameters for CH4 modeling and highlight seasonality metrics that cannot be predicted by temperature or GPP (i.e., seasonality of CH4 peak). FLUXNET-CH4 is a powerful new resource for diagnosing and understanding the role of terrestrial ecosystems and climate drivers in the global CH4 cycle, and future additions of sites in tropical ecosystems and site years of data collection will provide added value to this database. All seasonality parameters are available at https://doi.org/10.5281/zenodo.4672601 (Delwiche et al., 2021). Additionally, raw FLUXNET-CH4 data used to extract seasonality parameters can be downloaded from https://fluxnet.org/data/fluxnet-ch4-community-product/ (last access: 7 April 2021), and a complete list of the 79 individual site data DOIs is provided in Table 2 of this paper.
The impact of differential lignin S/G ratios on mutagenicity and chicken embryonic toxicity
(Journal of Applied Toxicology, 2021-08-27) Zhang, Xinwen; Levia, Delphis F.; Ebikade, Elvis Osamudiamhen; Chang, Jeffrey; Vlachos, Dionisios G.; Wu, Changqing
Lignin and lignin-based materials have received considerable attention in various fields due to their promise as sustainable feedstocks. Guaiacol (G) and syringol (S) are two primary monolignols that occur in different ratios for different plant species. As methoxyphenols, G and S have been targeted as atmospheric pollutants and their acute toxicity examined. However, there is a rare understanding of the toxicological properties on other endpoints and mixture effects of these monolignols. To fill this knowledge gap, our study investigated the impact of different S/G ratios (0.5, 1, and 2) and three lignin depolymerization samples from poplar, pine, and miscanthus species on mutagenicity and developmental toxicity. A multitiered method consisted of in silico simulation, in vitro Ames test, and in vivo chicken embryonic assay was employed. In the Ames test, syringol showed a sign of mutagenicity, whereas guaiacol did not, which agreed with the T.E.S.T. simulation. For three S and G mixture and lignin monomers, mutagenic activity was related to the proportion of syringol. In addition, both S and G showed developmental toxicity in the chicken embryonic assay and T.E.S.T. simulation, and guaiacol had a severe effect on lipid peroxidation. A similar trend and comparable developmental toxicity levels were detected for S and G mixtures and the three lignin depolymerized monomers. This study provides data and insights on the differential toxicity of varying S/G ratios for some important building blocks for bio-based materials.
Downscaling satellite soil moisture for landscape applications: A case study in Delaware, USA
(Journal of Hydrology: Regional Studies, 2021-10-15) Warner, Daniel L.; Guevara, Mario; Callahan, John; Vargas, Rodrigo
Study region: Delaware, USA and its surrounding watersheds. Study focus: An ensemble using multiple Kernel K-nearest neighbors (KKNN) models was trained to predict daily grids of SSM at 100-meter resolution based on SSM estimates from the European Space Agency’s Climate Change Initiative Soil Moisture Product, terrain data, soil maps, and local meteorological network data. Estimated SSM was evaluated against independent in situ SSM observations and were investigated for relationships with land cover class and vegetation phenology (i.e., NDVI). New hydrological insights for the region Downscaled daily mean SSM estimates had lower error in space (27%) and greater predictive performance over time compared to the raw, coarse resolution remotely sensed SSM dataset when calibrated to field observed values. Downscaled SSM identified stronger and more widespread temporal relationships with NDVI than other estimation methods. However, both coarse and fine resolution datasets greatly underestimated SSM in wetland areas. The findings highlight the need for enhanced in situ SSM monitoring across diverse settings to improve landscape-level downscaled SSM. The downscaling methodology developed in this study was able to produce daily SSM estimates, providing a framework that can support future SSM modeling efforts, hydroecological investigations, and agricultural studies in this and other regions around the world when used in conjunction with ground-based monitoring networks.
Culturally appropriate shifts in staple grain consumption can improve multiple sustainability outcomes
(Environmental Research Letters, 2021-11-24) Wei, Dongyang; Davis, Kyle Frankel
Diets exercise great influence over both human and environmental health. While numerous efforts have sought to define and identify sustainable diets, there remains a poor understanding of the extent to which such shifts are feasible when taking into account local dietary preferences. Accounting for 40% of dietary calories and 46% of global cropland, cereals offer an important food group by which culturally appropriate dietary shifts may achieve large sustainability benefits. Here we combine country-specific information on dietary cereal supply with nutrient content values, CO2 nutrient penalties, and environmental footprints to quantify the outcomes of adopting two feasible dietary shifts—maximizing the share of C4 cereals (e.g. maize, millet, sorghum) based on historical shares and increasing the share of whole grains. Our results show that increasing the share of whole grains can increase nutrient supply (+7% protein, +37% iron, +42% zinc) and overcome the nutrient-depleting effects of elevated CO2 (eCO2) and that maximizing the share of C4 cereals can substantially reduce environmental burden (−12% greenhouse gas emissions, −11% blue water demand), particularly in Africa and the Middle East. We also find that a combination of the two strategies would likely produce strong co-benefits between increased nutrient supply and reduced environmental impacts with mixed outcomes for offsetting the effects of eCO2. Such simultaneous improvements are particularly important for food insecure regions such as West Africa and Southeast Asia. These findings demonstrate important opportunities to identify sustainable diets that incorporate local preferences and cultural acceptability. Such considerations are essential when developing demand-side solutions to achieve more sustainable food systems.
Heterogeneity in soil chemistry relates to urbanization while soil homogeneity relates to plant invasion in small temperate deciduous forests
(Landscape Ecology, 2022-02-07) Trammell, Tara L. E.; Pouyat, Richard V.; D ’Amico, Vince III
Context: Soil heterogeneity versus homogeneity patterns are observed within and across urban landscapes at multiple scales. To fully evaluate human-mediated influences on soil properties and processes, we need to understand spatial patterns and variation in soil characteristics within a single ecosystem patch type (e.g., forests) in and near cities. Objectives: Our research objectives were to: (1) identify soil characteristics important in driving variation in soil chemistry within urban forests, and (2) examine whether urbanization and invasion gradients were related to variation in soil chemistry within these forests. Methods: We measured soil chemical properties within 36 forests across the U.S. mid-Atlantic. The forests are spatially distributed across an urbanization gradient and comprise a gradient of non-native plant invasion. Results: Urbanization was related to more variation in soil chemistry, whereas plant invasion was related to less variation in soil chemistry within our forests. Soil Ca and Mg concentrations increase with plant invasion yet are less variable within invaded forests most likely due to invasive plants taking up and concentrating these elements. Soil pH, Ca, Mg, Zn, and Cu increase in forests surrounded by greater urbanization, however, these elements are more variable within urban forests likely due to edge effects altering element deposition. Conclusions: Our results demonstrate that while urbanization and invasion can increase soil chemical concentrations, they differentially alter variation in soil chemistry within urban forests. Plant invasion and urban environmental conditions need separate consideration in future conceptual models of urban ecological theory since non-native invasive plants influence soil chemistry independent of other urban factors.
Maize brace root mechanics vary by whorl, genotype, and reproductive stage
(Annals of Botany, 2022-03-03) Hostetler, Ashley N.; Erndwein, Lindsay; Ganji, Elahe; Reneau, Jonathan W.; Killian, Megan L.; Sparks, Erin E.
Background and Aims: Root lodging is responsible for significant crop losses world-wide. During root lodging, roots fail by breaking, buckling, or pulling out of the ground. In maize, above-ground roots, called brace roots, have been shown to reduce root lodging susceptibility. However, the underlying structural-functional properties of brace roots that prevent root lodging are poorly defined. In this study, we quantified structural mechanical properties, geometry, and bending moduli for brace roots from different whorls, genotypes, and reproductive stages. Methods: Using 3-point bend tests, we show that brace root mechanics are variable by whorl, genotype, and reproductive stage. Key Results: Generally, we find that within each genotype and reproductive stage, the brace roots from the first whorl (closest to the ground) had higher structural mechanical properties and a lower bending modulus than brace roots from the second whorl. There was additional variation between genotypes and reproductive stages. Specifically, genotypes with higher structural mechanical properties also had a higher bending modulus, and senesced brace roots had lower structural mechanical properties than hydrated brace roots. Conclusions: Collectively these results highlight the importance of considering whorl-of-origin, genotype, and reproductive stage for quantification of brace root mechanics, which is important for mitigating crop loss due to root mechanical failure.
Rice husk and charred husk amendments increase porewater and plant Si but water management determines grain As and Cd concentration
(Plant and Soil, 2022-03-09) Linam, Franklin; Limmer, Matt A.; Tappero, Ryan; Seyfferth, Angelia L.
Purpose Rice is a staple crop worldwide and a silicon (Si) hyperaccumulator with Si levels reaching 5–10% of its mass; this can result in desilication and Si-deficiency if plant residues are not managed correctly. Rice is also uniquely subject to arsenic (As) and cadmium (Cd) contamination depending on soil conditions. Our goal is to quantify the effects of rice husk (a Si-rich milling byproduct) amendments and different water management strategies on rice uptake of Si, As, and Cd. Methods We employed 4 husk amendment treatments: Control (no husk), Husk (untreated husk), Biochar (husk pyrolyzed at 450 °C), and CharSil (husk combusted at > 1000 °C). Each of these amendments was studied under nonflooded, alternate wetting and drying (AWD), and flooded water management in a pot study. Porewater chemistry and mature plant elemental composition were measured. Results Husk and Biochar treatments, along with flooding, increased porewater and plant Si. Vegetative tissue As decreased with increasing porewater Si, but grain As and plant Cd were primarily controlled by water management. Grain As and Cd were inversely correlated and are simultaneously minimized in a redox potential (Eh) range of 225–275 mV in the studied soil. Ferrihydrite in root iron plaque decreased As translocation from porewater to grain, but amendments were not able to increase plaque ferrihydrite content. Conclusion We conclude moderate husk amendment rates (i.e., 4 years’ worth) with minimal pretreatment strongly increases rice Si content but may not be sufficient to decrease grain As in low Si and As soil.
Aggregation-induced emission of 5-(benzylidene)pyrimidine-2,4,6-triones
(Bulletin of the University of Karaganda – Chemistry, 2022-03-30) Mendigalieva, S. S.; Birimzhanova, D. A.; Irgibaeva, I. S.; Barashkov, N. N.; Sakhno, Y. E.
5-(Benzylidene)pyrimidine-2,4,6-triones with different substituents on the phenyl rings: 5-(4’-dimethylaminobenzylidene) barbituric acid and 5-(4’-methoxybenzylidene) barbituric acid were synthesized, and their spectral-luminescent properties were investigated. A decreasing fluorescence efficiency in the solid-state is general and is mainly attributed to the intermolecular vibronic interactions, which induce the nonradiative deactivation process. Whereas the isolated dye molecules are virtually non-luminescent in dilute solutions, they become highly emissive upon solution thickening or aggregation in poor solvents or in the solid-state, show an increase of luminescence intensity, the phenomenon of the aggregation-induced emission (AIE phenomenon). The development of efficient luminescent materials is a topic of great current interest. The emission color is changed from red (maximum at 630 nm) to green (maximum at 540 nm) by varying the substituent on the phenyl ring from dimethylamino to the methoxy group. Theoretical calculation shows that the dye molecules' aggregation-induced emission characteristics result from intermolecular interactions. Utilizing such features, the molecules can be employed as fluorescent probes for the detection of the ethanol content in aqueous solutions.
Crop harvests for direct food use insufficient to meet the UN’s food security goal
(Nature Food, 2022-05-12) Ray, Deepak K.; Sloat, Lindsey L.; Garcia, Andrea S.; Davis, Kyle F.; Ali, Tariq; Xie, Wei
Rising competition for crop usage presents policy challenges exacerbated by poor understanding of where crops are harvested for various uses. Here we create high-resolution global maps showing where crops are harvested for seven broad use categories—food, feed, processing, export, industrial, seed and losses. Yields for food crops are low relative to other crop-use categories. It is unlikely, given current trends, that the minimum calorie requirement to eliminate projected food undernourishment by 2030 will be met through crops harvested for direct food consumption, although enough calories will be harvested across all usages. Sub-Saharan African nations will probably fall short of feeding their increased population and eliminating undernourishment in 2030, even if all harvested calories are used directly as food.
Evaluation of Brace Root Parameters and Its Effect on the Stiffness of Maize
(in silico Plants, 2022-05-12) Obayes, Shaymaa K.; Timber, Luke; Head, Monique; Sparks, Erin E.
Plant mechanical failure (lodging) causes significant yield loss for crops such as maize. Understanding this failure has relied on static measurements of plant biomechanics. In this study, digital image correlation techniques are used to capture dynamic motion to understand the plant mechanical behavior of maize stalks in the presence and absence of brace roots, which are stem-borne aerial roots known to stabilize the maize stalks. The data show that brace roots function to secure the maize stalk, limiting both deflection and uplift. A finite element (FE) model is developed using ABAQUS software to validate the non-contact, video-based measured deflections captured by the dynamic motion and confirm the linear elastic behavior of the stem, following fundamental principles of engineering mechanics. Good agreement is found between the field data captured using video-based measurements and the physics-based FE model when a rotational connector element is connected at the base to quantify the 1) relative contribution and moment resistance provided by the root system, 2) displacement at any location along the stalk, and 3) flexural rigidity of the brace-stem system, where the rigidity can be associated with various phenotypes to design plant systems that are more resilient to lateral loading.
First report of Rhizoctonia solani AG 4 causing brown bean of lima bean in Delaware
(Plant Disease, 2022-06-11) Ginn, Adam Nicholas; Evans, Tom; Ernest, Emmalea; Koehler, Alyssa M.
Lima bean production has been an economically valuable staple in Delaware agriculture for almost a century, with annual revenue approaching 8 million dollars (USDA-NASS, 2019; Evans et al. 2007). From 2019-2021, lima beans displaying symptoms of brown discoloration, referred to as “brown bean” were observed in the green baby lima variety ‘Cypress’ across multiple commercial and research fields. Symptoms were present in approximately 1-5% of beans and not visible until pods were opened for harvest. Thirty-seven symptomatic beans were collected and surface disinfested in 0.85% sodium hypochlorite for 30 s, rinsed in sterile deionized water for 30 s, sectioned into four pieces and plated onto potato dextrose agar (PDA) amended with 50 µg/ml penicillin G and streptomycin sulfate. Petri dishes were incubated at 23ºC and observed for colony morphology. Pure cultures were obtained with tan colonies that had mycelia with right angle branching and septations near the branch, consistent with the description of Rhizoctonia solani Kuhn (Sneh et al. 1991). DNA extraction and pathogen identification was confirmed by sequencing of the internal transcribed spacer (ITS) region of nuclear ribosomal DNA using primers ITS4/ITS5 (White et al. 1990) for thirty-seven isolates collected in 2019 and 2020. Isolates were identified as Rhizoctonia solani AG 4 (99.9% sequence identity with GenBank Accession [MN106359.1].) A representative isolate was selected to complete Koch’s postulates and the sequence was deposited in GenBank as accession number MW560551. To observe colonization ability, 10 detached pods were sterilized in 75% EtOH for 60 s, then rinsed in Milli-Q water. The detached pods were divided among two 150 mm Petri dishes containing a single 150 mm filter paper saturated with Milli-Q water. Five 1 mm2 agar plugs colonized with the representative R. solani isolate were placed 0.5 cm apart along the length of the pod. Plates were sealed with parafilm and left at room temperature. Control pods were kept in identical conditions but inoculated using clean agar plugs. The trial was repeated and a second trial was conducted on 12 attached asymptomatic pods from C-Elite Select lima bean plants at the succulent seed stage to complete Koch’s Postulates. Pods were surface disinfested with 70% ethanol. Three attached pods were wounded with the tip of a sterile scalpel blade where a colonized agar plug was placed and loosely wrapped with a thin parafilm layer to maintain contact. Three attached pods not wounded were also inoculated with a colonized agar plug and wrapped by parafilm. Three wounded and non-wounded pods received clean agar plug controls. Both attached and detached pods were kept at room temperature for one week until symptoms began to manifest on the pod surfaces, at which point the beans from infected pods were removed and placed on PDA, three to a plate. In the attached assay, all beans of both wounded and non-wounded pods developed symptoms. The plates were stored in identical conditions and monitored for 5 days until tan colonies were observed. Culture morphology was consistent with the original isolate in all beans. Sequencing of the ITS region confirmed identity as R. solani AG-4. No symptoms were observed on control pods or seeds. Rhizoctonia solani is most frequently associated with symptoms of root rot (Sharma-Poudyal et al. 2015), but no stem symptoms are associated with the late season “brown bean” that has been observed throughout production in recent years. To our knowledge, this is the first report of Rhizoctonia solani AG 4 causing symptoms of brown bean of lima bean in Delaware. In preliminary observations, symptoms seem to be worse in pods that could have had contact with the soil directly or via rain splash. This disease cannot be detected until pods are split open, which has potential to reduce lima bean quality at harvest. Further monitoring should be conducted to quantify yield impacts and develop appropriate preventative and curative techniques.
Spatial variability and uncertainty of soil nitrogen across the conterminous United States at different depths
(Ecosphere, 2022-07-27) Smith, Elizabeth M.; Vargas, Rodrigo; Guevara, Mario; Tarin, Tonantzin; Pouyat, Richard V.
Soil nitrogen (N) is an important driver of plant productivity and ecosystem functioning; consequently, it is critical to understand its spatial variability from local-to-global scales. Here, we provide a quantitative assessment of the three-dimensional spatial distribution of soil N across the United States (CONUS) using a digital soil mapping approach. We used a random forest-regression kriging algorithm to predict soil N concentrations and associated uncertainty across six soil depths (0–5, 5–15, 15–30, 30–60, 60–100, and 100–200 cm) at 5-km spatial grids. Across CONUS, there is a strong spatial dependence of soil N, where soil N concentrations decrease but uncertainty increases with soil depth. Soil N was higher in Pacific Northwest, Northeast, and Great Lakes National Ecological Observatory Network (NEON) ecoclimatic domains. Model uncertainty was higher in Atlantic Neotropical, Southern Rockies/Colorado Plateau, and Southeast NEON domains. We also compared our soil N predictions with satellite-derived gross primary production and forest biomass from the National Biomass and Carbon Dataset. Finally, we used uncertainty information to propose optimized locations for designing future soil surveys and found that the Atlantic Neotropical, Pacific Northwest, Pacific Southwest, and Appalachian/Cumberland Plateau NEON domains may require larger survey efforts. We highlight the need to increase knowledge of biophysical factors regulating soil processes at deeper depths to better characterize the three-dimensional space of soils. Our results provide a national benchmark regarding the spatial variability and uncertainty of soil N and reveal areas in need of a better representation.
Relative Roles of Sediment Transport and Localized Erosion on Phosphorus Load in the Lower Susquehanna River and Its Mouth in the Chesapeake Bay, USA
(Journal of Geophysical Research: Biogeosciences, 2022-08-05) Li, Qiang; Gray, Katelyn E.; Jaisi, Deb P.
Particle size greatly influences the fate of phosphorus (P) in estuaries as P adheres more readily to the larger surface area in smaller sized particles. Here, data on two size fractions of particulate matter, permanently suspended particulate matter (PSPM, ≤40 μm) and resuspended particulate matter (RSPM, >40 μm), from field and controlled laboratory erosion experiments were analyzed to determine their relative contribution to water column P in the mouth of the Susquehanna River in the upper Chesapeake Bay. Based on the composition of sequentially extracted P pools, C and N isotopes, and elemental data, all PSPM and the majority of RSPM are most likely derived from allochthonous sources through river transport. A minor fraction of particulate matter in the water column was derived from sediment resuspension, which had a dominant role above the sediment-water interface in the river's mouth. The proportion of biologically available P pools to recalcitrant P pools in suspended particulate matter decreased with water column depth, indicating their preferential removal or biological utilization during settling. Suspended particulate matter (SPM) mobilized during sediment erosion experiments, regardless of particle size, was richer in biologically available P pools than SPM in the field, suggesting higher mobility of these pools in the field. These complementary results from field and field-simulated laboratory erosion experiments provide unique insights into the composition of particulate matter under different hydrodynamic regimes in the river estuary. Plain Language Summary: Phosphorus (P) is often the limiting nutrient for eutrophication. Of importance is the P load from the Susquehanna River into the Chesapeake Bay, as it contributes about a fourth of the total bay load. Paired field measurements and erosion experiments showed that the majority of suspended particulate matter and P load was derived from external, upstream riverine sources. Localized sediment erosion was present only in the mouth of the river in the northernmost Chesapeake Bay. Comparative analyses showed that P was more likely to be transported in fine grained suspended particulate matter and in forms that were more biologically available. Key Points: - Concentration of total particulate matter increased downstream with water column depth but P content decreased with water depth - P pools and δ13C and δ15N values of in situ and eroded particulate matter indicated riverine input as the major source - Sediment resuspension marginally contributed to P load
Maize plants and the brace roots that support them
(New Phytologist, 2022-09-14) Sparks, Erin E.
Brace roots are a unique but poorly understood set of organs found in some large cereal crops such as maize. These roots develop from aerial stem nodes and can remain aerial or grow into the ground. Despite their name, the function of these roots to brace the plant was only recently shown. In this article, I discuss the current understanding of brace root function and development, as well as the multitude of open questions that remain about these fascinating organs.
Nitrogen Sinks or Sources? Denitrification and Nitrogen Removal Potential in Riparian Legacy Sediment Terraces Affected by Milldams
(Journal of Geophysical Research: Biogeosciences, 2022-09-19) Peck, Erin K.; Inamdar, Shreeram; Sherman, Melissa; Hripto, Johanna; Peipoch, Marc; Gold, Arthur J.; Addy, Kelly
Riparian zones are key ecotones that buffer aquatic ecosystems through removal of nitrogen (N) via processes such as denitrification. However, how dams alter riparian N cycling and buffering capacity is poorly understood. Here, we hypothesized that elevated groundwater and anoxia due to the backup of stream water above milldams may enhance denitrification. We assessed denitrification rates (using denitrification enzyme assays) and potential controlling factors in riparian sediments at various depths upstream and downstream of two relict U.S. mid-Atlantic milldams. Denitrification was not significantly different between upstream and downstream, although was greater per river km upstream considering deeper and wider geometries. Further, denitrification typically occurred in hydrologically variable shallow sediments where nitrate-N and organic matter were most concentrated. At depths below 1 m, both denitrification and nitrate-N decreased while ammonium-N concentrations substantially increased, indicating suppression of ammonium consumption or dissimilatory nitrate reduction to ammonium. These results suggest that denitrification occurs where dynamic groundwater levels result in higher rates of nitrification and mineralization, while another N process that produces ammonium-N competes with denitrification for limited nitrate-N at deeper, more stagnant/poorly mixed depths. Ultimately, while it is unclear whether relict milldams are sources of N, limited denitrification rates indicate that they are not always effective sinks; thus, milldam removal—especially accompanied by removal of ammonium-N rich legacy sediments—may improve riparian N buffering. Plain Language Summary: Floodplains adjacent to rivers are important ecosystems that provide valuable services including nutrient removal, especially nitrogen, from stream water. Because nitrogen is a major polluter of coastal waters, river floodplains are increasingly being restored as part of watershed best management practices. For example, millions of dollars are being spent annually in the Chesapeake Bay to install 900 miles of riparian buffers and on other watershed practices to mitigate nutrient pollution. However, the impact of small, colonial-era milldams on floodplain nitrogen mitigation is poorly understood, despite >14,000 such structures still present across streams of the eastern United States. We studied the impact of two small milldams (Roller mill on Chiques Creek, Lancaster, Pennsylvania, and Cooch mill on Christiana River, Newark, Delaware) on the ability of floodplains to remove or store nitrogen. We found that the stagnant water that accumulates behind milldams restricts floodplains from effectively removing nitrogen and may actually cause the accumulation of nitrogen. Whether accumulated nitrogen is released back into streams is unknown but concerning. Removal of dams would likely improve many ecosystem services of both streams and floodplains, with minimal consequences for the nitrogen mitigation abilities of these ecosystems. Key Points: Riparian denitrification rates are similar above and below milldams but deeper, wider upstream zones result in more nitrogen removal Denitrification rates peak in shallow sediments of riparian areas above milldams with higher hydrologic variability Stagnant hydrologic conditions upstream of milldams promote nitrogen processes that result in ammonium accumulation at deep sediment depths

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