A Mass Balance Approach to Identify and Compare Differential Routing of \u3csup\u3e13\u3c/sup\u3eC-Labeled Carbohydrates, Lipids, and Proteins In Vivo

All animals route assimilated nutrients to their tissues where they are used to support growth or are oxidized for energy. These nutrients are probably not allocated homogeneously among the various tissue and are more likely to be preferentially routed toward some tissues and away from others. Here we introduce an approach that allows researchers to identify and compare nutrient routing among different organs and tissues. We tested this approach by examining nutrient routing in birds. House sparrows Passer domesticus were fed a meal supplemented with one of seven 13C-labeled metabolic tracers representing three major classes of macronutrients, namely, carbohydrates, amino acids, and fatty acids. While these birds became postabsorptive (2 h after feeding), we quantified the isotopic enrichment of the lean and lipid fractions of several organs and tissues. We then compared the actual 13C enrichment of various tissue fractions with the predictions of our model to identify instances where nutrients were differentially routed and found that different classes of macronutrients are uniquely routed throughout the body. Recently ingested amino acids were preferentially routed to the lean fraction of the liver, whereas exogenous carbohydrates were routed to the brain and the lipid fraction of the liver. Fatty acids were definitively routed to the heart and the liver, although high levels of palmitic acid were also recovered in the adipose tissue. Tracers belonging to the same class of molecules were not always routed identically, illustrating how this technique is also suited to examine differences in nonoxidative fates of closely related molecules. Overall, this general approach allows researchers to test heretofore unexamined predictions about how animals allocate the nutrients they ingest

Phenotypic plasticity and water flux rates of Citrus root orders under salinity

Knowledge about the root system structure and the uptake efficiency of root orders is critical to understand the adaptive plasticity of plants towards salt stress. Thus, this study describes the phenological and physiological plasticity of Citrus volkameriana rootstocks under severe NaCl stress on the level of root orders. Phenotypic root traits known to influence uptake processes, for example frequency of root orders, specific root area, cortical thickness, and xylem traits, did not change homogeneously throughout the root system, but changes after 6 months under 90 mM NaCl stress were root order specific. Chloride accumulation significantly increased with decreasing root order, and the Cl− concentration in lower root orders exceeded those in leaves. Water flux densities of first-order roots decreased to <20% under salinity and did not recover after stress release. The water flux densities of higher root orders changed marginally under salinity and increased 2- to 6-fold in second and third root orders after short-term stress release. Changes in root order frequency, morphology, and anatomy indicate rapid and major modification of C. volkameriana root systems under salt stress. Reduced water uptake under salinity was related to changes of water flux densities among root orders and to reduced root surface areas. The importance of root orders for water uptake changed under salinity from root tips towards higher root orders. The root order-specific changes reflect differences in vulnerability (indicated by the salt accumulation) and ontogenetic status, and point to functional differences among root orders under high salinity

Soil geochemistry – and not topography – as a major driver of carbon allocation, stocks, and dynamics in forests and soils of African tropical montane ecosystems

The lack of field-based data in the tropics limits our mechanistic understanding of the drivers of net primary productivity (NPP) and allocation. Specifically, the role of local edaphic factors - such as soil parent material and topography controlling soil fertility as well as water and nutrient fluxes - remains unclear and introduces substantial uncertainty in understanding net ecosystem productivity and carbon (C) stocks. Using a combination of vegetation growth monitoring and soil geochemical properties, we found that soil fertility parameters reflecting the local parent material are the main drivers of NPP and C allocation patterns in tropical montane forests, resulting in significant differences in below- to aboveground biomass components across geochemical (soil) regions. Topography did not constrain the variability in C allocation and NPP. Soil organic C stocks showed no relation to C input in tropical forests. Instead, plant C input seemingly exceeded the maximum potential of these soils to stabilize C. We conclude that, even after many millennia of weathering and the presence of deeply developed soils, above- and belowground C allocation in tropical forests, as well as soil C stocks, vary substantially due to the geochemical properties that soils inherit from parent material

The interplay between ozone and urban vegetation – BVOC emissions, ozone deposition, and tree ecophysiology

Tropospheric ozone (O3) is one of the most prominent air pollution problems in Europe and other countries worldwide. Human health is affected by O3 via the respiratory as well the cardiovascular systems. Even though trees are present in relatively low numbers in urban areas, they can be a dominant factor in the regulation of urban O3 concentrations. Trees affect the O3 concentration via emission of biogenic volatile organic compounds (BVOC), which can act as a precursor of O3, and by O3 deposition on leaves. The role of urban trees with regard to O3 will gain further importance as NOx concentrations continue declining and climate warming is progressing—rendering especially the urban ozone chemistry more sensitive to BVOC emissions. However, the role of urban vegetation on the local regulation of tropospheric O3 concentrations is complex and largely influenced by species-specific emission rates of BVOCs and O3 deposition rates, both highly modified by tree physiological status. In this review, we shed light on processes related to trees that affect tropospheric ozone concentrations in metropolitan areas from rural settings to urban centers, and discuss their importance under present and future conditions. After a brief overview on the mechanisms regulating O3 concentrations in urban settings, we focus on effects of tree identity and tree physiological status, as affected by multiple stressors, influencing both BVOC emission and O3 deposition rates. In addition, we highlight differences along the rural-urban gradient affecting tropospheric O3 concentrations and current knowledge gaps with the potential to improve future models on tropospheric O3 formation in metropolitan areas

Faba Bean Cultivation – Revealing Novel Managing Practices for More Sustainable and Competitive European Cropping Systems

Faba beans are highly nutritious because of their high protein content: they are a good source of mineral nutrients, vitamins, and numerous bioactive compounds. Equally important is the contribution of faba bean in maintaining the sustainability of agricultural systems, as it is highly efficient in the symbiotic fixation of atmospheric nitrogen. This article provides an overview of factors influencing faba bean yield and quality, and addresses the main biotic and abiotic constraints. It also reviews the factors relating to the availability of genetic material and the agronomic features of faba bean production that contribute to high yield and the improvement of European cropping systems. Emphasis is to the importance of using new high-yielding cultivars that are characterized by a high protein content, low antinutritional compound content, and resistance to biotic and abiotic stresses. New cultivars should combine several of these characteristics if an increased and more stable production of faba bean in specific agroecological zones is to be achieved. Considering that climate change is also gradually affecting many European regions, it is imperative to breed elite cultivars that feature a higher abiotic–biotic stress resistance and nutritional value than currently used cultivars. Improved agronomical practices for faba bean crops, such as crop establishment and plant density, fertilization and irrigation regime, weed, pest and disease management, harvesting time, and harvesting practices are also addressed, since they play a crucial role in both the production and quality of faba bean

Organic matter cycling along geochemical, geomorphic and disturbance gradients in forests and cropland of the African Tropics – Project TropSOC Database Version 1.0

The African Tropics are hotspots of modern-day land-use change and are, at the same time, of great relevance for the cycling of carbon (C) and nutrients between plants, soils and the atmosphere. However, the consequences of land conversion on biogeochemical cycles are still largely unknown as they are not studied in a landscape context that defines the geomorphic, geochemically and pedological framework in which biological processes take place. Thus, the response of tropical soils to disturbance by erosion and land conversion is one of the great uncertainties in assessing the carrying capacity of tropical landscapes to grow food for future generations and in predicting greenhouse gas fluxes (GHG) from soils to the atmosphere and, hence, future earth system dynamics. Here, we describe version 1.0 of an open access database created as part of the project &ldquo;Tropical soil organic carbon dynamics along erosional disturbance gradients in relation to variability in soil geochemistry and land use&rdquo; (TropSOC). TropSOC v1.0 contains spatial and temporal explicit data on soil, vegetation, environmental properties and land management collected from 136 pristine tropical forest and cropland plots between 2017 and 2020 as part of several monitoring and sampling campaigns in the Eastern Congo Basin and the East African Rift Valley System. The results of several laboratory experiments focusing on soil microbial activity, C cycling and C stabilization in soils complement the dataset to deliver one of the first landscape scale datasets to study the linkages and feedbacks between geology, geomorphology and pedogenesis as controls on biogeochemical cycles in a variety of natural and managed systems in the African Tropics. The hierarchical and interdisciplinary structure of the TropSOC database allows for linking a wide range of parameters and observations on soil and vegetation dynamics along with other supporting information that may also be measured at one or more levels of the hierarchy. TropSOC&rsquo;s data marks a significant contribution to improve our understanding of the fate of biogeochemical cycles in dynamic and diverse tropical African (agro-)ecosystems. TropSOC v1.0 can be accessed through the supplementary material provided as part of this manuscript or as a separate download via the websites of the Congo Biogeochemistry observatory and the GFZ data repository where version updates to the database will be provided as the project develops.</p

Einfluss von Bodentrockenheit auf die hydraulischen Eigenschaften und das Konkurrenzverhalten von Baumwurzeln

Durch die mit dem Klimawandel einhergehende Temperaturerhöhung und den verringerten Niederschlag wird es in Zukunft häufiger zu Trockenperioden kommen. Wasser ist bereits heute ein das Pflanzenwachstum limitierender Faktor, insbesondere in Wäldern und Plantagen auf schwachgründigen, sandigen Böden sowie in Regionen mit geringem Niederschlag. Zudem fördert der erhöhte Bewässerungs-Bedarf unter trockeneren klimatischen Bedingungen die Versalzung von landwirtschaftlichen Böden. Obwohl die Wasseraufnahme und Konkurrenzprozesse um Wasser und Nährstoffe im Boden stattfinden, lag der Schwerpunkt bei der Erforschung von pflanzlichen Anpassungsstrategien an Trockenheit und Salz-Stress in der Vergangenheit häufig auf den oberirdischen Pflanzenorganen. Um die Effekte des Klimawandels vorhersagen zu können, ist jedoch ein besseres Verständnis für die Anpassungsfähigkeit von Wurzelsystemen an Trockenheit und unterirdische Konkurrenzprozesse nötig. Diese Studie über fünf Baumarten temperater Mischwälder und mediterraner Obstbaum-Plantagen untersucht den Einfluss reduzierter Bodenwasserverfügbarkeit und unterirdischer Konkurrenzprozesse auf die Struktur und Funktion von Wurzelsystemen. Insbesondere soll in dieser Studie geklärt werden, ob (i) die axiale hydraulische Leitfähigkeit von Wurzeln, analog zur Anpassung oberirdischer Organe, mit zunehmender Trockenheit abnimmt, (ii) Feinwurzeln im Boden-Pflanze-Atmosphäre-Kontinuum als „hydraulische Sicherungen“ fungieren, und (iii) die unterirdische Konkurrenzkraft symmetrisch zur Größe des Wurzelsystems ist bzw. (iv) zwischen Baumarten und mit der Wasser- und Nährstoffversorgung variiert. Durch diese Studie konnte nachgewiesen werden, dass i) Die axiale hydraulische Leitfähigkeit der Fein- und Grobwurzeln von Quercus petraea (MATT.) LIEBL., im Gegensatz zu Wurzeln von Fagus sylvatica L., bei starker Bodentrockenheit zunimmt. An Wurzeln von Olea europaea L. konnte zudem eine Zunahme der hydraulischen Wurzel-Leitfähigkeiten mit zunehmendem Salzgehalt des Bodens beobachtet werden. An Trockenheit und/oder Salz-Stress angepasste Baumarten wie Quercus petraea und Olea europea sind vermutlich in der Lage, den durch den Verlust an Wurzelbiomasse erhöhten hydraulischen Widerstand durch eine Verminderung der axialen Wurzel-Leitungswiderstände zu kompensieren. In Sprossen und Zweigen konnte ein ähnlicher Anpassungsmechanismus bislang nur vereinzelt nachgewiesen werden. ii) Feinwurzeln als „hydraulische Sicherungen“ im Boden-Pflanze-Atmosphäre-Kontinuum wirken können. Das Xylem von Quercus petraea und Fagus sylvatica Feinwurzeln emboliert bereits bei geringfügig verminderten Wasserpotentialen. Darüber hinaus erhöht sich die Embolieanfälligkeit der Feinwurzeln von Quercus petraea nach Bodentrockenheit. Neben dem Absterben von lateralen Feinwurzeln scheinen Embolien als weiterer, eventuell reversibler, hydraulischer Sicherungsmechanismus zu wirken. iii) Verschiedene Anzeichen auf die Asymmetrie der unterirdischen Konkurrenzprozesse hindeuten. Zum Einen ist die Feinwurzelbiomasse von Quercus petraea unter inter-spezifischen Konkurrenzbedingungen im Vergleich zu Reinbeständen überproportional reduziert, zum Anderen hängt die Wachstumsrate und Morphologie von Wurzeln von der Anwesenheit eines Konkurrenten und nicht von der Anfangsbiomasse ab. iv) Baumarten anhand ihrer unterirdischen Konkurrenzkraft gegliedert werden können. Den Ergebnissen über Wurzelbiomasse und -wachstum unter unterschiedlichen Konkurrenzbedingungen zur Folge, ist Fagus sylvatica nicht nur ober-, sondern auch unterirdisch eine der konkurrenzstärksten Baumarten Mitteleuropas. Unter zunehmendem abiotischem Stress verlieren artspezifische Unterschiede in der Konkurrenzkraft jedoch an Bedeutung und die Wichtigkeit biotischer Interaktionen ist vermindert. Eine Einschränkung der Ressourceverfügbarkeit, z.B. durch Trockenheit, scheint die Konkurrenzkraft von Fagus sylvatica und Quercus petraea in gleicher Weise zu beeinflussen

Plant roots and spectroscopic methods – analyzing species, biomass and vitality

In order to understand plant functioning, plant community composition, and terrestrial biogeochemistry, it is decisive to study standing root biomass, (fine) root dynamics, and interactions belowground. While most plant taxa can be identified by visual criteria aboveground, roots show less distinctive features. Furthermore, root systems of neighboring plants are rarely spatially segregated; thus, most soil horizons and samples hold roots of more than one species necessitating root sorting according to taxa. In the last decades, various approaches, ranging from anatomical and morphological analyses to differences in chemical composition and DNA sequencing were applied to discern species’ identity and biomass belowground. Among those methods, a variety of spectroscopic methods was used to detect differences in the chemical composition of roots. In this review, spectroscopic methods used to study root systems of herbaceous and woody species in excised samples or in situ will be discussed. In detail, techniques will be reviewed according to their usability to discern root taxa, to determine root vitality, and to quantify root biomass non-destructively or in soil cores holding mixtures of plant roots. In addition, spectroscopic methods which may be able to play an increasing role in future studies on root biomass and related traits are highlighted

It’s Complicated: Intraroot System Variability of Respiration and Morphological Traits in Four Deciduous Tree Species

International audienceWithin branched root systems, a distinct heterogeneity of traits exists. Knowledge about the ecophysiology of different root types is critical to understand root system functioning. Classification schemes have to match functional root types as closely as possible to be used for sampling and modeling. Among ecophysiological root traits, respiration is of particular importance, consuming a great amount of carbon allocated. Root architecture differs between the four deciduous tree seedlings. However, two types of terminal root segments (i.e. first and second orders), white colored and brown colored, can be distinguished in all four species but vary in frequency, their morphology differing widely from each other and higher coarse root orders. Root respiration is related to diameter and tissue density. The use of extended root ordering (i.e. order and color) explains the variance of respiration two times as well as root diameter or root order classes alone. White terminal roots respire significantly more than brown ones; both possess respiration rates that are greater than those of higher orders in regard to dry weight and lower in regard to surface area. The correlation of root tissue density to respiration will allow us to use this continuous parameter (or easier to determine dry matter content) to model the respiration within woody root systems without having to determine nitrogen contents. In addition, this study evidenced that extended root orders are better suited than root diameter classes to picture the differences between root functional types. Together with information on root order class frequencies, these data allow us to calculate realistic, species-specific respiration rates of root branches

AMF Inoculation Enhances Growth and Improves the Nutrient Uptake Rates of Transplanted, Salt-Stressed Tomato Seedlings

The study aimed to investigate the effects of commercially available AMF inoculate (Glomus sp. mixture) on the growth and the nutrient acquisition in tomato (Solanumlycopersicum L.) plants directly after transplanting and under different levels of salinity. Inoculated (AMF+) and non-inoculated (AMF−) tomato plants were subjected to three levels of NaCl salinity (0, 50, and 100 mM·NaCl). Seven days after transplanting, plants were analyzed for dry matter and RGR of whole plants and root systems. Leaf tissue was analyzed for mineral concentration before and after transplanting; leaf nutrient content and relative uptake rates (RUR) were calculated. AMF inoculation did not affect plant dry matter or RGR under fresh water-irrigation. The growth rate of AMF−plants did significantly decline under both moderate (77%) and severe (61%) salt stress compared to the fresh water-irrigated controls, while the decline was much less (88% and 75%,respectively)and statistically non-significant in salt-stressed AMF+ plants. Interestingly, root system dry matter of AMF+ plants (0.098 g plant–1) remained significantly greater under severe soil salinity compared to non-inoculated seedlings (0.082 g plant–1). The relative uptake rates of N, P, Mg, Ca, Mn, and Fe were enhanced in inoculated tomato seedlings and remained higher under (moderate) salt stress compared to AMF− plants This study suggests that inoculation with commercial AMF during nursery establishment contributes to alleviation of salt stress by maintaining a favorable nutrient profile. Therefore, nursery inoculation seems to be a viable solution to attenuate the effects of increasing soil salinity levels, especially in greenhouses with low natural abundance of AMF spores