Platanus Occidentalis Research Articles

BLANCO RIVER RIPARIAN FOREST REGENERATION FOLLOWING A RECORD FLOOD IN CENTRAL TEXAS

A record flood in 2015 resulted in widespread disturbance of the Blanco River riparian corridor with extensive loss of vegetation through floodplain stripping. The riparian forest along the Blanco River is slowly recovering via two primary pathways—natural regeneration from the seedbank and through resprouting of damaged trees. We conducted a study of woody riparian vegetation along the Blanco River to quantify the composition of the recovering forest community and the proportion of trees that are regenerating by resprouting vs. seedbank colonizers. The study captured overall compositional and density patterns as well as comparisons among three geomorphic settings including instream channel bars, the riverbank and near-channel lower elevation floodplain, and the higher-elevation floodplain to upland terraces. Seedlings represented 90% of the density and only 2% of the biomass; in contrast, resprouted trees represented 10% of the density and 98% of the biomass. Fast-growing pioneer species such as sycamore (Platanus occidentalis) and black willow (Salix nigra) were dominant nearest the river channel while facultative and upland species such as pecan (Carya illinoiensis) and hackberry (Celtis spp.) dominated plots higher on the floodplain. Seedlings were far more numerous than resprouts, and seedling density was highest in plots along the riverbank and closest to the channel.

Phenotypic plasticity of Platanus acerifolia (Platanaceae): morphological and anatomical trait variations in response to different pollution levels in Rome

Platanus acerifolia (Aiton) Willd was generated spontaneously around the beginning of the 1600s in Spain between Platanus orientalis L. and Platanus occidentalis L. The study was carried out on P. acerifolia trees in different sites in Rome in the period April-July 2019. Trees comparable for size were selected in A sites (historical parks), B sites (high traffic density streets) and in C sites (high traffic density avenues along the Tevere River characterized by a large water availability). At the morphological level, leaf area (LA) was significantly higher in A and C sites and leaf tissue density (LTD) in C sites. At anatomical level, the total leaf thickness (LT), the palisade parenchyma thickness (Pt), the spongy parenchyma thickness (St) and the abaxial epidermis thickness (Abet) were significantly higher in A sites, while the adaxial cuticle thickness (Adct) and the adaxial epidermis thickness (Adet) in B sites. The ratio between palisade and spongy parenchyma thickness (P/S) was significantly higher in C sites. The plasticity index (PI, 0.42) was calculated on all the considered leaf traits. Among the morphological traits, LTD had the highest plasticity (0.49) and among the anatomical traits, trichomes density (TD) and Adet (0.74 and 0.54, respectively). Overall, the results highlight the large adaptability of P. acerifolia to grow in different sites in Rome through several changes in leaf morphological and anatomical traits.

Effects of drying methods on plant lipid compounds and bulk isotopic compositions.

Plant lipid biomarkers, such as plant waxes and terpenoids, and the stable isotopic composition of bulk leaves are widely used in both modern and paleoclimate studies for tracking vegetation and climate. However, the effects of different drying methods on the preservation of plant lipid biomarkers and the stable isotopic compositions of leaves are less explored. Here, we investigated various drying methods for the measurement of plant lipid concentrations and bulk leaf isotopic compositions. Leaves from four tree species (Acer rubrum, Pinus sylvestris, Platanus occidentalis, and Taxodium distichum) were collected and dried using air, an oven, a freeze-dryer, and a microwave. We compared concentrations of leaf waxes and terpenoids and carbon (δ13 C) and nitrogen (δ15 N) isotopic compositions of leaves by different drying methods. The air, oven, freeze-dryer, and microwave drying methods did not affect lipid concentrations significantly, and only a few homologues differed (38.1% or 41.8 μg/g on average) possibly due to biological variations or enhanced extraction efficiencies. The δ13 C values were not affected by drying methods, whereas the δ15 N values in oven-dried leaves in some species were higher by 0.2-0.7‰ than those obtained by other methods. Though small, we attribute these patterns to loss of leaf compounds with lower isotope ratios during oven-drying. Based on our results, each drying technique yielded equivalent results for all plant wax and terpenoid concentrations and bulk leaf δ13 C values; however, oven-drying modified the δ15 N values.

Gray Bat (Myotis grisescens) Use of Trees as Day Roosts in North Carolina and Tennessee

We documented female Myotis grisescens (Gray Bat) from different colonies using 2 separate live trees and 1 snag as diurnal roosts during fall and spring migration periods. The live trees were both Platanus occidentalis (American Sycamore) located along the bank of the French Broad River in Madison County, NC, and the snag was a Fraxinus pennsylvanica (Green Ash) located in a swamp on the western edge of the city of Cookeville in Putnam County, TN. The Gray Bat is considered a year-round cave obligate and, to our knowledge, these observations represent the first documented use of tree roosts by this species.

Emission patterns of biogenic volatile organic compounds from dominant forest species in Beijing, China

Biogenic volatile organic compounds (BVOCs) have significant effects on atmospheric chemistry, ozone formation and secondary organic aerosol formation. Considering few investigations about BOVCs emissions in north China where is facing serious air pollution in recent years, emissions of various BVOCs from 24 dominant forest species in Beijing were measured from June to September in 2018, using a dynamic headspace sampling method. More than one hundred BVOCs in the collected samples were identified by using an automatic thermal desorption-gas chromatography/mass spectrometry, and their emission rates based on leaf biomass were calculated. Isoprene and monoterpenes were verified to be the dominant BVOCs emitted from the tree species, accounting for more than 50% of the total BVOCs. Generally, broad-leaved species displayed high isoprene emission rates, especially the Platanus occidentalis (21.36 µg/(g⋅hr)), Robinia pseudoacacia (11.55 µg/(g⋅hr)), and Lonicera maackii (9.17 µg/(g⋅hr)), while coniferous species emitted high rates of monoterpenes, such as Platycladus orientalis (27.18 µg/(g⋅hr)), Pinus griffithii (23.11 µg/(g⋅hr)), and Pinus armandii (7.42 µg/(g⋅hr)). High emission rates of monoterpenes from the broad-leaved species of Buxus megistophylla (13.07 µg/(g⋅hr)) and Ligustrum vicaryi (5.74 µg/(g⋅hr)), and high isoprene emission rate from the coniferous tree of Taxus cuspidata (5.86 µg/(g⋅hr)) were also observed. The emission rates of sesquiterpenes from each tree were usually 10–100 times smaller than those of isoprene and monoterpenes. Additionally, relatively high emission rates of oxygenated volatile organic compounds and other alkenes than isoprene and monoterpenes were also found for several tree species.

Biogeomorphic keystones and equivalents: Examples from a bedrock stream

AbstractBiogeomorphic keystone species profoundly impact landscapes, such that their introduction or removal would cause fundamental changes in geomorphic systems. This paper explores the concept of biogeomorphic keystone species by examining the general vs. species‐specific biogeomorphic impacts (BGIs) of trees on a limestone bedrock‐controlled stream, Shawnee Run, in central Kentucky. Field investigation identified three strong BGIs: (i) biogeomorphic pool formation via bioweathering; (ii) root bank‐associated bioprotection; and (iii) avulsion‐originated island development linked to bioprotection. This research evaluates these impacts in the context of keystone or other biogeomorphic roles. A field survey was conducted on nine stream reaches, each consisting of 10–12 hydraulic units of riffle, pool, and run. Results suggest that American sycamore (Platanus occidentalis) plays a keystone role by promoting the development of ~42% of pools in the study area. While geomorphic pools are formed by fluvial process–form linkages, these biogeomorphic pools are developed by sycamore root‐induced channel bed bioweathering. Only American sycamore and chinquapin oak (Quercus muehlenbergii) exhibited root‐bank development amongst 15 different species identified – and thus play a vital role in bank bioprotection. Lastly, trees can promote avulsion‐originated island formation by creating erosion‐resistant bioprotective patches. Mature trees (in terms of size), particularly large American sycamore and chinquapin oak, dominate Shawnee Run islands with a mean diameter at breast height (DBH) > 40 cm. However, other trees can provide comparable bioprotection, particularly at mature stages. Because its absence would result in fundamentally different stream morphology, sycamore can be considered a biogeomorphic keystone species in Shawnee Run. © 2020 John Wiley & Sons, Ltd.

Determination of Metal Concentration in Road-Side Trees from an Industrial Area Using Laser Ablation Inductively Coupled Plasma Mass Spectrometry

Historical pollution can be elucidated with variations of elements’ concentration in tree rings by using laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). However, the capacity of chemical elements’ absorption significantly depends on the tree species and element types. Metal concentrations in the rings for five species (Platanus occidentalis, Salix koreensis, Chamaecyparis obtusa, Pinus densiflora, Ginkgo biloba) were investigated in light of metal pollution history in ambient air of D industrial site located in Daejeon, Korea. The calibration for LA-ICP-MS was performed using cellulose-matrix matched standards with 13C normalization. Tree ring series except for Ginkgo sp. showed that the accumulation rates of Pb and Cd were higher between 1992 and 1999. Other elements, such as Fe, Cr, Mn, Cd, Zn, and Sr, showed a variation in the rings, likely due to the different physiological processes of element uptake and radial mobility. Concentrations of Pb and Cd in the annual rings of Pinus sp. corresponded to the metal monitoring data for the ambient air with the correlation coefficients of 0.879 and 0.579, respectively. Moreover, Cd in Platanus sp. and Pb in Salix sp. showed a positive correlation to ambient metal concentration compared to Chamaecyparis sp. and Ginkgo sp. Therefore, caution should be taken to select candidate elements as well as tree species to reconstruct the ambient air metal pollution history by measuring the concentration of metal in the tree ring.

Phenotypic plasticity of Platanus acerifolia (Platanaceae): morphological and anatomical trait variations in response to different pollution levels in Rome

Platanus acerifolia (Aiton) Willd was generated spontaneously around the beginning of the 1600s in Spain between Platanus orientalis L. and Platanus occidentalis L. The study was carried out on P. acerifolia trees in different sites in Rome in the period April-July 2019. Trees comparable for size were selected in A sites (historical parks), B sites (high traffic density streets) and in C sites (high traffic density avenues along the Tevere River characterized by a large water availability). At the morphological level, leaf area (LA) was significantly higher in A and C sites and leaf tissue density (LTD) in C sites. At anatomical level, the total leaf thickness (LT), the palisade parenchyma thickness (Pt), the spongy parenchyma thickness (St) and the abaxial epidermis thickness (Abet) were significantly higher in A sites, while the adaxial cuticle thickness (Adct) and the adaxial epidermis thickness (Adet) in B sites. The ratio between palisade and spongy parenchyma thickness (P/S) was significantly higher in C sites. The plasticity index (PI, 0.42) was calculated on all the considered leaf traits. Among the morphological traits, LTD had the highest plasticity (0.49) and among the anatomical traits, trichomes density (TD) and Adet (0.74 and 0.54, respectively). Overall, the results highlight the large adaptability of P. acerifolia to grow in different sites in Rome through several changes in leaf morphological and anatomical traits.

Using deciduous trees as bioindicators of trace element deposition in a small urban watershed, Indianapolis, IN, USA.

Annual and multiyear records of trace element deposition are difficult to develop using monitoring systems but have proven feasible using plant material in several settings. Here, we used material from several tree species (Populus deltoides W. Bartram ex Marshall, Platanus occidentalis L., and Ginkgo biloba L.) to detect atmospheric deposition of trace elements (Cd, Cu, Pb, and Zn) in six localities along a transect from near-urban to far-urban in southeastern Indianapolis, IN, and one control site. We captured soil (legacy footprint), bark (multiannual record), and leaves (seasonal record) across a broad swath of the urban landscape and using a multi-metal approach. Tree bark, leaf, and proximal soil samples were collected and analyzed for their trace element content. The highest trace metal concentrations occurred at the near-urban sites, with particularly high Cu and Pb values. The highest Zn values were found at one of the far-urban sites, which is located near a large brownfield that was a former coal and coke storage and processing facility. No correlation was found between soil trace element composition and that of bark and leaves, perhaps indicating a disconnect between legacy inputs recorded in soils and current inputs recorded in the biological materials. Overall, the tree species analyzed served well as trace element bioindicators, although less so for G. biloba, and thus this approach is promising for further understanding the role that airborne pollution and deposition play in urban watersheds.

Leaf litter identity alters the timing of lotic nutrient dynamics

Abstract The effects of resource quality on ecosystems can shift through time based on preferential use and elemental needs of biotic consumers. For example, leaf litter decomposition rates are strongly controlled by initial litter quality, where labile litter is processed and depleted more quickly than recalcitrant litters. We examined the effect of this processing continuum on stream nutrient dynamics. We added one of four different litter compositions differing in litter quality (cottonwood [Populus deltoides], labile; sycamore [Platanus occidentalis], recalcitrant; bur oak [Quercus macrocarpa], recalcitrant; and mixed [equivalent mixture of previous three species]) to 12 large (c. 20 m long, with riffle, glide and pool sections) outdoor stream mesocosms to assess the effect of litter species composition on whole‐stream nutrient uptake. Nutrients were dosed once weekly for 8 weeks to measure uptake of NH4–N, NO3–N, and PO4–P. We also measured changes in litter C, N, and P content on days 28 and 56 of the study. Nutrient uptake rates were highly variable, but occasionally very different among litter treatments (c. 5× between highest and lowest uptake rates by species). Uptake rates were generally greatest in cottonwood (labile) streams early in the study. However, during the last 4 weeks of the study, bur oak streams (recalcitrant) took up more nutrients than cottonwood streams, resulting in more cumulative NO3–N uptake in bur oak than in cottonwood streams. Cumulative NO3–N uptake was greater in mixed streams than expected (non‐additive) on two dates of measurement, but was generally additive. Changes in litter nutrient content largely corroborated nutrient uptake patterns, suggesting strong N immobilisation early in the study and some N mineralisation later in the study. P was strongly retained by most litters, but especially bur oak. Nutrient content of litter also largely changed additively, suggesting minimal evidence for non‐additive diversity effects on nutrient source/sink status. Our results demonstrate that litter species identity can have whole‐ecosystem effects on stream nutrient dynamics, with important implications for the form and fate of nutrients exported downstream. Further, diverse litter assemblages may serve as temporal stabilisers of ecosystem processes, such as nutrient sequestration, due to microbial nutrient requirements and differential decomposition rates, or the classic litter processing continuum.

Productivity and cost-effectiveness of short-rotation hardwoods on various land types in the southeastern USA

Despite the growing need to produce energy crops, information on comprehensive feasibility of growing short-rotation woody crops (SRWCs) on non-contentious and less-utilized lands and lands transitioning from previous uses in the southeastern USA is limited. An assessment model (SRWC-PEAM) was developed and tested for assessing the feasibility of SRWCs on lands targeted for ecosystem-service enhancements based on land conditions, species, and stand and economic variables in the southeastern USA. Productivity and economic returns of sweetgum (Liquidambar styraciflua L.), sycamore (Platanus occidentalis L.), and poplar (Populus) stand differed due to land types, species’ adaptability and biomass potential, and optimal land-type-based management schemes. Poplar stands had the greatest biomass and the highest returns on all land types although returns from the three species on most land types were poor using current reported regional delivered prices. Irrigating stands increased yields but returns were poorer than from non-irrigated stands due to high costs of irrigation. Longer rotations resulted in greater biomass and returns and were more crucial for irrigated stands. Significantly higher feedstock prices and productivities are requisite for SRWC viability in the southeastern USA. SRWC-PEAM is a web-based tool and can accommodate other SRWC species and assessment of environmental services associated with SRWCs.

BULK PRECIPITATION AND THROUGHFALL QUALITY AT DIFFERENTS FOREST STANDS IN NINEVA GOVERNMENT

The present study investigates the chemical composition of wet atmospheric precipitation over Mosul city ,bulk precipitation and throughfall under five different stands (Pinus brutia, Cupressus sempervirens, Platanus occidentalis, Populus nigra and Eucalyptus camaldulensis) were collected through rainy events during 2011-2012. The concentrations of the chemical constituents of water soluble ions included some cations such as (Ca+2 , Mg+2 ,Na+1 , and K+1) and anions (HCO3-, SO4-2,and Cl- ) and five of heavy metals (Zn ,Cu , Fe , Mn , and Pb)Electrical conductivity and pH of rain water and throughfall were also Measured . Results of the present study showed that mean value of the precipitation pH indicates that rainfall was slightly acidic whereas throughfall was almost neutral , also the concentration of most cations , anions and heavy metals increased in throughfall compared to open area precipitation

Tree roots as a dominant agent of streambed habitat, profile pattern, and grade control

Tree roots are a ubiquitous biotic agent in numerous fluvial settings, but their role in controlling streambed habitat and profile patterns is understudied. Although their importance in resisting bank erosion is more widely reported, tree roots also have the potential to span the channel bed, particularly in narrower first- to third-order streams. This enables tree roots to drive profile patterns and maintain important habitat elements such as steps that induce deep pools in both perennial and ephemeral systems. In a study across two humid-temperate ecoregions, tree roots were associated with more abundant and larger steps than large wood (LW), forming 91% of the steps in the high gravel load setting and 40% of the steps in the steeper, coarser, low sediment supply setting. When combined with LW, a majority of the steps in both settings were formed by biotic agents (97% and 55%, respectively). Furthermore, 70% of the deepest pools across all 40 study reaches were associated with biotic controls, with root steps being the most dominant driver: 45% of the deepest pools in all study reaches, including the maximum pool depths measured in both ecoregions (0.57-m and 0.38-m, respectively). Many questions need further exploration, for example, what tree sizes and species are most likely to form root steps (i.e. trunk diameters > 40 cm and American Sycamore (Platanus occidentalis) in this study); however, even this somewhat limited study has clear implications to land use planning and stormwater management. For example, on land developments draining to root-step dominated streams, maintaining the integrity of the riparian zone would seem to be as important as ensuring hydrologic mimicry if channel integrity is to be preserved. The study also has insights to the stream restoration industry where conventional practice typically involves large tree clearing operations to facilitate stream regrading.

Fast decolorization of cationic dyes by nano-scale zero valent iron immobilized in sycamore tree seed pod fibers: kinetics and modelling study

In the present work, Sycamore (Platanus occidentalis) tree seed pod fibers (STSPF) and nano-scale zero valent iron particles (nZVI) immobilized in Sycamore tree seed pod fibers (nZVIʘSTSPF) were produced. This biosorbent has been utilized as a viable effective biosorbent in the removing of methylene blue hydrate (MB), malachite green oxalate(MG), methyl violet 2B(MV) dyes from synthetic wastewater. The biosorbents were characterized by scanning electron microscopy (SEM) and Fourier transform infrared (FT-IR) spectroscopy. Various parameters such as contact time, solution concentration, pH and amount of biosorbent were investigated in order to evaluate the potential of the nanomaterials immobilized on natural wastes as sorbing biomaterials for the cationic dyes. Study on sorption kinetic and the sorption isotherm was carried out and best fitting models for the rate kinetics and isotherms were suggested. Langmuir isotherm was observed to be compatible with the isotherm models. The STSPF in the raw form showed the best dye sorption capacity of 43.67 mg/g for MG, 25.32 mg/g for MV, and 126.60 mg/g for MB. The magnetic nZVIʘSTSPF showed the best dye sorption capacity 92.59 mg/g for MG, 92.59 mg/g for MV, and 140.80 mg/g for MB. The iron nanoparticles immobilized biosorbent exhibited a higher removal capacity for all dyes compared to the raw biosorbent.

The effects of pulsed fertilization and chronic herbivory by periodical cicadas on tree growth.

Although many studies have investigated plant growth in the context of episodic herbivory and pressed resource availability, relatively few have examined how plant growth is affected by pulsed resources and chronic herbivory. Periodical cicada (Magicicada spp.) adults represent a pulsed detrital subsidy that fertilizes plants, and live cicada nymphs are long-lived root-feeding herbivores. Previous studies of cicada herbivory effects have been inconclusive, and previous studies of cicada-mediated fertilization did not examine effects on trees, or on a multiyear timescale. Here, we describe the results of a 3-yr experiment that factorially manipulated the presence and absence of cicada fertilization and herbivory in a population of 100 American sycamore (Platanus occidentalis) trees. We found that cicada fertilization strongly increased tree growth in the year of emergence, creating differences in tree size that persisted at least 2yr later. By comparison, we did not detect reductions in tree growth associated with cicada herbivory in any year of this experiment. However, cicada herbivory reduced the densities of, and damage from, other aboveground herbivores. These results suggest that cicadas affect the size structure of forests over multiple years, and raise questions about how cicada-mediated fertilization and herbivory will affect tree growth over longer timescales.

A Selective Ion HPLC-APCI-MS Method for the Quantification of Pentacyclic Triterpenes in an Anxiolytic Botanical Dietary Supplement for the Animal Health Market

A new anti-anxiety dietary supplement was developed for the animal health market, by combining 2 triterpene containing botanicals, Souroubea sympetala (Marcgraviaceae) with Platanus occidentalis (Platanaceae) A validated method for a quality control of the botanical blend was achieved using HPLC-APCI-MS. The method resulted in the detection and quantitative determination of betulinic acid (1), and ursolic acid (2) in P. occidentalis and 1, 2, lupeol (3), β-amyrin (4) and α-amyrin (5) in S. sympetala and the finished product ZentrolTM. Detections were at low ng on column for 1 and 2 and in low μg range for 3, 4 and 5 using calibration curves within 10-100 ng (R2 > 0.993). Recovery of spiked samples for all the recoveries observed were > 94%. Inter-day and intra-day variations were 0.8-3.5% and 5-10.4%, respectively. These results indicate the suitability of the developed analytical method to detect and quantify triterpenes of raw materials used in the manufacture of natural health products.

Pine sawdust biochar as a potential amendment for establishing trees in Appalachian mine spoils

Early growth and survival of tree seedlings is often poor on reclaimed coal surface mines in Appalachia. Biochar produced in bioenergy generation has potential for use as an amendment to improve seedling performance. Mine soil was collected from a recently reclaimed coal surface mine in Wise County, Virginia and mixed with loblolly pine (Pinus taeda L.) sawdust biochar, simulating application rates of 2.3, 11.2 and 22.5 Mg ha-1. Unplanted leaching columns and 4 L tree planting pots were filled with these biochar-soil mixtures, plus controls of pure mine soil and pure biochar. For the tree planting pots, additional pots were created where the biochar was applied as a topdressing at the same application rates as in the mixtures. One-year-old seedlings of both American sycamore (Platanus occidentalis L.) and black locust (Robinia pseudoacacia L.) were planted. Unplanted leaching columns were leached with collected rainwater for six months to simulate weathering. Trees were grown for one growing season. Black locust had higher average above-ground dry woody biomass (24.4 g) than American sycamore (17.0 g), and also higher below-ground biomass (61.0 g compared to 30.2 g). The pure biochar produced greater average below-ground biomass (99.9 g) than the pure mine soil (46.9 g). All of the biochar treatments produced greater average above-ground woody biomass (19.1 g – 33.4 g) than the pure mine soil (10.9 g). After weathering, biochar provided less available soil phosphorus, calcium and iron than the mine soil itself while increasing soil carbon and organic matter. High (22.5 Mg ha-1) biochar applications increased soil volumetric water holding capacity to 18.6% compared to 13.4% for pure mine soil. Naturally-occurring herbaceous biomass in the pots was negatively correlated with above-ground woody biomass at r = -0.483. Topdressing and full incorporation of biochar were not significantly different in their effects on biomass. Results suggest that pine biochar either broadcast at 2.3 - 22.5 Mg ha‑1, or mixed in planting holes with backfill soil, will promote faster above-ground growth and larger root systems in seedlings in mine soils. Further studies should test these methods in the field over multiple years and further refine recommendations of the rate of biochar to use and how best to apply it. New systems are being developed in Appalachia to produce biofuels and biochar from local biomass and to recycle biochar into the land base to enhance future biomass productivity. Applying 4 L of biochar mixed with the backfill of newly-planted trees is the top recommended practice for tree performance.

Effect of an anxiolytic botanical containing Souroubea sympetala and Platanus occidentalis on in-vitro diazepam human cytochrome P450-mediated metabolism

A novel anxiolytic natural health product (NHP) containing Souroubea sympetala and Platanus occidentalis is available for the companion animal market and is currently being developed for clinical evaluation. Addressing the risk of potential NHP-drug interactions, this study investigated S.sympetala and P.occidentalis plant extracts, and their identified bioactive compounds, for effects on the activity of cytochrome P450 (CYP) isozymes and the metabolism of the conventional anti-anxiety medication diazepam. Souroubea sympetala and P.occidentalis extracts, a 1:1 blend of the two extracts, and five triterpenes were tested for inhibitory effects on human recombinant CYP3A4, CYP2D6, CYP2C9 and CYP2C19 activity using a fluorometric plate assay. Direct effects on the metabolism of diazepam were evaluated using human liver microsomes with drug and metabolite quantification by ultra-high-pressure liquid chromatography and mass spectroscopy. The active substances betulinic acid (BA) and ursolic acid (UA) strongly inhibited CYP3A4 activity while UA and lupeol moderately inhibited CYP2C19. All extracts exhibited strong activity against the tested isozymes at 50-100μg/ml. BA and all plant extracts blocked the formation of major diazepam metabolites. Betulinic acid, UA and both the extracts and blended product are expected to affect the metabolism of diazepam when given in high dose.

How wind drives the correlation between leaf shape and mechanical properties

From a geometrical point of view, a non-sessile leaf is composed of two parts: a large flat plate called the lamina, and a long beam called the petiole which connects the lamina to the branch/stem. While wind is exerting force (e.g. drag) on the lamina, the petiole undergoes twisting and bending motions. To survive in harsh abiotic conditions, leaves may have evolved to form in different shapes, resulting from a coupling between the lamina geometry and the petiole mechanical properties. In this study, we measure the shape of laminae from 120 simple leaf species (no leaflets). Leaves of the same species are found to be geometrically similar regardless of their size. From tensile/torsional tests, we characterize the bending rigidity (EI) and the twisting rigidity (GJ) of 15 petioles of 4 species in the Spring/Summer: Red Oak (Quercus Rubra), American Sycamore (Platanus occidentalis), Yellow Poplar (Liriodendron tulipifera), and Sugar Maple (Acer saccharum). A twist-to-bend ratio EI/GJ is found to be around 4.3, within the range in previous studies conducted on similar species (EI/GJ = 2.7~8.0 reported in S. Vogel, 1992). In addition, we develop a simple energetic model to find a relation between geometrical shapes and mechanical properties (EI/GJ = 2LL/WC where LL is the laminar length and WC is the laminar width), verified with experimental data. Lastly, we discuss leaf’s ability to reduce stress at the stem-petiole junction by choosing certain geometry, and also present exploratory results on the effect that seasons have on the Young’s and twisting moduli.

Breakdown rates and associated nutrient cycling vary between novel crop-derived and natural riparian detritus in aquatic agroecosystems

Freshwater ecosystem function within agricultural landscapes may be altered by differences in processing of organic matter (OM) detritus entering freshwater habitats. We compared litter breakdown rates between crop residues; maize, cotton and soybean, and native riparian species: willow oak, American sycamore and cottonwood from inundated remnant river meander channels located within the Lower Mississippi River Basin (LMRB). Litter breakdown varied among the six species with the highest and lowest breakdown rates represented by crop ( $$\bar{X}$$ k day−1 = 0.007–0.011) and riparian species ( $$\bar{X}$$ k day−1 = 0.003–0.005), respectively. OM nutrient concentration varied widely across the six species. OM C:N ratios declined with time for all species except cotton. Temporal patterns in C:P ratios varied among crop residues but initially increased before declining for all three riparian species. Riparian OM breakdown rates were more negatively related to increasing C:N ratios of OM at the end of the study compared to crop species. Historic shifts in landscape-scale OM sources from diverse bottomland tree assemblages to crop residues has likely altered LMRB bayou and oxbow ecosystems by shifting both the timing and lability of OM pulses and decreasing long-term storage of OM, an important habitat and food resource for aquatic communities.