Aboveground Root Research Articles

TopoRoot+: computing whorl and soil line traits of field-excavated maize roots from CT imaging

BackgroundThe use of 3D imaging techniques, such as X-ray CT, in root phenotyping has become more widespread in recent years. However, due to the complexity of the root structure, analyzing the resulting 3D volumes to obtain detailed architectural root traits remains a challenging computational problem. When it comes to image-based phenotyping of excavated maize root crowns, two types of root features that are notably missing from existing methods are the whorls and soil line. Whorls refer to the distinct areas located at the base of each stem node from which roots sprout in a circular pattern (Liu S, Barrow CS, Hanlon M, Lynch JP, Bucksch A. Dirt/3D: 3D root phenotyping for field-grown maize (zea mays). Plant Physiol. 2021;187(2):739–57. https://doi.org/10.1093/plphys/kiab311.). The soil line is where the root stem meets the ground. Knowledge of these features would give biologists deeper insights into the root system architecture (RSA) and the below- and above-ground root properties.ResultsWe developed TopoRoot+, a computational pipeline that produces architectural traits from 3D X-ray CT volumes of excavated maize root crowns. Building upon the TopoRoot software (Zeng D, Li M, Jiang N, Ju Y, Schreiber H, Chambers E, et al. Toporoot: A method for computing hierarchy and fine-grained traits of maize roots from 3D imaging. Plant Methods. 2021;17(1). https://doi.org/10.1186/s13007-021-00829-z.) for computing fine-grained root traits, TopoRoot + adds the capability to detect whorls, identify nodal roots at each whorl, and compute the soil line location. The new algorithms in TopoRoot + offer an additional set of fine-grained traits beyond those provided by TopoRoot. The addition includes internode distances, root traits at every hierarchy level associated with a whorl, and root traits specific to above or below the ground. TopoRoot + is validated on a diverse collection of field-grown maize root crowns consisting of nine genotypes and spanning across three years. TopoRoot + runs in minutes for a typical volume size of \\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\:40{0}^{3}$$\\end{document} on a desktop workstation. Our software and test dataset are freely distributed on Github.ConclusionsTopoRoot + advances the state-of-the-art in image-based phenotyping of excavated maize root crowns by offering more detailed architectural traits related to whorls and soil lines. The efficiency of TopoRoot + makes it well-suited for high-throughput image-based root phenotyping.

Impact of mangrove forest structure and landscape on macroplastics capture

Complex networks of above-ground roots and trunks make mangrove forests trap plastic litter. We tested how macroplastics relate to tree biomass, root abundance, mangrove geomorphology and river mouth proximity, surveying landward and seaward margins of seven forests in the Philippines, a global hotspot for marine plastic pollution. Macroplastics were abundant (mean ± s.e.: 1.1 ± 0.22 items m−2; range: 0.05 ± 0.05 to 3.79 ± 1.91), greatest at the landward zone (mean ± s.e.: 1.60 ± 0.41 m−2) and dominated by land-derived items (sachets, bags). Plastic abundance and weight increased with proximity to river mouths, with root abundance predicting plastic litter surface area (i.e., the cumulative sum of all the surface areas of each plastic element per plot). The study confirms rivers are a major pathway for marine plastic pollution, with mangrove roots are the biological attribute that regulate litter retention. The results suggest land-based waste management that prevent plastics entering rivers will reduce marine plastic pollution in Southeast Asia.

Accumulation Pathway of Cd, Pb, and Zn in Chinese Cabbage under the Condition of Exogenous Pollution Superposition in High Geological Background Area

Northwest Guizhou is a karst area with a high geological background. Affected by historical soil zinc smelting, the heavy metal content of atmospheric dust in the region is high, and soil pollution is severe. In order to explore the accumulation pathway of heavy metals in leafy vegetables, Chinese cabbage was used as the test crop, and the geological high background soil and zinc smelting-contaminated soil with the same contents of Cd, Pb, and Zn were selected. A pot experiment was carried out in the polluted area of zinc smelting and the non-polluting control area. The heavy metal content, enrichment coefficient (BCF), and transport coefficient (TF) of Chinese cabbage were studied under open-air, plastic mulching film, and greenhouse cultivation conditions. The results showed that the contents of Cd, Pb, and Zn in Chinese cabbage in the polluted area and the control area were 0.10-1.01 and 0.10-0.91 mg·kg-1, 0.31-0.62 and 0.23-0.37 mg·kg-1, and 7.50-32.74 and 4.88-21.79 mg·kg-1, respectively. Overall, the contents of heavy metals in the polluted area were relatively high. The contents of Cd and Pb in Chinese cabbage planted in soil with a high geological background met the requirements of the national food safety standard limits. Affected by atmospheric deposition, the contents of Pb and Zn in Chinese cabbage in the polluted area were significantly higher than that in the control area, and the difference in Cd was insignificant. The proportions of weak acid-soluble Cd, Pb, and Zn in the contaminated soil were 48%, 3.0%, and 16%, respectively, which were 3.15, 1.01, and 1.57 times higher than those in the control soil with a high geological background. Affected by the activity of heavy metals, the contents of Cd and Zn in Chinese cabbage planted in the contaminated soil exceeded the national standard and were significantly higher than those in the control soil. The root-soil BCF of Cd, Pb, and Zn in polluted soil was significantly higher than that in the control soil, and the BCF of Cd and Zn was higher than that of Pb. The TF aboveground root Cd and Zn in Chinese cabbage was significantly higher than in the control soil, whereas the TF aboveground root Pb in the polluted area was significantly higher than that in the control area. The Pb content of Chinese cabbage in the two study areas showed open field>plastic mulching film>greenhouse cultivation. In conclusion, the content of Cd and Zn in Chinese cabbage was greatly affected by the activity of heavy metals in soil, and the main accumulation pathway was root absorption and transportation. In addition to root absorption, atmospheric deposition was an important accumulation pathway of Pb. Therefore, in areas with high geological backgrounds, attention should be paid to controlling the exposure risk of Cd and Zn in leafy vegetables planted on exogenously polluted soils. Additionally, greenhouse cultivation could effectively reduce the accumulation of Pb.

Maize brace root mechanics vary by whorl, genotype and reproductive stage.

Root lodging is responsible for significant crop losses worldwide. 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 susceptibility to root lodging. 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. Using 3-point bend tests, we show that brace root mechanics are variable by whorl, genotype and reproductive stage. 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. Collectively these results highlight the importance of considering whorl-of-origin, genotype and reproductive stage for the quantification of brace root mechanics, which is important for mitigating crop loss due to root mechanical failure.

EFFECTS OF FOREST FLOOR ENVIRONMENTAL FACTORS ON THE SPATIAL DISTRIBUTION PATTERNS OF POLYMESODA SPP. IN THE MANGROVE FOREST OF IRIOMOTE ISLAND, JAPAN

Polymesoda spp., which represent bivalves in the mangrove ecosystem, inhabit the mangrove forests of the Indo-Pacific region. They are edible bivalves consumed by inhabitants located around the mangrove forests in the region. The bivalves also have a cultural significance because their shells are used for religious ceremonies on the Yaeyama Islands in Japan. However, detailed studies of these bivalves is scarce and their biology is not well understood. We conducted this study in the mangrove forest along Urauchi River of Iriomote Island, Japan. The spatial distribution patterns of the bivalves and the forest floor environment were surveyed. We used 75 large (10m2 quadrat) plots to survey plant species and above-ground root density, and small (1m2 quadrat) plots to count the number of bivalves and measure median particle diameter, sediment temperature and Oxygen Reduction Potential (ORP) in each large plot. In addition, the relationships between these forest floor environmental factors and the spatial distribution patterns of the bivalves were analyzed. Polymesoda spp. was present in 34 plots. Bruguiera gymnorhiza was dominant in 79.4% of plots. A correlation between the distribution and median particle diameter and ORP and sediment temperature was not found. In 94% of the plots, the above-ground root density was over 50% of the large plot. The relationships between the spatial distribution patterns of the bivalves and plant species and the above-ground root density were revealed.

Antibacterial and phytotoxic activity of the Schiff’s bases of 5-phenyl-4-amino-3-mercapto-4H-1,2,4-triazole with the donor substituents in the 4th position on heterosystem

Background. Triazoles and Schiff’s bases have a high biological activity. For the practical use of the derivatives, their low toxicity is important. The purpose of this work was to investigate the antibacterial and phytotoxic properties of Schiff’s bases of 5-phenyl-4-amino-3-mercapto-4H-1,2,4-triazole with donor substituents in the 4th position of heterosystem. Materials and methods. In the study of antibacterial activity of the derivatives, corrosion-active 4-day association cultures of ammonifying and sulfate-reducing bacteria were used as a test culture of microorganisms. Sensitivity of bacteria to derivatives was determined by diffusion method in agar using sterile paper disks according to the standard method. In the investigation of phytotoxic activity of the derivatives, Lepidium sativum of the “Ajour” cultivar was used as a test plant. Seed germination and biometric indices (length, weight of the aboveground part and roots) of 5-day sprouts were determined, the phytotoxic effect of the derivatives was calculated. Experimental data were processed using methods of mathematical statistics. Results. The introduction of substituents does not provide for an increase in antibacterial properties of the studied compounds in relation to some corrosion active ammonifying and sulfate-reducing bacteria. Low activity was observed regarding the association culture of ammonifying bacteria to the compound without substituents in the phenyl fragment and the compound with fluor as a substituent in the phenyl fragment at a concentration of 2.0%. Derivatives with the methoxyl substituent in the phenyl fragment and with the hydroxyl substituent in the phenyl fragment did not show any antibacterial activity against the association culture of ammonifying bacteria isolated from ferrosphere in meat-peptone broth. Antibacterial action against the association of sulfate-reducing bacteria Desulfovibrio orizae with organic acid-producing bacteria Anaerotignum propionicum for derivatives were not detected. Phytotoxic properties were observed for the compound with the hydroxyl substituent that influenced the processes of growth in the test plant. Conclusion. The introduction of electron-donor substituents into the basic structure did not provide for an increase in antibacterial properties against corrosive bacteria. Phytotoxic properties were observed for the compound with the hydroxyl substituent in the phenyl fragment, which influenced the L. sativum growth processes by inhibiting growth of the above-ground part and roots. Other compounds either did not show any action, or demonstrated a weak stimulating effect on the growth and development of the test plant.

Дикорастущее растительное сырьё – источник обогащающих добавок к пище

Gentle technologies have been developed for processing wild plant raw materials growing on the territory of the Krasnoyarsk Territory, namely large burdock, medicinal dandelion, medicinal hemophlebus, common yarrow, carried out in order to obtain natural food fortifiers for bakery, flour confectionery and other food products. Vegetable powders of various degrees of grinding, with a particle size of 60-180mkm and less than 60mkm, containing inulin and other substances useful for health, were obtained. The technology of obtaining inulin from burdock and dandelion officinalis has been developed. A method of drying vegetable raw materials with infrared rays of various wavelengths was applied and studied. The obtained kinetic drying curves allowed us to establish that the drying rate depends on the type of raw material. As a result, drying modes (wavelength, heat flux power, duration) were determined for different parts of plants: for the aboveground part (leaves and inflorescences) and roots. The process of storing the obtained powders in sealed polymer packages of 3-5 kg at a temperature of (20±5)°C and relative humidity (70±5)% was studied. According to the results of organoleptic, physico-chemical and microbiological indicators, the shelf life of powders under these conditions is 18 months. Technical documentation for powders has been developed, approved and approved: roots of burdock, dandelion, medicinal hemophlebus and yarrow.

Extending the CSM-CERES-Beet Model to Simulate Impact of Observed Leaf Disease Damage on Sugar Beet Yield

A CSM-CERES-Beet pest damage routine was modified to simulate the impact of Cercospora leaf spot disease effects on sugar beet yield. Foliar disease effects on sugar beet growth and yield were incorporated as daily damage to leaf area and photosynthesis, which was linked to daily crop growth and biomass accumulation. An experiment was conducted in Southwest Germany (2016–2018) with different levels of disease infection. Data collected included time-series leaf area index, top weight, storage root weight and Cercospora leaf spot disease progress. The model was calibrated using statistical and visual fit for one treatment and evaluated for eight treatments over three years. Model performance of the calibration treatment for all three variables resulted in R2 values higher than 0.82 and d-statistics higher than 0.94. Evaluation treatments for all three observation groups resulted in high R2 and d-statistics with few exceptions mainly caused by weather extremes. Root mean square error values for calibration and evaluation treatments were satisfactory. Model statistics indicate that the approach can be used as a suitable decision support system to simulate the impact of observed Cercospora leaf spot damage on accumulated above-ground biomass and storage root yield on a plot/site-specific scale.

Nitrogen Cycling and Mass Balance in the World’s Mangrove Forests

Nitrogen (N) cycling in mangroves is complex, with rapid turnover of low dissolved N concentrations, but slow turnover of particulate N. Most N is stored in soils. The largest sources of N are nearly equal amounts of mangrove and benthic microalgal primary production. Dissolved N fluxes between the forests and tidal waters show net uptake, indicating N conservation. N2-fixation is underestimated as rapid rates measured on tree stems, aboveground roots and cyanobacterial mats cannot currently be accounted for at the whole-forest scale due to their extreme patchiness and the inability to extrapolate beyond a localized area. Net immobilization of NH4+ is the largest ecosystem flux, indicating N retention. Denitrification is the largest loss of N, equating to 35% of total N input. Burial equates to about 29% of total inputs and is the second largest loss of N. Total inputs slightly exceed total outputs, currently suggesting net N balance in mangroves. Mangrove PON export equates to ≈95% of PON export from the world’s tropical rivers, but only 1.5% of the entire world’s river discharge. Mangrove N2O emissions, denitrification, and burial contribute 0.4%, 0.5–2.0% and 6%, respectively, to the global coastal ocean, which are disproportionate to their small worldwide area.

Compost and Biochar to Promote Soil Biological Activities under Sweet Potatoes Cultivation in a Subtropical Semiarid Region

South Texas is located in a subtropical semiarid climate, and due to high temperature and irregular precipitation, farmers opt to leave their fields fallow during the summer months jeopardizing overall soil health. We evaluated whether sweet potato (Ipomoea batatas) cultivation coupled with drip irrigation could restore soil biological activities compared with bare fallow. Additionally, because sweet potatoes have high demand of soil nutrients, especially potassium (K), we evaluated the nutrient supply of locally sourced soil amendments. Sweet potato was cultivated during summer 2018 in McAllen, Texas, under control (no fertilizer), NPK (synthetic fertilizer), RC (yard-waste compost), and AC (compost produced under an enhanced composting process), and biochar (gasified walnut shell at 900°C), each with three replicates. Soil amendments were applied at different amounts to result in a rate of 80 kg K ha−1. Soil biological indicators were microbial biomass phosphorous, phosphatase activity, and the rate of fluorescein diacetate hydrolysis (FDA). Available nitrogen, phosphorus, potassium, and sodium were also quantified. Aboveground biomass and storage root yield estimated sweet potato’s agronomic performance. Cultivation and irrigation stimulated soil enzyme activities and microbial biomass-phosphorous. Sweet potato yields were the highest in NPK treatment but still 2.8 times lower than variety’s potential yield. Storage root yield was inversely related to aboveground biomass, suggesting that growing conditions benefited the production of shoot versus roots. Both biochar and AC treatments stimulated FDA rates and K availability. Soil pH and sodium concentration increased in all treatments over the growing season, possibly due to river-sourced irrigation water. Together, these findings show that crop cultivation promoted soil biological activities and the maintenance of nutrient cycling, compared to bare-fallow conditions. For a better agronomic performance of sweet potato, it would be necessary to identify management practices that minimize increase in soil pH and salinity.

Stem and root assessment in mangrove forests using a low-cost, rapid-scan terrestrial laser scanner

Accurate assessment of forest structure and biomass is hampered by extensive field measurements that are time-consuming, costly, and inefficient. This is especially true in mangrove forests that have developed complex above-ground root structures for stability and survival in the harsh, anaerobic, and reducing conditions of water-logged sediments. These diverse structures can differ even among similar species, providing complex three dimensional structures and making them difficult to accurately assess using traditional allometric methods. Terrestrial laser scanners (TLS) have been used widely in collecting forest inventory information in recent years, mainly due to their fine-scale, detailed spatial measurements and rapid sampling. In this work we detected stems and roots in TLS data from three mangrove forests on Pohnpei Island in Micronesia using 3D classification techniques. After removing noise from the point cloud, the training set was acquired by filtering the facets of the point cloud based on angular orientation. However, many mangrove trees contain above-ground roots, which can incorrectly be classified as stems. We consequently trained a supporting classifier on the roots to detect omitted root returns (i.e., those classified as stems). Consistency was assessed by comparing TLS results to concurrent field measurements made in the same plots. The accuracy and precision for TLS stem classification was 82% and 77%, respectively. The same values for TLS root detection were 76% and 68%. Finally, we simulated the stems using alpha shapes for volume estimation. The average consistency of the TLS volume assessment was 85%. This was obtained by comparing the plot-level mean stem volume (m3/ha) between field and TLS data. Additionally, field-measured diameter-at-breast-heights (DBH) were compared to the lidar-derived DBH using the reconstructed stems, resulting in 74% average accuracy and an RMSE of 7.52 cm. This approach can be used for automatic structural evaluation, and could contribute to more accurate biomass assessment of complex mangrove forest environments as part of forest inventories or carbon stock assessments.

Modeling Biomass and Nutrients in a Eucalyptus Stand in the Cerrado

The prediction of biological processes, which involve growth and plant development, is possible via the adjustment of mathematical models. In forest areas, these models assist in management practices, silviculture, harvesting, and soil fertility. Diameter, basal area, and height are predictors of volume and biomass estimates in forest stands. This study utilized different non-linear models for estimating biomass and nutrient values in the aerial biomass and roots of an unmanaged eucalypt stand in Cerrado dystrophic soil. It was hypothesized that the models would estimate the nutrients of the aboveground biomass and roots after meeting the selection and validation criteria. By statistical analysis of the parameters and subsequent validation, the Schumacher–Hall model was presented to be the best fit for biomass and nutrients. This result confirmed the ability of different variables, including diameter, basal area, and height, to be predicted. Estimating the nutrient values in the aboveground biomass and roots allowed a better understanding of the quality of the vegetal residues that remained in the soil. For dystrophic soils, which occur in the Cerrado, these estimates become even more relevant.

Genotype-by-environment interaction for dual-purpose traits in sweetpotato

ABSTRACT Development of high-yielding dual-purpose sweetpotato (Ipomoea batatas [L.] Lam) genotypes is useful for cultivation in mixed crop-livestock farming systems. The objective of this study was to determine genotype-by-environment interaction (GEI) for storage root yield (SRY), vine yield (VY), root: vine ratio (RVR), total above-ground and below-ground biomass (TABGB) and root dry matter content (RDMC) among newly developed sweetpotato clones to select promising dual-purpose clones. Forty-five sweetpotato genotypes, of which 32 were newly developed candidate clones, were evaluated across six diverse environments in Rwanda. Additive main effects and multiplicative interaction (AMMI) and genotype and genotype-by-environment (GGE) biplot analyzes were used to analyze GEI. AMMI analysis revealed a relatively larger proportion of the GEI effect for SRY (31.21%), VY (37.17%), RVR (41.73%), TABGB (35.24%) and RDMC (36.23%) than for genotype and environmental effects, suggesting differential response of test genotypes across environments for the assessed traits. GGE-biplot analysis explained total variation of 72.98% for SRY, 83.26% for VY, 74.03% for RVR, 78.82% for TABGB and 56.78% for RDMC. Clone 21 with enhanced SRY and TABGB, and clone 42 for SRY had broad adaptation. For better VY, clone 733 was the best performer in environments E2 and E6 which are designated as mega-environment (MGE) 2, and clone 321 in E1, E3 and E4 (MGE 3). For RVR, clone 577 had best adaptation in E3, E4 and E5 (MGE 1), while clone 460 in E2 and E6 (MGE 2). Clones 42 and 381 were best performers for RDMC with specific adaptation in environments E3 and E1, respectively.

BIOCHEMICAL INDICATORS OF DROUGHT TOLERANCE OF CORN

Abstract The paper deals with impact of water deficit and heat shock on activity of sucrose-phosphate synthase ( SPS ) – ( UDP-glucose: D-fructose-6-phosphat-2- α -glucosyltransferase, E.C. 2.4.1.14) – an enzyme involved in sucrose synthesis, on activity of lectins, as well as sucrose and abscisic acid ( ABA) content in germinating kernels of corn lines with different drought tolerance ( Zea mays L.). The paper demonstrates that corn lines, which are positively different in terms of drought tolerance, are characterized by varying activity of lectins, abscisic acid, sucrose-phosphate synthase and sucrose content in tissues of the aboveground part and roots of sprouts under the impact of adverse abiotic factors (water deficit and hyperthermia).

CO2, CH4 and N2O fluxes in an alpine meadow on the Tibetan Plateau as affected by N-addition and grazing exclusion

Limited understanding of the effects of enhanced nitrogen (N) addition and grazing exclusion (E) on greenhouse gases fluxes (GHGs: CO2, CH4, and N2O) in grasslands constrains our ability to respond to the challenges of future climate change. In this study, we conducted a field experiment using a static closed opaque chamber to investigate the response of GHG fluxes to N addition (69 kg N ha−1 year−1 applied in 3 splits) and grazing exclusion in an alpine meadow on the Tibetan Plateau during the growing seasons from 2011 to 2013. Our results showed that winter grazing significantly raised soil temperature (ST), while grazing exclusion (E) had no effect on soil moisture (SM), and N fertilizer (F) had no effect on ST or SM. Aboveground biomass (AB) and root biomass (RB) were not significantly affected by E in 2011-2013 (p > 0.05), but F significantly affected AB and RB (p < 0.05). Compared with winter grazing, only E substantially reduced seasonal mean CO2 emissions (by about 20.1%) during the experimental period. E did not significantly directly affect CH4 uptake, whereas N addition reduced seasonal mean CH4 uptake by about 6.5%, and N addition changed seasonal average absorption of N2O into an emission source. CO2 flux is the major contributor to CO2 equivalent emissions in this area. Our results indicate that exclosure from livestock grazing might be a promising measure to reduce CO2 emissions, while enhanced N addition might reduce CH4 uptake and increase N2O emission in the alpine meadow under future climate change.

ВЛИЯНИЕ ВОЗДУШНЫХ ЭКЗОМЕТАБОЛИТОВ РАСТЕНИЙ И ИХ ИНФОРМАЦИОННО-ЭНЕРГЕТИЧЕСКИХ ПОЛЕЙ НА БИОТЕСТЫ

The paper demonstrates that air exometabolites of plant natural and cut leaves and flowers are proved to effect the bio tests – seed germination. The degree and character of this influence quantity and character differ for various donor and acceptor plants. The biological action of products of plants transpiration remains under its accumulation in the activated carbon and frozen water. It is shown that the interaction of some plants on the others is caused by the interrelation of both aboveground organs and root systems. So,under beetroot seed generation the size of the seedlings roots in the controlled variant was 5.5 ± 0.9 cm, the stem size was 4.6 ± 06 cm. When growing sorrel and beetroot seeds together,the beetroot size of the roots was 3.1 ± 1.0 cm; the stem size was 3.1 ± 1.0 cm. It seems feasible to take into consideration this influence under combined planting of several crops.

Heavy metals accumulation and translocation by Typha elephantina roxb. and Typha domingensis pers. in an arid habitat: perspectives for phytoremediation

The present study investigated the ability of two emergent macrophytes Typha elephantina and Typha domingensis for accumulation of six heavy metals in an arid habitat in Saudi Arabia. Plant samples (aboveground shoot and belowground root and rhizome) as well as sediment samples were collected and analyzed. Regarding the variation in sediment characters, PH, EC, Cu, Ni, Pb and Zn concentrations of the T. elephantina sites were significantly higher than those of the T. domingensis sites; while Fe and Mn concentrations of the T. domingensis sites were significantly higher than those of the T. elephantina sites. T. elephantina allocated approximately 57.8% of its total biomass to leaves, 5.9% to flowers, 7.0% to peduncles, 18.7% to rhizomes and 10.6% to roots. The total above-ground biomass was 2.4 times that of the total below-ground biomass. T. domingensis allocated approximately 61.3% of its total biomass to leaves, 8.6% to flowers, 11.3% to peduncles, 9.8% to rhizomes and 9.0% to roots. The total above-ground biomass was 4.3 times that of the total below-ground biomass. Significant variations in Mn was recorded between T. elephantina and T. domingensis, while significant variations in Fe, Ni and Pb were recorded between the different organs. All heavy metals concentrations were significantly higher in belowground organs as compared to other plant organs. The heavy metal contents of T. elephantina and T. domingensis organs differed significantly between different plant organs. All the investigated species were characterized by a bioaccumulation factor > 1.0 for all heavy metals. In the present study, the translocation factor varied among plant species, among organs and among heavy metals. Finally, T. elephantina and T. domingensis could be regarded as a good candidates as phytoremediator for mitigating heavy metals pollution.

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.

Application of Terrestrial Laser Scanner to Evaluate the Influence of Root Collar Geometry on Stump Height after Mechanized Forest Operations

The height of tree stumps following mechanized forest operations can be influenced by machine-, tree-, terrain-, and operator-related characteristics. High stumps may pose different economic and technical disadvantages. Aside from a reduction in product recovery (often associated with sawlog potential), leaving high stumps can complicate future entries if smaller equipment with low ground clearance is used, particularly in the case where new machine operating trails are required. The objective of this exploratory study was to examine if correlations existed between the height of tree stumps following mechanized harvesting and the shape of the above-ground root collar, stump diameter, and distance to the machine operating trail. In total, 202 sample stumps of Norway spruce (Picea abies (L.) Karst.) and the surrounding terrain were scanned with a terrestrial laser scanner. The collected data was processed into a 3D-model and then analyzed. Stump height was compared with different characteristics such as stump diameter at the cut surface, distance to the machine operating trail, number of visible root flares per stump, and the root collar. The number of root flares per stump had a positive influence on stump diameter and height, showing a general trend of increasing diameter and height with the increasing number of root flares. Root angles also had an influence on the stump diameter. The diameter of a stump and the shape of the root collar at the cut surface together had a significant effect on stump height and the model reported explained half of the variation of stump heights. Taken together, these findings suggest that other factors than the ones studied can also contribute in influencing stump height during mechanized harvesting operations. Further investigations, including pre- and post-harvest scans of trees selected for removal, are warranted.

Gemmorhizogenesis in poysean (Euphorbia×lomiRauh): the production of ‘likely-asexuate’ vivipary offsprings

Poysean (Euphorbia × lomi Rauh) is a natural hybrid of E. milii Des Moulins × E. lophogona Lamarck. This hybrid has a high tolerance to drought and high temperature and the ability to withstand long periods in the complete absence of water. In its native environment, Madagascar, it colonizes wide arid areas and this occurs both due to its stress tolerance and its ability to produce ‘likely-asexuate’ vivipary offsprings (aboveground LAVOs) from the aerial parts. These propagules show completely differentiated aboveground organs and root primordial or sometimes radicles when still standing on their mother plant. However, no information is available about the ability of this hybrid to produce such offsprings. In the present work, we studied the production of aboveground LAVOs of a cultivar of E. × lomi, namely the Thailand’s cultivar ‘Porn ying yai’, in a 2-years pot experiment with 2 contrasting growing media (coconut fibre/perlite, CCP, or peat/perlite, PTP) under greenhouse conditions. In total, 24 mother plants per year per substrate were grown, propagules were counted, and length and weight measured and divided per class of quality, corresponding to a length class (1st class below 5.0 cm, 2nd class between 5.1 and 10.0 cm, and 3rd class above 10.1 cm). Thus, propagules were planted to check for their vitality. Plants grown in PTP yielded 2.3-fold more propagules than CCP. However, such difference solely occurred for 1st class propagules, whereas no differences were found for 2nd and 3rd class propagules between growth substrates. Since the pots were widely fertirrigated, and thus not limited by water or nutrient availability, this suggests that the chemical or other traits of the growing media mostly modulate the conditions for the above-ground LAVOs induction rather than their growth. Since this plant has low maintenance needs and can withstand water lack and high temperature, these results have implication in urban environments, where colonization of green areas could occur after planting without anthropic intervention.