Eucalyptus Roots Research Articles

Combined transcriptomic, metabolomic and physiological analysis reveals the key role of nitrogen, but not phosphate and potassium in regulating anthocyanin biosynthesis induced by nutrient deficiency in Eucalyptus.

Anthocyanin biosynthesis in Eucalyptus plants can be flexibly and rapidly modulated in response to hormones or environmental stimuli, including nutrient deprivation (ND). However, the underlying mechanism of ND in inducing anthocyanin biosynthesis in plants remains largely elusive. In this study, we discovered that anthocyanin levels in leaves and stems could well reflect nitrogen availability in Eucalyptus. Supplementation with nitrogen, but not with phosphate or potassium, effectively inhibited ND-induced anthocyanin biosynthesis. To further investigate how nitrogen regulates this process, comprehensive time-resolved transcriptomic and targeted metabolomic analyses were conducted. The results revealed that 3405, 2706, and 3153 genes were differentially regulated by nitrogen treatment at 1, 2, and 3 d, respectively. Pathway analysis indicated the majority of the enriched KEGG pathways were associated with cellular metabolism, such as amino acid and flavonoid biosynthesis. Moreover, metabolomic analysis showed that the most abundantly accumulated anthocyanins, cyanidin-3-O-galactoside and cyanidin-3-O-glucoside, along with key intermediates in the flavonoid pathway, were downregulated by nitrogen treatment. Furthermore, nitrogen-responsive MYB-bHLH-WDR complex genes were identified, including six EgrMYB113 family members. Overexpression of one of the EgrMYB113-like genes induced anthocyanin biosynthesis in the transgenic hairy roots of Eucalyptus. Interestingly, mutation of AtMYB113 inhibited nitrogen deficiency-induced anthocyanin biosynthesis in Arabidopsis, suggesting that MYB113 is a novel N-responsive MYB transcriptional regulator of anthocyanin biosynthesis. Additionally, nitrogen treatment upregulated a few GA biosynthesis genes while simultaneously downregulated the expression of several GA2ox genes. Exogenous application of GA3 decreased ND-induced anthocyanin biosynthesis. Conclusively, this study provides novel insights into the molecular mechanism of nitrogen in the regulation of anthocyanin biosynthesis in Eucalyptus.

Comparison Study Between Inherited and Biogenic Calcium Carbonate Formation on The Surface Roots of Eucalyptus Trees Using X-Ray Technique and Field Observations

Background: This study aims to explain the mechanism of formation of calcite and it's to shed light on the synthetic carbonate crystallization on the surface of roots due to this mechanism is poorly understood and highly controversial. It is accepted that calcite formed originally from parent rocks and not in soils. Method: The origin of calcite in calcareous soil, in Aldiwaniya city, Iraq was investigated, by selecting two soil samples, one from the contact zone with root surface and the other sample from bulk soil and out of the root system. Results: X-ray diffraction showed that the calcite has two types, first one is well crystallized and ordered, with only minor deviations in lattice unit cell parameters relative to typical calcite. The clay-sized calcite (active calcite) is enriched in A and C-horizons relative to biogenic calcite and this mineral exist in larger size separates, and it's clearly appears in the shape of white crystals around eucalyptus root surfaces as shown in graphs. The results of X-ray showed that the appearance of smectite mineral which was diagnosed by the peak 14.21 A° in air dry magnesium-saturated treatment which expanded to 16.28 A° when saturated with ethylene glycol, where clarity of peak was increased, Also, the results showed that the appearance of peak 14.21 A° in magnesium saturation air dried, as a shoulder on the peak of the mica (10.14 A°). Conclusion: In general, calcite minerals have characteristic x-ray diffraction peaks at the following angles: 29.5, 31.7, 34.5, 35.7, 47.3, 56.4, and 63.4 degrees.

Changes in the Arbuscular Mycorrhizal Fungal Community in the Roots of Eucalyptus grandis Plantations at Different Ages in Southern Jiangxi, China.

Eucalyptus roots form symbiotic relationships with arbuscular mycorrhizal (AM) fungi in soil to enhance adaptation in challenging environments. However, the evolution of the AM fungal community along a chronosequence of eucalypt plantations and its relationship with soil properties remain unclear. In this study, we evaluated the tree growth, soil properties, and root AM fungal colonization of Eucalyptus grandis W. Hill ex Maiden plantations at different ages, identified the AM fungal community composition by high-throughput sequencing, and developed a structural equation model among trees, soil, and AM fungi. Key findings include the following: (1) The total phosphorus (P) and total potassium (K) in the soil underwent an initial reduction followed by a rise with different stand ages. (2) The rate of AM colonization decreased first and then increased. (3) The composition of the AM fungal community changed significantly with different stand ages, but there was no significant change in diversity. (4) Paraglomus and Glomus were the dominant genera, accounting for 70.1% and 21.8% of the relative abundance, respectively. (5) The dominant genera were mainly influenced by soil P, the N content, and bulk density, but the main factors were different with stand ages. The results can provide a reference for fertilizer management and microbial formulation manufacture for eucalyptus plantations.

Fine Root Density Dynamics and Carbon Stock of Eucalyptus spp.: Interplay of Age, Genotype, and Edaphoclimatic Conditions.

Roots play a fundamental role in forest ecosystems, but obtaining samples from deep layers remains a challenging process due to the methodological and financial efforts required. In our quest to understand the dynamics of Eucalyptus roots, we raise three fundamental questions. First, we inquire about the average extent of the roots of two contrasting Eucalyptus genotypes. Next, we explore the factors that directly influence the growth and depth of these roots, addressing elements such as soil type, climate, and water availability. Lastly, we investigate how the variation in Eucalyptus species may impact root growth patterns, biomass, and carbon stock. In this study, we observed that the maximum root depth increased by an average of 20% when genotypes were grown on sites with higher water availability (wet site). E. urophylla stands had a higher biomass and carbon stock (5.7 Mg C ha-1) of fine roots when cultivated on dry sites (annual rainfall~727 mm) than the wet sites (annual rainfall~1590 mm). In E. grandis × E. camaldulensis stands, no significant differences were observed in the stock of fine root biomass (3.2 Mg C ha-1) between the studied environments. Our results demonstrated that genotypes with greater drought tolerance (E. grandis × E. camaldulensis) tend to maintain higher stocks of fine root biomass (3.2-6.3 Mg ha-1) compared to those classified as plastic (E. urophylla), regardless of the edaphoclimatic conditions of the cultivation site. Finally, our research helps understand how Eucalyptus trees adapt to their environment, aiding sustainable forest management and climate change mitigation. We also provide a practical tool to estimate underground biomass, assisting forest managers and policymakers in ensuring long-term forest sustainability.

Nitrogen limitation in eucalypt roots: a cascading influence on the mobilization of soil organic matter

Nitrogen limitation in eucalypt roots: a cascading influence on the mobilization of soil organic matter

Fine root dynamics in a tropical integrated crop-livestock-forestry system

Integrated crop-livestock-forestry (ICLF) systems explore synergistic interactions between soil, plant, and animals, maximizing land-use efficiency and sustainability. However, belowground dynamics under ICLF have not been investigated deeply, particularly the role of incorporating dead root material, a forefront strategy for releasing nutrients and storing carbon. To better understand belowground interactions, we conducted a 21-month assessment of fine-root growth and decomposition in an ICLF system, starting when Eucalyptus urograndis trees were three years old. Eucalyptus rows were spaced 15 m apart and integrated with annual crops and pasture. Distances of 1.9, 4.3, and 7.5 m from the trees were evaluated under two successional periods: (i) annual crop, when corn was interspaced with palisade grass (Urochloa brizantha); and (ii) pasture, when palisade grass was grazed. We used the minirhizotron technique to track fine-root production and decomposition down to a depth of 70 cm, capturing 2400 images. Root longevity was estimated per root diameter class (0-0.5-, 0.5–1.0-, and 1.0–2.0-mm) and phenotypical groups (e.g., grasses [corn + palisade grass] and Eucalyptus). Our data showed that root decomposition rate and necromass inputs into the soil were reduced at the closest distance from the Eucalyptus rows (i.e., 1.9 m). The incorporation of decomposed roots was higher in the topsoil (0–28 cm) and declined with increasing soil depths. The total decomposed root incorporation was 101 m m−2 of soil image for 7.5 and 4.3 m inter-row positions, almost twice as high as the recorded at 1.9 m (54 m m−2) from the trees. Daily root decomposition rates increased during the last rainy season, benefited from numerous dead corn roots, and facilitated by higher soil moisture and temperature. Grasses and Eucalyptus roots at 7.5 m from the tree rows had shorter longevity than those at 1.9 m, remaining 88 and 152 days less, respectively. Root diameter influenced the decomposition rate as thicker roots (diameter between 1.0 and 2.0 mm) of grasses and Eucalyptus stood in the soil for 243 and 261 days longer than the finest roots (diameter <0.5 mm). Our results highlight that root necromass accretion and decomposition are heterogeneous in ICLF systems. Furthermore, 3-to-5-year-old Eucalyptus trees drive the interactions, creating microclimate conditions that impair corn and palisade grass root production and reduce root turnover close to the trees. These findings provide a scientific base for managing the ICLF system (spatial and temporal arrangements) and developing models of soil carbon addition via roots in such complex and heterogeneous systems.

Transcriptome-Based Construction of the Gibberellin Metabolism and Signaling Pathways in Eucalyptus grandis × E. urophylla, and Functional Characterization of GA20ox and GA2ox in Regulating Plant Development and Abiotic Stress Adaptations.

Gibberellins (GAs) are the key regulators controlling plant growth, wood production and the stress responses in perennial woody plants. The role of GA in regulating the above-mentioned processes in Eucalyptus remain largely unclear. There is still a lack of systematic identification and functional characterization of GA-related genes in Eucalyptus. In this study, a total of 59,948 expressed genes were identified from the major vegetative tissues of the E. grandis × E. urophylla using transcriptome sequencing. Then, the key gene families in each step of GA biosynthesis, degradation and signaling were investigated and compared with those of Arabidopsis, rice, and Populus. The expression profile generated using Real-time quantitative PCR showed that most of these genes exhibited diverse expression patterns in different vegetative organs and in response to abiotic stresses. Furthermore, we selectively overexpressed EguGA20ox1, EguGA20ox2 and EguGA2ox1 in both Arabidopsis and Eucalyptus via Agrobacterium tumefaciens or A. rhizogenes-mediated transformation. Though both Arabidopsis EguGA20ox1- and EguGA20ox2-overexpressing (OE) lines exhibited better vegetative growth performance, they were more sensitive to abiotic stress, unlike EguGA2ox1-OE plants, which exhibited enhanced stress resistance. Moreover, overexpression of EguGA20ox in Eucalyptus roots caused significantly accelerated hairy root initiation and elongation and improved root xylem differentiation. Our study provided a comprehensive and systematic study of the genes of the GA metabolism and signaling and identified the role of GA20ox and GA2ox in regulating plant growth, stress tolerance, and xylem development in Eucalyptus; this could benefit molecular breeding for obtaining high-yield and stress-resistant Eucalyptus cultivars.

Degradation of lignin in different lignocellulosic biomass by steam explosion combined with microbial consortium treatment

The difficulty of degrading lignin is the main factor limiting the high-value conversion process of lignocellulosic biomass. The biodegradation of lignin has attracted much attention because of its strong environmental friendliness, but it still faces some dilemmas such as slow degradation rate and poor adaptability. The microbial consortia with high lignin degradation efficiency and strong environmental adaptability were obtained in our previous research. To further increase the lignin degradation efficiency, this paper proposes a composite treatment technology of steam explosion combined with microbial consortium degradation to treat three kinds of biomass. We measured the lignin degradation efficiency, selectivity value (SV) and enzymatic saccharification efficiency. The structural changes of the biomass materials and microbial consortium structure were also investigated. The experimental results showed that after 1.6 MPa steam explosion treatment, the lignin degradation efficiency of the eucalyptus root reached 35.35% on the 7th days by microbial consortium. At the same time, the lignin degradation efficiency of the bagasse and corn straw treated by steam explosion followed by microbial biotreatment was 37.61–44.24%, respectively, after only 7 days of biotreatment. The microbial consortium also showed strong selectivity degradation to lignin. The composite treatment technology can significantly improve the enzymatic saccharification efficiency. Saccharomycetales, Ralstonia and Pseudomonadaceae were the dominant microorganisms in the biomass degradation systems. It was proved that the combined treatment technology of steam explosion and microbial consortium degradation could overcome the drawbacks of traditional microbial pretreatment technology, and can facilitate the subsequent high-value conversion of lignocellulose.

Effects of Elevated Aluminum Concentration and Distribution on Root Damage, Cell Wall Polysaccharides, and Nutrient Uptake in Different Tolerant Eucalyptus Clones.

Aluminized acidic soil can damage Eucalyptus roots and limit tree growth, hindering the productivity of Eucalyptus plantations. At present, the negative impacts of elevated aluminum (Al) on the cell morphology and cell wall properties of Eucalyptus root tip are still unclear. In order to investigate the responses of two different tolerant clones, Eucalyptus urophylla (G4) and Eucalyptus grandis × Eucalyptus urophylla (G9), to Al toxicity, seedling roots were treated hydroponically with an Al solution, and the polysaccharide content in the root tip cell wall and the characteristics of programmed cell death were studied. The results show that the distribution of Al was similar in both clones, although G9 was found to be more tolerant to Al toxicity than G4. The Al3+ uptake of pectin in root tip cell walls was significantly higher in G4 than in G9. The root tip in G4 was obviously damaged, enlarged, thickened, and shorter; the root crown cells were cracked and fluffy; and the cell elongation area was squeezed. The lower cell wall polysaccharide content and PME activity may result in fewer carboxylic groups in the root tip cell wall to serve as Al-binding sites, which may explain the stronger Al resistance of G9 than G4. The uptake of nitrogen and potassium in G4 was significantly reduced after aluminum application and was lower than in G9. Al-resistant Eucalyptus clones may have synergistic pleiotropic effects in resisting high aluminum-low phosphorus stress, and maintaining higher nitrogen and potassium levels in roots may be an important mechanism for effectively alleviating Al toxicity.

Eucalyptus Leaves as Potential Indicators of Gold Mine in Indonesia

Eucalyptus is a plant that is able to absorb gold (Au) particles from the soil and store them in the leaves. Eucalyptus roots have the ability to penetrate the soil of the calcrete zone, which is rich in the mineral calcium (Ca). Calcium is a chemical element with the symbol Ca and atomic number 20. As an alkaline earth metal, calcium is a reactive metal that forms a dark oxide-nitride layer when exposed to air. and contains Au particles as impurities, making this plant a potential natural indicator (biogeochemical) of potential Au metal mining. The Au content in eucalyptus leaves can be determined by using the XRF (X-Ray Fluorescence) instrumentation material analysis method for qualitative analysis and AAS (Atomic Absorption Spectroscopy) for quantitative results. The form of XRF characterization of the intensity versus energy spectrum of certain elements from the XRF analysis results obtained is a spectrum with a peak power of 9.731 keV which indicates the presence of Au metal in the sample. The results obtained qualitatively are the Au metal content in the eucalyptus leaf sample of (9.0 ± 0.5) ppm. However, the Au metal content in each leaf sample was different. This provides information that Eucalyptus from different plants has the potential to be a biogeochemical indicator of potential Au metal mining in Indonesia

Supergene geochemistry of arsenic and activation mechanism of eucalyptus to arsenic source.

Arsenic (As) migration and transformation in the supergene environment and eucalyptus planting have essential effects on ecology or even human health, respectively. However, the combined environmental impact of As migration and transformation and eucalyptus planting has not been studied. Here we report a case of soil As contamination caused by eucalyptus planting and address the fate of As in Longmen county, Guangdong Province, China. We found high As content in weathered arsenopyrite bearing granite or granite-derived soil, where a large area of eucalyptus is planted. The release of organic acids from eucalyptus roots promoted the electrochemical reaction of arsenopyrite to produce AsO33-. In the subsequent supergene migration process, As species change from arsenite to arsenate with the addition of oxygen and the effect of clay minerals, last with As infiltration, precipitation, and enrichment, forming the As contamination in soil. The whole process reveals the activation process of eucalyptus to the As source (arsenopyrite), the migration and transformation process of As in the supergene environment, and the formation mechanism of soil As contamination. This finding provides a new perspective of soil As contamination around arsenopyrite bearing granite of the Nanling area with eucalyptus planting and proposes that the negative effects of Nanling eucalyptus planting may be greater than expected.

Using arbuscular mycorrhizal fungi (Gigaspora margarita) as a growth promoter and biocontrol of leaf blight disease in eucalyptus seedlings caused by Cylindrocladium quinqueseptatum

The leaf blight disease is a common threat to the growth and production of eucalyptus seedlings in Thailand. This work then aimed to apply a biocontrol approach to help plants survive the disease. Cylindrocladium quinqueseptatum KKU-H4-B12, a pathogen causing leaf blight disease, was isolated from the lesion of eucalyptus leaves. Its pathogenicity was confirmed before use in the field experiments. An AMF Gigaspora margarita KKU-BH-01, previously proved to efficiently promote growth of eucalyptus, was pre-inoculated into eucalyptus seedlings for 30 days prior to pathogen infection. The results showed that an AMF could successfully colonize eucalyptus roots even in the pathogen-infected plants (≥56%). The disease assessment indicated that plants pre-inoculated with AMF and later infected with the pathogen (PM) had a disease reduction of 33.4%. Plant height, SPAD, fresh weights of roots and shoots in PM plants were relatively equal to those of the control plants, suggesting that AMF could relieve detrimental effects of the disease in plants. Moreover, we found that AMF induced plant chitinase and β-1,3-glucanase enzymes resulting in improved disease resistance in plants. This work is the first to report the application of a single AMF species to effectively enhance the growth and help eucalyptus seedlings to survive leaf blight disease.

Eucalyptus tree influence on spatial and temporal dynamics of fine-root growth in an integrated crop-livestock-forestry system in southeastern Brazil

Integrated farming systems are promising strategies towards land-use efficiency and sustainable agriculture. The integrated crop-livestock-forestry (ICLF) system stablish complex interactions were synergies or competition depend on the arrangements throughout time and space. Fine root (≤2 mm) growth dynamics of crops, pasture and trees remains unclear when these species are integrated. We aimed to assess root growth dynamics after Eucalyptus urograndis introduction into an integrated crop-livestock (ICL) system. Previous ICL area was used as a reference. We assessed ICLF 1.9, 4.3 and 7.5 m distances from tree rows, starting the study when trees had three years of age. Eucalyptus rows were spaced 15 m apart and integrated to annual crops and pasture. We evaluated the root growth under two different successional periods: (i) corn cultivation interspaced with palisade grass (Urochloa brizantha); and (ii) a pasture, when palisade grass was grazed. We tracked fine root length using the minirhizotron technique, capturing 3200 images scanning up to 70 cm soil depth. Data of photosynthetically active radiation (PAR) transmission, soil bulk density, rainfall and air temperature were used as complementary information to support the discussion. Our results showed that Eucalyptus trees impaired root growth of annual crops cultivated in the interrow position, regardless of distance from the row. From 31 to 80 days after corn germination, root length production in ICLF was reduced by 120–179 cm m−2.d−1 along the tree interrow space. For the pasture period, total produced root length density reduced 6% at 1.9 m but increased 25% at 4.3 and 7.5 m, when compared to ICL. Shade of Eucalyptus trees at ICLF 1.9 m position, with PAR transmission mainly below 60%, sharply impaired root growth. Eucalyptus roots represented 12% from total root length produced in ICLF system, and 38% of these roots had positive ectomycorrhizal status. In conclusion, under Eucalyptus trees higher than 20 m, pasture of palisade grass is more adaptable than corn when considering the root growth dynamics of our studied ICLF arrangement. Based on our findings, corn intercropped with palisade grass should not be introduced in future management of the ICLF system, unless part of the trees is chopped to reduce light competition. However, implemented pasture of palisade grass showed belowground synergies with Eucalyptus, increasing root growth in intermediary interrow positions and emerging new fungal symbiosis, which could be playing important functions in soil, as soil carbon storage and nutrient cycling.

The potential of endophytic bacteria from the root of Eucalyptus pellita as a biocontrol agent against Ralstonia solanacearum

Abstract. Susanti Y, Giyanto, Sinaga MS, Mutaqin KH, Tjahjono B. 2021. The potential of endophytic bacteria from the root of Eucalyptus pellita as a biocontrol agent against Ralstonia solanacearum. Biodiversitas 22: 3454-3462. Bacterial wilt disease (BWD) caused by Ralstonia solanacearum is one of the most damaging eucalyptus (Eucalyptus pellita F. Muell.) diseases. However, endophytic bacteria can be utilized to control it. This study aims to obtain and screen endophytic bacteria isolated from the root of eucalyptus as a biocontrol agent against BWD. A pathogenic R. solanacearum was isolated for artificial inoculation; subsequently, isolation, characterization and screening of the potential endophytic bacteria were conducted. Isolates of R. solanacearum demonstrated the pathogenicity for BWD in eucalyptus, with the highest virulence found in Rs 18. In total, 24 isolates of endophytic bacteria were obtained and screened for their biocontrol potential. The endophytic bacteria conveyed the capacity of antibiosis, indole acetic acid (IAA) hormone, nitrogen fixation, phosphate dissolution, protease enzyme and AHL-lactonase, which are the main indicators of bioagent characteristics in endophytic bacteria, as well as being plant growth stimulators. Four isolates were selected with the highest according to the analytic hierarchy process (AHP), identified on the 16S rRNA gene. Most isolates belonged to gram-negative bacteria. The four isolates, namely B33/77 (Serratia nematodiphila), B32/77 (Paenibacillus polymyxa), B13/497 (Brevundimonas olei) and B17/111 (Bacillus megaterium), indicated their potential for biocontrol as plant growth promoters. This study is the first report on the isolation of endophytic bacterial from eucalyptus roots with regard to its benefit as a plant growth promoter. It provides basic information about the characteristics of the endophytic bacteria, which showed potential as a biocontrol agent of R. solanacearum on eucalyptus.

Variability in soil physical–chemical properties along the root-explored profile in deep Oxisols of commercial eucalypt plantations

While deep soils commonly characterize tropical forests, direct measurements of soil physical–chemical properties, fine root distributions, and relationships among them are scarce. In this paper, we report results from a project in Brazil that were obtained from experimental areas selected for their representative tropical climatic and edaphic features. Our objective was to evaluate vertical and spatial soil physical–chemical properties along the root-explored profile of Eucalyptus plantations to better understand the relationship between each component. Soil was collected from four sites (Três Lagoas-Site 13, Mogi Guaçu-20, Telemaco Borba-22, and Bocaiuva-30) and characterized for physical–chemical properties (pH, texture, organic matter, cation exchange capacity, and nutrient content) and fine root density (FRD). Soil was sampled up to 2 m beyond the deepest observed roots, or until a cemented horizon or R layer was detected. Spatial variability was investigated through a geostatistical approach using ordinary kriging. Data were subjected to ANOVA as well as bi- and multivariate statistics using a correlation matrix and robust principal factor analysis (PFA), respectively. Results showed that investigated Oxisols reached the maximum depth of 19 (Site 13), 8 (20), 11 (22), and 8 (30) m. In most investigated sites (20, 22, and 30) and for most soil properties, a typical soil horizonation was observed along the first 2.5/3.0 m. Deeper horizons (>3.0 m) of clayey Oxisols were characterized by the presence of typical porthole shapes dramatically interrupting soil horizonation, indicating spatial pedovariability and demonstrating underestimates of vertical and spatial pedovariability can occur under standard soil investigations to 2.0 m in depth. Correlation matrix and PFA showed that Eucalyptus roots strongly affected most investigated soil properties. Our study considered vertical and spatial dimensions of soil physical–chemical properties as well as the deep-rooting properties of Eucalyptus, which is critical for improving soil management in infertile Eucalyptus plantations.

Nutrient supply modulates species interactions belowground: dynamics and traits of fine roots in mixed plantations of Eucalyptus and Acacia mangium

Belowground interactions are still poorly understood in mixed-species forests. We investigated the effects of soil fertility on belowground processes in mixed planted forests. The dynamics and traits of Eucalyptus and Acacia mangium fine roots (diameter < 2 mm) in plantations with 50% of each species were studied in a randomized block design established in a nutrient depleted soil. Stands with NPK fertilization applied at planting (F+) were compared to unfertilized stands (F-). In the 0–15 cm soil layer, Eucalyptus root mass density (RMD) was higher than Acacia RMD by 50% in F+ and 10% in F-, considering both ages. At 34 months of age, Eucalyptus RMD was 94% higher near Acacia trees than near Eucalyptus trees in F-. In this layer, Eucalyptus specific root length (SRL) was 21% higher than Acacia SRL at 16 months of age and was 10% higher in F- than in F+ at 34 months of age. The cumulative Eucalyptus fine root length production between 16 and 34 months was 66% higher in F- than in F+ in the 0–1 m soil layer. Fertilization increased the competition between species and led to a partial exclusion of Acacia fine roots from the nutrient-rich topsoil. Soil exploration by Eucalyptus roots in the vicinity of Acacia trees was higher in F- than in F+, which suggests that unfertilized trees benefited from facilitation through higher soil N availability and direct N transfer from Acacia trees.

Root and shoot interactions in a tropical integrated crop–livestock–forest system

Integrated crop–livestock–forest systems (ICLFS) have potential advantages compared to monoculture, but most studies quantifying plant biomass in integrated production systems, have quantified only the aboveground component rather than the total biomass. The objective of this study was to investigate the ecological interactions of Eucalyptus trees intercropped with palisade grass in a tropical region. The study was conducted in an 8-year-old ICLFS in which Eucalyptus trees were introduced into a palisade grass pasture [Urochloa brizantha (Hochst. Ex A. Rich.) R. Webster ‘Marandu’]. Samples were collected at four locations from the Eucalyptus trees: 0.0 (planting line), 2.0, 4.0, and 6.0 m (middle of the plots). A monoculture palisade grass pasture was included for comparison. The addition of Eucalyptus in the pasture reduced the forage yield, root length density, root density and root diameter of palisade grass close to the Eucalyptus trees. Eucalyptus roots were more abundant near the trees, and decreased with distance from the tree at soil depths up to 1.0 m. The total amount of roots decreased by 36 % with the addition of the forest component compared with the monoculture pasture, i.e., 11.6 Mg ha−1 in the ICLFS compared with 18.4 Mg ha−1 in the pasture. In the ICLFS, the proportion of palisade grass roots in the soil profile increased with distance from the tree line. However, the high degree of competition in root development in the ICLFS resulted in 20% lower root length and fine roots densities compared with monoculture pasture in the upper 0–0.20 m soil layer.

Comparative metabolomics implicates threitol as a fungal signal supporting colonization of Armillaria luteobubalina on eucalypt roots.

Armillaria root rot is a fungal disease that affects a wide range of trees and crops around the world. Despite being a widespread disease, little is known about the plant molecular responses towards the pathogenic fungi at the early phase of their interaction. With recent research highlighting the vital roles of metabolites in plant root-microbe interactions, we sought to explore the presymbiotic metabolite responses of Eucalyptus grandis seedlings towards Armillaria luteobuablina, a necrotrophic pathogen native to Australia. Using a metabolite profiling approach, we have identified threitol as one of the key metabolite responses in E. grandis root tips specific to A. luteobubalina that were not induced by three other species of soil-borne microbes of different lifestyle strategies (a mutualist, a commensalist, and a hemi-biotrophic pathogen). Using isotope labelling, threitol detected in the Armillaria-treated root tips was found to be largely derived from the fungal pathogen. Exogenous application of d-threitol promoted microbial colonization of E. grandis and triggered hormonal responses in root cells. Together, our results support a role of threitol as an important metabolite signal during eucalypt-Armillaria interaction prior to infection thus advancing our mechanistic understanding on the earliest stage of Armillaria disease development. Comparative metabolomics of eucalypt roots interacting with a range of fungal lifestyles identified threitol enrichment as a specific characteristic of Armillaria pathogenesis. Our findings suggest that threitol acts as one of the earliest fungal signals promoting Armillaria colonization of roots.

Experiential learning of ethnopharmacological sources of drugs through rotating trios micro discussion in MBBS students: an innovative I-tray teaching methodology

Background: Complementary and alternative medicine is very robust in some parts of the world. The study was done to impart the experiential learning related to sources of drugs in a pharmacy practical class for MBBS students.Methods: We used ingredient-tray (I-Tray) teaching tool consisting of two parts to generate experiential learning in MBBS students about ethno pharmacological sources of drugs. Innovatively designed I -tray filled with two sizes plastic containers (100 ml and 50 ml sizes used for collecting biological samples of sputum and urine) containing crude drug medicinal sources which were arranged in gutters of the tray. They were sorted into five categories such as plants (flowers of Vinca rosea, bark of Terminalia arjuna, roots of Rauwolfia serpentine and Eucalyptus leaves); animals (formalin preservatives freshwater leech, shells and vaccines); minerals (kaolin, potassium permanganate and charcoal); oils and others. Three charts of 4 square feet sizes were used for demonstration of synthetic, microbiological and genetically engineered drug sources.Results: The students’ approval rate of I-tray was mean yes value of 105.78 for a tool of active learning out of total 113 students. Around 100%, 98.23 % and 97.35% students utilised application of concept (cognition), faculty of smell (affective) and volunteering (psychomotor) in the class. However female students had statistically significant score against this set up of the class depicting gender specificity of the learning process.Conclusions: Thus teaching traditional sources of drugs through I-tray impart higher order social, place based and experiential learning of medicine.

Arsenic detoxification in Eucalyptus: subcellular distribution, chemical forms, and sulfhydryl substances.

The Eucalyptus cultivation acreage was large in Guangxi provinces. Guanglin 9 (Eucalyptus grandis × Eucalyptus urophylla) is a widely cultivated Eucalyptus species and has been found to grow normally in soils contaminated by heavy metals such as arsenic (As), but the detoxification mechanisms are not clear yet. Through hydroponic experiment, the adsorption and detoxification of As in Eucalyptus were studied from three aspects, namely subcellular distribution of As, chemical forms of As, and the response of sulfhydryl substances. The subcellular distribution data showed that in the Eucalyptus roots, As was mainly present in the soluble fraction (66.3-79.9%), in leaves in the soluble fraction (50.6-53.8%), and the cell wall fraction (35.6-40.0%) under As stress. The chemical form data showed that in roots, As was mainly present in ethanol extraction state (29.5-40.0%), deionized water extraction state (28.3-31.7%), and sodium chloride extraction state (24.1-33.8%). As stress can induce the formation of non-protein thiols (NPT), glutathione (GSH), and phytochelatins (PCs). With the increasing As concentration, the NPT (maximum increase 55.9%) and GSH (maximum increase 79.9%) contents in roots significantly increased, while the PC content significantly increased and then significantly decreased. It is concluded that the As detoxification mechanisms of Eucalyptus are mainly vacuolar compartmentalization and the chelation of sulfhydryl substances, while cell wall adsorption and As chemical forms have limited effects on As detoxification.