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Spatio-temporal development of the rhizosheath during root elongation has the potential to modify the function of the rhizosphere under abiotic stress. We quantified the impact of carbon (i.e. glucose) addition on the development and function of rhizosheath of drought tolerant and sensitive chickpea ( Cicer arietinum L.) by integrating soil pore volume obtained from X-ray microtomography (µCT), soil physical and microbial respiration measures, and measurements of root traits. Structural equation modelling indicated the feedback mechanisms between added carbon, root traits, pore geometry, and soil functions differed between the cultivars in a fashion congruent with the concept of soil as a self-organising system that interacts with an introduced root system. The drought tolerant cultivar partitioned more photosynthetically fixed carbon to the roots, had more root hairs and more porous rhizosheath, as compared with the sensitive cultivar.

X-ray computed tomography (X-ray CT) is a non-destructive method of soil analysis which can provide three-dimensional (3D) view, quantitative information of the internal organization of the soil. In this paper, we discuss the potential application of X-ray CT in characterization of soil properties like porosity and pore size distribution (PSD), root architecture, soil phase classification, water and solute transport in soil, and highlight the research during last 10–15 years. Here, we review the recent development of X-ray CT in soil science, use of artificial intelligence and machine learning in image analysis, point out the major challenges associated with its use, discuss few improvements to overcome these difficulties and elaborate the possible future technological developments for non-invasive/destructive soil characterization by integrating X-ray CT with recently available complementary techniques.

Summary The mechanisms controlling the genesis of rhizosheaths are not well understood, despite their importance in controlling the flux of nutrients and water from soil to root. Here, we examine the development of rhizosheaths from drought‐tolerant and drought‐sensitive chickpea varieties; focusing on the three‐dimensional characterization of the pore volume (> 16 μm voxel spatial resolution) obtained from X‐ray microtomography, along with the characterization of mucilage and root hairs, and water sorption. We observe that drought‐tolerant plants generate a larger diameter root, and a greater and more porous mass of rhizosheath, which also has a significantly increased water sorptivity, as compared with bulk soil. Using lattice Boltzmann simulations of soil permeability, we find that the root activity of both cultivars creates an anisotropic structure in the rhizosphere, in that its ability to conduct water in the radial direction is significantly higher than in the axial direction, especially in the drought‐tolerant cultivar. We suggest that significant differences in rhizosheath architectures are sourced not only by changes in structure of the volumes, but also from root mucilage, and further suggest that breeding for rhizosheath architectures and function may be a potential future avenue for better designing crops in a changing environment.

Aggregates play a key role in protecting soil organic carbon (SOC) from microbial decomposition. The objectives of this study were to investigate the influence of pore geometry on the organic carbon decomposition rate and bacterial diversity in both macro- (250–2000 μm) and micro-aggregates (53–250 μm) using field samples. Four sites of contrasting land use on Alfisols (i.e. native pasture, crop/pasture rotation, woodland) were investigated. 3D Pore geometry of the micro-aggregates and macro-aggregates were examined by X-ray computed tomography (μCT). The occluded particulate organic carbon (oPOC) of aggregates was measured by size and density fractionation methods. Micro-aggregates had 54% less μCT observed porosity but 64% more oPOC compared with macro-aggregates. In addition, the pore connectivity in micro-aggregates was lower than macro-aggregates. Despite both lower μCT observed porosity and pore connectivity in micro-aggregates, the organic carbon decomposition rate constant (Ksoc) was similar in both aggregate size ranges. Structural equation modelling showed a strong positive relationship of the concentration of oPOC with bacterial diversity in aggregates. We use these findings to propose a conceptual model that illustrates the dynamic links between substrate, bacterial diversity, and pore geometry that suggests a structural explanation for differences in bacterial diversity across aggregate sizes.

Australia’s “Direct Action” climate change policy relies on purchasing greenhouse gas abatement from projects undertaking approved abatement activities. Management of soil organic carbon (SOC) in agricultural soils is an approved activity, based on the expectation that land use change can deliver significant changes in SOC. However, there are concerns that climate, topography and soil texture will limit changes in SOC stocks. This work analyses data from 1482 sites surveyed across the major agricultural regions of Eastern Australia to determine the relative importance of land use vs. other drivers of SOC. Variation in land use explained only 1.4% of the total variation in SOC, with aridity and soil texture the main regulators of SOC stock under different land uses. Results suggest the greatest potential for increasing SOC stocks in Eastern Australian agricultural regions lies in converting from cropping to pasture on heavy textured soils in the humid regions.

Arbuscular mycorrhizal fungi (AMF) are beneficial soil organisms that can form symbiotic associations with the host plant roots. Mycorrhizal symbiosis between plant root and fungi can influence plant diversity and ecosystem productivity. However, the impacts of AMF frequently documented in the loamy to sandy soil, whereas it has no precise mechanism of influencing plant productivity, macronutrient uptake, and aggregation in a clay soil. A pot experiment was carried out to investigate the impact of AMF on plant growth, nutrient uptake and soil aggregation in a clay soil of Bangladesh. Okra (Abelmoschus esculentus L.) was cultivated over 105 days with AMF and without AMF (NAMF) with 5 replications. Plant productivity, nutrient uptake, soil organic carbon (SOC), microbial biomass carbon (MBC), aggregate stability (MWD), and glomalin-related soil protein (GRSP) were measured after 105 days. Results showed that the plant productivity and nutrient availability in soil and their subsequent uptake in AMF were significantly higher compared to the NAMF treatment (p < 0.01). We observed 17% increase in aggregate stability (measured as mean weight diameter) and 28% increase in organic carbon in AMF inoculated soil compared to NAMF. The microbial biomass carbon and GRSP were significantly higher in the AMF than NAMF treatment (p < 0.01). The findings highlight that AMF introduction can be a promising tool for improving plant production and soil condition in the clay soil instead of conventional farming system.

Owing to the loss of subcarrier orthogonalities in high-speed applications, the use of conventional frequency-domain-based channel estimation in high mobility orthogonal frequency division multiple access (OFDMA) systems such as mobile WiMax may give rise to an unacceptable high channel estimation error floor. To alleviate this problem, the authors develop some basis expansion model (BEM)-based estimation schemes for the OFDMA uplink. Specifically, the authors express the time-varying channel as a superposition of a small number of complex exponential basis functions spanning the entire Doppler range, and then formulate least square and linear minimum mean square error algorithms to estimate the basis coefficients for two different types of pilot patterns. The authors also derive the respective Cramer-Rao lower bounds for these estimators. It has been shown that the time domain BEM using a pilot scheme where pilots are placed over time axis will give better performance under a high Doppler scenario.

Trichogramma zahiri Polaszek sp. n. is described from Bangladesh. It has been collected at several localities from the major pest of rice Dicladispa armigera (Olivier) on which it has an important controlling impact. Trichogramma zahiri is compared with known Trichogramma species from the region, and diagnostic differences are presented. Data on developmental period, adult longevity, egg-laying frequency, host egg age preference and seasonal parasitism rate are presented and discussed. Other records of parasitoids of D. armigera are briefly reviewed and discussed.

The central part of the mitochondrial coxII gene was amplified from 38 different dicots and two monocots using polymerase chain reaction. In 30 of the 40 plants studied, the amplified coxII gene-fragment contains an intron, ranging from 930 bp in Capsicum (pepper) in Solanaceae to 1,635 bp in Ampelamus albidans (climbing milkweed) in Asclepiadaceae. The composition of this intron varies as revealed by Southern hybridizations using oligonucleotide probes specific to the coxII intron-regions in maize, wheat, and rice. In the Apocynaceae, Catharanthus roseus (Madagascar periwinkle) and Vinca minor (common periwinkle) lack the coxII intron, while other members of the same family (various Mandevilla species, Nerium oleander and Apocynum cannabinum) and members of the closely related Asclepiadaceae (Asclepias incarnata, Ampelamus albidans and Asclepias tuberosa) retain the intron. Analysis of these data suggest a selective loss of the coxII intron from a plant, ancestral to both Catharanthus and Vinca, after the divergence of the Asclepiadaceae and Apocynaceae. The remaining eight plants from the Brassicaceae, Cucurbitaceae, Fabaceae, and Onagraceae lacking the intron fall into a single group or clade using the phylogenetic tree proposed by Chase et al. (Annals of the Missouri Botanical Garden: 80:528-580,1993) based on sequence of the chloroplast rbcL gene