Root Patterning Research Articles

Antagonistic interaction between Ezh2 and Arid1a coordinates root patterning and development via Cdkn2a in mouse molars.

Patterning is a critical step during organogenesis and is closely associated with the physiological function of organs. Tooth root shapes are finely tuned to provide precise occlusal support to facilitate the function of each tooth type. However, the mechanism regulating tooth root patterning and development is largely unknown. In this study, we provide the first in vivo evidence demonstrating that Ezh2 in the dental mesenchyme determines patterning and furcation formation during dental root development in mouse molars. Mechanistically, an antagonistic interaction between epigenetic regulators Ezh2 and Arid1a controls Cdkn2a expression in the dental mesenchyme to regulate dental root patterning and development. These findings indicate the importance of balanced epigenetic regulation in determining the tooth root pattern and the integration of roots with the jaw bones to achieve physiological function. Collectively, our study provides important clues about the regulation of organogenesis and has general implications for tooth regeneration in the future.

Rice straw biochar amended soil improves wheat productivity and accumulated phosphorus in grain

Biochar is a pyrolyzed biomass produced under limited oxygen or oxygen absent conditions. Few investigations have been conducted to determine the combined effect of biochar with chemical fertilizer on growth, yield and nutrient distribution pattern in root, shoot and grain in wheat as well as changes in soil physiochemical properties. This research was designed to study the combined effect of chemical fertilizer and rice straw-derived biochar on soil physio-chemical properties, growth, yield and nutrient distribution pattern within wheat plant tissue and grain. Results showed that rice straw biochar caused a significant decrease in soil pH and increase in soil organic matter as well as nutrients like total nitrogen (TN), potassium (K), magnesium (Mg) and boron (B) due to incubation. Result also showed that root biomass and straw did not differ between Bangladesh Agricultural Research Council (BARC) and ½ BARC + rice straw biochar treatment. Similarly, thousand grain weight and grain yield did not differ between the same treatments. The phosphorus concentration in wheat grain was highest in ½ BARC + rice straw biochar as compared to other treatments. The use of rice straw biochar in addition to the chemical fertilizers in wheat production systems is an economically feasible and practical nutrient management practice. Our findings urged that reduction of chemical fertilizer application is possible with supplementation of rice straw biochar.

Strigolactones and their crosstalk with other phytohormones.

Strigolactones (SLs) are a diverse class of butenolide-bearing phytohormones derived from the catabolism of carotenoids. They are associated with an increasing number of emerging regulatory roles in plant growth and development, including seed germination, root and shoot architecture patterning, nutrient acquisition, symbiotic and parasitic interactions, as well as mediation of plant responses to abiotic and biotic cues. Here, we provide a concise overview of SL biosynthesis, signal transduction pathways and SL-mediated plant responses with a detailed discourse on the crosstalk(s) that exist between SLs/components of SL signalling and other phytohormones such as auxins, cytokinins, gibberellins, abscisic acid, ethylene, jasmonates and salicylic acid. SLs elicit their control on physiological and morphological processes via a direct or indirect influence on the activities of other hormones and/or integrants of signalling cascades of other growth regulators. These, among many others, include modulation of hormone content, transport and distribution within plant tissues, interference with or complete dependence on downstream signal components of other phytohormones, as well as acting synergistically or antagonistically with other hormones to elicit plant responses. Although much has been done to evince the effects of SL interactions with other hormones at the cell and whole plant levels, research attention must be channelled towards elucidating the precise molecular events that underlie these processes. More especially in the case of abscisic acid, cytokinins, gibberellin, jasmonates and salicylic acid for which very little has been reported about their hormonal crosstalk with SLs.

Comparative analysis of B-BOX genes and their expression pattern analysis under various treatments in Dendrobium officinale

BackgroundStudies have demonstrated that BBX (B-BOX) genes play crucial roles in regulatory networks controlling plant growth, developmental processes and stress response. Nevertheless, comprehensive study of BBX genes in orchids (Orchidaceae) is not well studied. The newly released genome sequences of Dendrobium officinale and Phalaenopsis equestris have allowed a systematic analysis of these important BBX genes in orchids.ResultsHere we identified 19 (DoBBX01–19) and 16 (PeBBX01–16) BBX genes from D. officinale and P. equestris, respectively, and clustered into five clades (I-V) according to phylogenetic analysis. Thirteen orthologous, two DoBBXs paralogous and two PeBBXs paralogous gene pairs were validated. This gene family mainly underwent purifying selection, but five domains experienced positive selection during evolution. Noteworthy, the expression patterns of root, root_tips, stem, leaf, speal, column, lip, and flower_buds revealed that they might contribution to the formation of these tissues. According to the cis-regulatory elements analysis of BBX genes, qRT-PCR experiments were carried out using D. officinale PLBs (protocorm-like bodies) and displayed that these BBX genes were differentially regulated under AgNO3, MeJA (Methyl Jasmonate), ABA (abscisic acid) and SA (salicylic acid) treatments.ConclusionsOur analysis exposed that DoBBX genes play significant roles in plant growth and development, and response to different environmental stress conditions of D. officinale, which provide aid in the selection of appropriate candidate genes for further functional characterization of BBX genes in plants.

Physiological and antioxidative responses to GO/PANI nanocomposite in intact and demucilaged seeds and young seedlings of Salvia mirzayanii

The current study aimed to investigate the impacts of different concentrations of GO/PANI nanocomposites (25, 50 and 100 mg L−1), in comparison with GO and PANI, on seed germination behaviors, morpho-physiological and biochemical traits in intact (mucilaginous) and demucilaged seeds, and young seedlings of the medicinal plant Salvia mirzayanii. Upon exposure to GO, seed germination was delayed and reduced, and growth attributes (root and shoot length, shoot fresh weight, and total chlorophyll content) declined, all of which could be attributed to the reductions in water uptake and oxidative stress particularly in demucilaged seeds. A hormetic dose-dependent response was observed for the growth traits in both intact and demucilaged seedlings upon exposure to GO/PANI concentrations, i.e. low-concentration stimulation and high-concentration repression. Elevated levels of H2O2 in shoot tissue of the seedlings exposed to GO and high concentration of GO/PANI, in comparison with those exposed to low levels of GO/PANI and control, were linked with the activities of the antioxidant enzymes SOD, CAT, POD, and total phenolics. Overall, the results showed high toxicity of GO on germination and early growth of S. mirzayani that was more evident in demucilaged seedlings, whereas GO/PANI stimulated germination, and the effects on seedling growth were stimulatory or inhibitory depending on the application dose and presence of mucilage. Furthermore, the capacity of GO/PANI nanocomposites to improve germination and cause a regular porosity pattern in roots accompanied by improved water uptake and early establishment of S. mirzayanii propose potential implications of GO/PANI nanocomposites for seeds/plants in drought-prone ecosystems.

Mechanical response of root-reinforced loess with various water contents

The control of erosion process is an important issue in China, particularly in the northwest of China, in which loess erosion is a widespread problem with environmental and social consequences. Previous studies have shown the benefits of root-reinforced soil to control the erosion by increasing the shear strength of soil. In this study, we have investigated the shear strength of loess reinforced with root by carrying out consolidated-undrained triaxial tests. The effect of Robinia pseucdoacacia root distribution patterns including horizontal, vertical and crossed reinforcement on the shear strength is explored under 16% water content by weight and saturated condition, which represent natural water content and saturated condition that soil would experience, respectively. The results show that root insertion in loess causes a distinctive increase in strength of specimen under consolidated-undrained condition for the whole range of water content studied. Compared with unreinforced specimen, the increase of internal cohesion contributes the most to the increase in strength of reinforced specimen. The internal friction angles of root-reinforced specimens, however, are hardly affected by root insertion and root distribution patterns. Furthermore, in comparison with the horizontal and vertical reinforcement patterns, the crossed reinforced pattern is found to be the most effective distribution pattern against shear failure in loess. Its shear strength increment is greater than that with the vertically reinforced root loess, followed by the horizontally reinforced root pattern. In general, the water content increment of loess greatly reduces the strength of both root-reinforced and unreinforced loess.

Evaluating trends in time series of distributions: A spatial fingerprint of human effects on climate

We analyze a time series of global temperature anomaly distributions to identify and estimate persistent features in climate change. We employ a formal test for the existence of functional unit roots in the time series of these densities, and we develop a new test to distinguish functional unit roots from functional deterministic trends or explosive behavior. Results suggest that temperature anomalies contain stochastic trends (as opposed to deterministic trends or explosive roots), two trends are present in the Northern Hemisphere while one stochastic trend is present in the Southern Hemisphere, and the probabilities of observing moderately positive anomalies have increased. We postulate that differences in the pattern and number of unit roots in each hemisphere may be due to a natural experiment which causes human emissions of greenhouse gases and sulfur to be greater in the Northern Hemisphere, decreasing the mean temperature anomaly but increasing the spatial variance relative to the Southern Hemisphere. Together, these results are consistent with the theory of anthropogenic climate change.

Short-term effects of cover crops and tillage methods on soil physical properties and maize growth in a sandy loam soil

Soil compaction is a serious threat to agricultural production because of an expanding agricultural mechanization. Conservation tillage and use of pioneer plants can be an environmentally solution to alleviate the adverse effects of soil compaction. Root penetration into compacted soil of two winter cover crops with different rooting patterns, i.e. tap-rooted white mustard (Sinapis alba L.), and fibrous-rooted winter rye (Secale cereal L.), and of maize (Zea mays L.) in the consecutive growing season was assessed. Additionally, the effects of two spring tillage methods were evaluated, i.e. strip tillage and intensive tillage (by mouldboard ploughing). Winter rye showed significantly higher root penetration than white mustard in the top 15 cm, while an opposite trend was observed at 20–45 cm depth. After one season, maize root penetration was significantly greater following white mustard than winter rye at 30–40 cm depth. Strip tillage, like intensive tillage, could sufficiently loosen soil for adequate maize growth even though maize root distribution was restricted to tilled rows in contrast with intensive tillage. In conclusion, white mustard already showed positive short-term effects on maize growth, whereas strip tillage did not negatively affect it. Combining both is a viable option to reduce the negative impact of soil compaction on maize growth.

Clinical diagnosis scale for pain lumbar of facet origin: systematic review of literature and pilot study.

Lumbar pain affects between 60-90% of people. It is a frequent cause of disability in adults. Pain may be generated by different anatomical structures such as the facet joint. However, nowadays pain produced by the facet joint has no clinical diagnosis. Therefore, the purpose of this article is to propose a clinical diagnostic scale for lumbar facet syndrome. The study was conducted by means of 6 phases as follows, Phase 1, a systematic review of the literature was performed regarding the clinical diagnosis of facet-based lumbar pain based on the PRISMA checklist; Phase 2, a list of signs and symptoms proposed for diagnosis lumbar pain of facet origin was made. Phase 3, the list of signs and symptoms found was submitted to a committee of experts to discriminate the most significant signs and symptoms, these were linked to general sociodemographic variables to develop an evaluation questionnaire; Phase 4, the evaluation questionnaire was applied, including those selected signs and symptoms to a group of patients with clinical diagnosis of facet disease lumbar pain and who underwent a selective facet block. Phase 5, under standard technique selective facet block and subsequent postoperative clinical control at 1 month. Phase 6, given pre and postsurgical results associated with signs present in the patients we propose a clinical scale of diagnosis scale. Descriptive statistics and Stata 12.0 were used as statistical software. A total of 36 signs and symptoms were found for the diagnosis of lumbar facet syndrome that were submitted to the group of experts, where a total of 12 (8 symptoms and 4 signs) were included for the final survey. 31 patients underwent selective lumbar facet blockade, mostly women, with an average of 60±11.5 years, analogous visual scale of preoperative pain of 8/10, postoperative of 1.7/10, the signs and symptoms most frequently found included in a diagnostic scale were: 3 symptoms 1) axial or bilateral axial lumbar pain, 2) improvement with rest, 3) absence of root pattern, may have pseudoradicular pattern, however, the pain is greater lumbar than pain in the leg and 3 clinical signs 1) Kemp sign, 2) pain induced in joint or transverse process, 3) facet stress sign or Acevedo sign. The clinical diagnosis of lumbar facet pain is still debated. Few diagnostic scales have been postulated, with little or no external validity, so the present study proposes a diagnostic scale consisting of 3 symptoms and 3 clinical signs.

Drought-Tolerant Barley: I. Field Observations of Growth and Development

An ever-growing challenge to agricultural production worldwide is the reduced availability of water and increased incidence of drought. The development of low-irrigation barley cultivars marks a significant achievement in breeding efforts for drought tolerance, but specific traits conferring adaptation to water stress remain unclear. Here, we report results from two years of replicated field trials comparing yield, phenology, water usage, and rooting characteristics of low-irrigation varieties “Solar” and “Solum” to high-input, semi-dwarf varieties “Kopious” and “Cochise”. The objective was to identify differential performance of varieties under high- and low-water conditions through comparison of growth and developmental traits. Rooting characteristics were analyzed by digging in-field root profile walls to a depth of 1.8 m. Varieties were compared under high (877 mm) and low (223 mm) water regimes including irrigation and precipitation. Observed traits associated with improved performance of the low-irrigation varieties under drought conditions included early vigor, early flowering, greater root growth at 40–80 cm depth, and more effective water use exhibited by greater water extraction post-anthesis. The deeper rooting pattern of the low-irrigation varieties may be related to their ability to use more water post-anthesis under water stress, and thus, to fill grain, compared to high input varieties.

Genome-wide identification, phylogeny and function analysis of GRAS gene family in Dendrobium catenatum (Orchidaceae)

BackgroundIn recent years, the molecular mechanism of plant growth and development has been reported in detail. GRAS genes, a plant-specific family of transcription factor, play critical roles in the process. GRAS transcription factors are associated with axillary shoot meristem formation, radial root patterning, phytohormones (gibberellins) signal transduction, light signaling, and abiotic or biotic stress. ObjectiveHere, we firstly investigated GRAS gene family in Dendrobium catenatum, an important medicinal and flowering orchid in China. MethodsThe GRAS gene family in D. catenatum was cloned based on RNA-Seq data. Selected GRAS genes were introduced into Escherichia coli to express proteins. ResultsBased on phylogenetic relationship with the Arabidopsis and Oryza GRAS family members, 47 GRAS genes from D. catenatum are identified and their deduced proteins are classified into 11 subgroups. Most of these GRAS genes contain one exon and closely related members in the phylogenetic tree have similar motif composition. Our result also reveals that GRAS genes in D. catenatum are widely distributed and expressed in different tissue. In addition, 35 GRAS genes are successfully cloned from different subgroups and 7 DoGRAS fusion proteins are induced using E. coli system. Moreover, 8 genes were up-regulated in different tissue following exposure to heat and salt stresses. ConclusionOur findings provide valuable information and candidate genes for future functional analysis for improving the resistance of D. catenatum growth.

Effect of paleopolyploidy and allopolyploidy on gene expression in banana

BackgroundBananas (Musa spp.) are an important crop worldwide. Most modern cultivars resulted from a complex polyploidization history that comprised three whole genome duplications (WGDs) shaping the haploid Musa genome, followed by inter- and intra-specific crosses between Musa acuminata and M. balbisiana (A and B genome, respectively). Unresolved hybridizations finally led to banana diversification into several autotriploid (AAA) and allotriploid cultivars (AAB and ABB). Using transcriptomic data, we investigated the impact of the genome structure on gene expression patterns in roots of 12 different triploid genotypes covering AAA, AAB and ABB subgenome constitutions.ResultsWe demonstrate that (i) there are different genome structures, (ii) expression patterns go beyond the predicted genomic groups, and (iii) the proportion of the B genome influences the gene expression.The presence of the B genome is associated with a higher expression of genes involved in flavonoid biosynthesis, fatty acid metabolism, amino sugar and nucleotide sugar metabolism and oxidative phosphorylation. There are cultivar-specific chromosome regions with biased B:A gene expression ratios that demonstrate homoeologous exchanges (HE) between A and B sub-genomes. In two cultivars, aneuploidy was detected. We identified 3674 genes with a different expression level between allotriploid and autotriploid with ~ 57% having recently duplicated copies (paralogous). We propose a Paralog Inclusive Expression (PIE) analysis that appears to be suitable for genomes still in a downsizing and fractionation process following whole genome duplications. Our approach allows highlighting the genes with a maximum likelihood to affect the plant phenotype.ConclusionsThis study on banana is a good case to investigate the effects of alloploidy in crops. We conclude that allopolyploidy triggered changes in the genome structure of a crop and it clearly influences the gene.

Genetic response of diverse sunflower genotypes in contrasting moisture regimes for various physiological and growth parameters at early developmental stage

Abstract Sunflower has great capacity for bridge the edible oil gap in Pakistan. It ranks second to soybean in worldwide vegetable oil production. A greenhouse experiment was performed in the research area of Department of Plant Breeding and Genetics, University of Agriculture, Faisalabad. Eleven (11) advanced lines along with Hysun-37 (Check) were evaluated under complete randomized design (CRD) replicated thrice for two water regimes and three harvestings at early developmental stage. Different morphological and physiological plant traits were recorded to find out genetic analysis of water stress tolerance in sunflower. Results for analysis of variance exhibited significantly differences among all sunflower genotypes for all the traits. Genotypes performed different under contrasting water regimes. Genotypes like A-25, A-50 and A-57 performed best under both normal and water stress condition due to increased shoot length, deep rooting pattern, increased number of root branches and possessing enormousmass of fresh and dry shoot and root traits. Presence of these enviable plant traits make them superior among all genotypes in comparison with hybrid variety. Correlation analysis indicated strong genotypic and phenotypic correlation between shoot length and shoot dry weight. Traits that possessed significant positive phenotypic correlation with shoot length were dry root weight and fresh root weight. Stress tolerant genotypes viz. A-25, A-50 and A-57 could be recommended for utilization in future sunflower breeding program and can be grown under water stress conditions for high yield. Keywords: Correlation; Genetic variability; Seedling traits; Sunflower http://dx.doi.org/10.19045/bspab.2019.80024

Influence of plant growth promoting rhizobacterial strains Paenibacillus sp. IITISM08, Bacillus sp. PRB77 and Bacillus sp. PRB101 using Helianthus annuus on degradation of endosulfan from contaminated soil

Endosulfan is a broad spectrum insecticide used in agriculture for protection of various food and non-food crops. It is persistent in nature and hence found in soil, air and water. The potential use of plants and microorganisms for the removal of endosulfan from soil was studied. Helianthus annuus plant was grown in soil spiked with 5, 10, 25 and 50 mg kg−1 concentrations of endosulfan and inoculated with plant growth promoting rhizobacterial strains Paenibacillus sp. IITISM08, Bacillus sp. PRB77 and Bacillus sp. PRB101 for 40, 80 and 120 days. Potential of plant for endosulfan uptake was evaluated by investigating the endosulfan levels in plant tissues (root and shoot). The results indicated that endosulfan accumulation followed the pattern of root > shoot as well as decrease in uptake of endosulfan in root and shoot of a plant grown in bacterial inoculated soil as compared to un-inoculated soil. Bacterial inoculation had a positive effect on endosulfan degradation. Maximum degradation of 92% at 5 mg kg−1 of endosulfan in soil was observed on inoculation with PRB101 after 120 days of inoculation. The results showed that plant growth promoting bacteria enhances plant biomass production. Lipid peroxidation was also estimated by determining the malondialdehyde (MDA) production, which is a biomarker of oxidative damage. Decrease in MDA formation by root and leaves of plants grown in the bacteria inoculated plant was also observed. The results suggested the effectiveness of plant growth promoting rhizobacteria to boost accumulation potential, biomass production and enhance remediation of endosulfan contaminated soil.

Evaluation of Water Uptake and Root Distribution of Cherry Trees under Different Irrigation Methods

Although water-saving measures are increasingly being adopted in orchards, little is known about how different irrigation methods enhance water use efficiency at the root system level. To study the allocation of water sources of water absorption by cherry roots under two irrigation methods, surface irrigation and drip irrigation, oxygen isotope tracing and root excavation were used in this study. We found that different irrigation methods have different effects on the average δ18O content of soil water in the soil profile. The IsoSource model was applied to calculate the contribution rate of water absorption by cherry roots under these irrigation methods. During the drought period in spring (also a key period of water consumption for cherry trees), irrigation water was the main source of water absorbed by cherry roots. In summer, cherry roots exhibited a wide range of water absorption sources. In this case, relative to the surface irrigation mode, the drip irrigation mode demonstrated higher irrigation water use efficiency. After two years of the above experiment, root excavation was used to analyze the effects of these irrigation methods on the distribution pattern of roots. We found that root distribution is mainly affected by soil depth. The root system indexes in 10–30 cm soil layer differ significantly from those in other soil layers. Drip irrigation increased the root length density (RLD) and root surface area (RSA) in the shallow soil. There was no significant difference in root biomass density (RBD) and root volume ratio (RVR) between the two irrigation treatments. The effects of these irrigation methods on the 2D distribution of cherry RBD, RLD, RSA and RVR, which indicated that the cherry roots were mainly concentrated in the horizontal depths of 20 to 100 cm, which was related to the irrigation wet zone. In the current experiment, more than 85% of cherry roots were distributed in the space with horizontal radius of 0 to 100 cm and vertical depth of 0 to 80 cm; above 95% of cherry roots were distributed in the space with the horizontal radius of 0 to 150 cm and the vertical depth of 0 to 80 cm. Compared with surface irrigation, drip irrigation makes RLD and RSA more concentrated in the horizontal range of 30–100 cm and vertical range of 0–70 cm.

Topological traits of a cellular pattern versus growth rate anisotropy in radish roots

The topology of a cellular pattern, which means the spatial arrangement of cells, directly corresponds with cell packing, which is crucial for tissue and organ functioning. The topological features of cells that are typically analyzed are the number of their neighbors and the cell area. To date, the objects of most topological studies have been the growing cells of the surface tissues of plant and animal organs. Some of these researches also provide verification of Lewis’s Law concerning the linear correlation between the number of neighboring cells and the cell area. Our aim was to analyze the cellular topology and applicability of Lewis’s Law to an anisotropically growing plant organ. The object of our study was the root apex of radish. Based on the tensor description of plant organ growth, we specified the level of anisotropy in specific zones (the root proper, the columella of the cap and the lateral parts of the cap) and in specific types of both external (epidermis) and internal tissues (stele and ground tissue) of the apex. The strongest anisotropy occurred in the root proper, while both zones of the cap showed an intermediate level of anisotropy of growth. Some differences in the topology of the cellular pattern in the zones were also detected; in the root proper, six-sided cells predominated, while in the root cap columella and in the lateral parts of the cap, most cells had five neighbors. The correlation coefficient rL between the number of neighboring cells and the cell area was high in the apex as a whole as well as in all of the zones except the root proper and in all of the tissue types except the ground tissue. In general, Lewis’s Law was fulfilled in the anisotropically growing radish root apex. However, the level of the applicability (rL value) of Lewis’s Law was negatively correlated with the level of the anisotropy of growth, which may suggest that in plant organs in the regions of anisotropic growth, the number of neighboring cells is less dependent on the cell size.

DYNAMICS OF ROOT AND TUBER CROPS ACREAGE ALLOCATION AND YIELD ADJUSTMENT IN NIGERIA

This paper empirically studied the growth pattern and supply response of root and tuber crops farmers in Nigeria using annual time series data sourced from FAO database. The data spanned from 1961-2014 and covered area, yield and price of yam, cassava and potatoes crops. The data were analyzed using the growth model, instability index, production decomposition analysis model and Engel-Granger two-step model. Findings showed that area was responsible for the paradigm shift in the production of selected root and tuber crops in Nigeria and not productivity which is very essential for sustainable agriculture due to shrinking of land resource owing to competing demand for its use as evidenced by incessant attacks of herdsmen on arable crop farmers. Generally, the farmers respond to price incentives in reallocating their area and adjusting their yield for all the selected crops. It was also observed that acreage and yield for all the selected crops had long-run association with the price and non-price factors; likewise, it established long-run equilibrium. So the need for price forecast mechanism to checkmate cob-web cycle which affects the balance between supply and demand for the root and tuber crops in the country and increase in production of crops achieved by increasing productivity of land-combination of technology and efficiency in the utilization of resources is recommended.

Light and auxin signaling cross-talk programme root development in plants

Root development in plants is affected by light and phytohormones. Different ranges of light wavelength influence root patterning in a particular manner. Red and white light promote overall root development, whereas blue light has both positive as well as negative role in these processes. Light-mediated root development primarily occurs through modulation of synthesis, signaling and transport of the phytohormone auxin. Auxin has been shown to play a critical role in root development. It is being well-understood that components of light and auxin signaling cross-talk with each other. However, the signaling network that can modulate the root development is an intense area of research. Currently, limited information is available about the interaction of these two signaling pathways. This review not only summarizes the current findings on how different quality and quantity of light affect various aspects of root development but also present the role of auxin in these developmental aspects starting from lower to higher plants.

Native shrubland and managed buffelgrass savanna in drylands: Implications for ecosystem carbon and water fluxes

Land cover and land-use change (LCLUC) between woody- and grass-dominated ecosystems in drylands comprise one of the largest uncertainties in the land CO2 sink. This is especially true for the widespread transition from shrublands to grasslands/savannas caused by the establishment of exotic C4 grass species for grazing or through biological invasion of these species, where information about its impacts on ecosystem CO2 fluxes is limited. For studying this, we used three years of eddy covariance measurements of net ecosystem production (NEP), gross primary production (GPP), ecosystem respiration (Reco) and evapotranspiration (ET) over a Sonoran Desert shrubland and an adjacent grazing savanna of buffelgrass (Cenchrus ciliaris L.), established 35 years ago. At monthly, seasonal and annual time scales, we assessed whether between-site differences in CO2 fluxes were related to differences in ecosystem water use, measured as the fraction ET to precipitation, water use efficiency (WUE, i.e. the ratio between GPP and ET) and/or to the relation between Reco and GPP. Although the savanna had higher WUE than the shrubland, its summer NEP was limited by water use, due to limitations in leaf area index and likely rooting patterns. Conversely, the savanna had higher NEP than the shrubland during fall to spring due to increased WUE; possibly due to activity of buffelgrass and remaining woody species using (summer) water from deeper soil layers. However, differences across these seasons compensated each other at the inter-annual scale, and both sites had comparable net carbon sinks over the three-year study period. Further studies are needed to understand and reduce the uncertainty associated with carbon and water fluxes associated with LCLUC in dryland ecosystems.

The Geometrical Modeling of Aortic Root Complex.

Background:This study was designed to investigate the anatomical relationship of the different levels of aortic root.Materials and Methods:The morphological features of the aortic root were examined using of 12 adult hearts from fixed male cadavers who had expired due to noncardiac causes by magnetic resonance imaging and applied mathematical analyses to the results. The measurements of the aortic root were done at four levels: at the ventriculoarterial junction (annulus), at the largest level of the Valsalva sinuses (sinus), at the level of commissures (sinotubular junction [STJ]), and at 1 cm above the STJ (aorta ascendens). We derived an equation that allows calculation of the appropriate diameter of the aortic root from four levels. Statistical analysis among the variation of the diameters at the four levels of aortic root was achieved using test one-way analysis of variance.Results:The data showed a geometric pattern of the aortic root. The comparison of the values from four levels showed that the narrowest at the sinotubular junctional level and the widest at the sinus level.Conclusion:The analysis of our data shows that the aortic root has a consistent shape with varying size and that is a definable mathematical relationship between root diameter.