Degradation of crude oil in the rhizosphere of Sorghum bicolor

Dissipation of petroleum contaminants in the rhizosphere is likely the result of enhanced microbial degradation. Plant roots may encourage rhizosphere microbial activity through exudation of nutrients and by providing channels for increased water flow and gas diffusion. Phytoremediation of crude oil in soil was examined in this study using carefully selected plant species monitored over specific plant growth stages. Four sorghum (Sorghum bicolor L.) genotypes with differing root characteristics and levels of exudation were established in a sandy loam soil contaminated with 2700 mg crude oil/kg soil. Soils were sampled at three stages of plant growth: five leaf, flowering, and maturity. All vegetated treatments were associated with higher remediation efficiency, resulting in significantly lower total petroleum hydrocarbon concentrations than unvegetated controls. A relationship between root exudation and bioremediation efficiency was not apparent for these genotypes, although the presence of all sorghum genotypes resulted in significant removal of crude oil from the impacted soil.     

高粱遗传转化研究进展

高粱（Sorghum bicolor）是一种重要的多用途作物, 其遗传转化研究对于高粱的分子育种和分子遗传学基础研究都具有重要意义。该文对高粱遗传转化的方法、标记基因、遗传转化的启动子和受体系统进行了综述, 并提出了今后高粱遗传转化应当集中研究的问题。     

New techniques and findings in the study of a candidate allelochemical implicated in invasion success

Allelopathy has been hypothesized to promote the success of invasive plants. Support for the role of allelopathy in invasions has emerged from research on the candidate allelochemical (?)‐catechin, which is secreted by spotted knapweed. Here we describe new methods to quantify catechin in liquid and soil. With a new technique, we assayed catechin production by individual plants in liquid media and found levels up to two orders of magnitude less than previously reported. An acetone/water solution provided consistent recovery of catechin from soil, with percent recovery depending upon soil type. We evaluated soils from two spotted knapweed sites in Montana, USA, but found no measurable catechin. Idaho fescue, a native species reportedly sensitive to catechin, only exhibited slightly reduced growth at concentrations 10 times higher than previously reported to cause 100% mortality. Our results emphasize that more research is required to clarify the role of catechin in the invasion of spotted knapweed.     

Equilibrium processes cannot explain high levels of short- and medium-range linkage disequilibrium in the domesticated grass Sorghum bicolor

Patterns of linkage disequilibrium (LD) are of interest because they provide evidence of both equilibrium (e.g., mating system or long-term population structure) and nonequilibrium (e.g., demographic or selective) processes, as well as because of their importance in strategies for identifying the genetic basis of complex phenotypes. We report patterns of short and medium range (up to 100 kb) LD in six unlinked genomic regions in the partially selfing domesticated grass, Sorghum bicolor. The extent of allelic associations in S. bicolor, as assessed by pairwise measures of LD, is higher than in maize but lower than in Arabidopsis, in qualitative agreement with expectations based on mating system. Quantitative analyses of the population recombination parameter, rho, however, based on empirical estimates of rates of recombination, mutation, and self-pollination, show that LD is more extensive than expected under a neutral equilibrium model. The disparity between rho and the population mutation parameter, , is similar to that observed in other species whose population history appears to be complex. From a practical standpoint, these results suggest that S. bicolor is well suited for association studies using reasonable numbers of markers, since LD typically extends at least several kilobases but has largely decayed by 15 kb.     

The in vitro substrate regiospecificity of recombinant UGT85B1, the cyanohydrin glucosyltransferase from Sorghum bicolor

The in vitro substrate specificity of UDP-glucose:p-hydroxymandelonitrile-O-glucosyltransferase from Sorghum bicolor (UGT85B1) was examined using a range of potential acceptor molecules, including cyanohydrins, terpenoids, phenolics, hexanol derivatives and plant hormones. Qualitative enzyme activity assays employing 20 different putative substrates were performed and 15 proved to be glucosylated using recombinant UGT85B1 isolated from Escherichia coli. K(m) and k(cat) values were determined for nine of these substrates including mandelonitrile, geraniol, nerol and beta-citronellol, 2-hydroxy-3-methoxybenzyl alcohol, 1-hexanol, cis-3-hexen-1-ol, 3-methyl-3-buten-1-ol and 3-methyl-2-buten-1-ol. UGT85B1 has a rather broad substrate specificity in vitro but shows regiospecificity, demanding the presence of a sterically unhindered hydroxyl group e.g. as part of a cyanohydrin function, as a primary alcohol or as a phenolic hydroxyl group and being influenced by the stereochemistry and/or interactive chemistry of the substituents on the hydroxyl-bearing carbon atom.     

Mechanisms of chloride partitioning in the leaves of salt-stressed Sorghum bicolor L.

Chloride transport in sheath and blade tissue and the cellular distribution of Cl^- were investigated in an attempt to determine the physiological basis of the preferential accumulation of Cl^- in sheaths of salt-stressed sorghum ( Sorghum bicolor L.). Import and export of ³⁶Cl^- in leaf sheaths and blades of intact sorghum were followed over a 2 week period. X-ray microanalysis of frozen-hydrated bulk tissue samples was used to determine the accumulation of Cl^- and other elements in the vacuoles of sheath and blade cells.
Sheath tissue accumulated Cl^- despite a relatively high Cl^- turnover rate. Chloride was shown to accumulate in most cell types of the sheath, particularly in adaxial epidermal cells. After an initial increase in the concentration of Cl^-, blade tissue regulated Cl^- levels within certain limits. Chloride levels in blades were greater in the abaxial and adaxial epidermal cells than in other cell types. The epidermal cells of blades accumulated Cl^- to approximately the same concentration as sheath epidermal cells. The Cl^- concentration in the photosynthetically active mesophyll and bundle sheath cells, however, remained low.
Thus, the partitioning of Cl^- previously observed in the leaves of salinized sorghum apparently results from the ability of bundle sheath and mesophyll cells to maintain concentrations of Cl^- at lower levels than do epidermal cells. In addition, the relatively large sheath parenchyma cells tend to serve as reservoirs for the storage of Cl^-.     

Adaptive nature of the transition phases in development: the case of Sorghum bicolor

An increase in tolerance to salinity is induced in Sorghum bicolor by exposure to a sublethal concentration of NaCl during early vegetative development. The phase of competence for induction of this response, termed salt adaptation, is well defined in time and it coincides with the emergence of the first adventitious roots. The link between these events was investigated. Competence for salt adaptation varies among genotypes. It is shown that competence is especially high for genotypes in which the link between the seminal root and the shoot is reduced during emergence of the adventitious root. These data relate the capacity for salt adaptation with development in the absence of NaCl, suggesting that: (i) functional integration of the adventitious roots within the whole plant has an adaptive nature in normal development; (ii) salt adaptation results from an integration of the environmental constraint (NaCl) during this developmental readjustment. It is concluded that perturbations generated by emergence of a new organ are the cause of rapid variations in sensitivity required to open a competence window.     

Effect of monoterpenes on lipid oxidation in maize

The monoterpenes 1,8-cineole, thymol, geraniol, menthol and camphor strongly inhibited the root growth of Zea mays L. seedlings. They induced an oxidative stress as measured by the production of malondialdehyde, conjugated dienes and peroxides. This oxidative stress depended on the length of the exposure and on the monoterpene applied. The total fatty acid content was measured and fatty acid composition was analyzed. Unsaturated fatty acids increased in the treated samples. The alcoholic and non-alcoholic monoterpenes appeared to have different modes of action.Abbreviations MDA Malondialdehyde - TFA Total fatty acid content - FA Fatty acid - IC₈₀ Concentration causing 80% inhibition     

Evaluation of chemical composition and antiedematogenic activity of the essential oil of Hyptis martiusii Benth

Evaluations of the therapeutic potential of medicinal plants and their components have been the subject of many studies. Furthermore, the biological activities of various plant species have been reported in various pieces of literature. Hyptis martiusii Benth (Lamiaceae), popularly known as “mad balm” is commonly found in the North, Southeast, and Northeast of Brazil. Its leaves are used ethnobiologically as antiulcerogenic, antimicrobial, antitumor and as insecticide. This study aimed to analyze the chemical composition of the essential oil of H. martiusii Benth (OEHM) by GC/MS as well as its possible topical activity as an antiedematogenic. This is verified by the models of ear edema induced by single (acute edema) and multiple (chronic edema) applications of croton oil topically, and systemically verified through the model of paw edema induced by carrageenan 1%. Doses of 50, 75 and 100 mg/kg OEHM were used in all tests. Chemical analysis of the oil revealed the 1,8-cineole (34.58%) and δ-carene (21:58%) as major components present in the essential oil. On the model of ear edema, acute and chronic OEHM in all the tested doses showed no significant antiedematogenic activity (p < 0.05). The systemic model of paw edema induced by carrageenin showed that a dose of 100 mg/kg effectively reduced swelling by 55.37% in the second hour evaluation when compared to the saline group. The anti-inflammatory systemic effect can give greater bioavailability of the components present in the essential oil and your interference in cytokines and leukotriene, thromboxane and prostaglandin biosynthesis. It is therefore concluded that OEHM presents systemic antiedematogenic activity but not topical activity at these doses.     

Restriction fragment variation in the nuclear and chloroplast genomes of cultivated and wild Sorghum bicolor

Summary Fifty-six accessions of cultivated and wild sorghum were surveyed for genetic diversity using 50 low-copy-number nuclear DNA sequence probes to detect restriction fragment length polymorphisms (RFLPs). These probes revealed greater genetic diversity in wild sorghum than in cultivated sorghum, including a larger number of alleles per locus and a greater portion of polymorphic loci in wild sorghum. In comparison to previously published isozyme analyses of the same accessions, RFLP analysis reveals a greater number of alleles per locus. Furthermore, many RFLP alleles have frequencies between 0.25–0.75, while the vast majority of isozyme alleles are either rare (< 0.25) or near fixation (> 0.75). Correlations between genetic and geographic distances among the accessions were stronger when calculated with RFLP than with isozyme data. Systematic relationships revealed by nuclear and chloroplast restriction site analysis indicate that cultivated sorghum is derived from the wild ssp. arundinaceum. The portion of the wild gene pool most genetically similar to the cultivars is from central-northeastern Africa. Previous published data also suggested that this is most likely the principal area of domestication of sorghum. Introgression between wild and cultivated sorghum was inferred from disconcordant relationships shown by nuclear and chloroplast DNA markers. Introgression apparently occurs infrequently enough that the crop and its wild relatives maintain distinct genetic constitutions.     

Ocimum gratissimum Linn. (Lamiaceae) essential oil for the management of Exorista sorbillans Wiedemann (Diptera: Tachinidae) menace of silkworm in seriecosystem

Although they act as biocontrol agents, Tachinid parasitoids attack economically beneficial insects, inviting the adoption of control measures against them. The uzi fly, Exorista sorbillans, infests silkworms incurring heavy loss. It is difficult to control such parasitoids as the larval stage is endoparasitic, and insecticides cannot reach them without subjecting the silkworms to potential risks. We selected the leaves of Ocimum gratissimum L. for testing their toxicity potential against E. sorboillans because of its low selective toxicity to Antheraea assamensis Helfer larvae. Assay for adulticidal efficacy of the leaf extracts showed the petroleum ether extract to be the most effective. But the essential oil (LC50 of 0.42%) was even more effective. GC–MS analysis of the oil revealed the presence of twenty-seven compounds with a high percentage of thymol (26.17%), indicating the plant oil as thymol rich chemotype. Thymol was the dominant constituent in the active fraction. The oil and constituents caused rapid death on topical application, indicating a higher penetration rate. We propose the exploration of the essential oil and its constituents as a sustainable solution for controlling E. sorbillans infestation of silkworms in the future.     

Involvement of cinnamyl-alcohol dehydrogenase in the control of lignin formation in Sorghum bicolor L. Moench

The lignin structure and enzyme activities of normal and brown-midrib (BMR-6) mutant lines of Sorghum bicolor have been compared to identify the enzyme(s) involved in the reduction of the lignin content of the mutant. The results indicate that cinnamyl-alcohol dehydrogenase (CAD) and caffeic acid O-methyltransferase are depressed in the BMR-6 line, whereas the structural modifications correspond only to a reduction of CAD activity. Apparently, the change in the Sorghum lignin content, caused by depression of CAD activity, is accompanied by the incorporation of cinnamaldehydes into the core lignin.Abbreviations CAD cinnamyl-alcohol dehydrogenase - HPLC high-performance liquid chromatography - m/z mass number - OMT caffeic acid O-methyltransferase     

Diversity of nifH gene pools in the rhizosphere of two cultivars of sorghum (Sorghum bicolor) treated with contrasting levels of nitrogen fertilizer.

The diversity of nitrogen-fixing bacteria was assessed in the rhizospheres of two cultivars of sorghum (IS 5322-C and IPA 1011) sown in Cerrado soil amended with two levels of nitrogen fertilizer (12 and 120 kg ha(-1)). The nifH gene was amplified directly from DNA extracted from the rhizospheres, and the PCR products cloned and sequenced. Four clone libraries were generated from the nifH fragments and 245 sequences were obtained. Most of the clones (57%) were closely related to nifH genes of uncultured bacteria. NifH clones affiliated with Azohydromonas spp., Ideonella sp., Rhizobium etli and Bradyrhizobium sp. were found in all libraries. Sequences affiliated with Delftia tsuruhatensis were found in the rhizosphere of both cultivars sown with high levels of nitrogen, while clones affiliated with Methylocystis sp. were detected only in plants sown under low levels of nitrogen. Moreover, clones affiliated with Paenibacillus durus could be found in libraries from the cultivar IS 5322-C sown either in high or low amounts of fertilizer. This study showed that the amount of nitrogen used for fertilization is the overriding determinative factor that influenced the nitrogen-fixing community structures in sorghum rhizospheres cultivated in Cerrado soil.     

Genotypic variation in the photosynthetic competence of Sorghum bicolor seedlings subjected to polyethylene glycol-mediated drought stress

Eleven varieties of Sorghum bicolor, subjected to PEG-mediated drought stress were compared for their photosynthetic performance. The varieties differed in their relative water content over a range of PEG concentrations (0-25%). CO2 assimilation, stomatal conductance and the quantum yield of PSII electron transport decreased with increasing PEG concentrations in all varieties. However the intercellular CO2 concentration showed a nonlinear PEG concentration-dependent change. At lower PEG concentrations there was a decrease in the levels of intercellular CO2 concentration in all varieties that could be attributed to stomatal closure. At higher PEG concentrations, some varieties showed an increase in the intercellular CO2 concentration, indicating an inhibition of photosynthetic activity due to non-stomatal effects, while others did not. It was seen that the varieties differed in the stress thresholds at which stomatal and metabolic limitations to photosynthesis occur. These differences in the photosynthetic adaptation of Sorghum varieties could be useful in identifying genotypes showing large differences in photosynthetic adaptation, which could be useful in mapping photosynthetic traits for drought stress tolerance.     

Comparative determination of the essential oil composition in Bulgarian endemic plant Achillea thracica Velen. during the process of ex situ conservation

Ex situ conservation of Bulgarian endemic plant Achillea thracica Velen. was achieved by successful in vitro cultivation of mono-nodal segments on MS-B5 medium supplemented with 1.0 mg/L BA for 20 days and subsequent transferring of regenerated plants on hormone free basal MS-B5 medium for root development and accumulation of leaf biomass. In vitro multiplicated plants were successfully acclimated in a growth chamber with 100% survival. GC–MS analysis of the essential oils resulted in the identification of 30, 10 and 28 compounds in in situ grown, in vitro cultivated and ex vitro adapted plants, respectively, constituting 77.7%, 99.9% and 84.1% of the total oils. The wider variety of compounds was found in the essential oils of in situ and ex vitro adapted plants where santolina alcohol, β-eudesmol, 1,8-cineole, germacrene D, α-cadinol and artemisia alcohol were the principal components comprising 68.7% and 69.3 of the oil, respectively. In vitro cultivated plants consist of mainly 1,8-cineole, germacrene D and artemisia alcohol representing 87% of the oil. Different growth conditions affect the composition of essential oils, suggesting their possible involvement in the process of adaptation and surviving in changing environmental conditions.     

The importance of analytical techniques in allelopathy studies with the reported allelochemical catechin as an example

Allelopathy can be challenging to demonstrate. Developing rigorous analytical techniques to detect and quantify compound(s) of interest from soil or liquid media lays the foundation for designing ecologically relevant experiments that incorporate candidate allelochemicals. In this paper, fundamental components of analytical techniques, including method development, validation, and appropriate controls are discussed. Research on the candidate allelochemical from spotted knapweed, catechin, is used as an example to demonstrate the importance of including these components both during data collection and in subsequent publications. This example shows how contrasting results between research groups can be difficult to interpret when information on controls and method validation are not included in publications. Recent research suggests that catechin is not likely driving spotted knapweed’s invasion, and thus future research on this system should focus on alternate candidate toxins from spotted knapweed. By employing appropriate analytical techniques, such as those outlined here, a strong foundation can be laid for ecologically oriented experiments that examine the role of allelochemicals in structuring communities.     

Chemical Constituents of the Fssential Oils from the Leaves of Laurus nobilis and Tendency in Changes of the Constituents Month by Month

The chemical constituents of the essential oils from the leaves of Laurus nobilis L., have been identified both by capillary GC-MS and fused silica capillary GC Kovats retention in,lex of components. From laurel leaf oil, 45 compounds have been identified, among which, 19 compounds such as 1,4-cineole, sabinene hydrate etc. have not been found in the leaf oil previously. This paper studies systematically the constituents of essential oil from dry, fresh leaves, and those of annual, perennial, different district, and reported the changes of the chemical constituents month by month. Results showed that the yield of essential oil and 1,8-cineole content is the highest in July.