1,720,991 research outputs found
Together, but not for ever: ectomycorrhizal symbiosis is an unstable affair
No full textEctomycorrhizal symbiosis continues to pose a number of
intriguing and so far partially unanswered questions. These
concern not only general aspects of mycorrhizal physiology,
host specificity, or the impact of ectomycorrhizas on forest
ecosystems, but also the evolutionary ecology of the
ectomycorrhizal symbiosis itself and the reasons why it has
evolved
Cytokinin oxidase strikes again
No full textResearch into the enzymes involved in several aspects of cytokinin metabolism (including storage and catabolic pathways) is undergoing an unprecedented period of success. We recently reported1 on new findings concerning the biochemical and molecular properties of cytokinin oxidase (CKO), a poorly characterized, but crucial enzyme, which irreversibly inactivates cytokinins. Although CKO has been classified as a copper-containing amine oxidase1, clear evidence is now emerging that argues against this classification [2], [3] and [4]. In particular, as previously described1, there is evidence that CKO from wheat is an FAD-containing flavoprotein (P. Galuszka et al., unpublished), and recent advances have further extended this finding [3] and [4]
Birth registration and child undernutrition in sub-Saharan Africa
Get PDFObjective In many countries of the world millions of people are not registered at birth. However, in order to assess children's nutritional status it is necessary to have an exact knowledge of their age. In the present paper we discuss the effects of insufficient or imprecise age data on estimates of undernutrition prevalence. Design Birth registration rates and levels of stunting, underweight and wasting were retrieved from Multiple Indicator Cluster Surveys and Demographic and Health Surveys of thirty-seven sub-Saharan African countries, considering the subdivision in wealth quintiles. The composition of the cross-sectional sample used for nutritional evaluation was analysed using a permutation test. Logistic regression was applied to analyse the relationship between birth registration and undernutrition. The 95 % probability intervals and Student's t test were used to evaluate the effect of age bias and error. Results Heterogeneous sampling designs were detected among countries, with different percentages of children selected for anthropometry. Further, registered children were slightly more represented within samples used for nutritional analysis than in the total sample. A negative relationship between birth registration and undernutrition was recognized, with registered children showing a better nutritional status than unregistered ones, even within each wealth quintile. The over- or underestimation of undernutrition in the case of systematic over- or underestimation of age, respectively, the latter being more probable, was quantified up to 28 %. Age imprecision was shown to slightly overestimate undernutrition. Conclusions Selection bias towards registered children and underestimation of children's age can lead to an underestimation of the prevalence of undernutrition. Correlated dataset thttp://hdl.handle.net/11584/13738
An overview of Cistus ectomycorrhizal fungi
No full textThe genus Cistus comprises a group of about 20 shrub species found in wide areas throughout the whole Mediterranean region to the Caucasus. Being one of the main constituents of the Mediterranean-type maquis, this plant genus is peculiar in that it has developed a range of specific adaptations to resist summer drought and frequent disturbance events, such as fire and grazing. In addition, it can form both ectomycorrhizas and arbuscular mycorrhizas. In this paper, we review the information available on the ectomycorrhizal fungi of Cistus across its entire geographic range, as gathered and critically sifted from both published literature sources and personal observations. Although the resulting data matrix was based primarily on accounts of sporocarp inventories in the field, existing knowledge on the features of Cistus natural and synthesized ectomycorrhizas was also included and discussed. In total, more than 200 fungal species belonging to 40 genera have been reported so far to be associated with Cistus. An analysis of the pattern of ectomycorrhizal diversity and host specificity revealed that members of the Cortinariaceae and Russulaceae make the most of both Cistus-aspecific and Cistus-specific mycobionts. Further studies are needed to expand our preliminary knowledge of the mycorrhizal ecology and biology of Cistus and its fungal associates, focusing on topics such as mycobiont diversity, host specificity, fungal succession, mycorrhizal influence on stress tolerance, and impact of disturbances, while comparing the findings with those from other ecosystems
Fungi in ectomycorrhizal associations of silver fir (Abies alba Miller) in Central Italy
No full textNaturally occurring ectomycorrhizas of silver fir (Abies alba Miller) were studied in two stands, one natural and one artificial, situated in Central Italy. A total of 25 mycorrhizal types was classified, for eight of which the mycobiont was identified at the species level. Analysis of macroscopic and microscopic features and matching of field-collected carpophores with associated mycorrhizas led to the tentative identification of several other types encountered during this study, at least at the genus level. No significant differences were noticed between natural and artificial stands in the relative richness of mycorrhizal types found on A. alba, indicating the maturity of the artificial stand with regard to succession of ectomycorrhizal fungi. Confocal laser scanning microscopy was used for visualization of mycorrhizal structures formed by Lactarius spp., without the need for specific staining with a fluorochrome, thanks to latex autofluorescence. This technique allowed observation of several structures in greater detail than with conventional light microscopy
Cytokinin oxidase: new insight into enzyme properties
No full textThe cytokinin group of plant hormones plays an essential role in the regulation of plant growth and differentiation, including the release of lateral buds from apical dominance and the delay of senescence [1] and [2]. Moreover, increasing evidence supports the hypothesis that cytokinins interact with auxins at multiple levels in a complex manner to control various physiological and developmental responses3. However, in spite of their fundamental role, our understanding of the molecular mode of action of cytokinins and of their metabolism remains rather rudimentary. In particular, the enzymes involved in the control of the cytokinin cell cycle have been poorly characterized
An assessment of below-ground ectomycorrhizal diversity of Abies alba Miller in central Italy
No full textIn the framework of an ongoing study on the mycorrhizal associations of silver fir (Abies alba Mill., we investigated the below-ground diversity of ectomycorrhizal communities in ten field sites located in five distinct natural A. alba woods, situated in the central part of the Apennine chain (Abruzzo region, Italy). Based on macro- and microscopic features, a total of 48 morphologically distinct ectomycorrhizal types have been classified on mature trees of A. alba, 37 of which are reported here for the first time. Ectomycorrhizal morphotypes were partially characterized, and their main features described; in many cases, the relevant fungal symbiont was identified at the level of species or genus. The number of distinguishable morphotypes per site was, with few exceptions, rather homogeneous, ranging from (5) 8 to 13 (20). Comparison of morphotype occurrence revealed that only few types were encountered in five or more sampled sites, whereas the vast majority of types was less frequent. The present study revealed a considerably high species diversity of the ectomycorrhizal symbionts of A. alba in a quite restricted area, thus raising interesting questions as to the ectomycorrhizal potential of this host tree over its entire, large natural range
Ectomycorrhizal fungal diversity: separating the wheat from the chaff
No full textThousands of ectomycorrhizal (ECM) fungal species exist, but estimates of global species richness of ECM fungi differ widely. Many genera have been proposed as being ECM, but ill a number of studies evidence for the hypothesized ECM habit is lacking. Progress in estimating ECM species richness is therefore slow. Ill this paper we have retrieved studies providing evidence for the ECM habit of fungal species and For the identification of the mycobiont(s) ill specific ECM associations, using published and web-based mycorrhiza literature. The identification methods considered are morpho-anatomical, characterization or naturally occurring ECMs, pure Culture synthesis, molecular identification, and isotopic evidence. In addition, phylogenetic information is also considered as a relevant criterion to assess ECM habit. OF 343 fungal genera for which all ECM status has been alleged, about two thirds have Supportive published evidence or ECM Status can be at least hypothesized. For the remaining taxa, Currently no indication exists as for their I-CM nutritional habit, besides field observations or associations with putative hosts. Our survey clearly indicates that current knowledge of ECM fungal diversity, as Supported by experimental evidence, is only partly complete, and that inclusion of many Funga genera in this trophic and ecological category is not verified at this stage. Care must thus be used when compiling lists of ECM and saprotrophic full studies oil the basis of published information only. On the basis of our literature search we conservatively estimate ECM species richness around 7750 species. However, oil the basis of estimates of knowns and unknowns in macromycete diversity, a final estimate or ECM species richness Would likely be between 20000 and 25000
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