493 research outputs found


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    This research aims to obtain information about students' creativity in arranging the results of practicum activities in the botany of non-vascular plant course.  This research was used descriptive design. The participants of this study were third semester biology education students (n=25) at a state university in Sumatera, Indonesia. The student was taken botany of non-vascular plant course. The instruments used in this research were performance instruments that measured students' creative thinking skills, questionnaires and observation guidelines that have been developed. The performance instrument used contains several indicators, namely: fluency, flexibility, originality dan elaboration. The data of creative thinking skills were processed by calculating the percentage (%) for each indicator and categorized into four levels (very creative, creative, quite creative and less creative). The results showed that students' creative thinking ability in compiling reports on the practicum activities is (2.68) classified into creative categories with an average of each indicator that are: fluency (3.06); flexibility (2.96), originality (2.95), and elaboration (1.76). The results show that the average student has good creative thinking skills in compiling reports of the practicum activities of botany of non-vascular plant cours

    Xanthomonas albilineans is able to move outside of the sugarcane xylem despite its reduced genome and the absence of a Hrp type III secretion system.

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    Xanthomonas albilineans, the causal agent of leaf scald disease of sugarcane, is a pathogen that experienced genome reduction during its speciation. Additionally, this xanthomonad is notably missing the Hrp type III secretion system and the xanthan gene cluster that are commonly found in pathogenic Xanthomonas species. X. albilineans was up to now considered as limited to the xylem of sugarcane. However, recently published studies suggested that X. albilineans was able to invade tissues other than the xylem of sugarcane leaves but the occurrence of X. albilineans outside the xylem has not been clearly proven. In this study, we used confocal microscopy and transmission electron microscopy to investigate the localization of this pathogen in diseased leaves and stalks of sugarcane. Three sugarcane cultivars with different levels of resistance to leaf scald were inoculated with the green fluorescent protein labelled X. albilineans strains XaFL07-1 (from Florida) and GPE PC73 (from Guadeloupe). Sections of sugarcane leaves and stalks were examined 8-60 days after inoculation in order to localize X. albilineans in the different plant tissues. Confocal microscopy observation of symptomatic leaves confirmed the presence of the pathogen in the protoxylem and the metaxylem, however, X. albilineans was also observed in the phloem, the parenchyma and the bulliform cells of the leaves. Similarly, the protoxylem and the metaxylem of infected sugarcane stalks were invaded by X. albilineans. Surprisingly, the pathogen was also observed in apparently intact storage cells of the stalk and in the intercellular spaces between these cells. Several of these observations made by confocal microscopy have been confirmed by transmission electron microscopy. X. albilineans can therefore no longer be considered as a xylem-limited pathogen. To our knowledge, this is the first description of a plant pathogenic bacterium invading apparently intact non-vascular plant tissue and multiplying in parenchyma cells. The mechanisms and virulence factors used by X. albilineans to enter and invade different tissues of sugarcane remain to be identified. (Résumé d'auteur

    Evolutionary Implications of a Peroxidase with High Affinity for Cinnamyl Alcohols from Physcomitrium patens, a Non-Vascular Plant

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    [Abstract] Physcomitrium (Physcomitrella) patens is a bryophyte highly tolerant to different stresses, allowing survival when water supply is a limiting factor. This moss lacks a true vascular system, but it has evolved a primitive water-conducting system that contains lignin-like polyphenols. By means of a three-step protocol, including ammonium sulfate precipitation, adsorption chromatography on phenyl Sepharose and cationic exchange chromatography on SP Sepharose, we were able to purify and further characterize a novel class III peroxidase, PpaPrx19, upregulated upon salt and H2O2 treatments. This peroxidase, of a strongly basic nature, shows surprising homology to angiosperm peroxidases related to lignification, despite the lack of true lignins in P. patens cell walls. Moreover, PpaPrx19 shows catalytic and kinetic properties typical of angiosperm peroxidases involved in oxidation of monolignols, being able to efficiently use hydroxycinnamyl alcohols as substrates. Our results pinpoint the presence in P. patens of peroxidases that fulfill the requirements to be involved in the last step of lignin biosynthesis, predating the appearance of true lignin.Xunta de Galicia; INCITE08PXIB103182PRPortugal. Fundaçao para a Ciência e a Tecnologia; SFRH/BPD/112587/2015This research was funded by Xunta de Galicia (Spain), grant number INCITE 08PXIB103182PR. E.N.-U. holds an FCT postdoctoral fellowship (SFRH/BPD/112587/2015)

    Biogeography of photoautotrophs in the high polar biome

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    The global latitudinal gradient in biodiversity weakens in the high polar biome and so an alternative explanation for distribution of Arctic and Antarctic photoautotrophs is required. Here we identify how temporal, microclimate and evolutionary drivers of biogeography are important, rather than the macroclimate features that drive plant diversity patterns elsewhere. High polar ecosystems are biologically unique, with a more central role for bryophytes, lichens and microbial photoautotrophs over that of vascular plants. Constraints on vascular plants arise mainly due to stature and ontogenetic barriers. Conversely non-vascular plant and microbial photoautotroph distribution is correlated with favourable microclimates and the capacity for poikilohydric dormancy. Contemporary distribution also depends on evolutionary history, with adaptive and dispersal traits as well as legacy influencing biogeography. We highlight the relevance of these findings to predicting future impacts on polar plant diversity and to the current status of plants in Arctic and Antarctic conservation policy frameworks


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    Bryophyte is a non-vascular plant, consisting of three classes: mosses, hornworts, and liverworts. The body forms have a thallus, and some have a leaf-like organ. The class division of the Bryophyte division is base on anatomical and morphological traits, such as meristem tissues, stomata, and vascular tissues. M Bryophyte has no vascular tissue, but it has a capillary that has functions like xylem and commonly refers to as hydroid. Mosses and hornworts have stomata on the sporophyte part, while in the liverworts, stomata are not found. Hornworts have a basal meristem that has an unpredictable cleavage. Meristem on the mosses only divides up the formation of sporangial. In the liverworts, the apical meristem does not see. Members of the hornworts consider the most advanced because the meristematic phase is more prolonged, so that it is closer to the characteristics of Tracheophyta group

    Scale-dependent plant diversity in Palaearctic grasslands: a comparative overview

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    Here we present an extensive overview of plant diversity values in Palaearctic grasslands for seven standard grain sizes from 0.0001 to 100 m². The data originate from 20 studies, including the Field Workshops of the Eurasian Dry Grassland Group (EDGG), ranging geographically from Spain in the west to Siberia in the east, from Sicily in the south to Estonia in the north and from the sea coast up to 3100 m a.s.l. The majority of data is from dry grasslands (Festuco-Brometea, Koelerio-Corynephoretea, Cleistogenetea squarrosae), but there are also some mesic, wet, saline, acidic, alpine and Mediterranean grasslands included. Among others, we compiled data from 1795 1-m², 1109 10-m² and 338 100-m² plots. In all cases we present mean, minimum and maximum richness for the seven grain sizes, plus, in cases where also terricolous bryophytes and lichens had been recorded, the same values for total “plant” species richness, non-vascular plant species richness and fraction of non-vascular plants. The maximum richness values were 82, 101 and 134 for all “plants”, and 79, 98 and 127 vascular plants at grain sizes of 1 m², 10 m² and 100 m², respectively (all in Transylvania, Romania). Our overview comprises new, hitherto unpublished world records of vascular plant species richness at the scales of 0.0001 m² (9) and 0.001 m² (19, both shoot presence), from meso-xeric, basiphilous grasslands in Navarre, Spain, which is much higher than the previously known maxima. The highest values of non-vascular plant richness at 1 m², 10 m² and 100 m², respectively, were 49, 64 and 64, respectively (all in Sedo-Scleranthenea communities of Öland, Sweden, and Saaremaa, Estonia). In general, the dry, alpine and Mediterranean grasslands were much richer than the studied mesic, wet or saline grasslands at any spatial scale. The presented set of mean, minimum and maximum values and their metadata is publically available and will be continuously updated. These data can serve as a reference of “normal” richness, both in fundamental and applied research. To facilitate the application, we provide an easy formula based on the power-law species-area relationship that allows the estimation of richness values at intermediate grain sizes not included in our dataset. In conclusion, our data emphasise the role of Palaearctic grasslands as global hotspot of small-scale vascular plant diversity, while at the same time highlighting that in some grassland types also the bryophyte and lichen diversity can be extraordinarily high

    Comparative genomics reveals conservative evolution of the xylem transcriptome in vascular plants

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    <p>Abstract</p> <p>Background</p> <p>Wood is a valuable natural resource and a major carbon sink. Wood formation is an important developmental process in vascular plants which played a crucial role in plant evolution. Although genes involved in xylem formation have been investigated, the molecular mechanisms of xylem evolution are not well understood. We use comparative genomics to examine evolution of the xylem transcriptome to gain insights into xylem evolution.</p> <p>Results</p> <p>The xylem transcriptome is highly conserved in conifers, but considerably divergent in angiosperms. The functional domains of genes in the xylem transcriptome are moderately to highly conserved in vascular plants, suggesting the existence of a common ancestral xylem transcriptome. Compared to the total transcriptome derived from a range of tissues, the xylem transcriptome is relatively conserved in vascular plants. Of the xylem transcriptome, cell wall genes, ancestral xylem genes, known proteins and transcription factors are relatively more conserved in vascular plants. A total of 527 putative xylem orthologs were identified, which are unevenly distributed across the <it>Arabidopsis </it>chromosomes with eight hot spots observed. Phylogenetic analysis revealed that evolution of the xylem transcriptome has paralleled plant evolution. We also identified 274 conifer-specific xylem unigenes, all of which are of unknown function. These xylem orthologs and conifer-specific unigenes are likely to have played a crucial role in xylem evolution.</p> <p>Conclusions</p> <p>Conifers have highly conserved xylem transcriptomes, while angiosperm xylem transcriptomes are relatively diversified. Vascular plants share a common ancestral xylem transcriptome. The xylem transcriptomes of vascular plants are more conserved than the total transcriptomes. Evolution of the xylem transcriptome has largely followed the trend of plant evolution.</p

    Characterisation of components and mechanisms involved in redox-regulation of protein import into chloroplasts

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    The vast majority of chloroplast proteins is encoded in the nucleus and thus has to be posttranslationally imported into the organelle, a process that is facilitated by two multimeric protein machineries, the Toc and Tic complexes (translocon at the outer/inner envelope of chloroplasts). Regulation of protein import, e.g. by redox signals, is a crucial step to adapt the protein content to the biochemical requirements of the organelle. In particular, one subunit of the Tic complex, Tic62, has been proposed as a redox sensor, whose possible function is to regulate protein import by sensing and reacting to the redox state of the organelle. To elucidate a potential redox regulation of protein import, structural features, redox-dependent properties and the evolutional origin of Tic62 were investigated. The results show that Tic62 consists of two very different modules: the N-terminal part was found to be mainly -helical and possesses dehydrogenase activity in vitro. It is furthermore an evolutionary ancient domain, as it is highly conserved in all photosynthetic organisms from flowering plants to cyanobacteria and even green sulfur bacteria. In contrast to this, the C-terminus is largely disordered and interacts specifically with ferredoxin-NADP+ oxidoreductase (FNR), a key enzyme in photosynthetic electron transfer reactions. Moreover, this domain was found to exist only in flowering plants, and thus the full-length Tic62 protein seems to be one of the evolutionary youngest Tic components. The results of this study make also clear that Tic62 is a target of redox regulation itself, as its localization and interaction properties depend on the metabolic redox state: oxidized conditions lead to fast membrane binding and interaction with the Tic complex, whereas reduced conditions cause solubilization of Tic62 into the stroma and increased interaction with FNR. This novel shuttling behaviour indicates a dynamic composition of the Tic complex. The NADP+/NADPH ratio was furthermore found to be able to influence the import efficiency of many precursor proteins. Interestingly, the import of not all preproteins depends on the stromal redox state. Hence it was proposed that not a single stable Tic translocon exists, but several Tic subcomplexes with different subunit compositions, which might mediate the import of different precursor groups in a redox-dependent or -independent fashion. Another redox signal that was analyzed in regard to an impact on protein import is the reversible reduction of disulfide bridges, which was found to affect the channel and receptor proteins of the Toc complex. The import of all proteins that use the Toc translocon for entering the chloroplast was shown to be influenced by disulfide bridge formation. Thus it can be concluded that a variety of redox signals, acting both on the Toc and Tic complexes, are able to influence chloroplast protein import

    Plant Cell Wall Plasticity under Stress Situations

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    [EN] This Special Issue, entitled “Plant Cell Wall Plasticity under Stress Situations”, is a compilation of five articles, whose authors deepen our understanding of the roles of different cell wall components under biotic and abiotic stress. The plant cell wall is mainly formed of complex polysaccharides, with multiple interactions between the components that form a network which must be extensible, so as to enable cell expansion, rigid, so as to resist compression and tension forces, and modifiable in response to environmental changes. Cellulose, the most abundant and resistant polysaccharide on earth, is the main component of the cell wall. The cellulose scaffold is involved in a matrix formed of polysaccharides, such as pectins and hemicelluloses, whose types and proportions vary depending on the species, tissue, and cell type. The deposition of lignin—the second most abundant polymer on earth—in secondary cell walls increases the resistance, leading to growth cessation. All these polymers are crosslinked into the wall in a process that can occur spontaneously and/or by the actions of different modifying enzymes. The control of the synthesis of these cell wall components and/or the interactions between them gives this structure a high plasticity, which is a key factor in the modulation of growth and defense responses under different types of stress.S

    Vegetation and peat characteristics of restiad bogs on Chatham Island (Rekohu), New Zealand

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    Restiad bogs dominated by Sporadanthus traversii on Chatham Island, New Zealand, were sampled to correlate vegetation patterns and peat properties, and to compare with restiad systems dominated by Sporadanthus ferrugineus and Empodisma minus in the Waikato region, North Island, New Zealand. Classification and ordination resulted in five groups that reflected a disturbance gradient. The largest S. traversii group, which comprised plots from central, relatively intact bogs, had the lowest levels of total nitrogen (mean 1.20 mg cm-3), total phosphorus (mean 0.057 mg cm-3), total potassium (mean 0.083 mg cm-3), and available phosphorus (mean 18.6 μg cm-3). Modification by drainage, stock, and fires resulted in a decline of S. traversii and an increase of Gleichenia dicarpa fern cover, together with elevated peat nutrient levels and higher bulk density. Compared with peat dominated by Sporadanthus ferrugineus or Empodisma minus in relatively unmodified Waikato restiad bogs, Chatham Island peat under S. traversii has significantly higher total potassium, total nitrogen, available phosphorus, bulk density, and von Post decomposition indices, and significantly lower pH. Sporadanthus traversii and Empodisma minus have similar ecological roles in restiad bog development, occupying a relatively wide nutrient range, and regenerating readily from seed after fire. Despite differences in root morphology, S. traversii and E. minus are the major peat formers in raised restiad bogs on Chatham Island and in Waikato, respectively, and could be regarded as ecological equivalents