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Rosner S.,Institute of Botany
IAWA Journal | Year: 2013

Secondary xylem (wood) fulfills many of the functions required for tree survival, such as transport of water and nutrients, storage of water and assimilates, and mechanical support. The evolutionary process has optimized tree structure to maximize survival of the species, but has not necessarily optimized the wood properties needed for lumber. Under the impact of global warming, knowledge about structure-function relationships in tree trunks will become more and more important in order to prognosticate survival prospects of a species, individuals or provenances. Increasing our knowledge on functional wood anatomy can also provide valuable input for the development of reliable, fast, and at best quasi-non-destructive (e.g. wood coring of mature trunks) indirect screening techniques for drought susceptibility of woody species. This review gives an interdisciplinary update of our present knowledge on hydraulic and biomechanical determinants of wood structure within and among trunks of Norway spruce (Picea abies (L.) Karst.), which is one of Europe's economically most important forest tree species. It summarizes what we know so far on 1) withinring variability of hydraulic and mechanical properties, 2) structure-function relationships in mature wood, 3) mechanical and hydraulic demands and their tradeoffs along tree trunks, and 4) the quite complex wood structure of the young trunk associated with mechanical demands of a small tree. Due to its interdisciplinary nature this review is addressed to physiologists, foresters, tree breeders and wood technologists. © International Association of Wood Anatomists, 2013.

Akhtar M.N.,COMSATS Institute of Information Technology | Bukhari S.A.,COMSATS Institute of Information Technology | Fazal Z.,COMSATS Institute of Information Technology | Qamar R.,COMSATS Institute of Information Technology | Shahmuradov I.A.,Institute of Botany
BMC Genomics | Year: 2010

Background: mRNA polyadenylation is an essential step of pre-mRNA processing in eukaryotes. Accurate prediction of the pre-mRNA 3'-end cleavage/polyadenylation sites is important for defining the gene boundaries and understanding gene expression mechanisms.Results: 28761 human mapped poly(A) sites have been classified into three classes containing different known forms of polyadenylation signal (PAS) or none of them (PAS-strong, PAS-weak and PAS-less, respectively) and a new computer program POLYAR for the prediction of poly(A) sites of each class was developed. In comparison with polya_svm (till date the most accurate computer program for prediction of poly(A) sites) while searching for PAS-strong poly(A) sites in human sequences, POLYAR had a significantly higher prediction sensitivity (80.8% versus 65.7%) and specificity (66.4% versus 51.7%) However, when a similar sort of search was conducted for PAS-weak and PAS-less poly(A) sites, both programs had a very low prediction accuracy, which indicates that our knowledge about factors involved in the determination of the poly(A) sites is not sufficient to identify such polyadenylation regions.Conclusions: We present a new classification of polyadenylation sites into three classes and a novel computer program POLYAR for prediction of poly(A) sites/regions of each of the class. In tests, POLYAR shows high accuracy of prediction of the PAS-strong poly(A) sites, though this program's efficiency in searching for PAS-weak and PAS-less poly(A) sites is not very high but is comparable to other available programs. These findings suggest that additional characteristics of such poly(A) sites remain to be elucidated. POLYAR program with a stand-alone version for downloading is available at http://cub.comsats.edu.pk/polyapredict.htm. © 2010 Akhtar et al; licensee BioMed Central Ltd.

Shevchenko G.,Institute of Botany
Microgravity Science and Technology | Year: 2012

Seedlings of Arabidopsis thaliana-ABD2-GFP were grown under slow clinorotation (2 rpm) and treated with actin and tubulin disrupting drugs in order to characterize the role of actin microfilaments in cell growth and gravisensing. Changes in microfilament organization and cell parameters have shown that the transition root zone (TZ) is rather sensitive to microfilament disruption in control plants. It is assumed that under clinorotation, organization of actin cytoskeleton in the TZ is coordinated in a different way than in the control. Organization of microfilaments depends upon organization of microtubules and clinorotation does not influence this interrelation significantly. © 2012 Springer Science+Business Media B.V.

Gurushidze M.,Leibniz Institute of Plant Genetics and Crop Plant Research | Gurushidze M.,Institute of Botany | Fuchs J.,Leibniz Institute of Plant Genetics and Crop Plant Research | Blattner F.R.,Leibniz Institute of Plant Genetics and Crop Plant Research
Systematic Botany | Year: 2012

Allium subgenus Melanocrommyum is a species-rich group of perennial onions with uniform karyology, ecology, and breeding system. Thus, the cytological, ecological, and physiological factors often correlated with genome size should have negligible effect on genome size variation in Melanocrommyum. We measured DNA content in subgenus Melanocrommyum using flow cytometry based on propidium iodide staining and analyzed the evolution of genome size in a phylogenetic context. The observed 2C genome size variation in 160 accessions of 70 species of the subgenus was high, varying from 26.2678.73 pg. The significant phylogenetic signal in genome size data suggests that distribution of genome size is in accordance with phylogenetic clades identified by the analysis of nuclear ITS sequences. Estimation of ancestral genome sizes using generalized least squares revealed lineages with increasing as well as decreasing DNA content. We found within-species genome size variation to be mostly below 2.5%. In species where intraspecific genome size differences were in a range of 69%, we suggest the existence of cryptic species, as previously inferred by molecular markers. Thus, genome size variation reflects incipient speciation or diversification in Allium subgenus Melanocrommyum. About two-fold differences in DNA content in several Melanocrommyum species indicate the occurrence of diploid and tetraploid cytotypes in these taxa, which for some species has been confirmed by chromosome counts. © Copyright 2012 by the American Society of Plant Taxonomists.

Rusch G.M.,Norwegian Institute for Nature Research | Wilmann B.,Norwegian Institute for Nature Research | Klimesova J.,Institute of Botany | Evju M.,Norwegian Institute for Nature Research
Folia Geobotanica | Year: 2011

Plant traits associated with resource acquisition strategies (specific leaf area (SLA), leaf dry matter content (LDMC), leaf size and plant height) change along gradients of soil properties, being the most conservative in a resource-poor environment and the most dynamic in a resource-rich environment. Clonal attributes also vary along soil and other environmental conditions. We hypothesized that in alpine communities in the Scandian Mts. (1) the average composition of traits in a plant assemblage in terms of i) the predominance of different clonal growth organ types, ii) the number of buds in the bud bank, iii) the distribution of the bud-bank (above-and below ground), iv) the distance of lateral spread and v) the longevity of plant - offspring connections would change along a gradient of soil properties and (2) that this variation would be in correspondence with that of traits associated with resource acquisition strategies (SLA, LDMC, leaf size and plant height). Analysis of clonal and bud bank traits for species of alpine communities supported our first hypothesis: with decreasing soil quality the most common clonal growth organs were rhizomes, and there was a predominance of perennial bud banks located at the soil surface or below-ground, low rates of lateral spread and long persistence of plant - offspring connections. Our second hypothesis was partly supported. As predicted, at the level of the plant assemblage, these clonal and bud bank traits were positively associated with LDMC, and negatively with leaf size and plant height. These observations reinforce the hypotheses about trade-offs between acquisition and retention strategies in plants. The only result that was in contradiction with our expectations was the lack of correspondence between clonal and bud bank traits and SLA that could be attributed to errors associated to the measurement of the area of narrow and small leaves or to the dependence of the SLA index on species-specific morphological attributes. © 2010 The Author(s).

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