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Kilpeläinen A Peltola H Ryyppö A Sauvala K Laitinen K Kellomäki S 《Tree physiology》2003,23(13):889-897
Impacts of elevated temperature and carbon dioxide concentration ([CO2]) on wood properties of 15-year-old Scots pines (Pinus sylvestris L.) grown under conditions of low nitrogen supply were investigated in open-top chambers. The treatments consisted of (i) ambient temperature and ambient [CO2] (AT+AC), (ii) ambient temperature and elevated [CO2] (AT+EC), (iii) elevated temperature and ambient [CO2] (ET+AC) and (iv) elevated temperature and elevated [CO2] (ET+EC). Wood properties analyzed for the years 1992-1994 included ring width, early- and latewood width and their proportions, intra-ring wood density (minimum, maximum and mean, as well as early- and latewood densities), mean fiber length and chemical composition of the wood (cellulose, hemicellulose, lignin and acetone extractive concentration). Absolute radial growth over the 3-year period was 54% greater in AT+EC trees and 30 and 25% greater in ET+AC and ET+EC trees, respectively, than in AT+AC trees. Neither elevated temperature nor elevated [CO2] had a statistically significant effect on ring width, early- and latewood widths or their proportions. Both latewood density and maximum intra-ring density were increased by elevated [CO2], whereas fiber length was increased by elevated temperature. Hemicellulose concentration decreased and lignin concentration increased significantly in response to elevated temperature. There were no statistically significant interaction effects of elevated temperature and elevated [CO2] on the wood properties, except on earlywood density. 相似文献
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We studied the spatial distribution of saplings in the vicinity of other saplings and mature trees in heavily worn urban forests. Our aim was to identify favorable microsites for saplings to regenerate under different levels of wear. We hypothesized that these safe microsites were situated close to tree trunks that might offer shelter from trampling caused by humans and their pet dogs. The distribution of saplings was explored at 0.1–0.6 m to the nearest sapling and 0.1–2 m to the nearest mature tree. Sorbus aucuparia was the most abundant sapling species, followed by Populus tremula, Betula pubescens and Picea abies. These species all tended to cluster with their conspecific saplings and were generally randomly distributed with respect to mature trees. Saplings of S. aucuparia and P. tremula favored growing close to mature P. abies (already at 0.4–0.8 up to 2 m from the trunk base, respectively) and S. aucuparia trees (at 0.2–0.4 m up to 2 m). Betula sp. and Acer platanoides grew close to Pinus sylvestris trees. Furthermore, with increased levels of wear, saplings clustered more likely together and close to tree trunks. The results are contrary to the gap regeneration hypothesis known from rural unworn forests where saplings often grow in canopy gaps. We suggest the idea of a ‘sheltering group’, i.e. tree groups and thickets of densely growing conspecific saplings, for the maintenance of regeneration of saplings and other vegetation in heavily worn recreational forests. Since urban forestry may strongly affect the existence and spatial location of a high variety of microhabitats, small-scale spatial exploration is needed to identify microsites that offer opportunities for natural regeneration under heavy recreational use. To maintain natural regeneration and the survival of saplings in worn urban forests, we recommend microhabitat-level species-specific forest management. 相似文献
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Valerie Van Craeyveld Emmie Dornez Ulla Holopainen Emilia Selinheimo Kaisa Poutanen Jan A. Delcour Christophe M. Courtin 《Cereal Chemistry》2010,87(4):283-291
Wheat bran‐derived arabinoxylan‐oligosaccharides (AXOS) recently have been shown to potentially exert prebiotic effects. In this study, 15 bran samples obtained by milling different wheat cultivars were treated with xylanases from Hypocrea jecorina (XHJ), Aspergillus aculeatus (XAA), and Pseudoalteromonas haloplanktis (XPH) to assess the effect of bran source and xylanase properties on the AXOS yield and structure. The total arabinoxylan (AX) extraction yield was higher with XHJ (8.2–10.7%) and XAA (8.2–10.8%) than with XPH (6.9–9.5%). Irrespective of the enzyme, a significant negative correlation was observed between extraction yield and arabinose to xylose (A/X) ratio of bran AX (r = –0.7), but not between yield and bran AX level. The A/X ratio of the extracted material was 0.27–0.34 for all bran samples and all enzymes, which combined with yield data and microscopic analysis, indicated primary hydrolysis of aleurone and nucellar epidermis AX. The average degree of polymerization (avDP) of the extracted AX was very low for all enzymes (2–3), owing to the release of high levels of monomeric arabinose and xylose. The release of these monosaccharides could be ascribed to 1) the activity of wheat bran‐associated enzymes (arabinofuranosidases and xylosidases); 2) the hydrolytic properties of the xylanases themselves; and 3) the presence of xylosidases as contaminations in enzyme preparation, in that order of importance. Heat treatment of bran before xylanase treatment significantly decreased the levels of monomeric arabinose and xylose in the extract, without affecting the extraction yield, resulting in a higher avDP of 3–7, thus yielding true AXOS. Overall, for AXOS production, wheat cultivars with a low bran A/X ratio of the AX are preferable as starting materials, and inactivation of bran‐associated enzymes before incubation is desirable. The XHJ xylanase was the best enzyme for wheat bran‐derived AXOS production. 相似文献
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Outi Santala Pekka Lehtinen Emilia Nordlund Tapani Suortti Kaisa Poutanen 《Journal of Cereal Science》2011,54(2):187-194
Arabinoxylan (AX) has a major impact on the functional properties of wheat bran, and it has been shown that technological properties of bran can be improved by using endoxylanases. Enzymatic treatments are typically conducted at high water content. However, in industrial applications, low water content may be advantageous, especially when targeting dry end products. The aim of the study was to examine the impact of water content, ranging from 20 to 90%, on the efficiency of endoxylanase treatment of wheat bran. Interestingly, AX solubilisation was highest at the water contents of 40 and 90%. At water contents 50–80%, AX solubilisation was lower than at 40 and 90%. Furthermore, at low water content, less depolymerisation was detected. At water content of 40%, the bran-water mixture was transformed from powder-like into compact mass. Probably the compact consistency of the material enhanced AX solubilisation by increased breakdown of bran cell walls due to shear forces or via enhanced enzyme binding to the substrate. The results show that solubilisation of bran AX can also be efficiently performed at low water content. 相似文献
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Edith K. Hüttner Fabio Dal Bello Kaisa Poutanen Elke K. Arendt 《Journal of Cereal Science》2009,49(3):363-370
The use of grains alternative to wheat or rye is a challenging task for cereal technologists, and currently new technologies are under investigation as tools to improve the performances of these alternative grains. In this work the effects of high Hydrostatic Pressure (HP) on oat batters were investigated. Oat batters were treated for 10 min at 200, 300, 350, 400 or 500 MPa. Scanning electron microscopy and bright field microscopy showed that high HP significantly affected oat batter microstructure, and both starch and proteins were affected. Treatment at high HP significantly improved batter viscosity and elasticity. At pressures ≤300 MPa the increase in the viscous component was higher than the increase in the elastic component. On the contrary, at pressures ≥350 MPa the elastic component was predominant. Differential scanning calorimetry revealed that high HP induced starch gelatinisation, which started at 300 MPa and was almost complete after treatment at 500 MPa. High HP also affected water- and salt-soluble as well as urea-soluble oat proteins. Analysis of proteins soluble in different buffers revealed that pressures ≥300 MPa induced the formation of urea-insoluble complexes and/or disulfide bonds. Overall, the extent of starch gelatinisation and protein modification was dependent on the applied pressure, but the results collected so far clearly show that high HP can be used to improve the functionality of oat batters. 相似文献
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Isabel Bondia-Pons Anna-Marja Aura Satu Vuorela Marjukka Kolehmainen Hannu Mykkänen Kaisa Poutanen 《Journal of Cereal Science》2009
Dietary intake of whole-grain foods is associated with a decreased risk of chronic diseases such as diabetes, obesity and heart disease. In addition to dietary fibre, various phytochemicals have been suggested to contribute to the health effects of whole grain products. This review focuses on phenolic compounds in rye (Secale cereale L.), which is one of the major bread grains in Europe. Data on phenolic concentrations in rye grain and foods, their bioavailability to tissues and effects in vivo, and their potential contributions to health are presented. Phenolic compounds in rye, such as phenolic acids, alkylresorcinols and lignans, are concentrated in the outer layers of the grain. Phenolic acids are the major phenolic compounds in whole grain rye (103–300 mg/100 g grain), ferulic acid being the most abundant. Rye lignans are present at concentrations of 2 mg/100 g grain and had been shown to be converted by the intestinal microflora to the mammalian lignans enterodiol and enterolactone in human intervention studies. Alkylresorcinols (36–320 mg/100 g grain), which have been found to be incorporated into human erythrocyte membranes, are of particular interest due to their potential use as biomarkers of the intake of rye and wheat. 相似文献
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Mähönen AP Bishopp A Higuchi M Nieminen KM Kinoshita K Törmäkangas K Ikeda Y Oka A Kakimoto T Helariutta Y 《Science (New York, N.Y.)》2006,311(5757):94-98
The cell lineages that form the transporting tissues (xylem and phloem) and the intervening pluripotent procambial tissue originate from stem cells near the root tip. We demonstrate that in Arabidopsis, cytokinin phytohormones negatively regulate protoxylem specification. AHP6, an inhibitory pseudophosphotransfer protein, counteracts cytokinin signaling, allowing protoxylem formation. Conversely, cytokinin signaling negatively regulates the spatial domain of AHP6 expression. Thus, by controlling the identity of cell lineages, the reciprocal interaction of cytokinin signaling and its spatially specific modulator regulates proliferation and differentiation of cell lineages during vascular development, demonstrating a previously unrecognized regulatory circuit underlying meristem organization. 相似文献
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Schreiber A Gábris A Rohde PP Laiho K Štefaňák M Potoček V Hamilton C Jex I Silberhorn C 《Science (New York, N.Y.)》2012,336(6077):55-58
Multidimensional quantum walks can exhibit highly nontrivial topological structure, providing a powerful tool for simulating quantum information and transport systems. We present a flexible implementation of a two-dimensional (2D) optical quantum walk on a lattice, demonstrating a scalable quantum walk on a nontrivial graph structure. We realized a coherent quantum walk over 12 steps and 169 positions by using an optical fiber network. With our broad spectrum of quantum coins, we were able to simulate the creation of entanglement in bipartite systems with conditioned interactions. Introducing dynamic control allowed for the investigation of effects such as strong nonlinearities or two-particle scattering. Our results illustrate the potential of quantum walks as a route for simulating and understanding complex quantum systems. 相似文献
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Elevated CO2 usually promotes plant growth, whereas elevated O3 often has a negative effect, especially on root biomass. Thus both these gases can indirectly affect the soil microbial community. We exposed Agrostis capillaris and Lathyrus pratensis to realistic levels of O3 (40-50 ppb) and CO2 (ambient air + 100 ppm) in open-top chambers during 2002-2004. The experiment shows negative effects of both O3 and CO2, especially on the bulk soil of L. pratensis, in terms of the decreased biomasses of total (25% and 31%), actinobacterial (29% and 31%), bacterial (26% and 33%) and mycorrhizal (AM fungal) (31% and 35%) indicator subgroups, analysed by the PLFA (phospholipid fatty acid) method. The fungal:bacterial PLFA biomass ratio decreased in the bulk soil of A. capillaris, especially with elevated CO2 alone (38%). These longer-term changes are considered to arise mainly from differences between the plant functional types (i.e. grass cf. N2-fixing legume) in litter quality and soil C:N ratio. The results also point to interactions and multi-trophic feedbacks between elevated O3, plant, parasitic rust fungi and soil readily available P, accompanied by a shift in N balance in favour of plants rather than soil microorganisms. 相似文献