Temperature signals contribute to the timing of photoperiodic growth cessation and bud set in poplar     

Rohde A  Bastien C  Boerjan W 《Tree physiology》2011,31(5):472-482

Bud set, the cornerstone delimiting the seasonal growth period in trees, is the dynamic net result of the often photoperiod-controlled growth cessation and the subsequent bud formation. Here, we show that in hybrid poplar, the critical day length for growth cessation and the duration of bud formation each vary with local climatic conditions in identical genotypes. The detailed dissection of bud set suggests temperature as one additional environmental factor that modifies the sensitivity to day-length signals at growth cessation and influences the duration of bud formation in poplar. The ability of perennial plants to integrate additional environmental signals with photoperiod signaling may add to short-term acclimatization to the predicted longer growing seasons in future climates.  相似文献   

Establishment of native tropical timber trees in monoculture and mixed-species plantations: Small-scale effects on tree performance and insect herbivory     

Mirco PlathKarsten Mody  Catherine PotvinSilvia Dorn 《Forest Ecology and Management》2011,261(3):741-750

Plantations of native timber species established on former pasture are a potential strategy to reduce the logging pressure on remnant natural forests in the tropics. Such plantations may help to mitigate or reverse the negative impacts of land degradation, and they may contribute to the long-term livelihood of livestock farmers. Planting native trees is, however, perceived as a risky activity due to limited knowledge of their performance and due to marked losses of newly established seedlings attributed to insect pests. Our study focuses on the small-scale effects of environmental heterogeneity, tree diversity and insecticide treatment on the performance of three native Central American timber species two years after establishment, and on damage inflicted by insect herbivores. Growth, survival and herbivore leaf damage were quantified for Anacardium excelsum (Anacardiaceae), Cedrela odorata (Meliaceae) and Tabebuia rosea (Bignoniaceae) planted in an experiment in Panama as (1) monocultures, (2) mixed stands, and (3) mixed stands protected by insecticides. Our study revealed that small-scale effects can have a substantial impact on the success of timber trees planted on former pasture. Growth performance and survival of the three species was strongly affected by small-scale environmental heterogeneity, which was expressed as significant differences in growth and survival among different plantation plots at the same study site. Establishment of trees in mixed stands did not have significant effects on tree survival and growth compared to pure stands, although it reduced herbivore pressure in one of the studied tree species. All tree species grew best and suffered lowest leaf damage when protected by insecticides, indicating a general influence of insect herbivory on growth of newly established trees. In contrast to growth performance, survival was not significantly affected by different management practices or herbivory. The large variability among plots in tree survival and growth, and also in the effects of management practices such as planting design and insecticide treatment, emphasizes the importance of small-scale environmental heterogeneity on tree survival and growth.  相似文献   

Carotenoid, chlorophyll, and chlorophyll-derived compounds in grapes and port wines     

Mendes-Pinto MM  Silva Ferreira AC  Caris-Veyrat C  Guedes de Pinho P 《Journal of agricultural and food chemistry》2005,53(26):10034-10041

Carotenoids and chlorophyll-derived compounds in grapes and Port wines were investigated by HPLC-DAD and HPLC-DAD-MS (ESP+) analysis. A total of 13 carotenoid and chlorophyll-derived compounds are formally reported in grapes, 3 are identified for the first time, pheophytins a and b and (13Z)-beta-carotene, and 3 others remain unknown. In Port wines 19 compounds with carotenoid or chlorophyll-like structures are present, 8 still unidentified. The young wines showed higher total carotenoid content and chlorophyll-like compounds compared to aged Ports, with lutein and beta-carotene as major carotenoids. Among samples analyzed of monovarietal Vitis vinifera L. cultivar wines produced with the five most important Douro varieties, Tinta Roriz contained the highest levels of carotenoids and Touriga Franca the lowest. The forced-aging study indicated that lutein was more sensitive to temperature than beta-carotene. Additionally, aged wines showed higher ratios of beta-carotene/lutein concentrations compared to new Ports. Rates of degradation of chlorophyll derivative compounds were higher than those for carotene and lutein.  相似文献   

In search of a maize ideotype for cell wall enzymatic degradability using histological and biochemical lignin characterization   总被引：1，自引：0，他引：1  

Méchin V  Argillier O  Rocher F  Hébert Y  Mila I  Pollet B  Barriére Y  Lapierre C 《Journal of agricultural and food chemistry》2005,53(15):5872-5881

Grass cell wall degradability is conventionally related to the lignin content and to the ferulic-mediated cross-linking of lignins to polysaccharides. To better understand the variations in degradability, 22 maize inbred lines were subjected to image analyses of Fasga- and M?ule-stained stem sections and to chemical analyses of lignins and p-hydroxycinnamic acids. For the first time, the nearness of biochemical and histological estimates of lignin levels was established. Combination of histological and biochemical traits could explain 89% of the variations for cell wall degradability and define a maize ideotype for cell wall degradability. In addition to a reduced lignin level, such an ideotype would contain lignins richer in syringyl than in guaiacyl units and preferentially localized in the cortical region rather than in the pith. Such enrichment in syringyl units would favor wall degradability in grasses, contrary to dicots, and could be related to the fact that grass syringyl units are noticeably p-coumaroylated. This might affect the interaction capabilities of lignins and polysaccharides.  相似文献   

Distribution of aluminum in black spruce saplings growing on two New Brunswick forest soils with contrasting acid sulfate sorption     

Paul A. Arp  Catherine Akerley  Kajetan Mellerowicz 《Water, air, and soil pollution》1989,48(1-2):277-297

Two adjacent soils with contrasting sulfate sorption were examined in terms of (i) water-soluble and ion-exchangeable Al, Fe, Ca, Mg, K, Mn and Zn, (ii), water- and bicarbonate-extractable sulfate, (iii) Truog-extractable P, (iv) dithionite-extractable Al, Mn and Fe and (v) treatment response to irrigation with simulated acid precipitation. The biomass of 8 year old black spruce saplings growing on the soils, and the distributions of Al, Fe, Ca, Mg, K, Mn, P and Zn within these plants, were also examined. The soils were well to moderately-well drained, with the mineral soil exposed by site preparation prior to planting. The exposed soil underneath individual saplings was treated with acid sulfate solutions (75 mm containing 2 to 50 mg L^?1 H₂SO₄) applied during each of three consecutive growing seasons. The results indicate that Al, much like Fe, Ca, Mn and Zn, accumulated with time in the foliage, but K, Mg and P were highest in young plant tissues. Much of Al and Fe taken up remained in the fine roots. Aluminum uptake increased with the amount of dithionite-extractable Al (free Al oxide) in the soil. Growth of the black spruce saplings was not visibly affected by readily accessed Al in each soil, or by acid irrigation.Instead, growth was restricted by factors other than soil Al and acid irrigation in spite of (i) low soil pH, (ii) high levels of exchangeable Al, and (iii) high levels of Al in fine roots. Sulfate retention across and within the two soils was positively correlated with free Al oxide. The two soils responded to acid irrigation by accelerated silicate weathering and enhanced ion leaching. Sulfate sorption reduced these effects.  相似文献   

Varietal difference in physicochemical properties of pigmented rice varieties     

Mi-Young Kang  Catherine W. Rico  Sang-Chul Lee 《Journal of Crop Science and Biotechnology》2011,14(2):111-118

The physicochemical properties of pigmented (Midorimochi, Jeokjinjubyeo, and Heukmichalbyeo) and non-pigmented (Hwayoungbyeo) rice varieties were investigated. Starch from non-pigmented rice consisted mainly of large polyhedral granules that were more loosely packed than those of the non-pigmented sample. Pigmented rice showed higher linoleic acid content (36–40%) and hydrolysis rate (63–79%) but lower oleic acid content (35–39%), blue value (0.05–0.17), and viscosity values than the non-pigmented one. Significantly higher mineral content, blue value, and pasting and viscosity values were observed in the Jeokjinjubyeo sample compared to those of the other pigmented rice samples. The Midorimochi variety, on the other hand, exhibited the highest total amino acid (816.82 ng mg⁻¹) and sugar (0.15–3.35 μg g⁻¹) contents and the lowest pasting and viscosity values. No substantial difference in the X-ray diffraction pattern was observed among the samples. Results of this study could serve as baseline information for the quality evaluation of three pigmented rice cultivars and provide a better understanding of their potential uses and food industry applications.  相似文献   

T cell activation by lipopeptide antigens   总被引：2，自引：0，他引：2  

Moody DB  Young DC  Cheng TY  Rosat JP  Roura-Mir C  O'Connor PB  Zajonc DM  Walz A  Miller MJ  Levery SB  Wilson IA  Costello CE  Brenner MB 《Science (New York, N.Y.)》2004,303(5657):527-531

Unlike major histocompatibility proteins, which bind peptides, CD1 proteins display lipid antigens to T cells. Here, we report that CD1a presents a family of previously unknown lipopeptides from Mycobacterium tuberculosis, named didehydroxymycobactins because of their structural relation to mycobactin siderophores. T cell activation was mediated by the alphabeta T cell receptors and was specific for structure of the acyl and peptidic components of these antigens. These studies identify a means of intracellular pathogen detection and identify lipopeptides as a biochemical class of antigens for T cells, which, like conventional peptides, have a potential for marked structural diversity.  相似文献   

Sirtuin 2 inhibitors rescue alpha-synuclein-mediated toxicity in models of Parkinson's disease     

Outeiro TF  Kontopoulos E  Altmann SM  Kufareva I  Strathearn KE  Amore AM  Volk CB  Maxwell MM  Rochet JC  McLean PJ  Young AB  Abagyan R  Feany MB  Hyman BT  Kazantsev AG 《Science (New York, N.Y.)》2007,317(5837):516-519

The sirtuins are members of the histone deacetylase family of proteins that participate in a variety of cellular functions and play a role in aging. We identified a potent inhibitor of sirtuin 2 (SIRT2) and found that inhibition of SIRT2 rescued alpha-synuclein toxicity and modified inclusion morphology in a cellular model of Parkinson's disease. Genetic inhibition of SIRT2 via small interfering RNA similarly rescued alpha-synuclein toxicity. Furthermore, the inhibitors protected against dopaminergic cell death both in vitro and in a Drosophila model of Parkinson's disease. The results suggest a link between neurodegeneration and aging.  相似文献   

Organic Food Demand: A Focus Group Study Involving Caucasian and African-American Shoppers     

Lydia Zepeda  Hui-Shung Chang  Catherine Leviten-Reid 《Agriculture and Human Values》2006,23(3):385-394

A focus group study using four groups of food shoppers provides insights into consumers’ knowledge, beliefs, and behaviors regarding organic foods. Two focus groups consisted of shoppers who regularly bought organic foods and two focus groups of shoppers who predominantly purchased conventional foods. Participants in one of the conventional groups were all Caucasian; in the other they were all African-American. While familiarity with organic foods was much lower in the African-American group, its members were more receptive and positive towards organic foods. Likewise, the African-American shoppers were more accepting of price premiums for organics foods. In comparing the two organic shopper groups with the two conventional shopper groups, it was found that the former were generally more knowledgeable about organic foods. They were also more likely to follow a special diet than conventional Caucasian shoppers. However, the behavior of organic shoppers varied widely. The research supports examining social justice and access as motivations for changing policies to support organic agriculture. Lydia Zepeda is a Professor of Consumer Science at University of Wisconsin and Senior Fellow of the Center for World Affairs and the Global Economy. Her research focuses on agricultural technology adoption, farm household decision making, and consumer perceptions and behavior towards agricultural technology and food. Hui-Shung Chang is a Senior Lecturer in the School of Economics at the University of New England, Armidale, New South Wales, Australia. Her research focuses on demand analysis and agribusiness marketing. Catherine Leviten-Reid is a research assistant and graduate student in the Department of Consumer Science at the University of Wisconsin–Madison. She is interested in household behavior and sustainable community development.  相似文献   

The V-antigen of Yersinia forms a distinct structure at the tip of injectisome needles     

Mueller CA  Broz P  Müller SA  Ringler P  Erne-Brand F  Sorg I  Kuhn M  Engel A  Cornelis GR 《Science (New York, N.Y.)》2005,310(5748):674-676

Many pathogenic bacteria use injectisomes to deliver effector proteins into host cells through type III secretion. Injectisomes consist of a basal body embedded in the bacterial membranes and a needle. In Yersinia, translocation of effectors requires the YopB and YopD proteins, which form a pore in the target cell membrane, and the LcrV protein, which assists the assembly of the pore. Here we report that LcrV forms a distinct structure at the tip of the needle, the tip complex. This unique localization of LcrV may explain its crucial role in the translocation process and its efficacy as the main protective antigen against plague.  相似文献