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841.
Gonzalo Caballé María Elena Fernández Javier Gyenge Alejandro Aparicio Tomás Schlichter 《Agroforestry Systems》2011,83(1):13-24
The integrated relationship in a simple mechanistic model between the critical environmental factors controlling leaf photosynthesis
of understory species would be a useful tool to optimize the management of the silvopastoral systems. Individual effect of
leaf temperature, water stress and light environment over net maximum photosynthetic rate (Pmax) was evaluated on Festuca pallescens leaves grown in a silvopastoral system of two Pinus ponderosa canopy covers (350 and 500 trees ha−1) and natural grassland. The aim was to integrate individual functions for Pmax against these environmental factors into a multiplicative model. We measured pre-dawn water potential (ψ
pd), leaf temperature and net photosynthetic rate (Pn), stomatal conductance (gs) and intercellular CO2 concentration (Ci) as a function of photosynthetic photon flux density (PPFD). The highest Pmax under non-limiting conditions was 20.4 μmol CO2 m−2 s−1 and was defined as standardized dimensionless Pmax
s
= 1 for comparison of environmental factors. The leaf temperature function showed an optimum range between 20.2 and 21.8°C
where Pmax
s
= 1. Then, Pmax
s
declined by an average 1 μmol CO2 m−2 s−1 C−1 from the optimum to 4.7 and 38.5°C. Pmax
s
decreased at a rate of 9.49 μmol CO2 m−2 s−1 MPa−1 as water potential reaches −1.9 MPa and showed a lower slope as water potential decreased down to −4.3 MPa. The light environment
was estimated from hemispherical photograph analysis. Pmax
s
was 20% higher in leaves of open control plants than under the maximum tree canopy cover. The simple multiplicative model
accounted for 0.82 of the variation in Pmax. Such a simple mechanistic model is the first step towards a more effective decision support tool. 相似文献
842.
Cristina Valls Óscar Gallardo Teresa Vidal F. I. Javier Pastor Pilar Díaz M. Blanca Roncero 《Wood Science and Technology》2011,45(3):433-448
Since xylanases can differ widely in their bleaching efficiency, the performance of one new and two commercial xylanases was
evaluated in an eucalyptus kraft pulp following XD (X: xylanase; D: chlorine dioxide) and XP (P: hydrogen peroxide) sequences.
The new xylanase did not show a significant bleach boosting effect but increased the hexenuronic acid (HexA) removal by 10%
after the D stage. The two commercial xylanases behaved in a different way, being one of them (XC) the most effective in increasing delignification (9%) and brightness (3%ISO). Its effectiveness was related to its greater
action on releasing the xylan polymer, thus producing also a strong decrease in the HexA contents during the enzymatic stage
(15%). All xylanases produced morphological changes in the fibre surfaces, but only with XC cracks and holes that improved the diffusion of reactives were observed. Finally, the best bleaching results were obtained
with the XD sequence and therefore, a complete bleaching sequence XDEopD1 (Eop: alkaline extraction with oxygen and peroxide) was carried out with the best enzyme. 相似文献
843.
Corral-Rivas Jose Javier; Barrio-Anta Marcos; Aguirre-Calderon Oscar Alberto; Dieguez-Aranda Ulises 《Forestry》2007,80(1):29-40
Foresters may require to estimate the diameter at breast height(d.b.h.) and the volume of trees that have been cut, and mayonly have available the stumps as an indicator of the size ofthe trees. In the present study, equations for predicting bothd.b.h. and volume from stump diameter inside bark were developedfor major pine species in the forest region of El Salto, Durango(Mexico). The d.b.h. was estimated with relatively high accuracywith a simple linear model. The tree volume was also estimatedwith high precision by use of an allometric equation. Weightedlinear and non-linear least squares methods were used to takeinto account the problem of heteroscedasticity observed in thevolumestump diameter relationships. The results of thenon-linear extra sum of squares method and of the F tests indicatedthat species-based equations for estimating both d.b.h. andvolume from stump diameter are required. 相似文献
844.
Achard F Eva HD Stibig HJ Mayaux P Gallego J Richards T Malingreau JP 《Science (New York, N.Y.)》2002,297(5583):999-1002
A recently completed research program (TREES) employing the global imaging capabilities of Earth-observing satellites provides updated information on the status of the world's humid tropical forest cover. Between 1990 and 1997, 5.8 +/- 1.4 million hectares of humid tropical forest were lost each year, with a further 2.3 +/- 0.7 million hectares of forest visibly degraded. These figures indicate that the global net rate of change in forest cover for the humid tropics is 23% lower than the generally accepted rate. This result affects the calculation of carbon fluxes in the global budget and means that the terrestrial sink is smaller than previously inferred. 相似文献
845.
Nene V Wortman JR Lawson D Haas B Kodira C Tu ZJ Loftus B Xi Z Megy K Grabherr M Ren Q Zdobnov EM Lobo NF Campbell KS Brown SE Bonaldo MF Zhu J Sinkins SP Hogenkamp DG Amedeo P Arensburger P Atkinson PW Bidwell S Biedler J Birney E Bruggner RV Costas J Coy MR Crabtree J Crawford M Debruyn B Decaprio D Eiglmeier K Eisenstadt E El-Dorry H Gelbart WM Gomes SL Hammond M Hannick LI Hogan JR Holmes MH Jaffe D Johnston JS Kennedy RC Koo H Kravitz S Kriventseva EV Kulp D Labutti K Lee E Li S Lovin DD 《Science (New York, N.Y.)》2007,316(5832):1718-1723
We present a draft sequence of the genome of Aedes aegypti, the primary vector for yellow fever and dengue fever, which at approximately 1376 million base pairs is about 5 times the size of the genome of the malaria vector Anopheles gambiae. Nearly 50% of the Ae. aegypti genome consists of transposable elements. These contribute to a factor of approximately 4 to 6 increase in average gene length and in sizes of intergenic regions relative to An. gambiae and Drosophila melanogaster. Nonetheless, chromosomal synteny is generally maintained among all three insects, although conservation of orthologous gene order is higher (by a factor of approximately 2) between the mosquito species than between either of them and the fruit fly. An increase in genes encoding odorant binding, cytochrome P450, and cuticle domains relative to An. gambiae suggests that members of these protein families underpin some of the biological differences between the two mosquito species. 相似文献
846.
Esteller M Fraga MF Paz MF Campo E Colomer D Novo FJ Calasanz MJ Galm O Guo M Benitez J Herman JG 《Science (New York, N.Y.)》2002,297(5588):1807-8; discussion 1807-8
847.
Ivens AC Peacock CS Worthey EA Murphy L Aggarwal G Berriman M Sisk E Rajandream MA Adlem E Aert R Anupama A Apostolou Z Attipoe P Bason N Bauser C Beck A Beverley SM Bianchettin G Borzym K Bothe G Bruschi CV Collins M Cadag E Ciarloni L Clayton C Coulson RM Cronin A Cruz AK Davies RM De Gaudenzi J Dobson DE Duesterhoeft A Fazelina G Fosker N Frasch AC Fraser A Fuchs M Gabel C Goble A Goffeau A Harris D Hertz-Fowler C Hilbert H Horn D Huang Y Klages S Knights A Kube M Larke N Litvin L Lord A 《Science (New York, N.Y.)》2005,309(5733):436-442
848.
Ybañez-Julca Roberto O. Palacios Javier Asunción-Alvarez Daniel Quispe-Díaz Ivan Nwokocha Chukwuemeka R. de Albuquerque Ricardo Diego Duarte Galhardo 《Plant foods for human nutrition (Dordrecht, Netherlands)》2022,77(3):460-466
Plant Foods for Human Nutrition - Lepidium meyenii Walp (red maca) is a high Andean plant cultivated since the Incas and has innumerable therapeutic properties. The study aims to identify its... 相似文献
849.
850.
Francisco Cen-Pacheco Manuel Norte Martín José Javier Fernández Antonio Hernández Daranas 《Marine drugs》2014,12(10):5188-5196
Three new norzoanthamine-type alkaloids, named 2-hydroxy-11-ketonorzoanthamide B (1), norzoanthamide B (2) and 15-hydroxynorzoanthamine (3), were isolated from Zoanthus sp. specimens collected at the Canary Islands. Their structures were determined by interpretation of NMR and HR-ESIMS data. Relative configurations of their chiral centers were proposed on the basis of ROESY spectra and by comparison of their spectroscopic data with those of the well-known compound, norzoanthamine. 相似文献