A Review of Fine Root Dynamics in Populus Plantations   总被引：1，自引：0，他引：1  

R. M. A. Block  K. C. J. Van Rees  J. D. Knight 《Agroforestry Systems》2006,67(1):73-84

Production of native and hybridized varieties of Populus has received considerable interest in temperate regions as an alternative to agricultural crops and an additional wood source, while acting as a potential carbon (C) sink to offset emissions of fossil fuel-based greenhouse gases. Research of root system dynamics in Populus species is expanding, however, our understanding of the nature and role of fine roots (FR) is incomplete. The study objective, therefore, was to review the literature regarding FR production, mortality and longevity in Populus, and evaluate the magnitude and significance of the FR fraction to C sequestration. FRs, conventionally defined as less than 2 mm in diameter and responsible for water and nutrient uptake, are an essential component of the tree. Populus FRs are relatively short-lived, with reported lifespans ranging from 30 to 300 days, depending on root diameter, tree species and age, and soil environmental factors. Standing FR biomass fluctuates throughout the growing season. Fine root production generally peaks in mid-summer, and ranges between 1.0 and 5.0 mg ha⁻¹ yr⁻¹, while FR mortality has less seasonal amplitude. Production and mortality dynamics in Populus are highly plastic in response to soil environmental conditions, and although opposing conclusions have been proposed, research suggests soil moisture and nitrogen to be most important. Results from the literature indicate annual FR turnover to the soil C pool may be small (0.2–1.6 mg C ha⁻¹ yr⁻¹), but substantial in maintaining or enhancing C levels in natural and managed stands of Populus.  相似文献   

Photosynthetic responses to phosphorus nutrition in two-year-old maritime pine seedlings     

Loustau D  Brahim MB  Gaudillère JP  Dreyer E 《Tree physiology》1999,19(11):707-715

We analyzed processes limiting photosynthesis in two-year-old, container-grown Pinus pinaster Ait. seedlings subjected to phosphorus (P) deficiency. After withholding P for 3 months, seedlings were supplied P at four relative addition rates (0, 0.005, 0.01 and 0.02 day(-1)) in a nutrient recycling system. At Weeks 12 and 22, responses of photosynthesis to CO(2) and irradiance were measured and the following parameters derived: maximal velocity of carboxylation by Rubisco, V(m); apparent quantum efficiency of electron transport, alpha maximal electron transport rate, J(m); stomatal conductance and relative stomatal limitation of photosynthesis. At Week 22, these measurements were combined with concurrent measurements of chlorophyll fluorescence to determine the quantum yield of PSII, and a theoretical partitioning of total light-driven linear electron flow between fractions used to regenerate carboxylated and oxygenated RuBP. After 12 weeks of treatment, needle P concentrations ranged from 0.04 to 0.15 x 10(-2) g g(DW) (-1), and then remained constant until Week 22. Values of J(m), alpha and V(m) increased with increasing needle P concentration (from 30 to 133 &mgr;mol m(-2) s(-1), 0.02 to 0.25 mol mol(-1) and 13 to 78 &mgr;mol CO(2) m(-2) s(-1) at the lowest and highest needle P concentrations, respectively). Under ambient conditions, net assimilation rates in P-deficient seedlings were limited by V(m) under saturating irradiance, and by J(m) under limiting irradiance, but not by triose-P regeneration. There was no detectable change in the partitioning of total light-driven linear electron flow between the fractions used for carboxylation and oxygenation. Predawn photochemical efficiency of PSII was significantly reduced in seedlings with low P concentrations. Although stomatal conductance tended to decrease with decreasing needle P concentration, relative stomatal limitation was not significantly affected. At Week 22, there was an attenuation of the effects of P nutrition on V(m) and an increase in alpha and J(m) that was probably related to cessation of growth and the seasonal decline in natural irradiance.  相似文献   

The virulence of phytopathogenic fungi associated with the bark beetles Tomicus piniperda and Orthotomicus erosus in Tunisia     

M. L. Ben Jamaa  F. Lieutier  A. Yart  A. Jerraya  M. L. Khouja 《Forest Pathology》2007,37(1):51-63

Phytopathogenic fungi associated with the bark beetles Tomicus piniperda and Orthotomicus erosus were isolated in various pine forests of Tunisia. Tomicus piniperda and its galleries yielded Leptographium wingfieldii, Ophiostoma minus, and Ophiostoma ips. Ophiostoma minus was the most frequent species associated with T. piniperda, in both the attacking and the emerging beetles. It was collected from most investigated forests, whereas O. ips and L. wingfieldii were obtained only from forests located in Central and Northern Tunisia. Frequencies of association with T. piniperda were always low, reaching 11.1% only once, for O. ips. Ophiostoma ips was the only blue stain fungus associated with O. erosus and its galleries. It was found in all the localities, but at a low and variable frequency, exceeding 15% very rarely. The virulence of 16 fungal isolates was tested by single inoculations into Pinus halepensis (Aleppo pine) at two localities. Differences were detected among species; L. wingfieldii was the most virulent and O. minus the least virulent species in terms of phloem reaction zone formation and fungal growth in the phloem. In a separate experiment, mass inoculations (400 and 800 inoculations per m² of bole on 1‐m high belts) were performed with two isolates of L. wingfieldii on Aleppo pine and on Pinus brutia (Brutia pine). Three months later, measurements of sapwood status (% of conductive transversal section) and of its specific hydraulic conductivity, as well as of the phloem reaction zone lengths, did not show any isolate or density effect. At these experimental sites, Brutia pines appeared significantly more susceptible than Aleppo pines.  相似文献   

Characterization of sumac (Rhus tripartitum) root barks tannin for a potential use in wood adhesives formulation     

S. Ben Mahmoud  H. Saad  B. Charrier  A. Pizzi  K. Rode  N. Ayed  F. Charrier-El Bouhtoury 《Wood Science and Technology》2015,49(1):205-221

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Characterisation of nasal Staphylococcus delphini and Staphylococcus pseudintermedius isolates from healthy donkeys in Tunisia          下载免费PDF全文

H. Gharsa  K. Ben Slama  E. Gómez‐Sanz  P. Gómez  N. Klibi  M. Zarazaga  A. Boudabous  C. Torres 《Equine veterinary journal》2015,47(4):463-466

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Exercise Induced Pulmonary Hemorrhage in Horses: American College of Veterinary Internal Medicine Consensus Statement          下载免费PDF全文

K.W. Hinchcliff  L.L. Couetil  P.K. Knight  P.S. Morley  N.E. Robinson  C.R. Sweeney  E. van Erck 《Journal of veterinary internal medicine / American College of Veterinary Internal Medicine》2015,29(3):743-758

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Incubation of ovine scrapie with environmental matrix results in biological and biochemical changes of PrPSc over time     

Ben C Maddison  John Spiropoulos  Christopher M Vickery  Richard Lockey  Jonathan P Owen  Keith Bishop  Claire A Baker  Kevin C Gough 《Veterinary research》2015,46(1)

Ovine scrapie can be transmitted via environmental reservoirs. A pool of ovine scrapie isolates were incubated on soil for one day or thirteen months and eluted prion was used to challenge tg338 mice transgenic for ovine PrP. After one-day incubation on soil, two PrP^Sc phenotypes were present: G₃₃₈ or Apl₃₃₈ii. Thirteen months later some divergent PrP^Sc phenotypes were seen: a mixture of Apl₃₃₈ii with either G₃₃₈ or P_338, and a completely novel PrP^Sc deposition, designated Cag₃₃₈. The data show that prolonged ageing of scrapie prions within an environmental matrix may result in changes in the dominant PrP^Sc biological/biochemical properties.  相似文献   

Schirmer tear test I and rebound tonometry findings in healthy calves          下载免费PDF全文

Kyle L. Tofflemire  Elizabeth M. Whitley  Stacie A. Gould  Renee D. Dewell  Rachel A. Allbaugh  Gil Ben‐Shlomo  Annette M. O'Connor  R. David Whitley 《Veterinary ophthalmology》2015,18(2):147-151

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Anhydrous goat's milk fat: thermal and structural behaviors studied by coupled differential scanning calorimetry and X-ray diffraction. 2. Influence of cooling rate     

Amara-Dali WB  Lesieur P  Artzner F  Karray N  Attia H  Ollivon M 《Journal of agricultural and food chemistry》2007,55(12):4741-4751

Crystallization and melting properties of triacylglycerols (TGs) in anhydrous goat's milk fat (AGMF) are investigated by X-ray diffraction as a function of temperature (XRDT) coupled with high-sensitivity differential scanning calorimetry (DSC), using synchrotron radiation and Microcalix. The polymorphic behavior of AGMF was monitored by varying the cooling rates between 5 and 1 degrees C/min from 45 to -20 degrees C with their subsequent melting at 1 degrees C/min. Quenching of AGMF at -20 degrees C was also examined to determine the metastable polymorphic form of AGMF. At intermediate cooling rates, TGs in AGMF crystallize, from about 18 degrees C in two different lamellar structures with triple chain length 3Lalpha stacking of 72 A and a double chain length 2Lalpha stacking of 48 A, which are correlated to two overlapped exothermic peaks recorded by DSC. A reversible transition sub alpha <--> alpha was observed. Subsequent heating at 1 degrees C/min shows numerous structural rearrangements before final melting. At fast cooling of AGMF (5 degrees C/min), similar unstable crystalline varieties are formed while three endotherms are recorded. Several new unstable lamellar structures are observed after quenching. All of these data are compared to those previously reported at slow cooling (0.1 degrees C/min) showing a relative stability of the structures formed. In spite of general similitude, the thermal and structural behavior of the goat's milk is more complex than that of the cow's milk.  相似文献   

沿淮稻茬麦区小麦的产量及籽粒灌浆特性     

姜沣益  王犇  任开明  李哲  黄正来  张文静  马尚宇  樊永惠 《安徽农业大学学报》2022,49(3):395

为给沿淮稻茬麦区小麦高产栽培及品种育种提供依据,在大田条件下,选取沿淮麦区6个高产小麦品种为供试材料,用三次多项式方程对籽粒灌浆过程进行拟合,通过相关性分析对小麦籽粒灌浆参数与粒重的关系进行探究,研究不同小麦品种间产量及其构成因素的差异。结果表明： 6个品种中,安农大1216的产量最高,为8 598.77 kg·hm^-²,烟农19最低,产量为6 031.07 kg·hm^-²;籽粒灌浆过程中安农大1216粒重最高,成熟期千粒重达到51.4 g,郑麦9023的千粒重最低,为47.78 g;各个品种间灌浆速率存在明显差异。不同小麦品种籽粒灌浆过程均呈“S”型变化,因品种不同,灌浆参数也有所不同,但“R²”均达到0.99以上。相关性分析表明,千粒重与理论最大粒重（W）显著相关,与平均灌浆速率（V）、最大灌浆速率（V_max）、有效灌浆持续期平均灌浆速率（Vs）、有效灌浆持续期粒重增加值（Ws）和最大灌浆速率出现时间（T）呈正相关但未达显著水平。可见筛选的W、V、V_max、Vs、Ws和T等灌浆参数值较高的小麦品种在该地区种植有利于提高小麦千粒重,增加产量。此外,必须考虑到小麦品种、高效栽培方式、管理手段和协调产量构成三因素,才会最大可能实现小麦高产高效。  相似文献