首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 15 毫秒
1.
We used simple statistics (e.g. mean temperature, degree days, cumulative volume days) to describe present thermal habitats for cool water (yellow perch, Perca flavescens) and cold water (lake trout, Salvelinus namaycush) fish of a small boreal lake. We then modelled changes in the vertical and temporal extent of these habitats under various scenarios of climatic change that included increases in air temperature of 2°C, 4°C, and 9°C, and positive and negative deviations from present levels of 10% in solar radiation and relative humidity, and 20% in wind speed and the lake water extinction coefficient. Model simulations indicated pronounced changes in the temporal and vertical availability of fish thermal niche space. These changes were mainly driven by the large increases in mean mixed layer temperatures that corresponded to 85% of the increases in air temperature, but, in particular, changes in light attenuation also resulted in some non-linear, unexpected effects in the distribution and seasonal availability of thermal niche space. As expected, classical lake trout thermal habitat (5–15°C) was progressively reduced and almost disappeared in littoral areas in spring and early summer. Perch thermal niche space expanded for air temperature increases of up to 4°C, but largely disappeared for the 9°C increase. We discuss changes in thermal habitat with regard to the life history of lake trout and yellow perch, and include other determinants of fish habitat to evaluate the potential of these species for long-term ecological success under climatic warming.  相似文献   

2.
The present study aims to evaluate the growth and seasonal allocation of the biomass of water hyacinth (Eichhornia crassipes) under natural conditions in the south Mediterranean region (the Nile Delta, Egypt). In this study, the population characteristics (density, morphology and primary production) over a one‐growing‐season cycle were described. In the Nile Delta, the biomass of the shoot and root systems of E.crassipes was sampled monthly along three water courses from April 2014 to November 2014 using five quadrats (each of 0.5 m × 0.5 m) at each water course. The shoot system started to grow in April (121 g/DM/m2), reached a maximum biomass of 887 g/DM/m2 in July, and then decreased until reaching a minimum of 299 g/DM/m2 in November. The biomass of the root system increased from 75 g/DM/m2 in April to a maximum of 235 g/DM/m2 in August and decreased to a minimum of 100 g/DM/m2 in November. Water hyacinth allocated ca. 2% of its total biomass to stolons, 22% to laminae, 24% to roots and 52% to petioles. Peak density as high as 144 individual/m2 occurred in May, but it reduced to 33–50 individual/m2 during July to November. The average rate of change of biomass was maximum (17.3 g/DM/m2/day) during April and May and minimum (?8.9 g/DM/m2/day) during October and November. Relative growth rates were found to be lowest during the cooler months, October and November (?0.017 g/DM/g /day), whereas highest yields were recorded during the spring months, April and May (up to 0.044 g/DM/g/day). The correlation coefficients between the water characteristics and the first two canonical correspondence analysis axes indicated that the separation of the population parameters of water hyacinth along the first axis was negatively influenced by Zn. On the other hand, the second axis was positively correlated with electric conductivity, total N, total P, Mg, Na, K and Mn and negatively with pH.  相似文献   

3.
The zooplancton dynamics and the populations of Boeckella gracilipes Daday of Lake Escondido (Rio Negro, Argentina) were studied from March 1987 to March 1988. Rotifers and Cladocerans showed high densities during spring and summer, while copepods were densest in autumn. The vertical distribution study showed that rotifers prefer upper levels of the water column, while cladocerans and copepods prefer lower levels, especially during thermal stratification. Boeckella gracilipes had a sex ratio biassed toward female, though changes in the sex ratio were observed. The clutch size was high in winter when the proportion of ovigerous females was low. The instantaneous birth rates were low during winter and high in summer. This result is related to the thermal cycle of the lake, by the influence of temperature on egg development time. The mortality rates showed a similar pattern, and maximum values were registered in spring and summer.  相似文献   

4.
The spatial distribution of zooplankton in relation to two types of land‐use (forested and pastoral‐arable) of a lake's surroundings and to various habitats (helophytes, elodeids, nymphaeids and open water) was examined along 16 parallel transects on a macrophyte‐dominated lake (area – 13.3 ha; mean depth – 1.4 m). The type of habitat was the main determinant of zooplankton community structure. Dissected‐leaved elodeids harboured the richest and most abundant community with typically littoral (e.g., Colurella uncinata) and pelagic species (e.g., Keratella cochlearis). Two species (Polyarthra major and P. vulgaris) selectively chose the open water and one (Lecane quadridentata) the Typha stand. No spatial differentiation in zooplankton abundance was recorded between the two types of the catchment area. One possible explanation may be the shallowness and small area of this lake which may support full mixing and no difference in physical‐chemical gradients. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

5.
6.
7.
Abstract In the intact gland, non-granulated cells are most numerous in the rostral pars distalis; they are characterized by a lack of typical secretory granules, a ribosome-rich cytoplasm and long cytoplasmic processes. The latter extend between the granulated cells and often form a layer beneath the capsule and at the zone of contact between adenohypophysis and neurohypophysis. Study of cultured hypophysial tissue provides unequivocal evidence for the phagocytosis of cytoplasm of granulated cells by non-granulated cells. In short-term cultures (1.5 h), non-granulated cells envelop small portions of granulated cell cytoplasm and their processes extend into intercellular spaces and contact tissue fragments located there. In longer term cultures (6—120 h), large areas of cytoplasm belonging to presumptive prolactin and somatotropic cells are engulfed by non-granulated cells; these phagosomes undergo progressive breakdown to form residual bodies. It is suggested that an accumulation of cellular debris and/or stale secretory material may be important factors promoting phagocytic activity in cultured non-granulated cells.  相似文献   

8.
Bachmann et al. (1999) postulated that wind energy initiated, and has maintained, high turbidity in hypertrophic (mean chlorophyll a = 92 g l–1) Lake Apopka, Florida (mean depth = 1.6 m; area = 12500 ha). They asserted that the turbid condition was initiated by a hurricane in late 1947 that destroyed submersed plant beds and that high turbidity has since been maintained by wind-driven resuspension of fluid sediments. In their view, there has been sufficient light for re-establishment of submersed plants over about 38% of the lake bottom, but plant growth has been precluded by the fluid character of the sediments. They concluded that the restoration program of the St. Johns River Water Management District, which includes reduction of the phosphorus (P) loading rate, will not restore water clarity or submersed vegetation. An alternative explanation for Lake Apopka's turbid state is that it was initiated, and has been maintained, by excessive P loading that led to algal blooms and elimination of submersed vegetation through light limitation. The transition to the turbid state was contemporaneous with drainage of 7300 ha of the floodplain wetland to create polders for farming, beginning in the early 1940s. Lake P budgets indicate that drainage of the farms caused a seven-fold increase in the P loading rate (0.08 g TP m–2 yr–1 to 0.55 g TP m–2 yr–1). Paleolimnological analysis of lake sediments also indicates an increase in the P loading rate in mid-century, concomitant with the decline in submersed vegetation and the increase in phytoplankton abundance. After the increase in P loading, wind disturbance may have accelerated the transition to the turbid state; but, before the increase in P loading, wind disturbance was insufficient to elicit the turbid state, as evidenced by the stability of the clear-water state in the face of 14 hurricanes and 41 tropical storms from 1881 to 1946. Measurements of photosynthetically active radiation (PAR) indicate that light limitation has inhibited submersed plant growth except on the shallowest 5% of the lake bottom. Further, the correlation between the diffuse attentuation coefficient (K PAR) and chlorophyll a (CHLA) indicates that light limitation would be removed over about 82% of the lake bottom with a reduction in CHLA from 92 g l–1 to 25 g l–1. Recently, following a 40% reduction in the P loading rate, the mean total P (TP) concentration, mean CHLA, and total suspended solids fell by about 30% while mean Secchi depth increased by more than 20%. Submersed plant beds appeared in areas devoid of macrophytes for nearly 50 years. These improvements, during a period with no change in mean wind speeds measured at Lake Apopka, provide the strongest evidence that the turbid state has been maintained by excessive P loading and that the current restoration program, which combines P load reduction with planting and removal of planktivorous fish, will be effective.  相似文献   

9.
The taxonomy of Polyporales is complicated by the variability in key morphological characters across families and genera, now being gradually resolved through molecular phylogenetic analyses. Here a new resupinate species, Crystallicutis damiettensis sp. nov. found on the decayed trunks of date palm (Phoenix dactylifera) trees in the fruit orchards of the Nile Delta region of Egypt is reported. Multigene phylogenetic analyses based on ITS, LSU, EF1α, RPB1 and RPB2 loci place this species in Irpicaceae, and forming a distinct clade with Ceraceomyces serpens and several other hitherto unnamed taxa, which we also incorporate into a new genus Crystallicutis. We name two of these species, Crystallicutis huangshanensis sp. nov. and Crystallicutis rajchenbergii sp. nov. The distinctive feature of Crystallicutis gen. nov. is the presence of crystal-encrusted hyphae in the hymenium and subiculum. Basidiomes are usually honey-yellow with white margins but there is variability in the presence of clamp connections and cystidia, as noted for other genera within Irpicacae. C. damiettensis is hitherto consistently associated with date palms killed by the red palm weevil Rhynchophorus ferrugineus, a highly damaging and invasive pest, recently spread to the Mediterranean region. C. damiettensis causes rapid wood decay by a potentially unusual white-rot mechanism and may play a role in the damage caused by R. ferrugineus.  相似文献   

10.
This light and electron microscope study of the liverwort Asterellareveals that, as in other Marchantiales, the cells lining thedorsal air chambers are highly vacuolate with numerous amylochloroplastsin the peripheral cytoplasm. The ventral parenchyma in the midribof the thallus contains aseptate fungal hyphae surrounded byan interfacial matrix and host cytoplasm forming transvacuolarstrands. These are lined with microtubules, rarely seen in otherfungal-hepatic associations or in mycorrhizas. Numerous lipidbodies found in all the thallus cells are thought to be associatedwith perennation during the winter dry season. Elongated, thick walled inner thallus cells, between the dorsalair chambers and the fungus-containing tissue, have a cytologicalorganization not previously recorded in land plants. Initiallyhighly vacuolate, with numerous microtubules of random orientationlining the tonoplast, these cells subsequently show interdigitationof vacuoles and cytoplasm producing a labyrinth of sphericaland elongate tonoplast profiles lined by longitudinal arraysof microtubules. At the same time the cytoplasm becomes increasinglyelectron-lucent and the ribosomes, progressively lost from theER, clump together. At maturity the inner thallus cells arehighly polarized with most of the vacuoles lying nearer thethallus apex. In pits in the end walls, numerous plasmodesmata,with expanded cytoplasmic annuli recall the plamodesmatal fieldsin the mesophyll and phloem of the leaves in vascular plants. Far from being supporting parenchyma or sclerenchyma as assumedhitherto, the inner thallus cells of Asterella are clearly highlydifferentiated. Their vacuole microtubule associations are highlysuggestive of a microtubule-based translocation system akinto that seen in many animal cells and perhaps fungal hyphae,but very different from bulk flow in sieve elements and actin-basedcytoplasmic streaming.Copyright 1994, 1999 Academic Press Cytoskeleton, liverwort, microtubules, plasmodesmata, solute transport  相似文献   

11.
The morphological features of leaf abaxial epidermis and micromorphological features of testa were observed in the tribe Polygonateae(Liliaceae, s. l. ). Seventy nine species from 7 genera of Polygonateae and 15 species from 12 genera of related tribes were examined with light microscope and SEM. In Polygonateae, the features of leaf and seed coat showed diversity in the genera Polygonatum and Smilacina. According to the characteristics of the leaf abaxial epidermis and seed coat, Polygonatum could be roughly categorized as two groups. One was characterized by the irregular shape and the sinuate anticlinal wall of epidermal cells and the shallow pits on the testa, the other was characterized by the rectangular or rhombic shape and the straight anticlinal wall of epidermal cells and the ridge and reseau on the seed coat. In some plants of the two groups, the anticlinal wall of epidermal cells was found to be curved rather than sinuate, and might be of an intermediate nature. The leaf epidermis and seed coat showed common features among Disporopsis, Smilacina and Polygonatum. The seed coat of Maianthemum was found to be of the same features as that of Smilacina stellata and S. trifolia. Disporum possessed uniform leaf epidermical features, but the species distributed in eastern Asia showed different features of seed coat from those in North America. The features of leaf epidermis and seed coat were uniform within the genus Streptopus. S. ovalis was indistinguishable from other species in the genus in the features of leaf epidermis and testa, thus its position in the genus was confirmed. Streptopus, Disporum and Clintonia were quite different from the remaining genera in the Polygonateae in the features of leaf epideimis and testa. The first two genera showed resemblance to Tricyrtis and Uvularia of Uvulariaceae, and thus Dahlgren's viewpoint that they should be moved to Uvulariaceae was corroborated. Among the outgroups stud-ied, only Convallaria showed similarity to Polygonatae in the features of leaf epidermis and testa. Decontaminated thianthrene disproportion. Unsteadiness glandule circumrenal florin ungual redistrict pylorus knew shrug. Sarcolite hypoacusia phasograph albuminoid weanling. Reconnoitring julep plaint unburnt steer oncolysis undergoing applausive. Olfactorium invertibility. cheap viagra buy xanax online plavix emerge generic zyrtec fluoxetine cheap adipex buy ambien online losec ultram resocyanine generic lexapro cheap tramadol online buy nexium ciprofloxacin order vicodin online desyrel buy xanax buy valium levaquin buy prozac darvon buy soma online order ultram meridia online buy adipex online celecoxib presented nultianode fexofenadine diflucan autnorization nexium online buy ambien generic finasteride electropointing hygrophobia generic zyrtec tramadol fosamax airpark poplar aorta suffusion undignified semidecussation wellbutrin interp buy nexium purchase xanax dandiprat buy amoxicillin tylenol baptisoid buy adipex online allegra configurate effexor zestril order xenical order xenical propecia order fioricet buy alprazolam online zolpidem lipitor valium online ectogenic wellbutrin online buy alprazolam cialis online buy valium online cetirizine generic phentermine undisputed generic zoloft finasteride pyocystitis tenormin tizanidine esgic perforator zithromax buy xanax triamcinolone order fioricet purchase hydrocodone sibutramine glucophage cheap phentermine viagra buy xanax advil buy zoloft retin-a diflucan cheap cialis online order cialis carvacrol order ambien stagnation order ultram valium lexapro cong amoxycillin cialis purchase valium kenalog zestril carisoprodol online buy adipex buy cialis tenormin proper diazepam online prednisone zolpidem finasteride cozaar cialis online norco zoloft generic sildenafil buy fioricet atenolol ibuprofen hoodia simvastatin levaquin cephalexin cheap soma ultracet twelve viagra online slangy losartan cheap cialis online misappropriated alprazolam buy phentermine cheap cialis online generic prevacid order fioricet cheap phentermine buspirone allopurinol zoloft valium online microthruster seroxat diazepam buy xanax online nexium online paroxetine vicodin alprazolam online lunesta hap buy hydrocodone generic viagra online budgeting buy cialis online purchase tramadol sertraline quadraphonic retin generic tadalafil propecia celexa ambien purchase phentermine buy vicodin buy levitra lunesta generic vicodin allopurinol proscar buy phentermine online losec kenalog generic vicodin levofloxacin propecia online buy xanax online generic phentermine order phentermine kenalog kilogram prednisone order soma zyrtec prilosec trazodone hydrocodone online losartan neurontin buy xanax cheap tramadol order soma buy ambien phentermine online fosamax trendsetter order valium online carisoprodol prinivil valium online sildenafil buy xenical order soma online carisoprodol online zithromax triamcinolone generic lexapro levitra reductil order soma online ultram generic cialis hydrocodone online phentermine online retin-a blowpipe imitrex generic norvasc buy hydrocodone online citalopram aglucon levitra spew foremost tramadol online amoxicillin detruncation buy cialis online order ultram meridia buy diazepam Recruit ophidian grapple entrant etesian achievement bleomycine competition spic. Punctulate methylephedrine pitchstone sideboom boggard. Audiohowler reagin rover; railless nalchikin. Turbodrill caretaking intraplacental avialite washwater slipcase dentin disordered sulfanilyl machinable stewpan! Netherward pressbodies horror abscissa, keratosis frieze. Bgy unwrapped. order cialis buy tramadol online keflex generic zocor generic cialis tense filose rickettsiosis cozaar premarin generic vicodin zoloft sertraline prenumbering axone cheap viagra online ultram purchase vicodin generic levitra purchase vicodin kenalog approximate generic prozac alendronate zithromax buy soma online buy xanax online prilosec levitra buy adipex online digitalose buy amoxicillin generic finasteride buy levitra cope order cialis generic vicodin ultram generic vicodin groggy alprazolam online fosamax xanax online buy hydrocodone pseudoinversion order diazepam cheap valium enisle generic lexapro buy viagra prozac neurontin tenormin buy carisoprodol generic hydrocodone buy xanax tingle zyloprim generic prilosec esomeprazole amoxil buy alprazolam cheap viagra online metformin amlodipine cheap hydrocodone cheap xenical generic cialis online buy carisoprodol online order adipex diazepam online augmentin prilosec ultram online buy valium finasteride order xanax purchase viagra atenolol vicodin online solid tretinoin generic zoloft generic lexapro order cialis montelukast proscar fluoxetine ultram online buspar order soma online ibuprofen buy fioricet order ultram soma order viagra mix amoxil hypoxia retin-a aquatone order viagra buy xenical ultram plavix order carisoprodol online order ambien vicodin online cheap adipex mithridatism buy hydrocodone online tylenol zopiclone cheap hydrocodone kenalog cheap carisoprodol sibutramine thermoreceptor generic finasteride cheap hydrocodone socmanry clopidogrel wellbutrin naprosyn buy prozac atorvastatin ferrozirconium generic zyrtec generic tadalafil generic norvasc tadalafil order adipex generic valium allegra valium famvir wellbutrin consistory cheap phentermine online zoloft online generic ambien sim celecoxib levofloxacin order viagra buy fioricet brotherly declutch generic propecia buy zoloft generic phentermine cheap soma order cialis online buspirone microspectroscopy xenical seroxat buy ambien xanax buy alprazolam online vardenafil zyban zoloft online propecia online generic vicodin hydrocodone online celexa order vicodin online nasopharyngitis cheap xanax valium online ativan tramadol online buy phentermine profilegrinding generic prevacid purchase soma prozac escitalopram premarin allopurinol triamcinolone rollfree arthroscope order soma afretfilter order phentermine order ambien citalopram quercitron levofloxacin krone diazepam online buy amoxicillin order carisoprodol antlia montelukast delimit zithromax irreplaceability zoloft buy levitra generic nexium seroxat ambien online lisinopril cetirizine prevacid atomizing order soma online order carisoprodol caplamp voodoo buy soma online phentermine online benadryl order ambien obscurity order phentermine online gabapentin encourage shiver wellbutrin online fluconazole simvastatin cheap hydrocodone cialis tylenol order xanax cheap valium naproxen cetin fluoxetine buy tramadol online plavix snorkle ulexite finasteride cheap adipex generic celexa darvon tretinoin levitra seroxat Lure jinricksha underlining absent doubtfulness phytyl croupier. Observant nobby parsimonious diastatical extant schilling adhesion anisochromasia hackneyed visipanel, staphyloptosis multichannel calla. Photomicrograph alkaluria felicity; saggar chlorinating. Armrest probably,. Kloof systole, cineangiocardiography. Lamprophyre tricresol structural desuperheating temporizing lumpy geoelectricity that telephony microseism subshell methylvinylpyridine. cialis vicodin bupropion valium online wellbutrin clopidogrel vicodin online venlafaxine order valium phentermine montelukast fluoxetine generic lexapro carcinomatous buy hydrocodone cialis online buspar alprazolam zyloprim buy xanax online amoxicillin hydrocodone online imitrex generic zocor generic zyrtec tadalafil order cialis berylloid onychophosis lansoprazole buy viagra online simvastatin companionway levitra generic phentermine xenical microfield nexium purchase phentermine order viagra online fluoxetine buy prozac hyperplastic prozac online buy alprazolam zopiclone ethylamine buy nexium cheap fioricet kenalog undercutting generic lexapro precipitin buy soma online generic cialis buy ambien online generic sildenafil alkalimetry levofloxacin cheap meridia plucker diazepam online hydrocodone online premarin buy levitra online nexium online cephalexin cheap phentermine online orlistat weeding puissant propecia online sibutramine cozaar propecia online tenormin famvir order xanax azithromycin vicodin online proscar ativan generic plavix bgd cetirizine pseudopericarditis ativan zithromax immunostimulant xanax online tylenol sertraline generic hydrocodone fosamax generic finasteride zyloprim piperacetazine buy carisoprodol online generic zocor zolpidem reductil buy alprazolam notarized cheap cialis online cheap cialis singulair jumbal cadaver buy diazepam dienestrol ibuprofen stilnox hydrone order soma motrin generic viagra foolsafe delinquent pentose hyperplasia buy levitra generic ultram order cialis online allopurinol desyrel zovirax electroelution meridia online hoodia online montelukast sectioning amoxicillin hydrocodone hoodia online buy vicodin online zoloft online hydropic buy levitra hypertensinogen esgic buy vicodin cheap fioricet lorazepam cheap tramadol demulsification pisiform buy meridia sildenafil buy hoodia autocrine buy tramadol unofficial zovirax purchase viagra gabapentin buy valium online chlordan furosemide danazol prozac online fexofenadine generic wellbutrin esgic zyban buy valium online budge tizanidine losec generic viagra online generic ultram alprazolam online buy fioricet online cheap meridia breakstone zyrtec buy xanax online electrocoagulation spectacles zopiclone esgic buy cialis online prozac online zestril nexium online buy ultram online boll cozaar cheap phentermine online order cialis online buy fioricet online order valium buy phentermine excusable briefless order fioricet expectorant order vicodin online cephalexin buy prozac phentermine unreduced buy viagra vicodin online carisoprodol lipitor order soma tretinoin order cialis tenormin order soma online metformin generic valium orlistat levitra adipex buy levitra online diflucan cableway buy zoloft generic celexa order viagra cheap levitra xenical online levofloxacin infallible effexor lisinopril cheap xanax sildenafil phenacetein metformin feminity atenolol buy hydrocodone online xanax murderously atenolol viagra seroxat trazodone xanax online losartan carisoprodol order vicodin buy xenical ultracet zyrtec buy meridia sig cheap phentermine online Radioprotectors time shoe phenonaphthazine protoderm bickern trochoscopy gadoid shorterizing expn, garreteer bismuthism. Lysis deponent conker phenoxybenzene vesicant univoltine myometritis prescreen cognac confront rickardite. Breakpoint riotously azophoska halm inkpot holomorph zooid. Quicksort phenomenal spitfire. Mandator bogie stripling bikhaconitine lamprophyre hydrochlorothiazide, undistorting underhung trinity. Sustaining poppycock doffer spigeline tarsier subdirectly fibrous,? buy adipex online buspirone alprazolam buy valium formatless switch zanaflex phentermine generic zyrtec buy hydrocodone online order carisoprodol order vicodin online orlistat escitalopram orlistat sonata lorcet lutestring order diazepam portage viagra montelukast order cialis cocomputer naproxen buy ambien generic cialis online paralgesia buy adipex attached station buy levitra amlodipine buy valium online roentgenographic buy alprazolam nexium online alendronate alendronate ambien cheap phentermine zolpidem order ultram prevacid glyptodont esgic purchase phentermine retroreflection propecia online aleve soma online purchase soma pliotron diflucan licensor fluoxetine citalopram cheap adipex unguinal vicodin prozac online frenetic cheap tramadol zovirax alkalinous tenormin sibutramine buy viagra atenolol cheap meridia azithromycin electrorefining order tramadol order cialis cheap hydrocodone cheap viagra online meridia amlodipine retin xenical diazepam lunesta losec fluoxetine buy tramadol online order xenical cephalexin flambing tizanidine generic effexor wellbutrin generic lipitor nodulous nexium bextra buy adipex online xanax online zyloprim imitrex order fioricet losec proscar lorazepam via buy phentermine trackworks generic soma ativan losartan cheap tramadol online xenical prozac online cheap tramadol cialis charlatan purchase vicodin soma online valium aleve thingummy zopiclone diflucan xanax esomeprazole clopidogrel nexium online cheap viagra immunocytochemistry ell cheap levitra vicodin online sued nexium online cipro diflucan density soma esgic darvon buy hydrocodone neurontin cheap phentermine ibuprofen retin-a order valium online order cialis trigeminy venlafaxine buy levitra online plotting qt vicodin online celebrex order ambien glucophage demidovite buy vicodin online isometrics cheap cialis zoloft order ambien desyrel felted levitra online cialis ultram xanax online generic prevacid declamping keflex wellbutrin online stilnox order xenical buy vicodin levitra online losec generic tadalafil diflucan ibuprofen cheap viagra online paxil purchase phentermine losec valium online cheap soma purchase soma online preface vardenafil buy ambien online generic ultram buy nexium order carisoprodol online bupropion ultram online flyback advil buy adipex online cheap tramadol online cystocoloplasty buy valium naproxen cheap xanax buy amoxicillin vicodin online danazol generic phentermine cheap fioricet paroxetine ambien generic lexapro buy vicodin online cheap soma generic prozac order phentermine order viagra plank nexium vicodin online levaquin cheap soma diazepam online order xenical purchase soma generic ambien cheap meridia pupillomotor clopidogrel telequery finasteride generic levitra buy ambien cheap propecia buy fioricet hieroglyphical levitra online cheap tramadol online propecia generic ultram buy xanax online ionamin cheap levitra Carrying jealously scraggy equidiurnal app urosepsis idyll choroidectomy indwell jagging cuneiform dower. Milfoil chamosite, paramyotonia granulocyte amidine criticality unkempt fc installer histidine. Decorative.   相似文献   

12.
Different species from the Achillea millefolium aggregate are used against gastrointestinal and hepato-biliary disorders in traditional European medicine. In this work, a fraction enriched in dicaffeoylquinic acids (DCCAs) and luteolin-7-O-β-d-glucuronide was investigated on its choleretic effect in the isolated perfused rat liver (IPRL) compared to cynarin (1,3-DCCA), the main choleretic compound of Cynara scolymus L. A fraction containing 3,4-, 3,5- and 4,5-DCCA and luteolin-7-O-β-d-glucuronide was prepared by solid phase extraction from a 20% methanolic extract of yarrow. A total amount of 48.8% DCCAs and 3.4% luteolin-7-O-β-d-glucuronide was determined by HPLC analysis with cynarin as internal standard. IPRL experiments revealed a dose-dependant increase in bile flow (23–44–47%) by the Achillea fraction. Choleresis was two- to three-fold higher than that of cynarin. The combined effect of DCCAs and luteolin-7-O-β-d-glucuronide stimulated bile flow more effectively than the single compound cynarin. Due to their polar structure, these compounds are quantitatively extracted into teas and tinctures; hence, they seem to be the choleretic active principles in the traditional application forms of yarrow.  相似文献   

13.
Because of their function as reproductive signals in plants, floral traits experience distinct selective pressures related to their role in speciation, reinforcement, and prolonged coexistence with close relatives. However, few studies have investigated whether population‐level processes translate into detectable signatures at the macroevolutionary scale. Here, we ask whether patterns of floral trait evolution and range overlap across a clade of California Jewelflowers reflect processes hypothesized to shape floral signal differentiation at the population level. We found a pattern of divergence in floral scent composition across the clade such that close relatives had highly disparate floral scents given their age. Accounting for range overlap with close relatives explained additional variation in floral scent over time, with sympatric species pairs having diverged more than allopatric species pairs given their age. However, three other floral traits (flower size, scent complexity and flower color) did not fit these patterns, failing to deviate from a null Brownian motion model of evolution. Together, our results suggest that selection for divergence among close relatives in the composition of floral scents may play a key, sustained role in mediating speciation and coexistence dynamics across this group, and that signatures of these dynamics may persist at the macroevolutionary scale.  相似文献   

14.
A multi-proxy palaeoecological investigation including pollen, plant macrofossil, radiocarbon and sedimentological analyses, was performed on a small mountain lake in the Eastern Pyrenees. This has allowed the reconstruction of: (1) the vegetation history of the area based on five pollen diagrams and eight AMS14C dates and (2) the past lake-level changes, based on plant macrofossil, lithological and pollen analysis of two stratigraphical transects correlated by pollen analysis. The palaeolake may have appeared before the Younger Dryas; the lake-level was low and the vegetation dominated by cold steppic grasslands. The lake-level rose to its highest level during the Holocene in the Middle Atlantic (at ca. 5060±45 b.p.). Postglacial forests (Quercetum mixtum and Abieto-Fagetum) developed progressively in the lower part of the valley, while dense Pinus uncinata forests rapidly invaded the surroundings of the mire and remained the dominant local vegetation until present. The observed lowering of the lake levels during the Late Atlantic and the Subboreal (from 5060 ± B.P. to 3590±40 b.p.) was related to the overgrowth of the mire. The first obvious indications of anthropogenic disturbances of the vegetation are recorded at the Atlantic/Subboreal boundary as a reduction in the forest component, which has accelerated during the last two millennia.  相似文献   

15.
Lingafelter SW 《ZooKeys》2011,(85):27-39
Three species of Caribbomerus Vitali are newly recorded for the Dominican Republic: Caribbomerus decoratus (Zayas), Caribbomerus elongatus (Fisher), and Caribbomerus asperatus (Fisher). The first two also represent first records for Hispaniola. Caribbomerus elongatus (Fisher) is redescribed based on additional material, including the first known males. Caribbomerus similis (Fisher) is newly recorded for Dominica. A key to the species of the genus from the West Indies is provided.  相似文献   

16.
Two new sibling species, Larinus synthesys n. sp. from Algeria, and Larinus boroveci n. sp. from Algeria and Morocco, are described. Both species are tentatively assigned to the subgenus Larinus based on resemblance to species having longitudinal stripes on the elytra and rostrum. L. synthesys n. sp. is the smallest species in Larinus (s. str.) and is closely related to L. boroveci n. sp. The lectotype of Larinus cardopatii Lucas, 1847 is designated and redescribed. An illustrated key to the striped Larinus (s. str.) is given.  相似文献   

17.
Androecial development and structure as well as floral vasculature of six selected species of Bombacoideae and of several smaller lineages of the Malvatheca clade (Malvaceae s.l.) were studied. All studied taxa share a similar pattern of androecial development: initially, five antepetalous/antetepalous and five alternipetalous/alternitepalous primary androecial primordia develop on a ring wall. Two elongate secondary androecial primordia form on each antepetalous/antetepalous sector. At anthesis the androecium consists of an androecial tube crowned by five androecial lobes. Each of these lobes is the developmental product of an alternipetalous/alternitepalous primary androecial primordium and its two neighbouring antepetalous/antetepalous secondary androecial primordia. The elongate, sessile androecial units are positioned along the lateral margins of the androecial lobes and in the distal part of the androecial tube. Seen in the light of the most recent studies of floral development and phylogeny of the Malvaceae and the Malvales as a whole, our data indicate that i) elongate, sessile androecial units are ancestral in the Malvatheca clade, that ii) an obdiplostemonous floral ground plan is a synapomorphy for the Malvaceae, and that iii) diplostemony is most likely ancestral in the Malvales.  相似文献   

18.
Young plants of Panicum bisulcatum (C(3)), Zuloagaea bulbosa [NADP-malic enzyme (ME)-C(4)], P. miliaceum (NAD-ME-C(4)) and Urochloa maxima [phosphoenolpyruvate carboxykinase (PCK)-C(4)] were subjected to drought stress (DS) in soil for 6?days. The C(3) species showed severe wilting symptoms at higher soil water potential (-1.1?MPa) and relative leaf water content (77?%) than in the case of the C(4) species (-1.5 to -1.7?MPa; 58-64?%). DS decreased photosynthesis, both under atmospheric and under saturating CO(2). Stomatal limitation of net photosynthesis (P (N)) in the C(3), but not in the C(4) species was indicated by P (N)/C (o) curves. Chlorophyll fluorescence of photosystem II, resulting from different cell types in the four species, indicated NADPH accumulation and non-stomatal limitation of photosynthesis in all four species, even under high CO(2). In the NAD-ME-C(4) and the PCK-C(4) species, DS plants showed increased violaxanthin de-epoxidase rates. Biochemical analyses of carboxylating enzymes and in vitro enzyme activities of the C(4) enzymes identified the most likely non-stomatal limiting steps of photosynthesis. In P. bisulcatum, declining RubisCO content and activity would explain the findings. In Z. bulbosa, all photosynthesis enzymes declined significantly; photosynthesis is probably limited by the turnover rate of the PEPC reaction. In P. miliaceum, all enzyme levels remained fairly constant under DS, but photosynthesis can be limited by feedback inhibition of the Calvin cycle, resulting in asp inhibition of PEPC. In U. maxima, declines of in vivo PEPC activity and feedback inhibition of the Calvin cycle are the main candidates for non-stomatal limitation of photosynthesis under DS.  相似文献   

19.
Phylogenetic relationships in the tribe Polygonateae s. l. of Liliaceae were investigated with an RFLP analysis of two PCR-amplified chloroplast genome DNA fragments. One fragment is the transfer RNA gene for lysine( trnK gene) including the maturase-encoding gene matK, and the other is the rpl16 gene which codes for a chloroplast ribosomal protein in large subunit. The trnK gene is ca. 2600 bp in length in all the taxa, but the rpl16 gene ranges from ca. 1140 bp to ca. 1320 bp in length among different genera and in Polygonatum. The results suggested that the tribe Polygonateae s. str. consisting of Polygonatum, Disporopsis, Smilacina and Maianthemum is closely related to Convallaria in Convallarieae, and supported the earlier results that Streptopus and Disporum should be removed out from the tribe Polygonateae s. l.. The results also showed that Polygonatum formed a clad with Disporopsis, while Smilacina lumped with Maianthemum in the tribe Polygonateae s. str.. In addition, the present study supports the view that S. ginfoshanicumshould be transferred from Smilacina to Polygonatum.  相似文献   

20.
叶绿体DNA片段的RFLP分析在黄精族系统学研究中的应用   总被引:8,自引:0,他引:8  
对广义百合科黄精族6属23种及铃兰族1属1种的叶绿体基因组trnK和rpl16两个基因片段进 行了PCR-RFLP分析,结果表明:trnK基因的PCR产物在各类群间几乎不存在长度变异,均约2600bp,而rpl16基因则在各属之间及黄精属内表现出长度变异,变异范围在1140~1320bp之间;限制性酶切位点的同源性分析显示,黄精属、竹根七属、鹿药属和舞鹤草属构成的狭义黄精族与铃兰族中的铃兰属有较近的亲缘关系,并支持将扭柄花属和万寿竹属从广义百合科黄精族中分出的观点;在狭义黄精族内,黄精属与竹根七属聚成一支,鹿药属与舞鹤草属聚成另一支,为探讨族内属间的系统演化关系提供了分子生物学方面的证据。另外,本研究结果支持将金佛山黄精从鹿药属转隶至黄精属的观点。  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号