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1.
How often do you read a book that has a large number of ‘aha!’moments in every chapter? This is a significant piece of synthesisand scholarship that brings together a very large number ofdisciplines and disparate chunks of data into a very satisfyingwhole. The book is dense, thorough and revealing—a lightand fast read it is not, but it is well worth the effort. Thetwo  相似文献   

2.
RAVEN  J. 《Annals of botany》2004,94(1):196-197
The back cover of this book states that ‘contrary to theclaims of the nativists, research shows that man-dispersed speciesincrease biological diversity, benefit ecosystems, and act asan important force for healing the planet’. This is anuncompromising statement, and David Theodoropoulos divides hisdevelopment of the arguments supporting this statement intothree parts. Part I (Chapters 1–6) is ‘Nature, Dispersaland Reaction’. Part II (Chapters 7 and 8) is ‘Why?Psychology, Politics and Pseudoscience’. Part III (Chapters9–11) is ‘Humanity and Diversity’. There isalso an ‘Introduction’ including a summary of findingsand ‘An outline for a new theory of anthropogenic dispersal’,  相似文献   

3.
Various forms of wounding result in increases in hydrostaticpressure in the laticiferous phloem tissue of Hevea brasiliensis;regular tapping, a form of controlled wounding, probably causesa similar response. When a tree is ring-barked, there is a transientfall in turgor immediately above and below the ring, presumablyowing to loss of latex during cutting. This is followed by apressure increase which is particularly marked above the ring,suggesting the accumulation of metabolites. Isolation of an‘island’ of tissue, by cuts down to the wood, resultsin a steep fall in turgor within it, although a relatively slowrecovery may follow. Partially isolated panels show smallerfalls and a more rapid rise. It appears that a functional phloemconnexion permits a more rapid recovery of osmotic and turgorpressures following latex losses, both in the isolation experimentsand in normal tapping. Growth regulators such as 2,4,5-trichlorophenoxyaceticacid (2,4,5-T) increase latex yields by prolonging latex flowafter tapping. In untapped trees treatment with 2,4,5-T resultsin a slow and fairly small increase in turgor pressure, butthis effect may not be apparent if trees are regularly tapped.When the tapping cut is opened, there is a rapid fall in pressureimmediately under the cut. This loss in turgor spreads throughthe latex-vessel system as latex flows towards the cut, butrecovery is apparent near the cut even before flow ceases. Pressuregradients indicate a rapid formation of a localized resistanceto flow at or near the cut surface. This process appears toplay a major part in restricting flow. The increased yieldswhich result both from regular tapping and after 2,4,5-T treatmentappear to result from a delay in this sealing process. The mechanismsby which the barrier to flow is built up and delayed by 2,4,5-Ttreatment are not clearly understood.  相似文献   

4.
In January 2000, an impressive cohort of evolutionary biologistsconvened in Irvine, California, to celebrate the 50th anniversaryof the publication of G. Ledyard Stebbins’ Variation andevolution in plants. The brief introductory appreciation ofStebbins by Peter Raven describes Variation as ‘the mostimportant book on plant evolution of the 20th century’(p. 5). This strongly worded claim is not entirely without justification.Among the ‘New Synthesists’, Stebbins achieved forbotanists what Theodosius Dobzhansky (later to be a colleagueof Stebbins at UC Davis) had previously achieved for geneticists,Ernst Mayr for zoologists and G. G. Simpson for palaeontologists.Admittedly, the  相似文献   

5.
We describe the migration distances and timing of the adult Pacific lamprey, Entosphenus tridentatus, in the Willamette River Basin (Oregon, U.S.A.). We conducted aerial surveys to track radio-tagged fish upstream of a major waterfall and hydropower complex en route to spawning areas. We detected 24 out of the 43 fish that passed the waterfall-hydropower complex. Of the detected fish, 17 were detected multiple times. Their maximum migration distance upstream in the mainstem Willamette approximated a normal distribution. The maximum distance migrated upstream did not significantly correlate with total body length (r = −0.186, P = 0.385) or date that the fish passed Willamette Falls (r = −0.118, P = 0.582). Fish migrated primarily during the spring to early summer period before stopping during the summer, when peak river temperatures (≥20°C). However, at least three fish continued to migrate upstream after September. Behavior ranged from relatively slow migration, followed by holding; to rapid migration, followed by slow migration further up in the basin. This study provides a basis for informing more detailed research on Pacific lamprey in the future.  相似文献   

6.
Females of the sac-spawning euphausiid Nyctiphanes simplex Hansenwere incubated under shipboard laboratory conditions to observethe embryonic and larval development time and hatching mechanism.Females ready to spawn have a pale pink ovary that extends fromthe back of the stomach to the first abdominal segment, fillingmost of the haemocoel. This species usually behaves as a totalspawner (produces one batch of oöcytes per cycle of theovary) leaving an ‘empty’ space in the cephalothoraxwhere the spent ovary is located. After spawning, the youngoöcytes mature and turn pale pink. The eggs do not havea measurable perivitelline space (PVS) in any of the embryonicstages (6.6 x magnification). The embryos hatch as nauplius(80–91 h after spawning, 16°C ± 1°C). Theyfurther develop into pseudometanauplii (PMN, 90–105 hafter spawning) and metanauplii (MN, 92–140 h after spawning)inside the ovigerous sac. The nauplius breaks the thin and fragilechorion by increasing the volume of the body and by using thefirst and second antennae. We call this an ‘expansion’hatching mechanism, the fifth distinct hatching mechanism observedso far among euphausiids. N. simplex larvae escape from theovigerous sac late in the MN stage (5 days after spawning),just a few hours before molting into calyptopis 1 (C1) (0.5–4h). This delayed release extends protection by the female, likelydecreasing the risk of predation or early cannibalism. Additionally,this may save energy by not swimming independently increasingthe time of not return if the calyptopis does not find favorablefeeding conditions. Females are not ready to spawn again untilat least two days after the previous batch of embryos leavesthe ovigerous sac. The interbrood period (IBP) observed rangedbetween 7 and 15 days at 16–18°C. This IBP is aboutone-fourth to half than was previously assumed for this speciessuggesting a significant underestimation of the fecundity ofthis species. N. simplex hatching success usually was 100%,except for a few females with all of their embryos dying duringembryonic development. Other females either molted before releasingthe embryos, or the oöcytes were spawned unfertilized (0%hatching success), particularly during winter conditions. Efficienthatching and late free-swimming strategy may partially explainwhy this species is the most abundant neritic euphausiid inthe southern part of the California Current System (CCS) andin the Gulf of California.  相似文献   

7.
Smyrnium perfoliatum L. (Apiaceae), an endangered forest herb with only one main locality in South-West Slovakia (Devínska Kobyla in the Little Carpathian Mountains), is capable to recover chlorophylls at the end of the growing season. This regreening only within bracts was observed during two weeks before achieving the so-called “point of no return” that leads to the last stage of ontogenesis — leaf senescence. The effect not only of endogenous cytokinins on chlorophyll content and carbon dioxide exchange (photosynthesis, mitochondrial respiration, and photorespiration) is discussed but also of other factors such as strong irradiance, high temperature or drought stress on studied parameters was considered.  相似文献   

8.
ATKINSON  D. 《Annals of botany》2004,94(1):195-197
This volume represents the proceedings of a meeting of the CambridgeSociety for the Application of Research held in 2002. The aimof the meeting was to clarify the current state of knowledgeof GM technology and its implications for the world. This hasresulted in a collection of papers that discuss some but notall of the current driving issues related to the applicationof biotechnology to crops. One of the most contentious thingsabout the volume is probably its choice of title. As sourcesof information, scientists have not been trusted by the publicto be objective on GM or to answer the public’s questionsin  相似文献   

9.
Smith  F. Andrew 《Annals of botany》2007,100(1):151-152
It is (or should be) self-evident that life on Earth dependsmainly on life in earth, and in this respect soil–plantinteractions are of key importance. This book brings togetherareas that are still often compartmented into fields such aschemical and physical aspects of soil science (where plantsare still sometimes regarded as a ‘black box’ ofuncertain relevance), plant physiology (now sometimes re-badgedas plant functional biology), and soil microbial ecology. Agriculturalscientists have, of course, rarely been guilty of ignoring soilfactors in relation to plant growth and productivity. Plantecologists sometimes have, and to some of them it's the soilthat is the ‘black box’ when it comes to understandingplant population and community ecology. Models of the  相似文献   

10.
This article argues that the rapid transfer of assisted conception technologies, such as in vitro fertilization, to India is not restricted merely to the modalities of offering potential biomedical resolution of infertility but includes, more crucially, how clinicians and infertile consumers assimilate the “Western technoscience” of conception. The article draws on a larger multisite ethnographic study of infertility and assisted conception in India’s five major cities and is principally based on narratives of clinicians and infertile couples and on clinic-based ethnographic observations. In this article I contend that the success or failure of assisted conception, when situated in the universe of Hindu faith, becomes a powerful critique of the “incompleteness” of the “Western” science of conception. Situating this contention in the broader context of a clinician’s faith, I assert that assisted conception—by conjoining seemingly disparate domains of the traditional and the modern, the sacred and the profane, the human and the superhuman, science and religion—produces clinical theodicies that help explain and contain the tentativeness permeating the conception technologies. The article concludes by arguing that this enchanted version of a thoroughly disenchanted worldview of biomedicine is part of a larger cultural process of indigenization of biomedicine in India.  相似文献   

11.
Maynard Smith’s defenses of adaptationism and of the value of optimization theory in evolutionary biology are both criticized. His defense does not adequately respond to the criticism of adaptationism by Gould and Lewontin. It is also argued here that natural selection cannot be interpreted as an optimization process if the objective function to be optimized is either (i) interpretable as a fitness, or (ii) correlated with the mean population fitness. This result holds even if fitnesses are frequency-independent; the problem is further exacerbated in the frequency-dependent context modeled by evolutionary game theory. However, Eshel and Feldman’s new results on “long-term” evolution may provide some hope for the continuing relevance of the game-theoretic framework. These arguments also demonstrate the irrelevance of attempts by Intelligent Design creationists to use computational limits on optimization algorithms as evidence against evolutionary theory. It is pointed out that adaptation, natural selection, and optimization are not equivalent processes in the context of biological evolution. It is a pleasure to dedicate this paper to the memory of John Maynard Smith. Thanks are due to James Justus and Samir Okasha for comments on an earlier draft.  相似文献   

12.
When young plants of Macroptilium atropurpureum, cv. Siratrowere deprived of external sulphate (-S plants) growth of shootsand roots continued at rates comparable to those in plants wellsupplied with sulphate (control) for 3 d and 5 d respectively.Dilution of internal sulphur therefore took place and redistributionof sulphur occurred between inorganic and organic forms andbetween roots and younger leaves. Even when S-deficiency limitedgrowth, plants contained 16% of their total sulphur as sulphate,but most of this was retained in old leaves and redistributedslowly to growing zones. The capacity for sulphate uptake increased in roots of –Splants very soon after they were deprived of external sulphate;within 24 h the absorption from 0.25 mol m–3 SO42–was more than five times that of control roots. Maximum increasedcapacity was reached after 2–3 d stress when the Vmaxof system 1 was 1948 nmol h–1g–1root fr. wt. in–S plants and 337 nmol h–1g–1root fr. wt.in controls. The Kmfor system 1 did not change significantlywith S-stress being between 5–8 µM in both setsof plants. Absorption of L-cysteine was not stimulated by S-stress. There was a close, positive relationship between plant growthrate and the rate at which sulphate uptake capacity was enhancedby withholding sulphate from culture solutions. When –S plants were replaced in sulphate-containing solutiontheir capacity for SO42– declined to the control levelwithin 24 h. Very marked repression of capacity was also foundwhen –S plants were treated with L-cysteine, but therewas no immediate effect with methionine. Roots of this species appear to have a very active system fordegrading L-cysteine to sulphate, 30% of the label in 35S-cysteineabsorbed by roots was recovered in 35SO42– after 20 minor 2 h incubation. By contrast, roots had a very weak abilityto reduce sulphate. When part of the root system was in solution lacking sulphatethere was enhanced uptake of sulphate by other parts which themselveswere amply supplied with sulphate. This is seen as an exampleof compensatory absorption. The response to S-stress is specific and there were no positiveinteractions between S-stress and the absorption of phosphate,or P-stress and the uptake of sulphate. The results are discussed in relation to the close control ofsulphate uptake by internal sulphate concentration, redistributionof forms of sulphur during stress and mobility of sulphate inthe phloem. Key words: Kinetics, Amino-S, Sulpholipid, Repression;, Deficiency  相似文献   

13.
HlyD has a single transmembrane domain (residues 59-80) and a large periplasmic domain, and is essential for the secretion of haemolysin from Escherichia coli. Using an antibody raised against HlyD, the protein was localised to the cell envelope by immunofluorescence and to the cytoplasmic membrane by sucrose gradient analysis. We have examined the stability of this protein in the presence and absence of other putative components of the translocator, HlyB and TolC. HlyD is normally highly stable but in the absence of TolC, the steady-state level of HlyD is greatly reduced and the protein has a half-life at 37° C of 36 min. In the absence of HlyB, HlyD is also unstable and specific degradation products are detected, which co-fractionate with the inner membrane, indicating in this case limited cleavage at specific sites. However, the effect of removing both HlyB and TolC is not additive. On the contrary, in the absence of both HlyB and TolC the half-life of HlyD is approximately 110 min. This result shows that in the presence of HlyB removal of TolC renders HlyD more unstable than it is in the absence of both HlyB and TolC. This suggests that the presence of HlyB induces a structural change in HlyD. In addition, HlyB itself appears to be less stable in the absence of HlyD. These results are consistent with an interaction between HlyD/TolC and HlyB/HlyD. A derivative of HlyD, HlyD22, lacking the 40 N-terminal residues of HlyD assembles into the inner membrane displaying the same stability with and without HlyB as wild type HlyD does. This N-terminal region therefore appears to play no role in stable localisation but is involved in secretion, since HlyD22 is completely secretion defective. Modification of the C-terminus on the other hand completely destabilised the molecule and HlyD was not detectable in the envelope. Secretion of active haemolysin is limited to a brief period during mid to late exponential phase. In contrast, HlyD is apparently synthesised constitutively throughout the growth phase, demonstrating that the production of this component of the translocator is not the limiting factor for growth phase-dependent secretion. Received: 10 July 1998 / Accepted: 19 October 1998  相似文献   

14.
ABROL  Y. P. 《Annals of botany》2004,93(6):785-786
Food from agriculture supports around 6 billion people who inhabitthis planet today. The population is expected to increase toabout 7·2 and 8·3 billion by 2015 and 2030, respectively.This scenario requires increased food production. Food productioncan be raised by cultivating more land, increasing the yieldof each crop, growing two or three crops per year on the samepiece of land, or by a combination of these possibilities. Eachcan have problems. The best land, that is the land that is mostproductive,  相似文献   

15.
This book is a collection of papersfrom the major researchers involved in physiological, molecularand genomic research on bryophytes, mainly, although not exclusively,using the moss Physcomitrella patens. This is a growing areaof research and the book aims to provide ‘... a synopsisof the outstanding basic research being conducted using mossesas a model multi-cellular eukaryote’. Bryophytes (mosses, liverworts and hornworts) are an importantand often neglected group  相似文献   

16.
Much of the primary vegetation at low altitudes has been greatly altered or destroyed by a long history of human activities. This is particularly true in eastern China, where low-altitude areas are now dominated by secondary forests or plantations. Altitudinal vegetation zonation of this region is often based on these secondary forests, resulting in seral vegetation with an obscure zonal sequence. Here, we deduced the potential climax vegetation according to the regeneration patterns of the dominant species of the secondary forests at low altitudes (below 1,000 m a.s.l.) on Mt. Tianmu (1,506 m a.s.l., 30°18′30″–30°21′37″N, 119°24′11″–119°27′11″E). Based on the potential climax vegetation combined with the floristic composition and community structure, three vegetation zones were identified, viz: (1) evergreen broad-leaved forest zone (400–950 m a.s.l.); (2) evergreen and deciduous broad-leaved mixed forest zone (950–1,100 m a.s.l.); (3) deciduous broad-leaved forest zone (1,100–1,506 m a.s.l.). The altitudinal vegetation zones identified in this study correspond with the thermal conditions on Mt. Tianmu. The distribution of vegetation on Mt. Tianmu was limited by lower temperatures in winter, and the altitudinal thermal vegetation zones on this mountain were more similar to the thermal vegetation of Japan than to that of China. The vertical distributions and roles of conifers were different between the eastern and the western regions along 30°N latitude in humid East Asia. Cryptomeria fortunei formed the emergent layer, towering above the broad-leaved canopy at middle altitudes as C. japonica on Yakushima, but disappeared at high altitudes with hydrothermal limitation on Mt. Tianmu.  相似文献   

17.
Chaffey  Nigel 《Annals of botany》2005,95(7):1253-1254
Over 40 years ago, in what is surelyone of the most famous ‘throw-away lines’ in botany,Ledbetter and Porter (1963) suggested that the similar orientationsof cytoplasmic microtubules and structures considered to becellulose microfibrils in the cell wall was not coincidental.This notion led almost single-handedly to the present and enduringinterest amongst certain plant cell biologists in understandingthe role of microtubules in wall formation. And as a resultof this intense interest in such matters, it has become clearthat microtubules are not only ‘just one’ componentamongst an ever-expanding array of  相似文献   

18.
The influence of storage conditions—temperature, moisturecontent, oxygen, nitrogen, and carbon dioxide—on dormancyin rice seed has been investigated. The effects of temperatureand oxygen when the seeds have been set to germinate have alsobeen studied. Storage in oxygen accelerates the breaking of dormancy; at lowertemperatures, the effect of oxygen is more noticeable. Carbondioxide and nitrogen have little or no effect except in so faras they exclude oxygen. It is shown that there is a negativelinear relationship between storage temperature and log. meandormancy period of intact seeds over the range 27°C. to47°C. In the variety tested, the Q10 for the rate of breakingdormancy is 3.38. Variation of moisture content over the range12.0–14.5 per cent, has little effect at 27°C. andno detectable effect at higher temperatures. When dormant seeds are soaked in water, they attain a moisturecontent close to 30 per cent. Pre-soaking seeds to achieve moisturecontents in this region can stimulate the breaking of dormancywhen compared with dry storage. At laboratory temperature (meanabout 27°C.) the stimulation caused by pre-soaking intactseeds is usually small and sometimes non-existent, but at alow temperature (3°C.) the stimulation is increased; butdry storage at 3°C. markedly delays the breaking of dormancy.When seeds are dehusked, a large proportion lose their dormancy.Much of the residual dormancy of dehusked seeds can be brokenby soaking at laboratory temperature. But in the sample of dehuskedseeds used, low temperature did not increase the effect of thepre-soaking, but slightly decreased the stimulation caused bythe soaking treatment in this case. The effect of temperature on wet seed has also been investigatedwhen the seed has been set to germinate. Maximum germinationof a partially dormant population of seed is achieved at anoptimum temperature which is near or somewhat below 27°C.In the sample tested, no germination occurred at 42°C.,although in populations which have completely broken dormancyfull germination will occur at this temperature. Non-dormantpopulations of rice seed can germinate at very low oxygen tensionsor probably even in the absence of oxygen, but germination ofa partially dormant sample is reduced under these circumstances.When oxygen tension is very low there is less germination at27°C. than at 37°C. In some varieties, at least, there is evidence that the seedsgo through a stage when they will germinate in daylight butnot in the dark. A simple practical method for rapidly breakingthe dormancy of intact seeds is described. The significanceof these results is discussed in relation to the published workon seeds of other species.  相似文献   

19.
The motto of the PhotosynthesisCongress in Brisbane in 2001 was that ‘photosynthesissimply sustains all life on Earth’. For this reason, photosynthesisis a large, well-researched area, so it is especially ambitiousto put together a handbook that attempts to cover the wholesubject. This volume is definitely not a handbook in the sensethat it provides a compendium for the novice, but instead itis a conspectus of areas of  相似文献   

20.
A new “reef ” of the serpulid polychaete Serpula narconensis Baird, 1885 is reported from the South Georgia Island shelf. This particular mass occurrence is the second serpulid “reef” reported in the Antarctic region. Its location, at 91- to 105-m depth, is very different from those serpulid reefs previously reported, usually sited at intertidal zone or at low depth, and this may be one of the largest, if not the largest, serpulid reef in the world. Accepted: 12 June 1999  相似文献   

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