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1.
王文采   《广西植物》1995,15(2):189-192
(1)在各种花对称的分类中,Ehrendorfer的分类包括了被子植物花对称方面从原始到进化的各种类型,最为全面广德国学者Strasburer在1911年编著的第11版植物学教科书中将具2对称面的荷包牡丹属的花称为bilateral或disymmetrisch.这个类型代表了被子植物花的一种较进化的构造,应该予以肯定。由于被指定为描述具2对称面的花的术语bilateral与被指定为描述具丑对称面的花的术语bilaterallysymmetrical颇为相似,而易引起混淆.为避兔发生混淆.建议不再应用这二术语.在描述具2对称面的花时,选用disymmetrical,中文译为双面对称的,在描述具1对称面的花时,选用zygomorphic(左右对称的)或monosymmetrical,后者的中文可译为单面对称的。(2)赞同将术语tepal译为花被片,而不赞同译为“被片”。  相似文献   

2.
Bayne T  Kolers A 《Bioethics》2003,17(3):221-242
What is it that makes someone a parent? Many writers – call them ‘monists’– claim that parenthood is grounded solely in one essential feature that is both necessary and sufficient for someone's being a parent. We reject not only monism but also ‘necessity’ views, in which some specific feature is necessary but not also sufficient for parenthood. Our argument supports what we call ‘pluralism’, the view that any one of several kinds of relationship is sufficient for parenthood. We begin by challenging monistic versions of gestationalism, the view that gestation uniquely grounds parenthood. Monistic and necessity gestationalism are implausible. First, we raise the ‘paternity problem’– necessity gestationalists lack an adequate account of how men become fathers. Second, the positive arguments that necessity gestationalists give are not compelling. However, although gestation may not be a necessary condition for parenthood, there is good reason to think that it is sufficient. After further rebutting an ‘intentionalist’ account of parenthood, in which having and acting on intentions to procreate and rear is necessary for parenthood, we end by sketching a pluralist picture of the nature of parenthood, rooted in causation, on which gestation, direct genetic derivation, extended custody, and even, sometimes, intentions, may be individually sufficient for parenthood.  相似文献   

3.
Neil C. Manson 《Bioethics》2019,33(5):540-549
The biobank consent debate is one with deeply held convictions on both the ‘broad’ and ‘specific’ side with little sign of resolution. Recently, Thomas Ploug and Soren Holm have developed an alternative to both specific and broad consent: a meta‐consent framework. The aim here is to consider whether meta‐consent provides a ‘solution’ to the biobank consent debate. We clarify what ‘meta‐consent’ actually is (arguing that the label is a misnomer and ‘consent à la carte’ is more accurate). We identify problems with Ploug and Holm's arguments, and some challenges for meta‐consent. We focus on whether there is any ethical obligation to provide consent à la carte. There may seem to be so, especially if we draw upon an unclear appeal to the ethical significance of ‘respect for autonomy’. Similarly, there might seem to be an intuitive inference from the fact that ethically legitimate research requires informed consent to the conclusion that it thereby requires consent à la carte. It is shown that this line of inference is mistaken.  相似文献   

4.
This paper contains a game theoretical analysis of animal contest situations which are asymmetric in more than one aspect: two opponents may for example be imagined which differ in ‘ownership status’ as well as in ‘relative fighting ability’. The following question is analysed: which aspect may or must be used for conventional settlement in a population ‘playing’ an evolutionarily stable strategy (ESS)? The contestants are assumed to be fully informed about the asymmetric features. In particular, the assessment of relative fighting ability is supposed to be unambiguous and without cost. This assumption of perfect information allows for a decomposition of the ‘evolutionary game’ into sub-games. Therefore an easy procedure for calculating the ESS's can be presented, and simple models are analysed. It is concluded that payoff-irrelevant aspects may be used for conventional settlement of a conflict even if payoff-relevant asymmetric aspects also exist. One of the aspects may, however, be of such strong relevance that, no matter which ESS is played, animals must base their decisions on that ‘dominant’ aspect. It may also occur that two different asymmetric features are each of strong payoff relevance for either of the opponents, such that they have no escalation-suppressing effect. The particular scenario of a conflict between an ‘owner of a resource’ and an ‘intruder’ is used to derive the more general conclusions.  相似文献   

5.
Monoclonal antibodies to beet soil-borne virus   总被引:1,自引:0,他引:1  
Four monoclonal antibodies (MCA) were obtained to the ‘Ahlum’ serotype of beet soil-borne virus (BSBV). On ELISA plates which had been precoated with polyclonal antibodies (PCA) all four MCA detected this serotype with a higher sensitivity than alkaline phosphatase-labelled PCA. Three of the MCA were specific for the ‘Ahlum’ serotype, but a fourth one also detected the distantly related ‘Wierthe’ serotype. Cross-reactions with wheat soil-borne or oat golden stripe furoviruses were not observed. One of the MCA reacted with an epitope which is exposed along the entire length of the BSBV particles, whereas two others were specific for epitopes which are exposed on one particle extremity only. Although these latter two epitopes occur apparently on the same extremity of the particles, they seem to be different, because one is found only on the particles of the ‘Ahlum’ serotype, whereas the other one is present also on the particles of the ‘Wierthe’ serotype. The fourth MCA is specific for a cryptotope which is not exposed on the intact virus particles, but presumably on some degradation product or precursor of the viral coat protein present in crude sap preparations. All four epitopes are SDS-labile; they are not detected on denatured viral coat protein on Western blots.  相似文献   

6.
S. Ali  G. Bala  S. Bala 《Animal genetics》1993,24(3):199-202
A synthetic oligodeoxyribonucleotide probe (OAT36) comprising nine repeats of 5'GACA 3′ and several enzymes were used to analyse cow, (Bos taurus) and buffalo (Bubalus bubalis) genomes and a number of monomorphic loci were detected in both the species. Different animals from the same species showed an almost ‘similar’ monomorphic hybridization pattern but animals from two separate species showed a different ‘genome specific’ pattern. The overall hybridization with any enzyme and probe combination was found to be unique to one species. This forms the basis of genome specific hybridization which is substantiated by our zoo-blot hybridization studies. The evolutionary aspect of these loci in the context of sequence polymorphisms is discussed.  相似文献   

7.
We have earlier analysed ESSs for the amount of parental investment (PI) that offspring are expected to solicit from their parents, given that parents acquiesce to offspring demands. The present paper considers evolutionary retaliation by the parent for species where only one parent provides PI. Two genetic loci are envisaged: one (the ‘conflictor’ locus) determines the extent of offspring solicitation; the other (the ‘suppressor’ locus) determines how parents retaliate. Solicitation is assumed to carry a cost which may affect a particular offspring uniquely if time and energy are the major costs, or may affect all offspring in a brood equally if the main cost is predation risk. Two kinds of parental retaliation are possible. Parents may supply PI in proportion to offspring demands, or may ignore solicitation altogether and give a fixed PI. Analytical models of conflict in which the parent supplies PI in proportion to solicitation yield pure ESSs with PI at a compromise level between parent and offspring interests. These are termed ‘pro rata’ ESSs. Where solicitation costs are high, an ‘offspring wins’ ESS (offspring get all they ‘want’) is possible especially for forms of conflict that affect future sibs, and a ‘parent wins’ ESS (parent supplies its optimum) is possible especially for conflict that affects contemporary sibs. When parental retaliation takes the form of ignoring offspring solicitation, this can lead to a ‘parent wins’ ESS if costs of ignoring solicitation are negligible, but where parental insensitivity carries costs, the result is an unresolvable evolutionary chase with cycling frequencies of alleles coding for parent and offspring strategies. ‘Pro rata’ ESSs cannot be invaded by ‘ignore solicitation’ mutants but ‘pro rata’ mutants can often invade at certain stages in ‘ignore solicitation’ limit cycles. We therefore conclude that the probable evolutionary end product for most species will be the ‘pro rata’ ESS in which the parent supplies more PI than would be optimal in the absence of conflict, but less PI than would be an ESS for the offspring in the absence of parental retaliation. Such ESSs will be characterized by solicitation costs; offspring will ‘ask’ for more PI than they get. In nature, under similar conditions, highest conflict will occur when both parents sustain equally the effects of conflict, or when conflict affects contemporary rather than future sibs.  相似文献   

8.
A critical review is presented of studies in which (for one reason or another) physiological measures in individually-housed rats are contrasted with those of group-housed counterparts. Most studies seem to focus on adrenocortical activity; gonadal hormone secretion and estimation of localized putative neuro-transmitters. An attempt is made to link these factors and to correlate them with the well-documented behavioral changes seen in ‘isolated’ rats. It is concluded that it is possible that the changes in biogenic amines and hormones are related. It seems unlikely, however, that one can dismiss the physiological changes seen in individually-housed rats as ‘isolation stress’. Adrenocortical reactivity may be increased in ‘isolated’ rats and this may account for their apparent increased basal activity. It is concluded that there is a distinct lack of ‘in depth’ studies in this area.  相似文献   

9.
Correction methods currently used in ‘binding’ experiments have been compared and a new approach is proposed. These methods have been applied to data on the ‘binding’ of GABA to a ‘synaptosomal-mitochondrial’ fraction of rat cerebral cortex under various conditions. Results indicated that values for ‘corrected binding’ can differ greatly, depending upon the method employed. Calculations based on data obtained when using a high concentration of unlabelled GABA to displace ‘specific’ binding of [3H]GABA (‘cold ligand method’) under-estimated the binding, because this method neglects the existence of a biochemically-inert space which exists within the pellet even at 0°C and which traps labelled ligand. The other correction method, in which an inert labelled substance (e.g. sucrose) is used to measure the portion of the pellet occupied by trapped supernatant fluid (‘sucrose space method’), is more accurate, but does not take into account the amount of ligand that may be non-specifically bound to the particulate portion of the pellet. The error with this method is small for ‘high-affinity’ ligand-receptor systems, but may be quite large for lower affinity systems. A method which takes into consideration both the inert space of the pellet and ligand that is non-specifically bound to the pellet (‘fully corrected method’) is proposed. The three correction methods have been applied to a study of the kinetic parameters of GABA binding to a ‘synaptosomal-mitochondrial’ fraction of rat cerebral cortex in the presence and absence of the GABA inhibitor, bicuculline-methiodide. In some cases, the results showed qualitative as well as large quantitative differences, depending on the correction method employed.  相似文献   

10.
1. It is suggested that specific carbohydrate side-chains of membrane glycoproteins are the sites for cell recognition or adhesion when the terminal sugar, sialic acid, is absent. 2. It is suggested that sialic acid plays a ‘protective’ or ‘blocking’ role in cell interactions so that addition of sialic acid to asialo side-chains converts them to forms inactive for recognition. This principle of ‘blocking’ by sialic acid has been observed in other situations as in covering tumour antigens and in protecting glycoproteins from uptake by the liver. It is here extended to cell-cell adhesions. 3. It is to be expected that specific ‘protective’ actions of sialic acid in membrane-bound glycoproteins will be difficult to detect. As a charged residue, sialic acid is likely to have a strong influence both on the glycoproteins on which it is borne and on their interactions with each other at the cell surface. Removal of sialic acid by enzymes could therefore perturb the structure of the cell surface in several ways and so obscure the ‘protective’ effects of sialic acid. Sialic acid is therefore suggested to have a structural role also. 4. Evidence is assembled in favour of a model in which sialysation of specific adhesive receptors affects the social behaviour of cells. This may be an effect associated with growing cells since the contact properties of mitotic cells (and populations rich in dividing cells) are decreased by the increased sialysation of receptors. One of the factors associated with malignant behaviour could be that adhesive receptors are permanently blocked by sialic acid. 5. A schematic representation of some of the points is given in Fig. 4.  相似文献   

11.
Grafting almond variety ‘Garrigues’ onto ‘GF305’ peach seedlings heavily infected by Plum pox virus (PPV) progressively produces the disappearance of viral symptoms and drastically reduces virus accumulation in ‘GF305’ rootstock, in most cases to undetectable levels. This response appears to be specific between almond and peach, as it was not consistently observed by grafting ‘Garrigues’ onto other Prunus species such as plum (‘Adesoto’) or apricot (‘Real Fino’). The ability to induce resistance to PPV in ‘GF305’ was transmitted to the sexual descendants of Garrigues. Furthermore, grafting ‘Garrigues’ onto ‘GF305’ before PPV inoculation completely prevented virus infection, showing that the resistance is constitutive and not induced by the virus. This fact suggests that resistance may be due to the transfer of a defence factor from ‘Garrigues’ almond through the graft union and its interaction with specific factors of ‘GF305’ peach to produce the antiviral response. These results open new avenues to potential protection against PPV in peach, the most economically important species among stone fruits.  相似文献   

12.
Natural‘antibodies’are substances found in the blood of animals that have not been immunised against infective agents. However, exposure to these agents or to cross-reacting antigens may well have taken place. Fish contain naturally-occurring, relatively nonspecific, lectin-like proteins or glycoproteins, which are distinct from immunoglobulins, and which react with a wide variety of antigens and may confer some degree of immunity against natural infection. In most cases the cause of the antigenic stimulus is not obvious although the formation of these‘antibodies’may have been brought about by exposure to various micro-organisms. Many of these antibody-like molecules behave in a similar manner to immune antibodies or immunoglobulins and cross-react with specific carbohydrate moieties on the cell walls of bacteria, erythrocytes and certain other cellular antigens, due to the presence of similar antigenic determinants. It is difficult to ascribe an appropriate definition to the term‘natural antibody’. In fish, these‘antibodies’have been so designated on the basis of functional rather than structural criteria. Such naturally-occurring, low grade, antibody-like‘immune’substances include‘acute phase’proteins, lysozyme and chitinase, interferon, agglutinins, lysins, complement and properdin, precipitins, and non-immunoglobulin, lectin-like molecules. In addition to the above non-immunoglobulin materials, natural immunoglobulins identifiable as IgM have also been reported in fish. Furthermore, mucus contains many biochemical agents capable of reaction against infective organisms and thus providing the host with an immediate or a first line of defence mechanism. This review compiles some of the relevant information in the literature concerned with natural‘immune’substances, present in the serum and mucus of fish, involved in protection against pathogens. Wherever possible the basic physicochemical properties of these substances are indicated and their potential immunobiological functions discussed.  相似文献   

13.
This article examines the dominant heritage discourse in Cyprus concerning preservation and destruction, and its implications for ethno-cultural identity construction and promotion. By exploring two heritage sites (one north and one south of the Buffer Zone) it suggests that heritage practice is more complex than commonly presented. Specifically, it shows how ethnic conflict has not only been responsible for heritage destruction but also for the preservation of it as an unintended consequence of ‘freezing’ development. It also examines how ethnic groups and individuals may come to evaluate their ‘own’ heritage negatively, specifically as an inconvenient cultural load, in efforts to develop ideologically specific or socially ‘progressive’ identities.  相似文献   

14.
Understanding fluctuating selection is important for our understanding of patterns of spatial and temporal diversity in nature. Host–parasite theory has classically assumed fluctuations either occur between highly specific genotypes (matching allele: MA) or from specialism to generalism (gene‐for‐gene: GFG). However, while MA can only generate one mode of fluctuating selection, we show that GFG can in fact produce both rapid ‘within‐range’ fluctuations (among genotypes with identical levels of investment but which specialise on different subsets of the population) and slower cycling ‘between ranges’ (different levels of investment), emphasising that MA is a subset of GFG. Our findings closely match empirical observations, although sampling rates need to be high to detect these novel dynamics empirically. Within‐range cycling is an overlooked process by which fluctuating selection can occur in nature, suggesting that fluctuating selection may be a more common and important process than previously thought in generating and maintaining diversity.  相似文献   

15.
Naming systems play a prominent role in discussions of land tenure by Aboriginal people. Reference to one area of land and its owners is most commonly in terms of name ‘X’, whereas reference to another area of land and its owners is most commonly made in terms of name ‘Y’. Much of the analytical literature examines how these names refer to groups of people. There is considerable dispute as to whether the reference of these names suffices to determine disjoint groupings of owners that can be described by the term ‘clan’. This paper proposes that the analysis of linkages between names and areas of land should have priority over the analysis of linkages between names and groups of people. The evidence shows that the attachment of names to areas of land is more stable and consistent than their attachment to groups of people. There are differences in the ways that names attach to the landscape, and these differences are significant—they determine whether or not more than one name from the same system may be attached to an area of land. This paper focuses on two areas of Australia: the northern Kakadu‐Oenpelli area and the Timber Creek area (both in the Northern Territory). It shows that naming systems identify disjunctive areas of land as the targets for claims of primary ownership in both areas. These disjunctive areas may reasonably be described with the translation term ‘estates’. In the northern Kakadu‐Oenpelli area, corresponding to these estates, there are disjunctive groupings of owners, which may be termed ‘clans’. However, groupings of owners are not clearly disjunctive in the Timber Creek area, and there is little motivation for using the term ‘clan’. This paper proposes that this difference reflects a general pattern in Aboriginal Australia, with naming systems stably and consistently identifying ‘estates’ across much of the continent. They do not identify ‘clans’ with equivalent stability and consistency.  相似文献   

16.
Phaseolin type, determined by one-dimensional sodium dodecyl sulfate polyacrylamide gel electrophoresis, was used to suggest dissemination routes of common bean (Thaseolus vulgaris) cultivars from their areas of domestication to Europe and Africa. In the Iberian Peninsula, ‘C’ was the most frequent phaseolin type. Only in Chile has a comparably high ‘C’ frequency been observed previously, indicating that many Iberian cultivars may have been introduced from Chile, or that many Chilean cultivars may have come from the Iberian Peninsula. In Europe (outside the Iberian Peninsula), most cultivars exhibited a ‘T’ type. The high frequency of this type may be related to the high frequency of green pod cultivars among European cultivars. Most African cultivars exhibited a ‘T’ or a ‘C’ type and may have been introduced from Brazil, the Iberian Peninsula, or western Europe. ‘T’ or ‘C’ cultivars had larger seeds than ‘S’ cultivars. The phaseolin patterns of cultivars with different seed types and of early French cultivars are discussed.  相似文献   

17.
王伟  崔红   《广西植物》1999,19(4):381-385
简要综述两种光敏色素(PhyA、PhyB) 的分子特性、感光性及作用模式等方面的研究进展。光敏色素是一种调节植物中许多光反应的色素蛋白复合体。不同光敏色素分子具有特异的感光性。PhyA负责‘甚低辐照反应’和远红光‘高辐照反应’; 而PhyB则调节‘低辐照反应’及红光‘高辐照反应’。另外, 讨论了PhyA和PhyB在光周期感受中的作用。  相似文献   

18.
This paper argues that, while the demise of apartheid has led to many situations in which South Africans now come into closer contact with one another, this increased ‘contact’ does not amount to greater racial integration. Contact occurs within a context of unequal power relations in which ‘whiteness’ continues to be privileged over ‘blackness’. The result is that white people tend to benefit more from contact with the racial ‘other’ than black people, who often experience this contact as reinforcing their expectations of continued white dominance and privilege. While contact may undermine blatantly racist practices and overt racial conflict, racialized patterns of reasoning continue to exist, often unnoticed and unchallenged. These include the assumption that race is an incontrovertible fact of experience, the privileging of whiteness, the assumption that there exist different (biological) races which evince different forms of social behaviour and that these are essential properties of people rather than being historically or socially contingent.  相似文献   

19.
20.
Stem explants from winter grown tomatoes cultured on a cytokinin, auxin-free medium, developed one or two adventitious shoots at the top end of the explant. Addition of the auxin transport inhibitor. 2,3,5-triiodobenzoic acid (TIBA) to the medium stimulated caulogenesis with loss of polarity. Callus, initiation in pelargonium and ‘geranium’ petiole explants requires both auxin and cytokinin. On transfer, after callus induction to an auxin-free medium, rhizogenesis occurs in pelargonium cultures followed by caulogenesis. Few shoots develop and unless these are removed, further caulogenesis is suppressed. Bud-like structures were formed in the callus. Subculture on auxin-free medium containing cytokinin and TIBA resulted in shoot formation from these bud-like organs. An analogy with apical dominance is suggested. In ‘geranium’ callus, shoots developed with a low frequency (c. in 2% of the cultures): caulogenesis was increased to 80% when calli were subcultured from auxin-free, cytokinin medium after green nodule formation to cytokinin-TIBA medium. Histological studies of green nodules in ‘geranium’ callus indicated a variation in morphological development within and between nodules. It is suggested that auxin synthesis may occur at some microscopic stage in morphogenesis in ‘geranium’ cultures which suppresses further caulogenesis. This may be overcome by the addition of TIBA to the medium at the appropriate stage in morphogenesis. The possible interaction of endogenous auxin in morphogenesis is discussed.  相似文献   

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