ISSN:0044-5983    

DOI:10.1111/j.1438-8677.1995.tb00789.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

ISSN:0044-5983    

DOI:10.1111/j.1438-8677.1995.tb00790.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

SUMMARYThis paper reviews the occurrence of biomacromolecules in fossil plants and animals. The range of techniques used in their release, preparation, microscopy and chemical analysis is described, as is the role of decay experiments in their investigation. The major plant parts that include resistant macromolecules are discussed: algal cell walls, cuticles, spore and pollen walls, propagules, periderm, secondary xylem, and secretions. The chemistry of animal cuticles preserved in the fossil record is briefly considered; they may incorporate macromolecules of plant origin during diagenesis. Some future directions for research are outlined: characterization of sporopollenin, characterization of extant and extinct tissues and organs, chemosystematic investigations, taphonomic processes, investigation of biomacromolecules in animal fossils.

ISSN:0044-5983    

DOI:10.1111/j.1438-8677.1995.tb00791.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

SUMMARYMolecular ecophysiology aims at understanding ecological adaptations at the level of molecules, andvice versa, the role of molecules in the ecological comportment of whole organisms. Hence, it continuously moves up and down a ladder of systems characterized by different levels of scaling like ecosystems and habitats, whole organisms, organs, tissues and cells, membranes and molecules.Membranes with controlled transport mechanisms are essential for the separation from and contact with the environment. The vacuole of plant cells is an intermediary or permanent sink for solutes which are resources in metabolism or waste compounds. Therefore, the transport molecules of the tonoplast—the membrane separating the vacuole from the cytoplasm—play a key role in stress responses.Among the membrane‐transport enzymes of the tonoplast the H+‐pumping V0V1‐ATPase has been characterized structurally and functionally, and it has recently been recognized as an enzyme both serving stress responses and undergoing stress‐related modifications. Therefore, we call it an ‘eco‐enzyme’. We define an eco‐enzyme as an enzyme which shows ecophysiological reactions by (i) mediating adaptations (i.e. in contrast to a house‐keeping enzyme), and (ii) undergoing modification itself (i.e. in contrast to a stress enzyme).The H+‐pumping tonoplast pyrophosphatase is known structurally, but its function in the whole plant remains enigmatic and therefore also its role in ecophysiology.Secondary‐active transporters are known to occur and to be essential in stress responses, but their molecular identity and therefore their precise role in molecular ecophy

ISSN:0044-5983    

DOI:10.1111/j.1438-8677.1995.tb00792.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

SUMMARYThis paper focuses on phenotypic plasticity as a major mode of adaptation in plants. A methodological critique examines difficulties in studying plasticity, including the conceptually critical distinction between functionally adaptive and inevitable aspects of response. It is argued that plasticity studies depend critically upon the genotypic sample, the choice of environmental factors and factor states, and the definition of phenotypic traits. Examples are drawn from recent studies showing adaptive response by genotypes to physical aspects of the environment, as well as to biotic factors such as neighbour density and the presence of bacterial symbionts. Alterations of offspring traits by parental plants ofPolygonum persicariaare discussed as a cross‐generational aspect of plastic response to environment. Finally, individual plasticity and local ecotypes are examined as alternative bases of species ecological breadth, and methodological problems in distinguishing these alternatives are discusse

ISSN:0044-5983    

DOI:10.1111/j.1438-8677.1995.tb00793.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

SUMMARYThe hermaphroditism of most plants and their reliance on vectors for pollen dispersal complicates mating patterns in comparison with most animal groups. Since Darwin's early work there has been considerable interest in the causes and consequences of self‐ and cross‐fertilization in plant populations. Most research on this topic has been ahistorical in perspective and conducted almost exclusively within a selectionist framework. It is suggested that a broadened view encompassing both micro‐ and macroevolutionary analysis is necessary for a comprehensive understanding of how and why mating systems evolve from one state to another. An attempt to illustrate the diverse approaches that can be used in studying mating‐system evolution in flowering plants is presented using the heterostylous, aquatic genusEichhorniaas a model system. Evidence from molecular phylogenetic reconstruction, large‐scale surveys of geographical variation and manipulations of experimental populations are used to address the issue of how often the shift from outcrossing to selfing has occurred and what evolutionary mechanisms are involved. Results indicate that selfing has originated on several occasions in the genus and that interactions between genetic drift and natural selection cause destabilization of heterostyly and the evolution of predominant self‐fertilization. It is argued that geographical patterns of intraspecific variation in reproductive traits are likely to provide the critical link between micro‐ and macroevolutionary approaches to the study of plant m

ISSN:0044-5983    

DOI:10.1111/j.1438-8677.1995.tb00794.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

SUMMARYThe ‘natural system’ of organisms reflects their phylogenetic relationship. It is the result of an historical process and has to be inferred from the available evidence. In the morphological phenotype, historical traces are intermeshed with functional adaptations. Overall similarity, even if quantified, can be a misleading indicator of relatedness. Cladistics uses shared derived character states (synapomorphies) to identify groups of common ancestry. Synapomorphies are mostly inferred from their taxonomic context. If apparently equally valid characters suggest mutually exclusive groups, parsimony is invoked: a phylogenetic reconstruction requiring a minimum of evolutionary steps to describe the present character distribution is accepted as the most likely one. Cladistics sets very stringent requirements for informative characters, and a rigorous analysis of morphology is likely to yield very few reliable characters. The direct analysis of DNA sequences provides theoretically the optimal evidence for phylogenetic reconstruction. In practice, very little of this information is readily accessible. Occasionally major sequence rearrangements can be unequivocal synapomorphies. Many phylogenetic problems can be solved by comparative sequencing of an appropriate segment of DNA. Comparative sequencing of the chloroplast generbcL has become the model for such studies. Molecular data have confirmed much traditional taxonomy, elucidated doubtful cases and corrected misinterpretations. Molecular data also have clearly shown the limits of the cladistic approach by revealing both known and previously unsuspected modes of reticulate evolution. Molecular approaches separate phylogenetic reconstruction from biological evaluation and will never replace morphological analysis in Systematics. However, molecular methods also facilitate the direct investigation of morphological evolution by revealing the genetic basis of morphogenesis in model systems or by permitting the genetic analysis of diagnostic character changes by genetic mapp

ISSN:0044-5983    

DOI:10.1111/j.1438-8677.1995.tb00795.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

SUMMARYThe processes of plant domestication and evolution are considered to have different objectives and are therefore treated as different. However, they are not independent. The dependence is discussed in terms of a contribution of the results of domestication to evolution and a contribution of knowledge about the included mechanisms. Reproductive isolation can be developed in the framework of domestication, and cultigens such asTriticum aestivum, Solanum tuberosum, Coffea arabicaandVicia fabaare treated as species in the evolutionary sense. Newly obtained character combinations as a result of plant breeding can be transferred to natural populations by means of hybridization. Several methods for analysing the rate of gene flow are discussed. The study of the occurrence of horizontal gene transfer in nature is stimulated by the development of the technique of genetic modification in biotechnologic research. Presumed cases of transfer of genetic material between unrelated Angiosperms are based on phylogenetic inconsistencies between gene trees and species trees, although evidence on the vector involved in nature is not available.

ISSN:0044-5983    

DOI:10.1111/j.1438-8677.1995.tb00796.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

SUMMARYThe floral ontogeny ofNeurada procumbensL. has been investigated to clarify the position of the family Neuradaceae and to elucidate a number of morphological problems, such as the nature of the epicalyx and the 10‐carpellate gynoecium. Morphological and ontogenetic evidence suggests a close affinity with the Rosaceae, contrary to reports ofrbcL sequence data. There is a strong gynoecial resemblance with Maloideae, but other characteristics suggest that the affinities of Neuradaceae lie at the base of the Rosacea

ISSN:0044-5983    

DOI:10.1111/j.1438-8677.1995.tb00797.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

SUMMARYIn a laboratory experiment the variation in plasticity of traits and trait mean values among populations ofSaxifraga osloensiswas examined.S. osloensisis a winter annual plant of allopolyploid origin, endemic to Scandinavia. Five populations from different parts of the species distribution range were grown in three treatments, differing in temperature and water availability. Most traits were plastic in response to the treatments. The pattern of plasticity varied among the populations, as well as the mean values of the traits. There was some correspondence in differentiation between the trait mean values and the plasticity of the traits. The pattern of differentiation was consistent with geographical distances between the populations. Correlation coefficients between traits were estimated for all populations. The start of flowering was correlated to the initial growth rate. The production of capsules and the number of seeds per capsule were not dependent on any of the other measured traits. There were no indications of buffering of reproductive traits by plasticity in other traits. The results are discussed in relation to local weather conditions at the population sites, but no consistent conclusions about environmental adaptation can be drawn.

ISSN:0044-5983    

DOI:10.1111/j.1438-8677.1995.tb00798.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY