دانلود کتاب Advances in Botanical Research, Vol. 12

Advances in Botanical Research provides an up-to-date source of information for students, lecturing staff and research workers in plant sciences. The topics discussed in Volume 12 span a wide area, ranging from the biochemical mechanisms involved in the light modulation of enzyme activity, to the phylogenetic significance of the dinoflagellate chromosome. This series specializes in articles evaluating particular areas of advanced botany and as such continues to be of interest to botanists in a variety of research areas. From the Preface: The changes in enzyme activity in green plants caused by the transition from light to dark are now regarded as important regulatory processes directing metabolism towards synthesis of sugars and storage compounds in the light, and their breakdown in the dark. Light affects chloroplast enzyme activity in a number of diverse ways, through alteration of stromal pH, ion and metabolite levels. However, there are also changes in activity in some enzymes that involve post-translation (probably covalent) modification of the enzyme protein, and these are generally referred to as 'light modulation'. In her article, Anderson reviews such plant enzyme systems, the biochemical mechanisms involved (probably by reduction of a disulphide bond), their potential molecular basis and the function of modulation in photosynthetic carbon metabolism. One of the most important developments in plant molecular genetics is the rapid improvement of our understanding of the nature and mechanisms of mutation induced by transposable elements. It is interesting to reflect that the origins of this lie in our fascination for variegated plants as horticultural curiosities! Because of our increasing interest in transposable elements for exploring the genetic origins of variation, or as systems for molecular biology and genetic engineering, the review of Plant Transposable Elements by the group at the Max-Planck Institute, K"ln (Nevers, Shepherd and Saedler) is particularly welcome. How transposons will be used to isolate genes known only for their phenotypic effects will be seen in the future. The unicellular dinoflagellates are major components of marine and freshwater ecosystems. Apart from their general ecological importance, there are a number of reasons why they are of interest to biologists. In this volume we consider two such aspects. The article by Sigee discusses the very high level of DNA possessed by these organisms, the particular configuration of their chromatin and their nuclear organisation. These are of phylogenetic significance, and to summarise the position as presented in Sigee's article, it now seems that dinoflagellates are to be regarded as true eukaryotes with some prokaryote features, and that probably they are 'primitive' rather than degenerate forms of more advanced ancestors. Algae that can produce toxins effective against animals are found in three of the eight algal divisions, including the dinoflagellates. Carmichael reviews various apsects of biology and chemistry of these chemically diverse toxins, some of which can exert potent effects on humans, and considers their potential natural role. Few ideas of such ecological roles appear to have been subject to critical experimentation, and this article should provide a framework for such future work.