THE DESIGN AND ANALYSIS OF EXPERIMENTS. By Oscar Kempthorne. New York, John Wiley and Sons, Inc., 1952. 631 pp. $8.50. This book by a teacher of statistics (as well as a consultant for \"experimenters\") is a comprehensive study of the philosophical background for the statistical design of experiment. It is necessary to have some facility with algebraic notation and manipulation to be able to use the volume intelligently. The problems are presented from the theoretical point of view, without such practical examples as would be helpful for those not acquainted with mathematics. The mathematical justification for the techniques is given. As a somewhat advanced treatment of the design and analysis of experiments, this volume will be interesting and helpful for many who approach statistics theoretically as well as practically. With emphasis on the \"why,\" and with description given broadly, the author relates the subject matter to the general theory of statistics and to the general problem of experimental inference. MARGARET J. ROBERTSON

The Design and Analysis of Experiments

Wood performs several essential functions in plants, including mechanically supporting aboveground tissue, storing water and other resources, and transporting sap. Woody tissues are likely to face physiological, structural and defensive trade-offs. How a plant optimizes among these competing functions can have major ecological implications, which have been under-appreciated by ecologists compared to the focus they have given to leaf function. To draw together our current understanding of wood function, we identify and collate data on the major wood functional traits, including the largest wood density database to date (8412 taxa), mechanical strength measures and anatomical features, as well as clade-specific features such as secondary chemistry. We then show how wood traits are related to one another, highlighting functional trade-offs, and to ecological and demographic plant features (growth form, growth rate, latitude, ecological setting). We suggest that, similar to the manifold that tree species leaf traits cluster around the 'leaf economics spectrum', a similar 'wood economics spectrum' may be defined. We then discuss the biogeography, evolution and biogeochemistry of the spectrum, and conclude by pointing out the major gaps in our current knowledge of wood functional traits.

Towards a worldwide wood economics spectrum

The colonization of land by plants appears to have coincided with the appearance of mycorrhiza-like fungi. Over evolutionary time, fungi have maintained their prominent role in the formation of mycorrhizal associations. In addition, however, they have been able to occupy other terrestrial niches of which the decomposition of recalcitrant organic matter is perhaps the most remarkable. This implies that, in contrast to that of aquatic organic matter decomposition, bacteria have not been able to monopolize decomposition processes in terrestrial ecosystems. The emergence of fungi in terrestrial ecosystems must have had a strong impact on the evolution of terrestrial bacteria. On the one hand, potential decomposition niches, e.g. lignin degradation, have been lost for bacteria, whereas on the other hand the presence of fungi has itself created new bacterial niches. Confrontation between bacteria and fungi is ongoing, and from studying contemporary interactions, we can learn about the impact that fungi presently have, and have had in the past, on the ecology and evolution of terrestrial bacteria. In the first part of this review, the focus is on niche differentiation between soil bacteria and fungi involved in the decomposition of plant-derived organic matter. Bacteria and fungi are seen to compete for simple plant-derived substrates and have developed antagonistic strategies. For more recalcitrant organic substrates, e.g. cellulose and lignin, both competitive and mutualistic strategies appear to have evolved. In the second part of the review, bacterial niches with respect to the utilization of fungal-derived substrates are considered. Here, several lines of development can be recognized, ranging from mutualistic exudate-consuming bacteria that are associated with fungal surfaces to endosymbiotic and mycophagous bacteria. In some cases, there are indications of fungal specific selection in fungus-associated bacteria, and possible mechanisms for such selection are discussed.

Living in a fungal world: impact of fungi on soil bacterial niche development⋆

Cellulose is the main polymeric component of the plant cell wall, the most abundant polysaccharide on Earth, and an important renewable resource. Basidiomycetous fungi belong to its most potent degraders because many species grow on dead wood or litter, in environment rich in cellulose. Fungal cellulolytic systems differ from the complex cellulolytic systems of bacteria. For the degradation of cellulose, basidiomycetes utilize a set of hydrolytic enzymes typically composed of endoglucanase, cellobiohydrolase and β-glucosidase. In some species, the absence of cellobiohydrolase is substituted by the production of processive endoglucanases combining the properties of both of these enzymes. In addition, systems producing hydroxyl radicals based on cellobiose dehydrogenase, quinone redox cycling or glycopeptide-based Fenton reaction are involved in the degradation of several plant cell wall components, including cellulose. The complete cellulolytic complex used by a single fungal species is typically composed of more than one of the above mechanisms that contribute to the utilization of cellulose as a source of carbon or energy or degrade it to ensure fast substrate colonization. The efficiency and regulation of cellulose degradation differs among wood-rotting, litter-decomposing, mycorrhizal or plant pathogenic fungi and yeasts due to the different roles of cellulose degradation in the physiology and ecology of the individual groups.

Degradation of cellulose by basidiomycetous fungi.

Brown-rot fungi such as Postia placenta are common inhabitants of forest ecosystems and are also largely responsible for the destructive decay of wooden structures. Rapid depolymerization of cellulose is a distinguishing feature of brown-rot, but the biochemical mechanisms and underlying genetics are poorly understood. Systematic examination of the P. placenta genome, transcriptome, and secretome revealed unique extracellular enzyme systems, including an unusual repertoire of extracellular glycoside hydrolases. Genes encoding exocellobiohydrolases and cellulose-binding domains, typical of cellulolytic microbes, are absent in this efficient cellulose-degrading fungus. When P. placenta was grown in medium containing cellulose as sole carbon source, transcripts corresponding to many hemicellulases and to a single putative β-1–4 endoglucanase were expressed at high levels relative to glucose-grown cultures. These transcript profiles were confirmed by direct identification of peptides by liquid chromatography-tandem mass spectrometry (LC-MS/MS). Also up-regulated during growth on cellulose medium were putative iron reductases, quinone reductase, and structurally divergent oxidases potentially involved in extracellular generation of Fe(II) and H2O2. These observations are consistent with a biodegradative role for Fenton chemistry in which Fe(II) and H2O2 react to form hydroxyl radicals, highly reactive oxidants capable of depolymerizing cellulose. The P. placenta genome resources provide unparalleled opportunities for investigating such unusual mechanisms of cellulose conversion. More broadly, the genome offers insight into the diversification of lignocellulose degrading mechanisms in fungi. Comparisons with the closely related white-rot fungus Phanerochaete chrysosporium support an evolutionary shift from white-rot to brown-rot during which the capacity for efficient depolymerization of lignin was lost.

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Genome, transcriptome, and secretome analysis of wood decay fungus Postia placenta supports unique mechanisms of lignocellulose conversion

Naturally durable heartwood: evidence for a proposed dual defensive function of the extractives

In recent years considerable progress has been made in elucidating wood decay mechanisms. This basic knowledge not only has the potential to develop alternative environmentally-benign wood preservatives, but may also impact other areas such as bioremediation and pulp and paper. This book will summarize the latest knowledge of the developments, potential impacts, and applications from some of the world's leading experts.

Wood Deterioration and Preservation: Advances in Our Changing World

Brown-rot fungal degradation of wood: our evolving view.

Development of environmentally-benign wood preservatives based on the combination of organic biocides with antioxidants and metal chelators.

Wood products used in exterior applications must be protected against biodeterioration by decay fungi, insects such as termites, and other organisms. Traditionally, wood products for residential or industrial applications have been protected by treatment with chromated copper arsenate (CCA) or older inexpensive organic biocides, but environmental and disposal concerns and governmental regulations have resulted in a rapid and dramatic worldwide shift to copper-based systems. The current development trend is towards employing totally organic biocides based on relatively benign and expensive agrochemicals, with continuing research directed towards developing non-biocidal methods to protect wood.

Darrel D. Nicholas

Papers

Naturally durable heartwood: evidence for a proposed dual defensive function of the extractives

Wood Deterioration and Preservation: Advances in Our Changing World

Brown-rot fungal degradation of wood: our evolving view.

Development of environmentally-benign wood preservatives based on the combination of organic biocides with antioxidants and metal chelators.

A brief review of the past, present and future of wood preservation