Spiral Grain and Wave Phenomena in Wood Formation

It is widely recognized that spiral grain in trees severely reduces the value of sawn timber through warping and loss of strength, and that it also causes problems for other wood uses as diverse as transmission poles or plywood. Yet, paradoxically, there are highly valued grain patterns including wavy and interlocked grain, whose origins in the cambium invite direct comparison with those of spiral grain, so that many authorities believe them to be related phenomena. In recent years this concept has prompted extensive research into the anatomy, genetics, and physiology of all such grain patterns in wood. As a result it has become apparent that tree cambia provide excellent systems through which to study the origins of stem polarity and the complex processes of morphogenetic control in plants. Beside these and other pressing topics for research, the book examines methods of measuring grain deviations, and considers their influence on wood properties, on the economics of timber production, and on wood manufacturing.

Contenu
1 Defining Spiral Grain.- 1.1 Patterns of Spirality.- 1.2 Interlocked Grain.- 1.3 Wavy Grain.- 1.4 Other Growth Patterns.- 1.5 Conclusions.- 2 Measuring Grain Angle.- 2.1 Detection of Grain Angle.- 2.2 Sampling for Grain Angle.- 2.3 Methods of Measurement and Analysis.- 2.4 Measurement of Interlocked and Wavy Grain.- 2.5 Conclusions.- 3 Effects of Grain Angle on Wood Properties and Uses.- 3.1 Consequences of Anisotropy.- 3.2 Effects on Shrinkage.- 3.3 Effects on Wood Strength.- 3.4 Effect on Other Aspects of Wood Physics.- 3.5 Effect on Conversion, Use and Economics.- 3.6 Effect of Interlocked Grain.- 3.7 Effect of Wavy Grain.- 3.8 Conclusions.- 4 Spiral Grain in Relation to the Environment.- 4.1 Effect of Environmental Variables.- 4.2 Effect of Growth Rate.- 4.3 Balance of Controls.- 4.4 Effects of Silviculture.- 4.5 Advantages for Survival.- 4.6 Conclusions.- 5 Anatomy of Changing Grain Angles.- 5.1 The Role of Cell Structure.- 5.2 Cambium.- 5.3 Morphogenetic Events.- 5.4 Cambial Domains.- 5.5 Wave Aspects of Domain Structure and Function.- 5.6 Anatomy of Slow Changes.- 5.7 Conclusions.- 6 Genetics of Spiral Grain.- 6.1 Basic Requirements.- 6.2 Geographical Variation.- 6.3 Clonal Variation.- 6.4 Sexually Propagated Progeny.- 6.5 Modification of Genotypes.- 6.6 Heritability of Wavy and Interlocked Grain.- 6.7 Strategies for Tree Improvement.- 6.8 Conclusions.- 7 Physiological Aspects of Changing Grain Angles.- 7.1 Requirements.- 7.2 Polarity.- 7.3 The Role of Auxin.- 7.4 Other Factors.- 7.5 Conclusions.- References.