Table Of ContentSpringer Series in Wood Science
Editor: T. E. Timell
Martin H. Zimmermann
Xylem Structure and the Ascent of Sap (1983)
John F. Siau
Transport Processes in Wood (1984)
Robert R. Archer
Growth Stresses and Strains in Trees (1986)
w. E. Hillis
Heartwood and Tree Exudates (1987)
W E.Hillis
Heartwood and
Tree Exudates
With 47 Figures
Springer-Verlag
Berlin Heidelberg New York
London Paris Tokyo
Dr. W. E. HILLIS
CSIRO (retired)
Division of Chemical and Wood Technology
Bayview Avenue
Clayton, Victoria 3168, Australia
Series Editor:
T.E. TIMELL
State University of New York
College of Environmental
Science and Forestry
Syracuse, NY 13210, USA
Cover: Transverse section of Pinus lambertiana wood. Courtesy of Dr. Carl de Zeeuw,
SUNY College of Environmental Science and Forestry, Syracuse, New York
ISBN-13: 978-3-642-72536-4 e-ISBN-13: 978-3-642-72534-0
001: 10.1007/978-3-642-72534-0
Library of Congress Cataloging in Publication Data. Hillis, W. E. Heartwood and tree exudates.
(Springer series in wood science) Includes bibliography and index. 1. Heartwood. 2. Plant exudates.
3. Forest products. I. Title. II. Series. QK647.H55 1987 582.16'010425 87-4832
This work is subject to copyright. All rights are reserved, whether the whole or part of the material is
concerned, specifically the rights of translation, reprinting, re-use of illustrations, recitation,
broadcasting, reproduction on microfilms or in other ways, and storage in data banks. Duplication of
this publication or parts thereof is only permitted under the provisions of the German Copyright Law
of September 9, 1965, in its version of June 24, 1985, and of copyright fee must always be paid.
Violations fall under the prosecution act of the German Copyright Law.
© Springer-Verlag Berlin Heidelberg 1987
Solkover reprint of the hardcover I st edition 1987
The use of registered names, trademarks, etc. in this publication does not imply, even in the absence of
a specific statement, that such names are exempt from the relevant protective laws and regulations and
therefore free for general use.
2131/3130-543210
Preface
Why prepare a treatise on Heartwood and Tree Exudates? Why
consider both topics together? What approach should be taken in
their treatment?
The exudates were one of the earliest items of trade between
family, tribal, and racial groupings in prehistoric times. They became
used extensively as items for the manufacture of implements and as
commercial goods for illumination, for cosmetic, religious and
magical purposes. Later heartwood from various trees entered intra
and international trade for prestigious and religious buildings (when
cedars were used), for the furniture (e.g., ebony, mahogany) of the
nobility, for boats and vehicles. Consideration of their relevance to
anthropology, and to the origin of technological developments in
different primitive cultures, would satisfy a personal life-long interest.
Attention to such a topic is urgently needed now that the development
and destruction of land and forests is increasing and wiping out the
traces of earlier people to meet the demands of the rapidly enlarging
populations of today. The latter represents an even more urgent need.
Increasingly, mankind will depend on renewable,resources produced
at low energy cost. Forest products are one of these and the greater
demands for them will require their growth and utilization with
reduced loss and waste.
One of the major products of trees is heartwood, and one of the
main features of heartwood is the presence of extractives. The forma
tion of extractives - not only in heartwood but also in other tissues -
and of exudates can assist the resistance of trees to disease and insect
attack. Greater understanding of their formation and their role in tree
protection is needed if our remaining forests and the new plantations
are to be maintained in a healthy and productive condition. On the
other hand, lower amounts of extractives than normal would improve
the use of wood for some purposes. The choice offast-growing species
for intensively managed forests or plantations, of management
strategies and shorter growth cycles is resulting in greatly increasing
proportions of sapwood being provided commercially. It is desirable,
and in some cases necessary, to control that proportion and this
depends on an improved understanding of the factors regulating
heartwood formation.
Eucalypts and pines are being planted on increasing areas
throughout the world as fast-growing sources of fiber and wood. In
their native habitat of Australia, the most commonly mentioned cause
of degrade in eucalypts is that of kino veins or pockets. Accordingly,
VI Preface
because of the increasing importance of the Eucalyptus genus,
information on the occurrence, etiology, and structure of kino veins
and their effect on wood quality should be readily available. On the
other hand, the features controlling the formation of resin in conifers
is important, as these extractives and exudates are the source of
chemicals for value-added products. These and related features have
been considered in this book.
Studies concerning the formation of extractives are complex and
interrelated, and to assist work in these areas this treatise considers
different facets of established knowledge that appear relevant. It will
be seen that even in closely related fields, the same basic principles
have sometimes been studied in one area and conclusions drawn
without recognition of the contemporaneous and similar develop
ments in the other fields. Knowledge of a broad picture would provide
mutual support for studies in basic sciences and enable specialists to
perceive the overall relevance of their conclusions. The different
segments have been classified so as to assist future inclusion of
information that will develop total understanding. The details of most
facets are available elsewhere; the major aspects of their relevance are
discussed here.
Chemical studies alone will not provide the answer to heartwood
formation and neither will anatomical, cytological, or other studies.
An interdisciplinary concept of this complex field is needed, but this
has its own problems. It has been attempted on the advice of
Schrodinger (1945; quoted by Berlyn 1970) " ... the spread, both in
width and depth, of the multifarious branches of kn~wledge during
the last hundred odd years has confronted us with a queer
dilemma .... 1 can see no escape from this dilemma (lest our true aim be
lost forever) than that some of us should venture to embark on a
synthesis offact and theories, albeit with second hand and incomplete
knowledge of some of them - and at the risk of making fools of
ourselves."
Although the extractives of heartwood (and bark) usually differ in
chemical composition from those of the exudates from the same tree,
they are formed by the same basic processes. It was the study of
extractives by stalwarts in different countries that laid the founda
tions of organic chemistry and biochemistry, and a summary of that
development has been presented elsewhere (Hillis 1986). The tree can
arrange its physiology and biochemistry to produce, with astonishing
selectivity, single compounds of considerable complexity in great
purity or a suite of particular compounds for reasons that are not yet
understood. Examples of the variations and aberrations of heartwood
and exudate formation to illustrate these remarkable events were
gathered in various centers. These sample collections are now being
abandoned and with the disappearance of virgin and over-mature
forests will never again be available. Consequently, the general
applicability of theories developed from young trees of a few genera
cannot be tested.
Preface VII
Some of the complex compounds from trees could serve as
intermediates in the manufacture of industrial and commercial needs
and be obtained without the frequent waste and pollution which
accompanies chemical methods. The establishment of chemotaxo
nomy enables the prediction of suitable sources of these complex
compounds from extractives or exudates. Their collection on a scale
similar to that practised many years ago could provide employment
for rural communities in some societies if supplies can be maintained
and quality assured. Greater understanding of their biosynthesis
should result in the enhancement of the consistent production of
required compounds in the tree. The development of chemo
morphology will enable the study of the relevant tissues to discern
and define the physiological apparatus with which specific com
pounds are formed. Perhaps in the future some technological societies
will develop this knowledge so that the required compounds are
synthesized selectively in "biotrons" from simple carbohydrates by
means of enzymes and with little pollution. This book should provide
a step in that direction.
My. scientific interest in exudates, heartwood and extractives was
aroused in CSIRO and mainly in the Division of Forest Products
during its spectacular existence. I am indebted particularly to Stan
Clarke, Eric Dadswell and Margaret Chattaway for their encourage
ment during my early development of studies; I thank Warren
Hewertson for his support and the use of CSIRO facilities at the end.
I have benefited from discussions with numerous scientists, too many
to list, both in my own and in many other countries. I thank them for
their contributions to this field of study. I acknowledge the help and
encouragement of Tore Timell, the Editor of this Series, and the staff
of Springer-Verlag during the preparation of this book.
Melbourne, Australia W.E. Hillis
Spring 1987
Contents
1 Introduction
1.1 Prehistoric and Ancient Use. 1
1.2 Changing Uses of Forests. 2
2 Definitions and Descriptions
2.1 Introduction 4
2.2 Sapwood. 4
2.2.1 Definitions 4
2.2.1.1 Sapwood 4
2.2.1.2 Included Sapwood. 5
2:2.2 Area of Sapwood in Log Cross-Sections . 5
2.2.3 Variation of Area of Sapwood 7
2.2.3.1 In a Species. 7
2.2.3.2 In Different S'pecies 9
2.2.3.3 Due to Age of Tree 9
2.2.3.4 Due to Rate of Growth. 10
2.2.3.5 Due to Environment 11
2.2.4 Sapwood Contents 13
2.2.5 Discolored Sapwood 14
2.3 Intermediate Wood 14
2.3.1 Description 14
2.3.2 Occurrence 15
2.4 Transition Zone . 16
2.4.1 Definition . 16
2.4.2 Description 18
2.4.3 Occurrence 19
2.4.3.1 Heartwood Boundary Stain 20
2.5 Heartwood 21
2.5.1 Definition. 21
2.5.2 Description 21
2.5.2.1 Appearance . 21
2.5.2.2 Level of Maximum Area 24
2.5.2.3 Regular Heartwoods . 24
2.5.2.4 Irregular Heartwoods 27
2.5.2.5 Variations in Appearance. 33
2.6 Tree Exudates and Extracellular Materials 39
2.6.1 Definitions 39
2.6.1.1 Intercellular Secretory Spaces, Cavities, and
Shakes. 39
X Contents
2.6.1.2 Intercellular Canals 41
2.6.1.3 Pitch Tubules and Stones . 42
2.6.1.4 Pockets, Veins, and Streaks 42
2.6.2 Types of Exudate or Deposit. 45
2.6.2.1 Resin 46
2.6.2.2 Gum. 49
2.6.2.3 Kino . 50
2.6.2.4 Latex 51
2.6.2.5 Manna . 53
2.6.2.6 Amber . 53
2.6.2.7 Balsam. 53
2.6.2.8 Maple Sugar 54
2.6.2.9 Crystalline Compounds. 54
2.6.3 Rate of Formation 56
3 Historical Aspects
3.1 The Use of Durable Woods. 58
3.2 Exudates. 59
3.3 Varnishes and Lacquers 59
3.4 Gums 60
3.5 Tannins 61
3.6 Dyes. 61
3.7 Perfumes 62
3.8 Rubber. 64
3.9 Medicines 64
3.10 Lessons from History 65
4 Influence of Forestry Aspects
4.1 Variation of Heartwood Volume. 68
4.1.1 Heritability 69
4.1.2 Effect of Growth Rate and Crown Size 69
4.1.3 Influence of Environment 70
4.1.4 Influence of Injury and Health 71
4.2 Formation of Exudates. 71
4.2.1 From Bark and Wood 71
4.2.2 From Wood. 72
4.2.3 Addition of Stimulants 73
5 Chemical Features
5.1 Water and Gases 76
5.2 Inorganic Compounds 83
5.3 Storage Substances and Intermediates 86
5.4 Nitrogenous Compounds 90
5.5 Ethylene 92
5.6 Type of Extractives 95
5.6.1 Galactans and Cyclitols 96
Contents XI
5.6.2 Terpenoids 96
5.6.3 Fatty Acids and Related Compounds 99
5.6.4 Phenolic Compounds . 99
5.6.4.1 Simple Phenols and Phenolic Acids. 99
5.6.4.2 Lignans 100
5.6.4.3 Stilbenoids 100
5.6.4.4 Flavonoids 101
5.6.4.5 Quinones . 103
5.6.4.6 Polymerized Polyphenols 103
5.6.4.7 In Different Tissues 104
5.7 Amount of Extractives . 105
5.7.1 Position of Sample in the Tree 105
5.7.2 Effects of Rate of Growth. 111
5.7.3 Effect of Site 112
5.7.4 Genetic Differences . 113
5.7.5 Crystals. 114
5.8 Reagents for Heartwood Detection. 115
5.9 Exudates. 117
5.9.1 Resin. 117
5.9.2 Gum. 117
5.9.3 Kino. 118
5.9.4 Latex. 118
5.9.5 Manna 119
6 Biological Features
6.1 Sapwood..... 120
6.1.1 Wood Tissues 120
6.1.2 Lumen Volume 121
6.1.3 Deposition of Extractives on Wall Surfaces 121
6.1.4 Impregnation of Cell Walls 126
6.1.5 Parenchyma. . . 128
6.1.5.1 Volume. . 129
6.1.5.2 Cell Wall . 130
6.1.5.3 Cytology . 132
6.1.6 Respiration and Enzymes Activity 137
6.2 Transition Zone. . . . . 139
6.2.1 Seasonal Variations. 139
6.2.2 Appearance . . . . 139
6.2.3 Water Content. . . 140
6.2.4 Pit Aspiration and Tylosis Formation. 141 .
6.2.5 Cytology of Parenchyma Cells 144
6.2.6 Respiration . . . . . . 147
6.2.7 Enzyme Activity . . . . 147
6.2.8 Formation of Extractives 151
6.3 Heartwood. . . . . . . 153
6.3.1 Seasonal Formation . . 153
