Chapter I: Preface

The author has had in mind a two-fold purpose in the preparation of this book. First, it is hoped that it may serve as a text or reference book for collegiate students of plant science who are seeking a proper foundation upon which to build a scientific knowledge of how plants grow. The late Dr. Charles E. Bessey, to whom I owe the beginning of my interest in plant life, once said to me: "The trouble with our present knowledge of plant science is that we have had very few chemists who knew any botany, and no botanists who knew any chemistry." This may have been a slightly exaggerated statement, even when it was made, several years ago. But it indicated a very clear recognition by this eminent student of plants of the need for a better knowledge of the chemistry of plant cell activities as a proper foundation for a satisfactory knowledge of the course and results of plant protoplasmic activities. It is hoped that the present work may contribute something toward this desired end.

Second, the purpose of the writer will not have been fully accomplished unless the book shall serve also as a stimulus to further study in a fascinating field. Even the most casual perusal of many of its chapters cannot fail to make clear how incomplete is our present knowledge of the chemical changes by which the plant cell performs many of the processes which result in the production of so many substances which are vital to the comfort and pleasure of human life. Studies of the chemistry of animal life have resulted in many discoveries of utmost importance to human life and health. It requires no great stretch of the imagination to conceive that similar studies of plant life might result in similar or even greater benefit to human life, or society, since it is upon the results of plant growth that we are dependent for most of our food, clothing, and fuel, as well as for many of the luxuries of life.

The material presented in the book has been developed from a series of lecture-notes which was used in connection with a course in "Phyto-chemistry" which was offered for several years to the students of the Plant Science Group of the University of Minnesota. In the preparation of these notes, extensive use was made of the material presented in such general reference works as Abderhalden's "Biochemische Handlexicon" and "Handbuch der Biochemischen Arbeitsmethoden," Oppenheimer's "Handbuch der Biochemie des Menschen und der Tiere," Czapek's "Biochemie der Pflanzen," Rohmann's "Biochemie," Frankel's "Descriptive Biochemie," and "Dynamische Biochemie," Euler's "Pflanzenchemie," and Haas and Hill's "Chemistry of Plant Products"; as well as of the most excellent series of "Monographs on Biochemistry," edited by Plimmer, several numbers of which appeared in print prior to and during the period covered by the preparation of these lectures. Frequent use was made also of the many special treatises on individual groups of compounds which are mentioned in the lists of references appended to each chapter, as well as of articles which appeared from time to time in various scientific journals.

Hence, no claim is made of originality for the statements presented herein, except in an insignificant number of studies of enzyme action, and of the possible physiological functions of certain specific compounds. The only contributions which the writer has felt qualified to make to this general subject are those of an intense personal interest in the chemistry of plant processes and a viewpoint with reference to the relation of chemical processes to vital phenomena which will be apparent as the various subjects are presented.

The text has been prepared upon the assumption that the students who will use it will have had some previous training in elementary inorganic and organic chemistry. A systematic laboratory course in organic preparations, such as is required of students who are preparing to become professional chemists, is not at all a necessary requisite to the understanding of the chemistry of the different groups of plant compounds as here presented; but it is assumed that the student will have had such previous training as is now commonly given in a one-year collegiate course in "General Chemistry," or a year's work in general inorganic chemistry followed by a brief course in "Types of Carbon Compounds" or "Elements of Organic Chemistry," such as is usually required of students who are preparing for advanced work in agricultural science, in animal or human nutrition, etc.

An attempt has been made to arrange the material in such a way as to proceed from simpler chemical principles and substances to those of more complex structures. This results in an arrangement of the groups to be studied in an order which is quite different than their biological significance might suggest. It is believed, however, that in the end a more systematic understanding and a more orderly procedure is obtained in this way than would result from the treatment of the groups in the order of their relative biological importance.

CONTENTS

INTRODUCTION PAGE

Development of biological science; characteristics of protoplasm;
plant and animal life, similarities and differences; protoplasmic
activity essentially chemical changes; objects of study of the
chemistry of plant life xiii-xvi

CHAPTER I--PLANT NUTRIENTS

Definitions; the plant food elements; available and unavailable
forms; the value of the different soil elements as plant foods;
functions of the different plant food elements in plant growth;
inorganic plant toxins and stimulants; references 1-15

CHAPTER II--ORGANIC COMPONENTS OF PLANTS

Plants as synthetic agents; types of changes involved in plant
growth; groups of organic compounds found in plants; physiological
use and biological significance defined; physiological uses of
organic groups 16-20

CHAPTER III--PHOTOSYNTHESIS

Definitions; physiological steps in photosynthesis; formaldehyde,
the simplest carbohydrate structure; the condensation of
formaldehyde into sugars; theories concerning photosynthesis;
the production of starches and sugars; references 21-29

CHAPTER IV--CARBOHYDRATES

Importance, nomenclature, and classification; groups of
carbohydrates; isomeric forms of monosaccharides; chemical
constitution of monosaccharides; characteristic reactions of
hexoses; the occurrence and properties of monosaccharides;
disaccharides; trisaccharides; tetrasaccharides; the relation of
molecular configuration to biochemical properties; polysaccharides,
dextrosans, levulosans, mannosans, and galactosans; physiological
uses and biological significance of carbohydrates; references 30-66

CHAPTER V--GUMS, PECTINS, AND CELLULOSES

Relation to carbohydrates; groups; the natural gums and pentosans;
mucilages; pectins; celluloses; physiological uses of celluloses;
references 67-75

CHAPTER VI--GLUCOSIDES

Definition; general structure; hydrolysis of the natural
glucosides; general properties; the phenol glucosides; the alcohol
glucosides; the aldehyde glucosides; the oxycumarin glucosides;
the cyanophoric glucosides; the mustard-oil glucosides; the pigment
glucosides; the digitalis glucosides; the saponins; physiological
uses; biological significance; references 76-93

CHAPTER VII--TANNINS

General properties; occurrence; chemical constitution; classes;
some common tannins; physiological uses; biological significance
of tannins in fruits; references 94-101

CHAPTER VIII--PIGMENTS

Types and classes; the chlorophylls, chemical constitution,
similarity of chlorophyll and hæmoglobin, properties of the
chlorophylls; the carotinoids, carotin, xanthophyll, lycopersicin,
and fucoxanthin; phycoerythrin and phycophæin; the anthocyans;
the anthoxanthins; the production of ornamental pigments in
flowers, etc.; the functions of pigments; references 102-123

CHAPTER IX--ORGANIC ACIDS, ACID SALTS, AND ESTERS

Chemical constitution; some common organic acids; physiological
uses of organic acids; biological significance of fruit acids and
esters 124-128

CHAPTER X--FATS AND OILS, WAXES, AND LIPOIDS

General composition; fats and oils, occurrence, chemical
constitution, acids which occur in natural fats, alcohols which
occur in natural fats, hydrolysis and synthesis of fats,
extraction of oils from plant tissues, identification of fats and
oils, physiological use; the waxes; the lipoids, lecithin, other
plant phosphatides, plant cerebrosides, physiological uses of
lipoids; references 129-145

CHAPTER XI--ESSENTIAL OILS AND RESINS

Definitions, classes, occurrence; the essential oils; the
resins; physiological uses and biological significance of
essential oils; references 146-150

CHAPTER XII--THE VEGETABLE BASES

Composition and groups; the plant amines; alkaloids; the purine
bases; the pyrimidines; the nucleic acids, composition and uses;
references 151-163

CHAPTER XIII--PROTEINS

Importance; general composition; amino-acids and peptid units;
individual amino-acids; composition of the plant proteins; general
properties of proteins; classification; differences between plant
and animal proteins; extraction of proteins from plant tissues;
synthesis in plants; physiological uses; references 164-180

CHAPTER XIV--ENZYMES

Reaction velocities; enzymes as catalysts; general properties;
extracellular and intracellular enzymes; chemical nature;
nomenclature and classification; occurrence and preparation;
general and individual enzymes; nature of enzyme action;
accelerators and inhibitors; coenzymes and antienzymes; zymogens;
physiological uses; further studies needed; references 181-201

CHAPTER XV--THE COLLOIDAL CONDITION

"Colloids" and "crystalloids"; the colloidal condition a
dispersion phenomenon; nomenclature and classification;
conditions necessary to the formation of sols; gel-formation;
general properties of colloidal solutions; suspensoids and
emulsoids; adsorption; catalysis affected by the colloidal
condition; industrial applications of colloidal phenomena;
natural colloidal phenomena; references 202-220

CHAPTER XVI--THE PHYSICAL CHEMISTRY OF PROTOPLASM

Heterogeneous structure of protoplasm; protoplasm a colloidal
gel; water; salts; osmotic pressure; surface boundary phenomena;
electrical phenomena; acidity and alkalinity; summary; vital
phenomena as chemical and physical changes; references 221-238

CHAPTER XVII--HORMONES, AUXIMONES, VITAMINES, AND TOXINS

External and internal stimulants; hormones; vitamines; auximones,
toxins 239-248

CHAPTER XVIII--ADAPTATIONS

General discussion; adaptations, accommodations, and adjustments;
chromatic adaptations; morphological adaptations; accommodations;
concluding statements 249-258

INDEX 259-268