Table Of ContentContributors to Volume I
MARY BELLE ALLEN
L. R. BLINKS
M. S. BLOIS, JR.
WINSLOW R. BRIGGS
STIG CLAESSON
RODERICK K. CLAYTON
ARTHUR C. GIESE
J. WOODLAND HASTINGS
STERLING B. HENDRICKS
M. LOSADA
A. D. MCLAREN
HEMMING I. VIRGIN
E. C. WEAVER
F. R. WHATLEY
PHOTOPHYSIOLOGY
Edited by
Arthur C. Giese
Department of Biological Sciences
Stanford University, California
Volume I
General Principles; Action of Light on Plants
1964
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LIST OF CONTRIBUTORS
Numbers in parentheses indicate the pages on which the author's contribution
begins.
MARY BELLE ALLEN, Kaiser Foundation Research Institute, Laboratory
of Comparative Biology, Richmond, California (83)
L. R. BLINKS, Hopkins Marine Station of Stanford University, Pacific
Grove, California (199)
M. S. BLOIS, JR., Biophysics Laboratory, Stanford University, Stanford,
California (35)
WINSLOW R. BRIGGS, Department of Biological Sciences, Stanford Uni-
versity, Stanford, California (223)
STIG CLAESSON, Institute of Physical Chemistry, University of Uppsala,
Uppsala, Sweden (19)
RODERICK K. CLAYTON, C. F. Kettering Research Laboratory, Yellow
Springs, Ohio (155)
ARTHUR C. GIESE, Department of Biological Sciences, Stanford Univer-
sity, Stanford, California (1)
J. WOODLAND HASTINGS, Biochemistry Division, University of Illinois,
Urbana, Illinois (333)
STERLING B. HENDRICKS, Mineral Nutrition Laboratory, Agricultural Re-
search Service, U. S. Department of Agriculture, Beltsville, Mary-
land (305)
M. LOSADA, Department of Cell Physiology, University of California,
Berkeley, California (111)
A. D. MCLAREN, College of Agriculture, University of California,
Berkeley, California (65)
HEMMING I. VIRGIN, Department of Plant Physiology, University of
Gothenburg, Gothenburg, Sweden (273)
E. C. WEAVER, Department of Plant Biology, Carnegie Institute of
Washington, Stanford, California (35)
F. R. WHATLEY, Department of Cell Physiology, University of Cali-
fornia, Berkeley, California (111)
v
PHOTOPHYSIOLOGY—PHYSIOLOGY OF PHOTIC
REACTIONS OF ORGANISMS
Preface
Photophysiology,* as here conceived, is a study of the physiology of
action of non-ionizing radiations (ultraviolet visible and infrared) upon
living things. Photobiology is a more inclusive term and has come to
mean any studies on the action of non-ionizing radiations upon organ-
isms (e.g., Pincussen, 1930), while the more inclusive field of radiation
biology considers the action upon life of all types of radiations, both
non-ionizing and ionizing (e.g., gamma and X-rays, alpha particles, elec-
trons and neutrons), the latter branch sometimes being called radio-
biology. The focus of the book is upon the fundamental mechanisms by
which non-ionizing radiations affect the living cell, at the molecular
level when such analysis is possible.
It is self evident that not all of the subject matter in photophysiology
can possibly be documented in the space of this book. Rather, the topics
have been selected to illustrate the principles of photophysiology, although
by this very selection some interesting subjects will have been omitted.
For completeness, references to these are given whenever possible.
Intensive researches on radiation biology have resulted in appearance
of many good books which treat various aspects of photobiological mate-
rial. However, a need was felt for a book which introduces and develops
some of the major themes of photophysiology. The original literature
has now become sufficiently complex and extensive to justify such an
introduction. If this account serves to stimulate others to participate in
studies of photobiological problems the aims of the book will have been
achieved.
The chapters in the present volume begin with an outline of the
principles of photochemistry (Chapter 1), and continue with basic
mechanisms which underlie action of light on chemical and biological
systems (Chapters 2, 3, 4). Then are considered photochemical and
* I am indebted for the title to Professor L. R. Blinks who, during a conversation
concerning a suitable title to cover the subject matter of the book, said: "We have
such terms as electrophysiology and neurophysiology, why not photophysiology"?
This title seemed most apt of the many considered.
vu
Vlll PREFACE
physical aspects of photosynthesis, accessory pigments in photosynthesis
(Chapters 5, 6, 7), phototropism and other photoreactions in plants
(Chapters 8, 9), photoperiodicity in plants and animals (Chapters 10,
12), the role of light in diurnal rhythms (Chapter 11), phototaxes
(Chapter 13), photoreception and vision in animals (Chapters 14, 15,
16), action of ultraviolet radiation on animal cells (Chapter 17), muta-
genic action of light (Chapter 18), photoreversal of ultraviolet damage
by visible light (Chapter 19), and the photochemistry of nucleic acids
(Chapter 20). The final chapter deals with the production of light by
organisms (bioluminescence).*
Because this treatise on Photophysiology grew beyond its intended
size it became necessary to subdivide it arbitrarily into two parts, but
the two volumes must be looked upon as forming an integral unit.
Volume I is concerned primarily with action of light upon plants, Volume
II mainly with effects of light upon microorganisms and animals. General
concepts and methods are introduced at the beginning of the treatise and
are further developed in each of the volumes.
The Editor takes this opportunity to thank the contributors who
cooperated in minimizing delays which accompany an extensive enter-
prise of this sort and the publishing staff who facilitated its production.
ARTHUR C. GIESE
Stanford University
October, 1963
* Because in the extensive literature referred to coenzymes I and II are abbrevi-
ated DPN and TPN (di- and triphosphopyridine nucleotide, respectively), some of
the authors contributing to this treatise prefer these abbreviations to the more
recently adopted synonyms NAD and NADP (nicotinamide-adenine dinucleotide
and nicotinamide-adenine dinucleotide phosphate, respectively).
CONTENTS OF VOLUME II
ANIMAL PHOTOPERIODISM
ALBERT WOLFSON
PHOTOTAXIS IN MICROORGANISMS
RODERICK Κ. CLAYTON
THE PHOTORECEPTOR PROCESS IN LOWER ANIMALS
DONALD KENNEDY
VISION AS A PHOTIC PROCESS
W. A. H. RUSHTON
THE PHYSICAL LIMITS OF VISUAL DISCRIMINATION
H. B. BARLOW
STUDIES ON ULTRAVIOLET RADIATION ACTION UPON ANIMAL CELLS
ARTHUR C. GIESE
MUTAGENIC EFFECTS OF ULTRAVIOLET AND VISIBLE LIGHT
G. ZETTERBERG
PHOTOREACTIVATION OF ULTRAVIOLET DAMAGE
CLAUD S. RUPERT
PHOTOCHEMISTRY OF THE NUCLEIC ACIDS
KENDRIC C. SMITH
BIOLUMINESCENCE—PRODUCTION OF LIGHT BY ORGANISMS
AURIN M. CHASE
AUTHOR INDEX—SUBJECT INDEX
Xlll
HISTORICAL INTRODUCTION
Arthur C. Giese
From the beginning of time man has stood in awe of the sun. The
very word radiation, in fact, stems from Aton Ra, the Egyptian sun god,
and the Egyptians depicted the rays of the sun ending in hands holding
the symbol of life (Menzel, 1959; Hawkes, 1962). The Persians had a
sun god, the Greeks have left us the legend of Helios, and in England
and Brittany are found the ruins of Druid temples to the sun. In the
New World, the Aztecs and the Incas worshipped the sun, as did many
primitive Indian tribes, such as the Dakotas (Oleott, 1914). It is not
surprising, therefore, that we should find an early interest in the nature
of the effect of sunlight upon life.
While the ancient Greeks and Romans probably built solaria pri-
marily for pleasure, a quotation from Herodotus tells us that "Ex-
posure to the sun is eminently necessary to those who are in need of
building themselves up and putting on weight. . . ." Jewish physicians
in Arabia recommended sunbaths for health, as did Avicenna in the
tenth century. Today, the cult of sunbathing persists all around the
globe. The initial reddening and the subsequent tanning of the human
skin after exposure to the sun is evidence to everyone that the sun has
photobiological effects, while a sunburn from excessive exposure empha-
sizes the destructive action of sunlight on living cells in the skin. The
development of photobiology and the analysis of the effects of light
upon the living cells, however, has been slow because our knowledge of
the very nature of light and its action in physical systems is also of
very recent date.
That nonvisible as well as visible light exists in the spectrum of the
sun came to general knowledge only after Herschel in 1800 discovered
light of wavelengths longer than red light (infrared light)* by the warm-
ing of a thermometer placed in a spectrograph beyond the red end of the
spectrum. The following year Ritter discovered ultraviolet light by its
photochemical action on silver chloride placed in a spectrograph beyond
the violet end of the spectrum. It was much later—in fact, only with
1 Claims have been made that infrared rays and radio waves have specific
effects upon cells, apart from heating. However, more careful studies indicate that
regardless of the means by which the temperature is achieved—provided the same
temperature is reached at the same rate—the effect is the same whether the cells
are heated directly or by radio waves (see discussion in Giese, 1947).
1
2 HISTORICAL INTRODUCTION
the development of radio astronomy during World War II—that the
sun was also recognized as a source of radio waves.1 Current rocket
research indicates that some ionizing radiations also come to the earth
from the sun (Menzel, 1959).
1. The Development of Photochemistry
Although Vitruvius reported the bleaching of pigments by light in
30 B.C., and at the end of the Middle Ages some experiments of a photo-
chemical nature were performed, it is often said that photochemical
studies as such began only about two centuries ago when Scheele (1742-
1786) found that the blackening of silver salts occurred most rapidly
in the short end of the sun's spectrum, a study further continued in 1827
by J. H. Schulze, professor of medicine at Altdorf, Switzerland. Senebier
(1742-1809) studied the bleaching of plant pigments under the in-
fluence of sunlight. Berthollet observed the decomposition of chlorine
water in sunlight in 1785, and de Saussure utilized this discovery in
1796 in making the first chemical actinometer for measuring light in-
tensity (see Dhar, 1931).
A large number of workers in the early nineteenth century studied
the effect of light on the reaction between chlorine and hydrogen, studies
which were to play an important role in the development of photo-
chemical concepts. Davy in 1812 studied the photochemical formation
of phosgene gas from carbon monoxide and chlorine, and emphasized the
reducing action of the more refrangible (shorter) wavelengths of light.
Also, the discovery of practical photography as a result of the experi-
ments of Niepce and Daguerre between 1814 and 1830, gave great
impetus to photochemistry. In 1818 Grotthus formulated the photo-
chemical absorption law which states that only the radiations which
are absorbed are effective in promoting a photochemical change. This
relationship, which has sometimes been called the first law of photo-
chemistry, was experimentally supported by the studies of Draper in
1839—hence its name, the Grotthus-Draper law. Bunsen (1811-1899)
and Roscoe (1833-1915) performed their classical investigations of the
photochemistry of chlorine-hydrogen interaction and demonstrated that
when the product of the intensity and the exposure time was constant,
the photochemical effect was the same—a relationship called the Bunsen-
Roscoe reciprocity law or the second law of photochemistry. (This rela-
tionship had already been suggested without experimental proof by
Senebier back in 1788.)
Vogel in 1873 showed that silver salts which are sensitive only to the
shorter wavelengths in the visible spectrum (e.g., violet and blue) could
be sensitized or made susceptible to longer wavelengths (e.g., green and
HISTORICAL INTRODUCTION 3
yellow) by mixing them first with a variety of coloring matters. There
are only certain conditions under which this can occur and not all mix-
tures are effective—the absorbing chemical species must be able to
transfer the light energy to the nonabsorbing molecules (Dhar, 1931).
The concept of sensitizing a substance to longer wavelengths of light,
by introducing a material which absorbs these wavelengths of light, has
been of much interest to biology (e.g., in photodynamic sensitization).
It is difficult to trace the many pathways which photochemistry took
after interest began to center on the mechanism of individual photo-
chemical reactions. Improved techniques of study made it possible to
work with light of known wavelengths, and, by measuring radiations
with a photometer or actinometer, to define the laws governing light
absorption.
The Lambert and Beer law of absorption, published in 1855-1859,
states that the fraction of incident light which is absorbed by a substance
in solution is independent of the initial light intensity and increases pro-
portionally with increase in concentration of the substance. It is usually
important to determine whether a given material under study obeys this
law, since a deviation usually indicates complications in the reaction
under study and at the same time gives clues as to the nature of the
reaction.
The quantum law, developed by Planck in 1900, states that radiation
is emitted, not continuously, but in small units called quanta. The law
of photochemical equivalence, subsequently formulated by Starck and
Einstein (1908-1912), states that when one quantum of light is absorbed
per molecule (atom, ion, etc.) of absorbing substance, one light-activated
molecule (atom, ion, etc.) is produced (primary reaction). What this
light-activated molecule does thereafter depends upon its nature and its
environment. The molecule may re-emit the light (as resonant light at
the same wavelength, or as fluorescence at longer wavelengths), or it
may undergo a variety of secondary reactions such as isomerization,
polymerization, oxidation, photolysis, union with some other molecule,
etc., or it may pass its energy to another molecule (sensitization) which
in turn may undergo a reaction because of this energy. Emil Warburg
(1846-1931) emphasized the concept of quantum yield (the number of
molecules altered or reacted as a result of the absorption of one quan-
tum) , a concept which Bodenstein had also used in the early part of the
twentieth century to determine the quantum yield of various photo-
chemical reactions (see Kistiakowsky, 1928). Sometimes a chain reaction
takes place, in which the excitation obtained from light is successively
passed from one molecule to another, as a result of which as many as a
million molecules may react. For example, the quantum efficiency of the
