Physiology of Plants and their Cells

463 Pages·1973·6.654 MB·English

by  James A. Goss and Peter P. Gray (Auth.)

About the Author
James A. Goss (Ph.D., University of California at Los Angeles) is
currently Associate Professor of Biology at Kansas State Univer-
sity and Treasurer of the Kansas Academy of Sciences. In the
interest of his work, Dr. Goss has travelled extensively through-
out the world and has written numerous articles, some of which
have appeared internationally. His research in plant physiology
has been sponsored by the U.S. Atomic Energy Commission, the
U.S. National Institute of Mental Health, and the Kansas Agri-
cultural Station. He has been awarded travel grants by the Ford
Foundation, the U.S. Agency for International Development, and
Sigma Xi. Dr. Goss has also held the positions of President and
Secretary of the Kansas State University Chapter of Sigma Xi.
Physiology of Plants
and Their Cells
James A. Goss
Division of Biology
Kansas State University
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Copyright© 1973, Pergamon Press Inc.
Library of Congress Catalog Card No. 72-77403
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Contribution No. 1047
Division of Biology and Kansas Agricultural Experiment Station
Printed in the United States of America
0-08 017036 6
Preface
THIS BOOK is only an introduction to a vast and interesting field of science,
plant physiology. It is also a very dynamic subject. Change is the keyword
and active research describes the activity of its adherents. One cannot
read all of the research reports published weekly on this subject through-
out the world. They are too numerous. In fact, it is not even likely that
one can keep up with the review articles. This change is exciting and
challenging. It is typical of our contemporary social and political life,
but it also means that our knowledge of plant physiology is so vast that
no text or set of books can entirely cover all of our knowledge of this
subject.
Although this book has been written as a text for a beginning course in
plant physiology, it will also be useful as a general reference for teachers
and scientists who have not studied plant physiology before but now
find themselves interested in certain aspects of the field, and for students
of biology and agriculture who would like to know more about how the
plant functions.
As a text, this book has not been written for plant physiologists, but
rather for students who plan to use the knowledge of plant physiology to
help them in their life's endeavors in other fields. It is a known fact that
very few of the students enrolled in a beginning course in plant physiol-
ogy ever intend to become plant physiologists. Still, many introductory
courses are taught ignoring this fact. As a result, the student ends up with
a great deal of confusion but with little that will be of use to him in his
future.
Rarely, if ever, is there an introductory course in plant physiology
which is not composed of at least some undergraduate students. Even
when graduate students are present, it is the obligation of the instructor
to teach the course on a level that is understandable for the undergraduates.
xiii
xiv Preface
Most writers of such books as this ignore the fact, and are more con-
cerned about the potential plant physiologist, who comprises less than
10% of the class, and ignore the majority. This book does not.
It has often been said that truth does not change, but only our inter-
pretation of it. This is logical if truth is defined as that which is infallible
and unchanging. Man is continually striving to find truth, to know what
is true and what is not. However, he is plagued by the many inherent
limitations. These limitations affect his ability to know the truth even
when it exists.
The only world a man can really know is the world created for him by
his senses. The things he sees, feels, smells, tastes, and hears, are the
things he really knows. Everything else is merely symbolic, although
useful in helping to explain the phenomena revealed by his senses. As an
example, a seed can be kept under favorable environmental conditions
and soon it will germinate. We can observe it through various stages of
development including the seedling, maturity, reproduction, senescence,
and, finally, death. Our senses reveal the plant in these various stages, so
we are certain of this knowledge concerning it. However, a plant physiol-
ogist is not satisfied with this knowledge. He desires to explain the
causes of these phenomena, and as a result must revert to symbolism.
The chemical elements are merely symbols which allow chemists to
explain phenomena. We shall never know if they represent reality.
Perhaps other symbols would serve just as well.
And so the goal of the plant physiologist is to symbolically explain
the cause of the phenomenon of life in the plant world. We might say
that he is interested in knowing what makes the plant tick. His ultimate
goal is to be able to interpret plant behavior. Since he will probably
never truly know whether or not these symbols, which he uses to explain
a cause, represent reality, the best he can hope to achieve is to find an
arrangement of symbols (a theory or hypothesis) which infallibly explains
these phenomena. This is the source of disagreement over our theories.
This is why we often have several theories to explain the mechanism of a
phenomenon and why we cannot always agree on the right one.
Since this book is written to give the student a firm foundation of know-
ledge on which to base his future studies, weight is not given equally to
all theories. In fact, usually only the one which is most widely accepted
is given. This gives the student some confidence in what he is learning,
rather than leaving him in a state of confusion. This also gives the in-
structor an excellent opportunity to supplement the text, rather than to
repeat it, in his lecture or recitation sessions. Using the text as a basis,
Preface xv
he can build on the student's knowledge either by using the historical
approach to the subject to show how various theories have developed, or he
can use the experimental approach to show contemporary efforts that are
being made in the field, or he can compare alternate theories. The student
can, and should support the facts found in this book with his own obser-
vations, with supplemental reading, with laboratory experience where
possible, and with lectures given by qualified teachers and scientists.
However, be cautious to always keep the facts and hypotheses separated
when learning about contemporary research achievements. Facts seldom
change but hypotheses often do.
Plant physiology is a study of the living activity of the plant. It is the
study of what makes a plant function. It is a study of the nutrition of a
plant, of its metabolic activities, and of how this metabolism is regulated
to cause the plant to grow, flower, and to produce seeds and fruit. It is
the study of life itself. What could be more exciting? It can be a study that
will help the student understand how to grow better and larger plants, to
grow better flowers in his or her backyard, to get better yields from crops
even under adverse conditions, to help alleviate pollution, and to under-
stand why plants are so important in helping to solve many of the inter-
national problems with which we are faced at the present time. It will
help us to lead this world in the future on a path of happiness and prosper-
ity for all rather than to a state of impoverishment and starvation, from
which we can never recover.
I've enjoyed writing this book, and I hope that you, the reader, will
enjoy reading it.
I wish to offer my thanks to the many people who have helped make this
book a reality. First, to the many past and present researchers who have
discovered the facts presented in this book. Second, to my wife for typing
part of this manuscript and to her and my children Larry, Lynn, Linda,
Gerald, Liana, and Lori, for getting by without a husband and father for
so long while the manuscript was being prepared. I wish, too, to thank
Lillian Woolley for whose interest in writing stimulated my work on this
book, and to Ted Barkley for the encouragement needed from the admin-
istration at Kansas State University.
I wish to extend my appreciation to the many authors and publishers
who allowed me to use materials previously published. These will be
specifically acknowledged with the presentation of their material in this
book.
And last, but not least, I want to thank the staff at Pergamon Press for
the help and encouragement they extended me. Perhaps this list of people
xvi Preface
to whom I owe a great deal appears extensive, but success in any endeav-
or can only be accomplished by the help of many associates.
Division of Biology JAMES A. Goss
Kansas State University
Chapter The Plant Cell
One and Its Nutrition
VALUES OF PLANTS TO MAN
The assumption can be safely made that as long as man is on this earth
he will be interested in, and in need of, plants. They currently serve many
functions, such as food, drugs, raw materials for industry, shelter, as
ornamentals whereby they satisfy some aesthetic value, and as an aid in
the conservation of our natural resources.
Plants as Food
Within the next 50 years, plants will continue to serve as man's prin-
cipal source of food. Synthetic diets are currently being produced that
are changing and will continue to change our eating habits so that we may
become less dependent upon natural foods, but these dietary components
are themselves derived from plant materials. Of course, carbon dioxide
can be taken from the atmosphere and used by man to produce organic
chemicals that can be used for food, but the amount of energy required
and the expense involved do not make this a practical undertaking, nor is
there any hope of it becoming so in the future. Plants can produce foods
much more cheaply and more efficiently, so they will continue to be our
chief source of food and a great deal of research eifort will be devoted to
improving the plant and its environment. Plant breeding will develop
better plants; a more favorable use of fertilizers will be practiced; pesti-
cides will be improved and their use extended; supplemental irrigation
will be used more extensively and plant growth regulators of numerous
types will be developed and used.
ι
2 The Plant Cell and Its Nutrition
Plants as Drugs
The use of drugs has increased tremendously within the past century
and will continue to increase as rapidly, or more so, in the future, as the
world population increases and as the level of civilization continues to
rise in all countries. In the past, most of these drugs have come from
plants. This source has certain disadvantages, such as problems of
extraction and purification, so the future will find more synthetic drugs
produced. However, the basic chemicals from which these are synthe-
sized will largely come from plants.
Plants as Raw Materials
The uses of plant products as raw materials for industry certainly have
not declined. In spite of the fact that less coal is used today than in the
past, and less wood is being burned as fuel in the United States, the vast
interest in and use of plastics and similar polymers, which may be made
from plant products, more than compensate for the reduced use of
plants as fuel, and there are good reasons to anticipate even greater
demands for these polymers in the future. Also, the use of oil, a plant
product, has increased greatly.
Plants as Wood
The use of wood for construction has been extensive in the past and
will continue into the future. It is easy to work with, inexpensive, and a
good building material especially for areas where the building may be
subjected to stresses and strains, such as those due to earthquakes,
strong winds, etc. Perhaps the limiting factors in the future will be the
lack of available trees for lumber rather than the presence of more desir-
able building materials. Even today, the diameter of the trunks of trees
being harvested for timber is smaller than in the past.
Oxygen Source
Both plants and animals, including man, must have oxygen to breathe
or they will soon perish. In nature, many chemical reactions are occurring
continuously that remove oxygen from the atmosphere. If no method
existed by which the oxygen could be restored to the atmosphere, man
would soon die. Plants provide that method of oxygen renewal. Through
the process of photosynthesis, they are continually freeing oxygen and
returning it to the atmosphere, where we can obtain it for breathing. If
for no other reason than this plants are essential.
Values of Plants to Man 3
Plants as Energy Sources
We have considered so far only how plants are valuable because of the
chemicals they produce, chemicals that we use. But plants are also very
important for the energy they make available. It is difficult for man to
grasp the importance of energy in his life, perhaps because energy cannot
usually be seen and because it is usually so abundant that it becomes
common and therefore uninteresting. Life itself is an energy-requiring
and energy-using process. All animals, including man, must use energy
continuously to survive. Any time this energy is not available, we die. The
energy needed is supplied by plants, either directly or indirectly, through
the foods we eat. Food is necessary not only for the chemicals it furnishes,
chemicals that serve as building blocks for our bodies, but also for the
energy the foods contain. Remember the calories?
Not only are we dependent upon plants for the energy needed for
survival, but also for the energy needed to maintain our high standard of
living, such as energy to drive our automobiles, energy required by
industry, energy to drive our airplanes, trains, ships, etc., and energy to
heat or cool our buildings. The statement has been made, and is certainly
justified, that there is not enough available energy on earth today to allow
all nations to have the standard of living that we enjoy. How will this
problem be solved in the future? By the available energy going to the
strongest nation?
Plants as Ground Cover
The importance of plants as ground cover is often ignored or un-
recognized. At times, flowers are planted to cover up an ugly bare spot in
our yards, but plants as cover crops provide even more important services,
namely, those of soil and water conservation. How much soil would
exist in much of the United States if it were not for plants? Certainly in
the Eastern and Southern states there would be little left, since it would
be eroded away by rain nearly as soon as the soil was formed. Only in
desert regions, where rainfall is light, would soil cover the rock of the
earth. This loss of soil would not only be due to water carrying the soil
away as it runs off, but also to increased runoff. More of the water coming
down in the form of precipitation would run off, with less sinking into the
soil. Plants are very helpful in reducing the amount of runoff, aiding a
greater percentage of the precipitation to enter the soil and remain as
reserve water. So it is evident that even the weeds are helpful, since they
serve as ground cover necessary to soil and water conservation.
There are a number of other important uses of plants, such as agents