Plant physiology (biological and medical physics, biomedical engineering)

Biological and Medical Physics, Biomedical Engineering

Maria Duca

Plant
Physiology

Tai Lieu Chat Luong


Plant Physiology


BIOLOGICAL AND MEDICAL PHYSICS,
BIOMEDICAL ENGINEERING
The fields of biological and medical physics and biomedical engineering are broad, multidisciplinary and dynamic.
They lie at the crossroads of frontier research in physics, biology, chemistry, and medicine. The Biological and
Medical Physics, Biomedical Engineering Series is intended to be comprehensive, covering a broad range of topics
important to the study of the physical, chemical and biological sciences. Its goal is to provide scientists and
engineers with textbooks, monographs, and reference works to address the growing need for information.
Books in the series emphasize established and emergent areas of science including molecular, membrane, and
mathematical biophysics; photosynthetic energy harvesting and conversion; information processing; physical
principles of genetics; sensory communications; automata networks, neural networks, and cellular automata.
Equally important will be coverage of applied aspects of biological and medical physics and biomedical
engineering such as molecular electronic components and devices, biosensors, medicine, imaging, physical
principles of renewable energy production, advanced prostheses, and environmental control and engineering.

Editor-in-Chief:
Elias Greenbaum, Oak Ridge National Laboratory, Oak Ridge, Tennessee, USA

Editorial Board:

Masuo Aizawa, Department of Bioengineering,
Tokyo Institute of Technology, Yokohama, Japan

Judith Herzfeld, Department of Chemistry,
Brandeis University, Waltham, Massachusetts, USA

Olaf S. Andersen, Department of Physiology,
Biophysics and Molecular Medicine,
Cornell University, New York, USA

Mark S. Humayun, Doheny Eye Institute,
Los Angeles, California, USA

Robert H. Austin, Department of Physics,
Princeton University, Princeton, New Jersey, USA
James Barber, Department of Biochemistry,
Imperial College of Science, Technology
and Medicine, London, England
Howard C. Berg, Department of Molecular
and Cellular Biology, Harvard University,
Cambridge, Massachusetts, USA
Victor Bloomfield, Department of Biochemistry,
University of Minnesota, St. Paul, Minnesota, USA
Robert Callender, Department of Biochemistry,
Albert Einstein College of Medicine,
Bronx, New York, USA
Britton Chance, University of Pennsylvania
Department of Biochemistry/Biophysics
Philadelphia, USA
Steven Chu, Lawrence Berkeley National

Laboratory, Berkeley, California, USA
Louis J. DeFelice, Department of Pharmacology,
Vanderbilt University, Nashville, Tennessee, USA
Johann Deisenhofer, Howard Hughes Medical
Institute, The University of Texas, Dallas,
Texas, USA
George Feher, Department of Physics,
University of California, San Diego, La Jolla,
California, USA
Hans Frauenfelder,
Los Alamos National Laboratory,
Los Alamos, New Mexico, USA
Ivar Giaever, Rensselaer Polytechnic Institute,
Troy, NewYork, USA
Sol M. Gruner, Cornell University,
Ithaca, New York, USA

Pierre Joliot, Institute de Biologie
Physico-Chimique, Fondation Edmond
de Rothschild, Paris, France
Lajos Keszthelyi, Institute of Biophysics, Hungarian
Academy of Sciences, Szeged, Hungary
Robert S. Knox, Department of Physics
and Astronomy, University of Rochester, Rochester,
New York, USA
Aaron Lewis, Department of Applied Physics,
Hebrew University, Jerusalem, Israel
Stuart M. Lindsay, Department of Physics
and Astronomy, Arizona State University,
Tempe, Arizona, USA

David Mauzerall, Rockefeller University,
New York, New York, USA
Eugenie V. Mielczarek, Department of Physics
and Astronomy, George Mason University, Fairfax,
Virginia, USA
Markolf Niemz, Medical Faculty Mannheim,
University of Heidelberg, Mannheim, Germany
V. Adrian Parsegian, Physical Science Laboratory,
National Institutes of Health, Bethesda,
Maryland, USA
Linda S. Powers, University of Arizona,
Tucson, Arizona, USA
Earl W. Prohofsky, Department of Physics,
Purdue University, West Lafayette, Indiana, USA
Andrew Rubin, Department of Biophysics, Moscow
State University, Moscow, Russia
Michael Seibert, National Renewable Energy
Laboratory, Golden, Colorado, USA
David Thomas, Department of Biochemistry,
University of Minnesota Medical School,
Minneapolis, Minnesota, USA

More information about this series at />

Maria Duca

Plant Physiology

123

Maria Duca
University of Academy of Sciences
of Moldova
Chişinău
Moldova

ISSN 1618-7210
ISSN 2197-5647 (electronic)
Biological and Medical Physics, Biomedical Engineering
ISBN 978-3-319-17908-7
ISBN 978-3-319-17909-4 (eBook)
DOI 10.1007/978-3-319-17909-4
Library of Congress Control Number: 2015939679
Springer Cham Heidelberg New York Dordrecht London
© Springer International Publishing Switzerland 2015
This work is subject to copyright. All rights are reserved by the Publisher, whether the whole or part
of the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations,
recitation, broadcasting, reproduction on microfilms or in any other physical way, and transmission
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The publisher, the authors and the editors are safe to assume that the advice and information in this
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Printed on acid-free paper
Springer International Publishing AG Switzerland is part of Springer Science+Business Media

(www.springer.com)


Preface

The past decades came with tremendous advances in understanding molecular
systems that lie at the core of life itself, a fact which has revolutionized biological
research and the field of plant physiology was not an exception. Moreover, with the
current advent of high throughput technologies in genomics and proteomics the
potential appears to reveal the most subtle details regarding the molecular actors
and the processes in which they are involved. But for being able to interpret and
make use of such complex data, to understand its place and significance in the
global context of plant metabolism, one must first hold basic knowledge of the key
processes in the life of the plants, integrated across several dimensions like structure, function, ecology, etc. Plant physiology can offer such an integrated view.
The subject of plant physiology is highly interdisciplinary and builds upon the
knowledge derived from fields like botany, zoology, plant morphology and anatomy, cytology, biochemistry, molecular biology, etc. While at the theoretical level
one of the priorities is to integrate the information from these scientific areas for a
most complete understanding of the processes undergoing in living system, at the
practical level this field comes with abundant experimental knowledge and wellestablished practices inherited from previous decades that allow to manipulate crop
species in the desired manner, even if the theoretical aspects are not always completely elucidated.
The course, presented by this book, offers the possibility to enter into the essence
of the most important phenomena of the living matter—photosynthesis, respiration,
growth and development, etc. By being conceived in agreement with the requirements of modern biology, Plant Physiology offers a perspective over the instruments and methods which allow the manipulation of the vegetal organism and
which lie at the foundation of biotechnology as we know it today.
The present book is not one that reflects only the principles and fundamental
directions of plant physiology by using the scientific literature passed through the
prism of own reflections, but also includes results of the personal research summarizing a big volume of experimental data.

v

vi

Preface

The presented content adheres to the principle of applicability of the provided
knowledge which means that theoretical topics are accompanied by real examples
of their relevance from agriculture, plant breeding, etc.
A special place is left for graphical illustrations, diagrams, pictures, which
occupy a significant proportion of the content and are meant to facilitate the process
of assimilating the information.
The author wants to thank the university professor, habilitated doctor
A.I. Derendovschi for the detailed analysis of the content of the book and for the
useful and constructive suggestions.
I am grateful and want to thank everyone who made a contribution to the
appearance of this book—PhDs in Biology Angela Port, Ana Căpăţână, Aliona
Glijin, Ana Bârsan, Elena Savca, Alexei Levitchi, Victor Lupascu, Ph.D. students
Lucia Ciobanu and all other students who helped me conceive this book.
I would like to thank Prof. V. Ciobanu, Prof. V. Reva, PhDs Elena Muraru,
Tatiana Homenco, Otilia Dandara for the important suggestions regarding the
undertaken approach and the full and complex support offered in the process of
preparing and editing this book.
For the help provided in obtaining and consulting the most up to date scientific
literature, I would like to thank my colleagues from the University of California,
Riverside (USA)—Professors Isgouhi Kaloshen, Carol Lovatt, Seymour Van
Gundy.
I would also like to express special gratitude to my family for the patience and
understanding that they showed all these years.
Chişinău

Maria Duca


Contents

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1

Introduction to the Educational Course of Plant Physiology
1.1 The Definition and Scope of Plant Physiology . . . . . . .
1.2 Purposes of Plant Physiology as a Science . . . . . . . . . .
1.3 Research Methods Used by Plant Physiology . . . . . . . .
References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

2

Plant Cell Physiology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.1 The Cell as a Structural, Morphological, Functional Unit
of Living Organisms . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.2 Structural Organization, Chemical Composition
and Function of the Cell Wall . . . . . . . . . . . . . . . . . . . . .
2.3 Structure and Ultrastructure of Cell Protoplasm . . . . . . . . .
2.4 Structure and Function of Biological Membranes . . . . . . . .
2.5 Exchange of Substances Between the Cell and the Medium .
2.5.1
Ion Flow into the Cell . . . . . . . . . . . . . . . . . . . . .
2.5.2
Water Flow into the Cell . . . . . . . . . . . . . . . . . . .
References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

3

Water Regime . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.1 Role of Water in Plants . . . . . . . . . . . . . . . . . . . . . . .
3.2 Water Content and State in Plants . . . . . . . . . . . . . . . .
3.3 Forms of Water in the Soil. Accessible and Inaccessible
Water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.4 The Root System as a Specialized Organ for Water
Absorption . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.5 The Influence of External Factors on Water Absorption
Intensity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.6 Water Elimination. Physiological Importance of Plant
Transpiration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.6.1
Indices of Transpiration . . . . . . . . . . . . . . . . .
3.7 Structure of the Leaf as an Organ of Transpiration . . . .

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viii

Contents

3.8

Stomatal and Cuticular Transpiration . . .
3.8.1
Stomatal Transpiration. . . . . . .
3.8.2
Cuticular Transpiration . . . . . .
3.9 Water Absorption Mechanism and Ways
of Its Circulation in Plants . . . . . . . . . .
3.9.1
Water Transport in Plants . . . .
3.10 Ecology of the Water Regime in Plants .
References. . . . . . . . . . . . . . . . . . . . . . . . . .
4

5

6

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Photosynthesis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.1 Importance of Photosynthesis and the Global Role
of Green Plants. . . . . . . . . . . . . . . . . . . . . . . . . .
4.2 The Leaf as a Specialized Photosynthesis Organ . . .

4.3 The Structure, Chemical Composition, Function
and Origin of Chloroplasts . . . . . . . . . . . . . . . . . .
4.4 Photosynthesis Pigments . . . . . . . . . . . . . . . . . . .
4.5 Photosynthesis Energetics . . . . . . . . . . . . . . . . . .
4.6 Photosynthesis Mechanism. . . . . . . . . . . . . . . . . .
4.6.1
Light Phase of Photosynthesis . . . . . . . . .
4.6.2
The Dark Phase of Photosynthesis . . . . . .
4.7 Photorespiration . . . . . . . . . . . . . . . . . . . . . . . . .
4.8 Endogenous Regulatory Elements of Photosynthesis
4.9 Ecology of Photosynthesis . . . . . . . . . . . . . . . . . .
References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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Respiration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
General Notions of Respiration. . . . . . . . . . . . . . . . . . .
Respiratory Enzymes. . . . . . . . . . . . . . . . . . . . . . . . . .
A.N. Bach’s and V.I. Palladin’s Theories . . . . . . . . . . . .
Respiration Mechanism . . . . . . . . . . . . . . . . . . . . . . . .
5.4.1
Genetic Link Between Respiration
and Fermentation . . . . . . . . . . . . . . . . . . . . . .
5.4.2
Glycolysis—The Anaerobic Phase of Respiration
5.4.3
Krebs Cycle (Tricarboxylic Acid Cycle) . . . . . .
5.4.4
The Electron Transport Chain and the Energetic
Outcome of Aerobic Respiration . . . . . . . . . . . .
5.5 Different Types of Respiratory Substrate Oxidation . . . . .
5.6 Ecology of Respiration . . . . . . . . . . . . . . . . . . . . . . . .
5.7 Regulation and Self-regulation of the Respiration Process

References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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Mineral Nutrition of Plants . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
6.1 Importance of Mineral Elements in Plant Nutrition . . . . . . . . .

6.2 Chemical Composition of the Ash. . . . . . . . . . . . . . . . . . . . .

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Plant
5.1
5.2
5.3
5.4

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Contents

ix

6.3
6.4

Methods of Mineral Nutrition Research . . . . . . . . . . . . . . .
The Root System as an Organ for Absorption and Transport
of Mineral Elements . . . . . . . . . . . . . . . . . . . . . . . . . . . .
6.5 Physiological Role of Macroelements . . . . . . . . . . . . . . . .
6.5.1
Absorption, Transport and Metabolism of Nitrogen .
6.5.2
Absorption, Transport and Metabolism of Sulfur. . .
6.5.3
Absorption, Transport and Metabolism
of Phosphorus . . . . . . . . . . . . . . . . . . . . . . . . . .
6.5.4

The Physiological Role of Other Macroelements. . .
6.6 Physiological Role of Microelements. . . . . . . . . . . . . . . . .
6.7 Mechanism of Absorption and Transport of Ions in Plants . .
6.7.1
Mineral Element Absorption. . . . . . . . . . . . . . . . .
6.7.2
Mineral Element Transport. . . . . . . . . . . . . . . . . .
6.8 Soil as a Substrate for Plant Nutrition . . . . . . . . . . . . . . . .
6.9 Influence of Various Environmental Factors on Mineral
Nutrition in Plants. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7

8

Plant Growth and Development. . . . . . . . . . . . . . . . . . . . .
7.1 The Concept of Plant Growth and Development . . . . . .
7.1.1
Dormancy in Plants (Repose) . . . . . . . . . . . . .
7.2 Types of Plant Growth . . . . . . . . . . . . . . . . . . . . . . .
7.3 Phases of Cell Growth and Development . . . . . . . . . . .
7.4 Phases of Plant Growth and Development . . . . . . . . . .
7.5 Genetic Aspects of Plant Morphogenesis . . . . . . . . . . .
7.6 Endogenous Factors of Plant Growth and Development .
7.6.1
Auxins . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7.6.2
Gibberellins . . . . . . . . . . . . . . . . . . . . . . . . .
7.6.3
Cytokinins . . . . . . . . . . . . . . . . . . . . . . . . . .

7.6.4
Abscisic Acid. . . . . . . . . . . . . . . . . . . . . . . .
7.6.5
Ethylene . . . . . . . . . . . . . . . . . . . . . . . . . . .
7.7 Photoperiodism and Yarovization . . . . . . . . . . . . . . . .
7.8 The Influence of Exogenous Factors on Plant Growth
and Development . . . . . . . . . . . . . . . . . . . . . . . . . . .
7.9 Plant Growth Movements—Tropism and Nasties . . . . .
7.10 Self-Regulation of Plant Growth and Development . . . .
References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Plant
8.1
8.2
8.3
8.4

Biorhythms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Classification and Mechanisms of Biological Rhythms
Biological Rhythms in Plants . . . . . . . . . . . . . . . . . .
Circadian Rhythms in Plants . . . . . . . . . . . . . . . . . .
The Molecular Mechanism of the Circadian Clock . . .
8.4.1
Environmental Signals Involved . . . . . . . . . .

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242


x

Contents

8.4.2
8.4.3
8.4.4
8.4.5
References. .

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242
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Elimination of Substances in Plants . . . . . . . . . . . . . . . .
9.1 Classification of the Types of Substance Elimination .
9.2 Excretion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
9.3 Secretion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
9.3.1
Lignin, Cutin and Wax Secretion . . . . . . . .
9.3.2
Nectariferous Glands and Nectar Secretion . .
9.3.3
Terpenoid Secreting Structures . . . . . . . . . .
9.4 Secretory Processes in Insectivorous Plants . . . . . . .
9.5 Water Elimination in Plants . . . . . . . . . . . . . . . . . .
9.6 Ecological Role of Substance Elimination . . . . . . . .
References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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303
308

Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

309

9

Temperature . . . . . . . . . . . . . . . . . . . . .
Light . . . . . . . . . . . . . . . . . . . . . . . . . .
The Molecular Targets of Light Signaling
Rhythmic Regulation of Light Signaling .
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10 Physiology of Plant Resistance to Unfavorable Environmental
Factors. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
10.1 The Concepts of Resistance and Adaptation . . . . . . . . . . .
10.2 Unfavorable Factors of the Winter-Spring Period . . . . . . .
10.3 Plant Resistance to Cold and Frost . . . . . . . . . . . . . . . . .
10.4 Plant Resistance to Drought . . . . . . . . . . . . . . . . . . . . . .
10.4.1 Physiological Basis of Irrigation . . . . . . . . . . . . .
10.5 Plant Resistance to Saltiness. . . . . . . . . . . . . . . . . . . . . .

10.6 Regulation of Physiological Processes in Halophyte Plants.
10.7 Plant Resistance to Environmental Pollution . . . . . . . . . . .
10.7.1 Resistance to Heavy Metals . . . . . . . . . . . . . . . .
10.7.2 Resistance to Radiation . . . . . . . . . . . . . . . . . . .
10.7.3 Resistance to Gases. . . . . . . . . . . . . . . . . . . . . .
10.8 Metabolism of Pollutants in Plants . . . . . . . . . . . . . . . . .
10.9 Biochemical Mechanism of Pollutant Transformation
in Plants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
10.10 Self-regulation of Plant Growth and Development
in Unfavorable Environmental Conditions . . . . . . . . . . . .
References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .


Chapter 1

Introduction to the Educational
Course of Plant Physiology

Abstract Plant physiology is a science that studies vegetal organisms in ontogenetic dynamics—the diversity, the laws and the mechanisms of physiological and
biochemical processes, their biological significance, their dependence on environmental factors. Traditionally, it was based on two directions: anatomical/morphological and physiological, but this division is somewhat relative, because structure
and function have evolved in parallel and cannot be studied separately. This
interdisciplinary research field focuses on a series of compartments like: plant cell
physiology; water regime; photosynthesis; mineral nutrition; respiration; growth
and development; resistance to unfavorable factors; phenomena of self-regulation at
all the levels of organization (including at the organism level by means of interacting centers of dominance). While as a theoretical science plant physiology tries
to obtain an integrated, detailed picture of the molecular, biochemical, physiological, morphogenetic processes going on in the living plant and the interconnection
between these, at the applicative level its aim is to be able to direct vital processes in
the life cycle of a plant like growth, development, metabolism, photosynthesis,
nutrition, resistance, fructification in order to control the vitality or yield of the crop
species and to maximize economic benefits. Classical research in plant physiology

is carried out in the field, in vegetation pots, solariums, greenhouses, phytotrons,
laboratories. Experiments make use of a diverse range of methods like: imaging
technologies (optical and electronic microscopy), centrifugation, chemical analysis,
chromatography, radioactive labeling, gel filtration, electrophoresis, X-ray analysis,
in vitro culture, but also in silico mathematical modeling to predict the behavior of
various systems and the output parameters.

© Springer International Publishing Switzerland 2015
M. Duca, Plant Physiology, Biological and Medical Physics,
Biomedical Engineering, DOI 10.1007/978-3-319-17909-4_1

1


2

1 Introduction to the Educational Course of Plant Physiology

Historical Background
1727—St. Hales identifies the pathways of water, mineral salts and organic substances circulation.
1771—J. Priestley discovers photosynthesis.
1775—M. Malphigi describes the cycle of substances in plants—the ascending and
descending currents.
1800—J. Senebier edits “Plant Physiology” in 5 volumes.
1804—J. Senebier and Th. Saussure argue that photosynthesis represents the
nutrition of plants with carbon.
Brief Updates
During the last decades, by using gene engineering methods, plants with recombinant DNA have been created, also called genetically modified plants (GMPs), this
fact favoring the emergence of a new direction in plant physiology—the physiology
of transgenic plants which aims to determine the physiological and biochemical

changes of transgenic plants as a result of the inclusion of new genes into their
genome. Thus, the use of GMPs has allowed the elucidation of the genetic and
physiologic mechanisms of the activity of genes artificially included in the plant


1 Introduction to the Educational Course of Plant Physiology

3

genome, among which are also those that are normally found in animal organisms,
such as the Green Fluorescence Protein gene (GFP) from certain jellyfish species.
The GFP emits a green fluorescence under UV light, and its fusion with any other
protein allows the positional analysis of the last within the cell, the mechanism
being similar to that of radio-labeling.
Inserting auxine phytohormone biosynthesis genes (iaaM and iaaH) into the
tobacco genome resulted in more viable transgenic plants with a more active
vegetative morphogenesis and reproductive development and with both a higher
amount of water stored in tissues and a higher resistance to drought.
Another example is represented by the ferric superoxide dismutase gene
(FeSOD) from Arabidopsis thaliana (one of the genes involved in antioxidative
protection) which was included into the genomes of tobacco and wheat. The
genetically modified plants proved more resistant to the oxidative stress than the
control, confirming that the gene is expressed.
Lately, to study a particular gene function the antisense strategies are often
applied. The best known example is given by the gene that encodes the synthesis of
the polygalacturonase enzyme, involved in cell wall degradation in ripening tomato
fruits. After including this gene in the tomato genome, in reverse orientation, sense
and antisense RNA will bind on the basis of complementarity, thus obstructing
translation and leading to longer fruit preservation.

1.1 The Definition and Scope of Plant Physiology
Plant physiology is a very important branch of biological sciences that studies the
life of plants—the laws and mechanisms of physiological and biochemical processes, their significance, their interdependence with environmental factors in
ontogenetic dynamics. The notion of physiology originated from Greek by joining
the words physis, which means “function” and logos—“science”.
Plant physiology has appeared in 1800, when the Frenchman J. Senebier edited
his first monograph in five volumes “Plant Physiology”, which included not only
his own experimental results, but also those obtained in this scientific field by:
M. Malpighi, who has described the flow of substances in the plant (1775);
St. Hales, who demonstrated that water and mineral salts flow through the xylem,
while organic substances—through the phloem (1727); J. Pristley, who has discovered photosynthesis (1771), etc.
During the development of plant physiology as a science, it has been based on
two directions: anatomical/morphological (descriptive) and physiological (experimental), which, in principle, can be considered two basic research methods. This
division is relative, because vegetal organs can’t be studied without taking into
account their function, just as any processes cannot be studied without knowing the


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1 Introduction to the Educational Course of Plant Physiology

structures they are localized in. Any physiological process should be regarded as a
product of long evolution, which forms the plant ability to adapt to variable
environmental conditions. The function has evolved in relationship with the
structure of the organism and the structure has stabilized under the action of
environmental factors and according to the function. Thus, to study respiration, it is
necessary to know the structure and ultrastructure of mitochondria, and to reveal the
mysteries of photosynthesis, a unique and specific process happening only in green
plants, it is important to know the structure and ultrastructure of the assimilatory
apparatus.

Most of the compartments of plant physiology have been delimited in the
nineteenth century and are valid even nowadays. These are:
1.
2.
3.
4.
5.
6.
7.
8.
9.

Cytophysiology (plant cell physiology);
Water regime of plants (H. Dutrochet, H. de Friz, J. Sachs);
Photosynthesis (G. Busengo, M. Ţsvet, J. Pristley, K.A. Timireazev);
Mineral nutrition (I. Leibih, G.B. Busengo, D.N. Preanishnikov);
Respiration (A.S. Famiţsin, I.P. Borodin, L. Paster);
Growth and development (J. Sachs, A.S. Famiţsin);
Plant movements (T. Nait, J. Sachs, Ch. Darwin);
Irritation (B. Sanderson, Ch. Darwin);
Resistance to unfavorable factors (D.I. Ivanovski).

Thus, plant physiology as a distinct branch of biology, aims to study successively
all vital processes that occur in vegetal organisms. In the second half of the twentieth
century the basics of a new branch of plant physiology named self-regulation were
laid. The phenomena of self-regulation and coordination of physiological processes,
as well as other processes, are studied at all the levels of organization of living matter
(molecular, intracellular, at the levels of tissue, organ, organism, biocoenosis) the
mechanisms of implementation being diverse and specific.
Self-regulation (autoregulation) is the property of biological systems to maintain

the stability of the physical and chemical conditions of the internal environment, of
the structure and properties of the organism in their elementary form, all these in
conditions of a dynamic equilibrium. Autoregulation represents the process, which
minimizes various deviations in the biological systems (pH, viscosity, redoxpotential, etc.), resulting from the influence of causative agents. Therefore, the
capacity of the vegetal organism of carrying out vital functions amidst changing and
unfavorable environmental conditions is implemented.
Such a stability has a dynamic and active character. It is maintained by complex
mechanisms, which determine the coordinated physiological activity of different
organs, thus allowing autoregulation of plant growth and development, organism
temperature, raw sap composition, regeneration of damaged tissues, adaptation to
stress conditions, etc. (Figure 1.1).
Self-regulation ensures integrity and homeostasis of plant organisms, allows
harmonious growth and development and helps react adequately to the alternating


1.1 The Definition and Scope of Plant Physiology

5

Fig. 1.1 Scheme representing regulative and directive processes in living organisms (Polevoy
1989)

factors of the environment. Autoregulation mechanisms are turned on automatically
in the appropriate place and time, according to the needs of the organism.
The notion of self-regulation is characteristic both for the whole vegetal
organism and for the individual cells. In fact, it is at the cellular level that the
integration of plant physiology with genetics, cytology, molecular biology, biochemistry, biophysics, etc. happens.
Study of the autoregulation phenomena may contribute to the transition from
describing the processes happening in plant organisms to their direct manipulation
by acting upon the corresponding regulatory systems. In the last decades, the number

of theoretical and experimental studies dealing with regulation and autoregulation of
gene and enzyme functional activity, with membrane, electro-physiological,
phytohormonal control (particularly related to the development of gene engineering
and biotechnology) has considerably increased. Self-regulation determines plant
homeostasis and creates conditions for the epigenesis of functions, which implies a
strong collaboration between the factors of the environment and the plant genome.
Consequently, it leads to the appropriate phenotypic expression.
Regulatory systems (Fig. 1.2) at the cellular level include:
• the mechanisms that determine qualitatively the enzymatic equipment of the
cells and which consequently determine the metabolic profile of the cells, tissues
and organisms;
• the mechanisms maintaining a relative constant of the cellular metabolism
(quantitative regulation of enzyme activity, of membrane transport etc.).
All these regulatory systems are interdependent. For example, gene activity
determines the properties of the cell membrane, and biological membranes also
influence the differential activity of the genes.
With the advent of multicellular organisms, intercellular regulatory systems have
emerged including trophic, hormonal, electrophysiological regulation, contributing


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1 Introduction to the Educational Course of Plant Physiology
Dominant centers

Polarity

Biorhythms

Channel connections

Regulatory contours

Phyto hormonal regulation

Electrophysiological
regulation

Trophic regulation

Genetic regulation

Membrane regulation

Enzymatic activity regulation

Fig. 1.2 Interaction of regulatory systems (Polevoy 1989). Regulatory level: I intracellular, II
intercellular, III organismal

to the interaction between plant organs. Such an interaction can be observed during
cultivation of different vegetative explants in vitro. However, the existence of
trophic, hormonal and electrophysiological interactions between cells, tissues and
organs does not fully explain the behavior of a plant as a whole living organism.
There are higher level regulatory systems and mechanisms connecting organs and
functional systems of the plant during the life cycle of the organism and its ontogenetic transitions.
The basic autoregulation mechanism at the organism level relies on the presence
of a few centers of dominance (the stem and the root apexes), which receive
information both from the external and internal medium and influence the living
organism by driving tissue morphogenesis, by creating physiological gradients,
polarity, channel connections (conductive fascicules), physiological oscillations.

1.1 The Definition and Scope of Plant Physiology

7

Polarity and channel connections coordinate the space orientation of morphological
processes, while oscillations help achieve time coordination.
At the organism level these regulatory centers unite in regulatory contours with
reversible relationships—positive or negative, which constitute the irritability effect.
Thus, the integrity of the plant organism is determined by the interaction of control
systems with central directing elements represented by the dominant centers.
All the physiological processes occurring in plants are studied from various
aspects.
From the biochemical aspect, plant physiology studies the biosynthesis of
organic compounds from inorganic ones, the functional importance of the diversity
of organic substances formed as a result of the primary and secondary metabolism
of the plant. It also researches the pathways of photosynthesis, reveals the laws of
mineral nutrition, the importance of mineral substances as regulators of metabolic
processes, their role in electrical phenomena occurring inside the cell or in the
synthesis of organic compounds, etc.
From the biophysical aspect the following problems are studied: cell energetics,
electrophysiology of vegetal organs, physical and chemical laws of the water
regime, those of nutrition via the root system, of growth, photosynthesis, respiration, the electrical aspects of irritability.
From the aspect of evolution, researchers study the physiology of the genus,
species, individual, as well as ontogenesis as a function of the genotype, which has
transformed during phylogenesis.
The ontogenetic aspect implies the analysis of the age-related laws governing
plant growth and development based on the physiological and biochemical processes
occurring in cells, tissues, organs as well as the study of morphogenesis and possible

ways of acting on plant development (interfering with the photoperiodism, hardening
plants, manipulating phytohormone signaling pathways to control plant stature, etc.).
The ecological aspect consists of studying the dependence of the internal
processes and of the particularities of individual development of the vegetal
organism on the multitude of environmental conditions.
Plant physiology is an experimental biological science that summarizes the
ensemble of theoretical and practical knowledge, based on which, by using the
principles of the scientific method, it is possible to intervene in the most important
processes in the life cycle of plants: growth, development, metabolism, photosynthesis, nutrition, resistance, fructification.
In describing the studied phenomena, plant physiology integrates knowledge
from different areas of biology and life sciences such as: botany and plant morphology (studying the structure and components of the vegetal organism), cytology
(studies the cells), biochemistry (investigates chemical substances and reactions
occurring in living organisms), biophysics (focuses on the description of physical
phenomena related to living organisms for instance energy exchange between
plants and the environment, etc.), ecology (provides data on the effect of environmental factors on plants), chemistry, physics, mathematics, etc. At the same
time, plant physiology represents a theoretical basis for plant cultivation, phytopathology, plant breeding, agriculture, agro-chemistry, genetics and pedology.


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1 Introduction to the Educational Course of Plant Physiology

1.2 Purposes of Plant Physiology as a Science
The possibility to constantly build up on available research knowledge and the
potential for implementing the final results make plant physiology a fundamental
science with practical applicability.
The purpose of plant physiology as a science is to investigate the peculiarities of
the life of different species of vegetal organisms both cultivated ones and those from
the spontaneous flora, in order to direct key processes like growth, development,
nutrition, metabolism and others.

Being a fundamental science, plant physiology aims to examine the molecular,
physiological, biochemical and morphogenetic mechanisms of the vital processes in
their dynamical succession and as a function of alternating environmental conditions, including:
• discovering the essence of the organism’s individual development and studying
the interaction of genetic, physiological, enzymatic mechanisms during growth
and development;
• elucidating regulatory and autoregulatory mechanisms under the action of
external factors;
• detailing the biochemical theory concerning mineral nutrition of plants;
• elucidating the ways used by plants to improve the efficiency of solar energy
utilization;
• investigating the mechanism of atmospheric nitrogen fixation and its utilization
by superior plants;
• developing and detailing the theoretical bases of the use of biologically active
substances;
• elucidating the laws of plant viability (mechanisms of nutrition, growth,
movement, reproduction);
• improving the theoretical knowledge on maximizing crop yields;
• researching endogenous mechanisms of regulating physiological functions,
including basic mechanisms of enzyme biosynthesis, transport of substances and
regulatory action of biomembranes;
• decoding mechanisms that control the chronological sequence of genetic program implementation during plant ontogenesis, including intracellular interdependence, interaction between vegetal organs during growth, reproduction and,
finally, during crop formation;
• studying the regulation of secondary metabolite biosynthesis (alkaloids, rubber,
phenolic compounds, etc.) which are often of great economical importance.
As an applicative science, plant physiology aims to increase plant productivity.
It is known that in an ear of wheat there are 3–5 flowers, of which only 1, 2 or 3 are
fructifying. To make all these flowers fructify is the kind of challenges put in front
of plant physiology. To achieve this goal, it is necessary to know the causes
preventing metabolite formation and grain filling. At the core of such phenomena

lies, for instance, the poor activity of the photosynthetic apparatus, caused by the


1.2 Purposes of Plant Physiology as a Science

9

depletion of chloroplast enzymes or the exhaustion of cell energy resources in the
form of adenosine triphosphate. In order to solve tasks like this, plant physiology
investigates:
•
•
•
•
•
•
•

photosynthetic apparatus activity and efficiency of solar energy use;
plant requirements for mineral nutrition;
water regime and efficiency of water utilization;
plant resistance to various unfavorable factors;
the possibility of using growth regulators;
critical phases of ontogenesis;
physiological bases of implementing the morphogenetic program.

A problem of the physiology of mineral nutrition, with promising prospects in
plant breeding, is to study the absorption of nutrients by the root system. Knowing
the rhythm and the rate of nutrient absorption in the multitude of varieties resulting
from plant breeding, we can choose the biological material with a maximum

capacity of fertilizer intake, this being a prerequisite for big crops.
Discovering the functions of growth regulators may have multiple practical
applications. Thus, gibberellins can be used to spray tree seedlings in greenhouses
to force their growth in the first year and to reduce the overall time spent in a
greenhouse, while auxins can be used to stimulate seedling rooting. It is again the
task of plant physiology to determine experimentally for various species the
duration of seedling exposure to these phytohormones, their optimal concentrations
and the optimum age of the treated sprouts in order to achieve the best results.
Another important task of plant physiology is to find out plant requirements with
regard to nutrients and water during different vegetation periods. In autumn cereals,
regrowth of the foliar system that has been destroyed during the winter by the frost
involves the consumption of large amounts of nitrogen in the early spring.
In vegetable production, the practical purpose is to obtain seedlings in greenhouses during winter, when the light intensity is low because of permanent
cloudiness. The etiolation phenomenon (plants have long, weak stems; smaller,
sparser leaves due to longer internodes; and a pale yellow color) can be prevented
by illuminating plants with artificial light or spraying them with diluted solutions of
retardant substances that hamper seedling elongation.

1.3 Research Methods Used by Plant Physiology
As mentioned above, plant physiology is a pronouncedly experimental science, the
experiment representing the main research method. The experiment is preceded by
the hypothesis. Studies and experiments on plants are performed under three basic
aspects:
(1) Passing from a higher level to a more elementary one, from analyzing complex
biological laws to studying simpler ones—physical and chemical. This


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1 Introduction to the Educational Course of Plant Physiology

research direction led to the advent of molecular biology, to the discovery of
the hereditary code, the protein biosynthesis mechanism, the main laws of
absorption and utilization of light quanta in photosynthesis. This, however, is
not sufficient to understand the laws of physiological processes occurring in
vegetal organisms.
(2) Currently another approach is used—from simple to complex, called by V.A.
Engelhardt integral. Generally, this path allows pursuing the evolution of
certain processes at the level of DNA–RNA–protein–enzyme–biochemical
reaction–physiological process–property of the cell. At any level of this path,
regulation is possible and there are also internal mechanisms of autoregulation
(targeting DNA replication, RNA and protein biosynthesis, enzymatic activity,
but also cell, tissue and organ differentiation).
(3) Physiological processes are studied in ontogenetic dynamics and in relationship with environmental factors.
Plant physiology research is carried out in the field, in vegetation pots, solariums, greenhouses and laboratories. The most modern investigations are carried
nowadays in phytotrons (the name was given by R.A. Millikan in 1949). Phytotrons
are constructions with special rooms with either natural or artificial illumination,
heated or cooled artificially, with adjustable air temperature and humidity. With the
help of automatic electrical installations, vegetation parameters can be maintained
at certain established levels. Investigations in the field of plant physiology imply
carrying out experiments and exploring processes and phenomena at different levels
of organization of the living matter by means of biochemical, biophysical, physicalchemical and biological methods.
At the molecular level the physical-chemical processes occurring in living
organisms are studied: the synthesis, assembly and restructuring of the proteins,
nucleic acids, polysaccharides, lipids and other substances, the energetic and
informational metabolism that regulate these processes. At the cellular level the
structure and properties of the cell and its components is studied, the relationship
between organelles etc. At the intercellular level knowledge from multiple disciplines is integrated and the principles of photosynthesis, respiration and interaction
between tissues and organs are provided. At the organismal level the processes and
phenomena taking place in an individual organism are studied as well as the

coordinated functioning of its organs and systems, interactions between different
organs and their individual roles, changes caused by accommodation.
At the population level research focuses on the basic unit of the evolutionary
process—the population. It means that the interactions between individuals that
inhabit a certain territory (more or less isolated) is investigated. The composition
and dynamics of the population is strongly correlated with the molecular, cellular,
intercellular and organismal levels of organization. At the level of the biosphere the
processes taking place in the biogeocenoses are studied including the interactions of
biotic and abiotic components of the ecosystems.
Each of the mentioned levels of organization has its own specific research
methods. The observation of various phenomena is carried out with the naked eye


1.3 Research Methods Used by Plant Physiology

11

(macroscopically) or using a microscope (microscopically). The discovery and
constant improvement of imaging technologies with the electronic microscope had
marked a significant stage in plant physiology development—the era of cellular
organelle physiology. The electronic microscope together with the range of methods for cellular homogenate ultracentrifugation allowed the study of the submicroscopic structure of cellular organelles, while chemical micro-analysis allowed
elucidation of their chemical composition. Based on knowledge about the ultrastructure and chemical composition it has become possible to decode physiological
functions of various cell organelles.
The scientific works in the field of plant physiology often make use of: ordinary
microscopy, electronic microscopy, centrifugation, chemical analysis, chromatography, radioactive labeling, gel filtration, electrophoresis, roentgen analysis, artificial modeling of systems, autoradiography, in vitro culture.
Lately, side by side with physiological and biochemical methods, mathematical
modeling of life processes and plant productivity in defined conditions of growth
and development is used by utilizing model-algorithm-program triads.

Glossary

Adaptation The evolutionary process by which the organism or species survives
and reproduces in new environmental conditions.
Self-regulation (autoregulation) The general feature of biological systems that
assures the control and autonomous coordination of the functioning of system
elements and the maintenance of a dynamic equilibrium in the system.
Evolution The progressive development of living organisms during successive
generations by means of accumulating favorable hereditary variations enforced
by natural selection.
Enzyme A protein produced by the cell which controls the reactions of synthesis
and degradation via its catalytic activity, playing a fundamental role in metabolic
processes regulation.
Phylogenesis The history of the development of a species or other taxonomical
unit during the evolutionary process.
Phytohormone A substance secreted by the plant cell in small quantities, which
controls various aspects of growth, developmental transitions, organ morphogenesis, response to various stress factors etc.
Photosynthesis The fundamental process of synthesis of organic compounds from
inorganic ones (CO2 and H2O) in the presence of light, carried out by green
plants and photosynthesizing microorganisms. During the process of photosynthesis the solar energy is transformed into the energy of chemical bonds in
organic molecules.


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1 Introduction to the Educational Course of Plant Physiology

Metabolism The totality of all the complex processes of synthesis (energy storage)
and degradation (energy release) undergone by the substances in a living
organism.
Morphogenesis Cyto-differentiation and development of visible structures (organs
or parts) in an organism during ontogenesis.

Levels of organization Systems with a specific organization (characteristic of
biological systems only) and with a character of universality.
Ontogenesis The series of transformations undergone by the organism, from egg
fecundation to death, according to the scenario for the respective species.
Respiration The process of oxidative degradation of complex organic substances
into inorganic ones accompanied by energy release.

References
Acatrinei Gh (1991) Reglarea proceselor ecofiziologice la plante. Editura Junimea, Iaşi, p 280
Burzo I, Toma S, Crăciun C ş. a (1994) Fiziologia plantelor de cultură, vol 1–4. Chişinău, Ştiinţa
Crăciun T, Crăciun L (1989) Dicţionar de biologie. Editura Albatros, Bucureşti, p 285
Derfling K (1985) Gormony rasteniy. Mir, 304 p
Duca M (1996) Sisteme şi mecanisme de autoreglare la plante. Chişinău, USM, 199 p
Duca Gh, Zănoagă C, Duca M, Gladchii V (2001) Procese redox ỵn mediul ambiant. Chişinău, 381 p
Lebedev SI (1982) Fiziologiya rasteniy. M. Kolos, 544 p
Milică C, Dorobanţiu N. ş. a (1982) Fiziologia vegetală. Bucureşti, Ed. Didactică şi Pedagogică,
375 p
Polevoy VV (1989) Fiziologiya rasteniy. M. Vysshaya shkola, 464 p
Polevoy VV (1982) Fitogormony. L. Izd. Leningradskogo universiteta, 248 p
Tarhon T (1992) Fiziologia plantelor, vol I, II. Chişinău, Lumina
Udovenko GV, Sheveluha VS (1995) Fiziologicheskie osnovy selektsii rasteniy, vol 2. VIR
Yakushina NI (1980) Fiziologiya rasteniy. M. Prosveshchenie, 303 p


Chapter 2

Plant Cell Physiology

Abstract The cell is the smallest structural and functional unit of all living
organisms, at the level of which all the fundamental characteristics of life are

manifested. The cell is composed of several structures which have evolved to
perform unique functions:
• the cell wall contains a middle lamella, a primary cell wall and a secondary cell
wall (in order of their formation as a result of cell division) and is composed of
cellulose micro and macrofibrils immersed in an amorphous matrix consisting of
hemicellulose, pectic substances, proteins, but also of optional substances like
suberin and lignin that add up to its rigidity. The primary function of the cell
wall is that of a mechanical exoskeleton and delimiting barrier. The system of
interconnected gaps in the cell wall forms the apoplast which is a transport path
for liquids in the vegetal organism along with the symplast formed by the
plasmodesmata which connect the cytoplasm of the cells.
• the protoplasm is made of a viscous liquid matrix—the hyaloplasma which
serves as a medium for metabolic and energy exchange reactions, deposition of
substances, etc. and is also the place where the cellular organelles reside: the
nucleus, mitochondria, plastids, the endoplasmic reticulum, the Golgi body,
ribosomes, the vacuole.
• biological membranes (plasmalemma, tonoplast, membranes of the organelles)
represent fluid amphiphilic phospholipid bi-layers with various amounts of
embedded proteins which perform a diversity of functions and determine the
unique properties of the membranes. Biological membranes perform a variety of
functions like: compartmentalization, mechanical barrier, transport of various
substances including water (by osmosis), ATP synthesis (in chloroplasts,
mitochondria), receptor function, etc.
Cells constantly exchange substances with the external environment via active or
passive transport of the ions into or out of the cell. Active transport requires energy
and happens via vesicles, ion pumps and some carrier proteins, while passive
transport (no energy requirement)—via simple diffusion through the selectively
permeable membrane, or via facilitated diffusion through some carrier proteins or
protein channels. Water can also enter or exit the cell by means of osmosis,
© Springer International Publishing Switzerland 2015

M. Duca, Plant Physiology, Biological and Medical Physics,
Biomedical Engineering, DOI 10.1007/978-3-319-17909-4_2

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electroosmosis, imbibition, water currents, diffusion. A high osmotic pressure is
essential for maintaining the normal physiological state of cell turgidity, while a
low content is detrimental and can cause the phenomenon of plasmolysis. The
totality of forces that contribute to water absorption by the cell form the suction
force.

Historical Background
1667—The cell was discovered by R. Hooke.
1838–1839—T. Schwann and M.J. Schleiden formulated the “Cell theory”.
1877—W. Pfeffer studied the osmosis phenomenon in vegetal cells.
1880—G.D. Thuret and J.B. Bornet discovered plasmodesmata.
1890—S. Altman discovered mitochondria.
1895—Ch. Owerton formulated the theory of protoplasm permeability.
1897—A. Garnier discovered the endoplasmic reticulum.
1898—C. Golgi discovered the dictyosomes.
1955—G.E. Palade discovered the ribosomes.
1958—R. Buvat launched the theory of vacuole emergence from the endoplasmic
reticulum.
1959—J. Robertson demonstrated the structural uniformity of all biological
membranes.