Plant Physiology (Biological and Medical Physics, Biomedical Engineering)

Biological and Medical Physics, Biomedical Engineering

Maria Duca

Plant

Physiology

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

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More information about this series at http://www.springer.com/series/3740

Editorial Board:

Masuo Aizawa, Department of Bioengineering,

Tokyo Institute of Technology, Yokohama, Japan

Olaf S. Andersen, Department of Physiology,

Biophysics and Molecular Medicine,

Cornell University, New York, 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

Judith Herzfeld, Department of Chemistry,

Brandeis University, Waltham, Massachusetts, USA

Mark S. Humayun, Doheny Eye Institute,

Los Angeles, California, 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

Editor-in-Chief:

Elias Greenbaum, Oak Ridge National Laboratory, Oak Ridge, Tennessee, USA

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

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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 struc￾ture, 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 anat￾omy, 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 well￾established practices inherited from previous decades that allow to manipulate crop

species in the desired manner, even if the theoretical aspects are not always com￾pletely 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 require￾ments of modern biology, Plant Physiology offers a perspective over the instru￾ments 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 sum￾marizing a big volume of experimental data.

v

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

vi Preface

Contents

1 Introduction to the Educational Course of Plant Physiology ..... 1

1.1 The Definition and Scope of Plant Physiology . . . . . . . . . . . . 3

1.2 Purposes of Plant Physiology as a Science . . . . . . . . . . . . . . . 8

1.3 Research Methods Used by Plant Physiology . . . . . . . . . . . . . 9

References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

2 Plant Cell Physiology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

2.1 The Cell as a Structural, Morphological, Functional Unit

of Living Organisms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

2.2 Structural Organization, Chemical Composition

and Function of the Cell Wall . . . . . . . . . . . . . . . . . . . . . . . 18

2.3 Structure and Ultrastructure of Cell Protoplasm . . . . . . . . . . . 21

2.4 Structure and Function of Biological Membranes . . . . . . . . . . 23

2.5 Exchange of Substances Between the Cell and the Medium . . . 27

2.5.1 Ion Flow into the Cell . . . . . . . . . . . . . . . . . . . . . . . 27

2.5.2 Water Flow into the Cell . . . . . . . . . . . . . . . . . . . . . 31

References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

3 Water Regime . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39

3.1 Role of Water in Plants . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41

3.2 Water Content and State in Plants. . . . . . . . . . . . . . . . . . . . . 43

3.3 Forms of Water in the Soil. Accessible and Inaccessible

Water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45

3.4 The Root System as a Specialized Organ for Water

Absorption. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46

3.5 The Influence of External Factors on Water Absorption

Intensity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49

3.6 Water Elimination. Physiological Importance of Plant

Transpiration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49

3.6.1 Indices of Transpiration . . . . . . . . . . . . . . . . . . . . . . 50

3.7 Structure of the Leaf as an Organ of Transpiration . . . . . . . . . 50

vii

3.8 Stomatal and Cuticular Transpiration . . . . . . . . . . . . . . . . . . . 51

3.8.1 Stomatal Transpiration. . . . . . . . . . . . . . . . . . . . . . . 51

3.8.2 Cuticular Transpiration . . . . . . . . . . . . . . . . . . . . . . 54

3.9 Water Absorption Mechanism and Ways

of Its Circulation in Plants . . . . . . . . . . . . . . . . . . . . . . . . . . 54

3.9.1 Water Transport in Plants . . . . . . . . . . . . . . . . . . . . 55

3.10 Ecology of the Water Regime in Plants . . . . . . . . . . . . . . . . . 58

References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63

4 Photosynthesis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65

4.1 Importance of Photosynthesis and the Global Role

of Green Plants. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68

4.2 The Leaf as a Specialized Photosynthesis Organ . . . . . . . . . . . 70

4.3 The Structure, Chemical Composition, Function

and Origin of Chloroplasts . . . . . . . . . . . . . . . . . . . . . . . . . . 72

4.4 Photosynthesis Pigments . . . . . . . . . . . . . . . . . . . . . . . . . . . 77

4.5 Photosynthesis Energetics . . . . . . . . . . . . . . . . . . . . . . . . . . 81

4.6 Photosynthesis Mechanism. . . . . . . . . . . . . . . . . . . . . . . . . . 86

4.6.1 Light Phase of Photosynthesis . . . . . . . . . . . . . . . . . 87

4.6.2 The Dark Phase of Photosynthesis . . . . . . . . . . . . . . 101

4.7 Photorespiration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107

4.8 Endogenous Regulatory Elements of Photosynthesis . . . . . . . . 110

4.9 Ecology of Photosynthesis . . . . . . . . . . . . . . . . . . . . . . . . . . 117

References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 122

5 Plant Respiration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123

5.1 General Notions of Respiration. . . . . . . . . . . . . . . . . . . . . . . 125

5.2 Respiratory Enzymes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 128

5.3 A.N. Bach’s and V.I. Palladin’s Theories. . . . . . . . . . . . . . . . 130

5.4 Respiration Mechanism . . . . . . . . . . . . . . . . . . . . . . . . . . . . 131

5.4.1 Genetic Link Between Respiration

and Fermentation . . . . . . . . . . . . . . . . . . . . . . . . . . 131

5.4.2 Glycolysis—The Anaerobic Phase of Respiration . . . . 132

5.4.3 Krebs Cycle (Tricarboxylic Acid Cycle) . . . . . . . . . . 135

5.4.4 The Electron Transport Chain and the Energetic

Outcome of Aerobic Respiration. . . . . . . . . . . . . . . . 138

5.5 Different Types of Respiratory Substrate Oxidation . . . . . . . . . 140

5.6 Ecology of Respiration . . . . . . . . . . . . . . . . . . . . . . . . . . . . 143

5.7 Regulation and Self-regulation of the Respiration Process . . . . 144

References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 148

6 Mineral Nutrition of Plants. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 149

6.1 Importance of Mineral Elements in Plant Nutrition . . . . . . . . . 151

6.2 Chemical Composition of the Ash. . . . . . . . . . . . . . . . . . . . . 153

viii Contents

6.3 Methods of Mineral Nutrition Research . . . . . . . . . . . . . . . . . 154

6.4 The Root System as an Organ for Absorption and Transport

of Mineral Elements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 155

6.5 Physiological Role of Macroelements . . . . . . . . . . . . . . . . . . 156

6.5.1 Absorption, Transport and Metabolism of Nitrogen . . . 156

6.5.2 Absorption, Transport and Metabolism of Sulfur. . . . . 165

6.5.3 Absorption, Transport and Metabolism

of Phosphorus . . . . . . . . . . . . . . . . . . . . . . . . . . . . 168

6.5.4 The Physiological Role of Other Macroelements. . . . . 170

6.6 Physiological Role of Microelements. . . . . . . . . . . . . . . . . . . 175

6.7 Mechanism of Absorption and Transport of Ions in Plants . . . . 178

6.7.1 Mineral Element Absorption. . . . . . . . . . . . . . . . . . . 178

6.7.2 Mineral Element Transport. . . . . . . . . . . . . . . . . . . . 181

6.8 Soil as a Substrate for Plant Nutrition . . . . . . . . . . . . . . . . . . 182

6.9 Influence of Various Environmental Factors on Mineral

Nutrition in Plants. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 183

References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 184

7 Plant Growth and Development. . . . . . . . . . . . . . . . . . . . . . . . . . 187

7.1 The Concept of Plant Growth and Development . . . . . . . . . . . 189

7.1.1 Dormancy in Plants (Repose) . . . . . . . . . . . . . . . . . . 190

7.2 Types of Plant Growth . . . . . . . . . . . . . . . . . . . . . . . . . . . . 193

7.3 Phases of Cell Growth and Development . . . . . . . . . . . . . . . . 193

7.4 Phases of Plant Growth and Development . . . . . . . . . . . . . . . 195

7.5 Genetic Aspects of Plant Morphogenesis . . . . . . . . . . . . . . . . 197

7.6 Endogenous Factors of Plant Growth and Development . . . . . . 199

7.6.1 Auxins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 203

7.6.2 Gibberellins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 207

7.6.3 Cytokinins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 210

7.6.4 Abscisic Acid. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 213

7.6.5 Ethylene . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 215

7.7 Photoperiodism and Yarovization . . . . . . . . . . . . . . . . . . . . . 218

7.8 The Influence of Exogenous Factors on Plant Growth

and Development . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 221

7.9 Plant Growth Movements—Tropism and Nasties . . . . . . . . . . 222

7.10 Self-Regulation of Plant Growth and Development . . . . . . . . . 225

References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 228

8 Plant Biorhythms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 231

8.1 Classification and Mechanisms of Biological Rhythms . . . . . . 233

8.2 Biological Rhythms in Plants . . . . . . . . . . . . . . . . . . . . . . . . 236

8.3 Circadian Rhythms in Plants . . . . . . . . . . . . . . . . . . . . . . . . 239

8.4 The Molecular Mechanism of the Circadian Clock . . . . . . . . . 241

8.4.1 Environmental Signals Involved . . . . . . . . . . . . . . . . 242

Contents ix

8.4.2 Temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 242

8.4.3 Light. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 243

8.4.4 The Molecular Targets of Light Signaling . . . . . . . . . 243

8.4.5 Rhythmic Regulation of Light Signaling . . . . . . . . . . 244

References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 245

9 Elimination of Substances in Plants . . . . . . . . . . . . . . . . . . . . . . . 247

9.1 Classification of the Types of Substance Elimination. . . . . . . . 249

9.2 Excretion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 251

9.3 Secretion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 253

9.3.1 Lignin, Cutin and Wax Secretion . . . . . . . . . . . . . . . 255

9.3.2 Nectariferous Glands and Nectar Secretion. . . . . . . . . 258

9.3.3 Terpenoid Secreting Structures . . . . . . . . . . . . . . . . . 259

9.4 Secretory Processes in Insectivorous Plants . . . . . . . . . . . . . . 261

9.5 Water Elimination in Plants . . . . . . . . . . . . . . . . . . . . . . . . . 262

9.6 Ecological Role of Substance Elimination . . . . . . . . . . . . . . . 266

References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 268

10 Physiology of Plant Resistance to Unfavorable Environmental

Factors. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 271

10.1 The Concepts of Resistance and Adaptation . . . . . . . . . . . . . . 273

10.2 Unfavorable Factors of the Winter-Spring Period . . . . . . . . . . 276

10.3 Plant Resistance to Cold and Frost . . . . . . . . . . . . . . . . . . . . 277

10.4 Plant Resistance to Drought . . . . . . . . . . . . . . . . . . . . . . . . . 280

10.4.1 Physiological Basis of Irrigation . . . . . . . . . . . . . . . . 285

10.5 Plant Resistance to Saltiness. . . . . . . . . . . . . . . . . . . . . . . . . 286

10.6 Regulation of Physiological Processes in Halophyte Plants. . . . 289

10.7 Plant Resistance to Environmental Pollution. . . . . . . . . . . . . . 292

10.7.1 Resistance to Heavy Metals . . . . . . . . . . . . . . . . . . . 294

10.7.2 Resistance to Radiation . . . . . . . . . . . . . . . . . . . . . . 295

10.7.3 Resistance to Gases. . . . . . . . . . . . . . . . . . . . . . . . . 298

10.8 Metabolism of Pollutants in Plants . . . . . . . . . . . . . . . . . . . . 299

10.9 Biochemical Mechanism of Pollutant Transformation

in Plants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 301

10.10 Self-regulation of Plant Growth and Development

in Unfavorable Environmental Conditions . . . . . . . . . . . . . . . 303

References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 308

Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 309

x Contents

Chapter 1

Introduction to the Educational

Course of Plant Physiology

Abstract Plant physiology is a science that studies vegetal organisms in ontoge￾netic dynamics—the diversity, the laws and the mechanisms of physiological and

biochemical processes, their biological significance, their dependence on environ￾mental factors. Traditionally, it was based on two directions: anatomical/morpho￾logical 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 inter￾acting centers of dominance). While as a theoretical science plant physiology tries

to obtain an integrated, detailed picture of the molecular, biochemical, physiolog￾ical, 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

Historical Background

1727—St. Hales identifies the pathways of water, mineral salts and organic sub￾stances 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 recom￾binant 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

2 1 Introduction to the Educational Course of Plant Physiology

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 pro￾cesses, 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 dis￾covered photosynthesis (1771), etc.

During the development of plant physiology as a science, it has been based on

two directions: anatomical/morphological (descriptive) and physiological (experi￾mental), 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

1 Introduction to the Educational Course of Plant Physiology 3

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. Cytophysiology (plant cell physiology);

2. Water regime of plants (H. Dutrochet, H. de Friz, J. Sachs);

3. Photosynthesis (G. Busengo, M. Ţsvet, J. Pristley, K.A. Timireazev);

4. Mineral nutrition (I. Leibih, G.B. Busengo, D.N. Preanishnikov);

5. Respiration (A.S. Famiţsin, I.P. Borodin, L. Paster);

6. Growth and development (J. Sachs, A.S. Famiţsin);

7. Plant movements (T. Nait, J. Sachs, Ch. Darwin);

8. Irritation (B. Sanderson, Ch. Darwin);

9. 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, redox￾potential, 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

4 1 Introduction to the Educational Course of Plant Physiology