Senescence and Aging in Plants

Contributors

Foreword

Preface


1 The Phenomena of Senescence and Aging

I. Emergence of Senescence as a Concept

II. Concepts

A. Senescence versus Aging

B. The Basic Units of Senescence

C. Death and Death Processes

D. The Senescence Syndrome: An Outline

III. Experimental Analysis of Senescence

A. Why Study Senescence?

B. Measures of Senescence

C. Correlative Controls

D. Attached versus Detached Structures

E. Hormonal Controls

IV. Patterns of Senescence

A. Overview

B. Cellular Patterns

C. Tissues

D. Organs

E. Organisms

F. Relationship between Stress and Senescence

G. Nonsenescence Processes

References


2 The Molecular Basis for Membrane Deterioration during Senescence

I. Introduction

II. Senescence of Microsomal and Plasma Membranes

A. Increased Production of Free Radicals

B. Changes in the Molecular Organization of Lipid Bilayers

C. A Tentative Model for Senescence of Microsomal Membranes

III. Thylakoid Membrane Senescence

A. Free Radical Production

B. Loss of Thylakoid Membrane Integrity

IV. Mitochondrial Membranes

V. Modulation of Membrane Senescence

VI. Conclusions

References


3 Photosynthesis

I. Introduction

II. Senescence of Chloroplasts

A. Ultrastructural Changes in Chloroplasts during Senescence

B. Autonomous Degradation of Chloroplasts

III. Chlorophyll Degradation

IV. Changes in Lipids during Chloroplast Senescence

V. Changes in Stromal Enzymes during Leaf Senescence

VI. Changes in the Components of the Chloroplast Thylakoid Membranes during Foliar Senescence

VII. Chloroplast Protein Degradation

VIII. Leaf Conductance and CO2 Assimilation in Senescing Leaves

IX. Conclusions

References


4 Respiration in Senescing Plant Organs: Its Nature, Regulation, and Physiological Significance

I. Introduction

II. Patterns of Respiration in Detached Plant Organs

A. Fruit

B. Leaves

C. Flowers

III. Causes of the Climacteric Rise in Respiration

IV. Mode of Action of Ethylene on Plant Respiration

V. Regulation of Plant Respiration

VI. Glycolysis

VII. Pentose Pathway

VIII. Tricarboxylic Acid Cycle

IX. Electron Transport

X. Residual

XI. Cellular Organization

XII. Physiological Significance of the Climacteric Rise in Plant Senescence

XIII. Summary

References


5 Nucleic Acid and Protein Synthesis

I. Introduction

II. Nucleic Acid and Protein Contents

A. DNA

B. RNA

C. Protein

III. Nucleic Acid and Protein Synthesis

A. DNA Synthesis

B. RNA Synthesis

C. Protein Synthesis

IV. Senescence Mutants

References


6 The Interplay between Proteolysis and Amino Acid Metabolism during Senescence and Nitrogen Reallocation

I. Introduction

II. Qualitative and Quantitative Description of Preanthesis Nitrogen Source

III. Protein Degradation

A. Generalized Concepts of Proteolysis

B. Protein Turnover

C. Nature of Protein-Degrading Enzymes

D. Generalized Concepts for the Regulation of Protein Degradation

IV. Senescence, Proteolysis, and the Metabolism of Nitrogen: Some Case Histories

A. Root and Nodule Senescence

B. Leaf Senescence

V. Concluding Remarks

References


7 Water Economy of Fruits and Fruiting Plants: Case Studies of Grain Legumes

I. Introduction

II. Water Balances of Developing Fruit and Seeds and Their Relationships to the Import of Carbon and Nitrogen through the Xylem and Phloem

III. Diurnal Water Balance of Fruit and the Fruiting Plant

IV. Structural Features of the Fruit and Their Significance in Terms of Water Relationships

V. Tracer Studies of the Phloem and Xylem Exchanges of Water and Solutes between Fruit, Peduncle, and the Remainder of the Plant

VI. General Conclusions

References


8 Ethylene and Plant Senescence

I. Introduction

II. Biosynthesis of Ethylene

A. Precursors and Pathway

B. Enzyme Systems

III. Regulation of Ethylene Biosynthesis

A. Methionine Recycling

B. Linkage with Polyamine Biosynthesis

C. Conjugation of ACC

D. Membrance Association and Involvement of Membrane Function

E. Feedback Controls

F. IAA-Induced Ethylene Production

IV. Ethylene in Fruit Ripening, Senescence, and Leaf Abscission

A. Ethylene and Fruit Ripening

B. Symptoms of Leaf Senescence

C. Exogenous Ethylene and Leaf-Blade Senescence

D. Endogenous Ethylene and Leaf-Blade Senescence

E. Interactions between Ethylene and Other Plant Hormones in Leaf-Blade Senescence

F. Exogenous Ethylene and Changes in the Abscission Zone

G. Interactions between Auxin and Ethylene in Abscission

H. Endogenous Ethylene in Abscission

I. Interactions between Ethylene and Other Factors in Natural Abscission

V. Mechanisms of Ethylene Action

VI. Conclusions

References


9 Cytokinins and Senescence

I. Introduction

II. Cytokinin Biochemistry and Physiology

A. Cytokinin Structure

B. Sites of Cytokinin Production

C. Cytokinin Transport

D. Cytokinin Metabolism

III. Evidence to Implicate Cytokinins in the Regulation of Senescence

IV. Cytokinins and Organ or Organism Senescence

A. Leaves

B. Cotyledons

C. Flowers

D. Fruit and Seed Senescence

E. Whole Plant Senescence

V. Relationships between Cytokinins and Other Hormones

VI. Conclusions

References


10 Abscisic Acid, Auxin, and Other Regulators of Senescence

I. Introduction

II. Abscisic Acid and Senescence Processes

A. Influence of Exogenous Abscisic Acid

B. Correlation with Endogenous Abscisic Acid

C. Relationships between Abscisic Acid and Other Hormones

III. Other Promoters of Senescence

A. Fatty Acids

B. Serine

C. Jasmonic Acid and Related Compounds

D. Miscellaneous Promoters

E. Unidentified Promoters

F. Hypersensitive Response

IV. Auxin and Senescence Processes

A. Influence of Exogenous Auxin

B. Correlation with Endogenous Auxin

C. Relationship between Auxin and Other Hormones

V. Gibberellin and Senescence Processes

A. Influence of Exogenous Gibberellin

B. Correlation with Endogenous Gibberellin

C. Relationship between Gibberellin and Other Hormones

VI. Other Retardants of Senescence

VII. Summary

A. What Hormone Is in Control?

B. Hormone Combinations

C. Integrated Hormone Systems

D. New Hormones?

E. Conclusion

References


11 Calcium and Senescence

I. Introduction

II. Calcium and Hormone Interactions

III. Cytosolic and Apoplastic Roles of Calcium

A. Cell Walls and Membranes

B. Calcium and Calmodulin

C. Protein Phosphorylation

IV. Role of Inositol Phospholipids in Calcium Messenger System

V. Conclusion

References


12 Whole Plant Senescence

I. Introduction

II. Patterns of Whole Plant Senescence

III. Correlative Controls

A. Cells and Organs as Components of the Organism

B. Control Centers versus Targets

C. Behavior of the Senescence Signal

IV. Cessation of Vegetative Growth as a Component of Whole Plant Senescence

V. Decline in Assimilatory Processes

A. Changes in Assimilation in the Roots and Leaves

B. Metabolic Decline in Plants with Reproductive Structures Removed ("Desinked")

VI. Partitioning and Redistribution of Assimilates in Relation to Senescence

A. Nutrient Diversion and Redistribution

B. Shift in Photosynthate Partitioning during Reproductive Development

C. Competition between the Fruits and Leaves for Mineral Nutrients Assimilated by the Roots

D. Controls of Assimilate Movement

E. Nutrient Redistribution

F. Exhaustion Death: Real or Apparent?

VII. Hormonal Controls

A. Introduction

B. The Senescence Signal

C. The Root/Shoot (Leaf) Interaction

VIII. Senescence of Polycarpic Plants

A. Introduction

B. Clonal Growth

C. Causes of Decline in Polycarpic Plants

D. Do Polycarpic Plants Senesce?

IX. Conclusions

References


13 Deterioration of Membranes during Aging in Plants: Evidence for Free Radical Mediation

I. Introduction

II. Evidence for Membrane Deterioraton during Aging

A. Seed Aging

B. Desiccation Tolerance

C. Freezing

D. Ice-Encasement

III. Physical Properties of Microsomal Membranes

A. Phase Properties

B. Freeze Fracture Electron Microscopy

C. Membrane Microviscosity

IV. Lipid and Protein Composition of Microsomal Membranes

A. Membrane Lipids

B. Membrane Proteins

V. Free Fatty Acids and Lipid Phase Properties

VI. Free Radicals

A. Phospholipid De-esterification

B. Free Radical Scavenging Systems

C. Production of Free Radicals

VII. Summary

References


14 Seed Aging: The Genome and Its Expression

I. Introduction

II. Historical Perspective

A. A False Dawn: Old Seeds of Oenothora Contain More "Mutants" Than New Seeds (1901-1931)

B. Chromosone Aberrations and Gene Mutations, or the Events That Give Rise to Them, Are Induced during Seed Storage (1933-1936)

C. Accumulation of Chromosome Damage Is a Function of Time, Temperature, and Moisture Content (1933-1939)

D. Recognition of a Simple Relation between Loss of Seed Viability and the Induction of Chromosome Damage (1967-1985)

E. The Concept of Repair during Moist Seed Storage (1974-1985)

F. The Amount of Chromosome Damage Associated with a Given Loss of Viability Is Large at Low-Moisture Contents and Is Minimal at High-Moisture Contents (1985)

III. The Nature of the Damage to the Genome and Its Expression

A. The Classical and Exchange Theories of Chromosome Damage

B. Chromatid-Type and Chromosome-Type Aberration in Seeds: Is the Damage Initiated during Aging or Afterward during Germination?

C. Speculations Concerning DNA Lesions That Result from Seed Aging

D. The Fate of Damage to the Genome

E. Damage to the Cellular Systems That Express the Genome

IV. Conclusions

References


15 Postlude and Prospects

I. Senescence versus Exogenously Driven Degeneration

II. What Is Senescence?

A. Required Processes

B. Central versus Peripheral Processes in Senescence

C. The Role of the Chloroplast in Senescence

D. Senescence as Parallel or Loosely Coupled Processes

E. Is Senescence One Process or Several?

F. Future Analyses of Senescence

III. What Hormone Is in Control?

IV. Limits on Life

V. Conclusions and Closing

References

Note Added in Proof

Index