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Lincoln Taiz
Professor Emeritus
University of California, Santa Cruz
Eduardo Zeiger
Professor Emeritus
University of California, Los Angeles
Sinauer Associates Inc., Publishers
Sunderland, Massachusetts U.S.A.
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Contents
CHAPTER 1 Plant Cells 1
Plant Life: Unifying Principles 2 Independently Dividing, Semiautonomous
Organelles 18
Overview of Plant Structure 2
Proplastids mature into specialized plastids in
Plant cells are surrounded by rigid cell walls 2
different plant tissues 21
New cells are produced by dividing
Chloroplast and mitochondrial division are
tissues called meristems 2
independent of nuclear division 21
Three major tissue systems make up the
plant body 4 The Plant Cytoskeleton 22
The plant cytoskeleton consists of microtubules
Plant Cell Organelles 4
and microfi laments 22
Biological membranes are phospholipid
Microtubules and microfi laments can assemble
bilayers that contain proteins 4
and disassemble 23
The Endomembrane System 8 Cortical microtubules can move around the cell by
The nucleus contains the majority of the “treadmilling” 24
genetic material 8 Cytoskeletal motor proteins mediate cytoplasmic
Gene expression involves both transcription streaming and organelle traffi c 24
and translation 10
Cell Cycle Regulation 25
The endoplasmic reticulum is a network
Each phase of the cell cycle has a specifi c set of
of internal membranes 10
biochemical and cellular activities 26
Secretion of proteins from cells begins with the
The cell cycle is regulated by cyclins and
rough ER (RER) 13
cyclin-dependent kinases 26
Glycoproteins and polysaccharides destined
Mitosis and cytokinesis involve both microtubules
for secretion are processed in the Golgi
and the endomembrane system 27
apparatus 14
The plasma membrane has specialized regions Plasmodesmata 29
involved in membrane recycling 16 Primary and secondary plasmodesmata help to
Vacuoles have diverse functions in plant cells 16 maintain tissue developmental gradients 29
Independently Dividing Organelles Derived SUMMARY 31
from the Endomembrane System 17
Oil bodies are lipid-storing organelles 17
Microbodies play specialized metabolic roles in
leaves and seeds 17
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CHAPTER 2 Genome Organization and Gene Expression 35
Nuclear Genome Organization 35 Epigenetic modifi cations help determine gene
The nuclear genome is packaged into activity 48
chromatin 36
Posttranscriptional Regulation of
Centromeres, telomeres, and nucleolar organizers Nuclear Gene Expression 50
contain repetitive sequences 36
RNA stability can be infl uenced by
Transposons are mobile sequences within cis-elements 50
the genome 37
Noncoding RNAs regulate mRNA activity via
Polyploids contain multiple copies of the entire the RNA interference (RNAi) pathway 50
genome 38
Posttranslational regulation determines
Phenotypic and physiological responses to the life span of proteins 54
polyploidy are unpredictable 41
Tools for Studying Gene Function 55
Plant Cytoplasmic Genomes: Mitochondria
Mutant analysis can help to elucidate
and Chloroplasts 42
gene function 55
The endosymbiotic theory describes the origin
Molecular techniques can measure the
of cytoplasmic genomes 42
activity of genes 55
Organellar genomes consist mostly of linear
Gene fusions can introduce reporter genes 56
chromosomes 43
Organellar genetics do not obey Genetic Modifi cation of Crop Plants 59
Mendelian laws 44 Transgenes can confer resistance to
herbicides or plant pests 59
Transcriptional Regulation of Nuclear
Genetically modifi ed organisms are
Gene Expression 45
controversial 60
RNA polymerase II binds to the promoter
region of most protein-coding genes 45 SUMMARY 61
UNIT I Transport and Translocation of Water and Solutes 65
CHAPTER 3 Water and Plant Cells 67
Water in Plant Life 67 Water Potential 73
The chemical potential of water represents the
The Structure and Properties of Water 68
free-energy status of water 74
Water is a polar molecule that forms hydrogen
Three major factors contribute to cell
bonds 68
water potential 74
Water is an excellent solvent 69
Water potentials can be measured 75
Water has distinctive thermal properties relative to
its size 69 Water Potential of Plant Cells 75
Water molecules are highly cohesive 69 Water enters the cell along a water potential
gradient 75
Water has a high tensile strength 70
Water can also leave the cell in response to a water
Diffusion and Osmosis 71
potential gradient 77
Diffusion is the net movement of molecules by
Water potential and its components vary with
random thermal agitation 71
growth conditions and location within the
Diffusion is most effective over short distances 72 plant 77
Osmosis describes the net movement of water
Cell Wall and Membrane Properties 78
across a selectively permeable barrier 73
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XVIII TABLE OF CONTENTS
Small changes in plant cell volume cause large Plant Water Status 80
changes in turgor pressure 78 Physiological processes are affected by plant water
The rate at which cells gain or lose water is status 80
infl uenced by cell membrane hydraulic Solute accumulation helps cells maintain turgor
conductivity 79 and volume 80
Aquaporins facilitate the movement of water across
SUMMARY 81
cell membranes 79
CHAPTER 4 Water Balance of Plants 85
Water in the Soil 85 Xylem transport of water in trees faces physical
A negative hydrostatic pressure in soil water challenges 94
lowers soil water potential 86 Plants minimize the consequences of
Water moves through the soil by bulk fl ow 87 xylem cavitation 96
Water Absorption by Roots 87 Water Movement from the Leaf to the
Atmosphere 96
Water moves in the root via the apoplast,
symplast, and transmembrane pathways 88 Leaves have a large hydraulic resistance 96
Solute accumulation in the xylem can generate The driving force for transpiration is the
“root pressure” 89 difference in water vapor concentration 96
Water loss is also regulated by the pathway
Water Transport through the Xylem 90
resistances 98
The xylem consists of two types of tracheary
Stomatal control couples leaf transpiration to
elements 90
leaf photosynthesis 98
Water moves through the xylem by
The cell walls of guard cells have specialized
pressure-driven bulk fl ow 92
features 99
Water movement through the xylem requires
An increase in guard cell turgor pressure
a smaller pressure gradient than movement
opens the stomata 101
through living cells 93
The transpiration ratio measures the relationship
What pressure difference is needed to lift water
between water loss and carbon gain 101
100 meters to a treetop? 93
The cohesion–tension theory explains water trans- Overview: The Soil–Plant–Atmosphere
port in the xylem 93 Continuum 102
SUMMARY 102
CHAPTER 5 Mineral Nutrition 107
Essential Nutrients, Defi ciencies, Some mineral nutrients can be absorbed by
and Plant Disorders 108 leaves 118
Special techniques are used in nutritional
Soil, Roots, and Microbes 119
studies 110
Negatively charged soil particles affect the adsorp-
Nutrient solutions can sustain rapid
tion of mineral nutrients 119
plant growth 110
Soil pH affects nutrient availability, soil microbes,
Mineral defi ciencies disrupt plant metabolism
and root growth 120
and function 113
Excess mineral ions in the soil limit plant
Analysis of plant tissues reveals mineral
growth 120
defi ciencies 117
Plants develop extensive root systems 121
Treating Nutritional Defi ciencies 117 Root systems differ in form but are based on
Crop yields can be improved by addition of common structures 121
fertilizers 118
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TABLE OF CONTENTS XIX
Different areas of the root absorb different Nutrients move from mycorrhizal fungi to
mineral ions 123 root cells 126
Nutrient availability infl uences root growth 124
SUMMARY 126
Mycorrhizal fungi facilitate nutrient uptake
by roots 125
CHAPTER 6 Solute Transport 131
Passive and Active Transport 132 The genes for many transporters have
been identifi ed 144
Transport of Ions across Membrane
Transporters exist for diverse
Barriers 133
nitrogen-containing compounds 146
Different diffusion rates for cations and anions
Cation transporters are diverse 147
produce diffusion potentials 134
Anion transporters have been identifi ed 148
How does membrane potential relate to ion
distribution? 134 Metal transporters transport essential
micronutrients 149
The Nernst equation distinguishes between
active and passive transport 136 Aquaporins have diverse functions 149
Proton transport is a major determinant of Plasma membrane H+-ATPases are highly
regulated P-type ATPases 150
the membrane potential 137
The tonoplast H+-ATPase drives solute
Membrane Transport Processes 137
accumulation in vacuoles 151
Channels enhance diffusion across H+-pyrophosphatases also pump protons at
membranes 139
the tonoplast 153
Carriers bind and transport specifi c substances 140
Ion Transport in Roots 153
Primary active transport requires energy 140
Solutes move through both apoplast and
Secondary active transport uses stored
symplast 153
energy 142
Ions cross both symplast and apoplast 153
Kinetic analyses can elucidate transport
Xylem parenchyma cells participate in xylem
mechanisms 143
loading 154
Membrane Transport Proteins 144
SUMMARY 156
UNIT II Biochemistry and Metabolism 161
CHAPTER 7 Photosynthesis: The Light Reactions 163
Photosynthesis in Higher Plants 164 Photosynthesis takes place in complexes
containing light-harvesting antennas and
General Concepts 164
photochemical reaction centers 169
Light has characteristics of both a particle
The chemical reaction of photosynthesis is
and a wave 164
driven by light 170
When molecules absorb or emit light,
Light drives the reduction of NADP and the
they change their electronic state 165
formation of ATP 171
Photosynthetic pigments absorb the light that
Oxygen-evolving organisms have two
powers photosynthesis 166
photosystems that operate in series 171
Key Experiments in Understanding
Organization of the Photosynthetic
Photosynthesis 167
Apparatus 172
Action spectra relate light absorption to
The chloroplast is the site of photosynthesis 172
photosynthetic activity 168
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XX TABLE OF CONTENTS
Thylakoids contain integral membrane proteins 173 The photosystem I reaction center
reduces NADP+ 185
Photosystems I and II are spatially separated
in the thylakoid membrane 174 Cyclic electron fl ow generates ATP but no
NADPH 185
Anoxygenic photosynthetic bacteria have a
single reaction center 174 Some herbicides block photosynthetic
electron fl ow 186
Organization of Light-Absorbing
Antenna Systems 176 Proton Transport and ATP Synthesis
in the Chloroplast 187
Antenna systems contain chlorophyll and
are membrane associated 176
Repair and Regulation of the
The antenna funnels energy to the Photosynthetic Machinery 189
reaction center 176
Carotenoids serve as photoprotective agents 190
Many antenna pigment–protein complexes
Some xanthophylls also participate in energy
have a common structural motif 176
dissipation 190
Mechanisms of Electron Transport 178 The photosystem II reaction center is easily
Electrons from chlorophyll travel through damaged 191
the carriers organized in the “Z scheme” 178 Photosystem I is protected from active oxygen
Energy is captured when an excited chlorophyll species 191
reduces an electron acceptor molecule 179 Thylakoid stacking permits energy partitioning
The reaction center chlorophylls of the two between the photosystems 191
photosystems absorb at different
Genetics, Assembly, and Evolution of
wavelengths 180
Photosynthetic Systems 192
The photosystem II reaction center is a
Chloroplast genes exhibit non-Mendelian patterns
multisubunit pigment–protein complex 181
of inheritance 192
Water is oxidized to oxygen by
Most chloroplast proteins are imported from
photosystem II 181
the cytoplasm 192
Pheophytin and two quinones accept electrons
The biosynthesis and breakdown of chlorophyll
from photosystem II 183
are complex pathways 192
Electron fl ow through the cytochrome b f
6 Complex photosynthetic organisms have evolved
complex also transports protons 183
from simpler forms 193
Plastoquinone and plastocyanin carry electrons
between photosystems II and I 184 SUMMARY 194
CHAPTER 8 Photosynthesis: The Carbon Reactions 199
The Calvin–Benson Cycle 200 Light-dependent ion movements modulate en-
The Calvin–Benson cycle has three stages: zymes of the Calvin–Benson cycle 208
carboxylation, reduction, and regeneration 200 Light controls the assembly of chloroplast enzymes
The carboxylation of ribulose 1,5-bisphosphate fi xes into supramolecular complexes 208
CO for the synthesis of triose phosphates 201
2 The C Oxidative Photosynthetic Carbon
2
Ribulose 1,5-bisphosphate is regenerated for Cycle 208
the continuous assimilation of CO 201
2 The carboxylation and the oxygenation of ribulose
An induction period precedes the steady state 1,5-bisphosphate are competing reactions 210
of photosynthetic CO assimilation 204
2 Photorespiration depends on the photosynthetic
Regulation of the Calvin–Benson Cycle 205 electron transport system 213
The activity of rubisco increases in the light 206 Photorespiration protects the photosynthetic ap-
paratus under stress conditions 214
Light regulates the Calvin–Benson cycle via the
ferredoxin–thioredoxin system 207 Photorespiration may be engineered to increase
the production of biomass 214
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TABLE OF CONTENTS XXI
Inorganic Carbon–Concentrating Formation and Mobilization of
Mechanisms 216 Chloroplast Starch 225
Starch is synthesized in the chloroplast
Inorganic Carbon–Concentrating Mechanisms:
during the day 225
The C Carbon Cycle 216
4 Starch degradation at night requires the
Malate and aspartate are carboxylation products of
phosphorylation of amylopectin 228
the C cycle 217
4 The export of maltose prevails in the nocturnal
Two different types of cells participate in the C
4 breakdown of transitory starch 230
cycle 218
Sucrose Biosynthesis and Signaling 231
The C cycle concentrates CO in the chloroplasts
4 2
of bundle sheath cells 220 Triose phosphates supply the cytosolic pool
of three important hexose phosphates in the
The C cycle also concentrates CO in single
4 2 light 231
cells 221
Fructose 2,6-bisphosphate regulates the hexose
Light regulates the activity of key C enzymes 221
4 phosphate pool in the light 235
In hot, dry climates, the C cycle reduces photo-
4 The cytosolic interconversion of hexose phos-
respiration and water loss 221
phates governs the allocation of assimilated
Inorganic Carbon–Concentrating Mechanisms: carbon 235
Crassulacean Acid Metabolism (CAM) 221 Sucrose is continuously synthesized in the
CAM is a versatile mechanism sensitive to environ- cytosol 235
mental stimuli 223
SUMMARY 237
Accumulation and Partitioning of
Photosynthates—Starch and Sucrose 224
Photosynthesis: Physiological and Ecological
CHAPTER 9
Considerations 243
Photosynthesis Is the Primary Function of There is an optimal temperature for
Leaves 244 photosynthesis 256
Leaf anatomy maximizes light absorption 245
Photosynthetic Responses to Carbon
Plants compete for sunlight 246 Dioxide 256
Leaf angle and leaf movement can control light Atmospheric CO concentration keeps rising 257
2
absorption 247
CO diffusion to the chloroplast is essential to
2
Plants acclimate and adapt to sun and shade photosynthesis 258
environments 248
Patterns of light absorption generate gradients of
Photosynthetic Responses to Light by the CO2 fi xation 259
Intact Leaf 249 CO imposes limitations on photosynthesis 260
2
Light-response curves reveal photosynthetic How will photosynthesis and respiration change in
properties 249 the future under elevated CO conditions? 261
2
Leaves must dissipate excess light energy 251
Identifying Different Photosynthetic
Absorption of too much light can lead to Pathways 263
photoinhibition 253
How do we measure the stable carbon isotopes of
Photosynthetic Responses to plants? 263
Temperature 254 Why are there carbon isotope ratio variations in
plants? 264
Leaves must dissipate vast quantities of heat 254
Photosynthesis is temperature sensitive 255 SUMMARY 266
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XXII TABLE OF CONTENTS
CHAPTER 10 Translocation in the Phloem 271
Pathways of Translocation 272 Phloem loading in the apoplastic pathway
Sugar is translocated in phloem sieve involves a sucrose–H+ symporter 287
elements 273 Phloem loading is symplastic in some
Mature sieve elements are living cells specialized species 288
for translocation 273 The polymer-trapping model explains
Large pores in cell walls are the prominent feature symplastic loading in plants with intermediary
of sieve elements 274 cells 288
Damaged sieve elements are sealed off 274 Phloem loading is passive in a number of
tree species 289
Companion cells aid the highly specialized sieve
elements 276 The type of phloem loading is correlated with a
number of signifi cant characteristics 290
Patterns of Translocation: Source to Sink 276
Phloem Unloading and Sink-to-Source
Materials Translocated in the Phloem 277 Transition 291
Phloem sap can be collected and analyzed 278 Phloem unloading and short-distance transport
Sugars are translocated in nonreducing form 279 can occur via symplastic or apoplastic
pathways 291
Other solutes are translocated in the phloem 280
Transport into sink tissues requires metabolic
Rates of Movement 280
energy 292
The Pressure-Flow Model, a Passive The transition of a leaf from sink to source is
Mechanism for Phloem Transport 281 gradual 292
An osmotically-generated pressure gradient drives Photosynthate Distribution: Allocation and
translocation in the pressure-fl ow model 281
Partitioning 294
The predictions of mass fl ow have been Allocation includes storage, utilization, and
confi rmed 282 transport 294
Sieve plate pores are open channels 283 Various sinks partition transport sugars 295
There is no bidirectional transport in single sieve Source leaves regulate allocation 295
elements 284
Sink tissues compete for available translocated
The energy requirement for transport through the photosynthate 296
phloem pathway is small 284
Sink strength depends on sink size and
Positive pressure gradients exist in the phloem activity 296
sieve elements 284
The source adjusts over the long term to changes
Does translocation in gymnosperms involve a in the source-to-sink ratio 297
different mechanism? 285
The Transport of Signaling Molecules 297
Phloem Loading 285
Turgor pressure and chemical signals coordinate
Phloem loading can occur via the apoplast or
source and sink activities 297
symplast 285
Proteins and RNAs function as signal molecules
Abundant data support the existence of
in the phloem to regulate growth and
apoplastic loading in some species 286
development 298
Sucrose uptake in the apoplastic pathway
requires metabolic energy 286 SUMMARY 299
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TABLE OF CONTENTS XXIII
CHAPTER 11 Respiration and Lipid Metabolism 305
Overview of Plant Respiration 305 Aerobic respiration yields about 60 molecules
of ATP per molecule of sucrose 322
Glycolysis 309
Several subunits of respiratory complexes
Glycolysis metabolizes carbohydrates from
are encoded by the mitochondrial genome 324
several sources 309
Plants have several mechanisms that lower
The energy-conserving phase of glycolysis
the ATP yield 324
extracts usable energy 310
Short-term control of mitochondrial
Plants have alternative glycolytic reactions 310
respiration occurs at different levels 326
In the absence of oxygen, fermentation
Respiration is tightly coupled to other
regenerates the NAD+ needed for
pathways 327
glycolysis 311
Respiration in Intact Plants and Tissues 327
Plant glycolysis is controlled by its products 312
Plants respire roughly half of the daily
The Oxidative Pentose Phosphate
photosynthetic yield 328
Pathway 312
Respiration operates during photosynthesis 329
The oxidative pentose phosphate pathway
Different tissues and organs respire at different
produces NADPH and biosynthetic
rates 329
intermediates 314
Environmental factors alter respiration rates 329
The oxidative pentose phosphate pathway is
redox-regulated 314 Lipid Metabolism 330
The Citric Acid Cycle 315 Fats and oils store large amounts of energy 331
Mitochondria are semiautonomous Triacylglycerols are stored in oil bodies 331
organelles 315 Polar glycerolipids are the main structural lipids in
Pyruvate enters the mitochondrion and is membranes 332
oxidized via the citric acid cycle 316 Fatty acid biosynthesis consists of cycles of two-
The citric acid cycle of plants has unique carbon addition 334
features 317 Glycerolipids are synthesized in the plastids
and the ER 335
Mitochondrial Electron Transport and
Lipid composition infl uences membrane
ATP Synthesis 317
function 336
The electron transport chain catalyzes a fl ow of
Membrane lipids are precursors of important
electrons from NADH to O 318
2 signaling compounds 336
The electron transport chain has supplementary
Storage lipids are converted into carbohydrates
branches 320
in germinating seeds 336
ATP synthesis in the mitochondrion is coupled to
electron transport 320 SUMMARY 338
Transporters exchange substrates and
products 322
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XXIV TABLE OF CONTENTS
CHAPTER 12 Assimilation of Mineral Nutrients 343
Nitrogen in the Environment 344 Establishing symbiosis requires an exchange of
Nitrogen passes through several forms in a biogeo- signals 354
chemical cycle 344 Nod factors produced by bacteria act as signals
Unassimilated ammonium or nitrate may be dan- for symbiosis 354
gerous 346 Nodule formation involves phytohormones 355
The nitrogenase enzyme complex fi xes N 357
Nitrate Assimilation 346 2
Amides and ureides are the transported
Many factors regulate nitrate reductase 347
forms of nitrogen 358
Nitrite reductase converts nitrite to
ammonium 347 Sulfur Assimilation 358
Both roots and shoots assimilate nitrate 348 Sulfate is the absorbed form of sulfur in
plants 358
Ammonium Assimilation 348
Sulfate assimilation requires the reduction of
Converting ammonium to amino acids requires
sulfate to cysteine 359
two enzymes 348
Sulfate assimilation occurs mostly in leaves 360
Ammonium can be assimilated via an
Methionine is synthesized from cysteine 360
alternative pathway 350
Transamination reactions transfer nitrogen 350 Phosphate Assimilation 360
Asparagine and glutamine link carbon and
Cation Assimilation 361
nitrogen metabolism 350
Cations form noncovalent bonds with carbon
Amino Acid Biosynthesis 351 compounds 361
Roots modify the rhizosphere to acquire iron 362
Biological Nitrogen Fixation 351
Iron forms complexes with carbon
Free-living and symbiotic bacteria fi x
and phosphate 363
nitrogen 351
Nitrogen fi xation requires anaerobic Oxygen Assimilation 363
conditions 352
The Energetics of Nutrient Assimilation 364
Symbiotic nitrogen fi xation occurs in
specialized structures 354
SUMMARY 365
CHAPTER 13 Secondary Metabolites and Plant Defense 369
Secondary Metabolites 370 Some terpenes have roles in growth and
Secondary metabolites defend plants against her- development 373
bivores and pathogens 370 Terpenes defend many plants against
Secondary metabolites are divided into three ma- herbivores 373
jor groups 370
Phenolic Compounds 374
Terpenes 370 Phenylalanine is an intermediate in the
Terpenes are formed by the fusion of fi ve-carbon biosynthesis of most plant phenolics 375
isoprene units 370 Ultraviolet light activates some simple
There are two pathways for terpene phenolics 377
biosynthesis 370 The release of phenolics into the soil may
IPP and its isomer combine to form larger limit the growth of other plants 377
terpenes 371 Lignin is a highly complex phenolic
macromolecule 377
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