Plant Physiology and Development

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Half Title
Title Page
Copyright Page
Brief Contents
Editors
Reviewers
Preface
Media and Supplements
Table of Contents
Chapter 1 Plant and Cell Architecture
	Plant Classification and Life Cycles
	Plant Life Processes: Unifying Principles
		Plant life cycles alternate between diploid and haploid generations
	Overview of Plant Structure
		Plant cells are surrounded by rigid cell walls
		Plasmodesmata allow the free movement of molecules between cells
		New cells originate in dividing tissues called meristems
		Biological membranes are phospholipid bilayers that contain proteins
	Plant Cell Organelles
	The Endomembrane System
		The nucleus contains the majority of the genetic material
		Gene expression involves both transcription and translation
		The endoplasmic reticulum is a network of internal membranes
		Secretion of proteins from cells begins with the rough ER
		Glycoproteins and polysaccharides destined for secretion are processed in the Golgi apparatus
		The plasma membrane has specialized regions involved in membrane recycling
		Vacuoles have diverse functions in plant cells
	Independently Dividing or Fusing Organelles Derived from the Endomembrane System
		Oil bodies are lipid-storing organelles
		Microbodies play specialized metabolic roles in leaves and seeds
	Independently Dividing, Semiautonomous Organelles
		Proplastids mature into specialized plastids in different plant tissues
		Chloroplast and mitochondrial division are independent of nuclear division
		The plant cytoskeleton consists of microtubules and microfilaments
	The Plant Cytoskeleton
		Actin, tubulin, and their polymers are in constant flux in the living cell
		Cortical microtubules move around the cell by treadmilling
		Cytoskeletal motor proteins mediate cytoplasmic streaming and directed organelle movement
	Cell Cycle Regulation
		Each phase of the cell cycle has a specific set of biochemical and cellular activities
		The cell cycle is regulated by cyclins and cyclin-dependent kinases
		Mitosis and cytokinesis involve both microtubules and the endomembrane system
	Plant Cell Types
		Dermal tissues cover the surfaces of plants
		Ground tissues form the bodies of plants
		Vascular tissues form transport networks between different parts of the plant
	Summary
	Web Material
	Suggested Reading
Chapter 2 Genome Structure and Gene Expression
	Nuclear Genome Organization
		The nuclear genome is packaged into chromatin
		Centromeres, telomeres, and nucleolar organizer regions contain repetitive sequences
		Transposons are mobile sequences within the genome
		Meiosis halves the number of chromosomes and allows for the recombination of alleles
		Chromosome organization is not random in the interphase nucleus
		Polyploids contain multiple copies of the entire genome
		Phenotypic and physiological responses to polyploidy are unpredictable
		The role of polyploidy in evolution is still unclear
	Plant Cytoplasmic Genomes: Mitochondria and Plastids
		The endosymbiotic theory describes the origin of cytoplasmic genomes
		Organellar genetics do not obey Mendelian principles
		Organellar genomes vary in size
		RNA polymerase II binds to the promoter region of most protein-coding genes
	Transcriptional Regulation of Nuclear Gene Expression
		Conserved nucleotide sequences signal transcriptional termination and polyadenylation
		Epigenetic modifications help determine gene activity
		Noncoding RNAs regulate mRNA activity via the RNA interference (RNAi) pathway
	Posttranscriptional Regulation of Nuclear Gene Expression
		All RNA molecules are subject to decay
		Posttranslational regulation determines the life span of proteins
	Tools for Studying Gene Function
		Mutant analysis can help elucidate gene function
		Molecular techniques can measure the activity of genes
		Gene fusions can introduce reporter genes
	Genetic Modification of Crop Plants
		Transgenes can confer resistance to herbicides or plant pests
		Genetically modified organisms are controversial
		Plant Cytoplasmic Genomes: Mitochondria and Plastids
	Summary
	Web Material
	Suggested Reading
Chapter 3 Water and Plant Cells
	Water in Plant Life
	The Structure and Properties of Water
		Water is a polar molecule that forms hydrogen bonds
		Water molecules are highly cohesive
		Water is an excellent solvent
		Water has distinctive thermal properties relative to its size
		Water has a high tensile strength
	Diffusion and Osmosis
		Diffusion is the net movement of molecules by random thermal agitation
		Diffusion is most effective over short distances
		Osmosis describes the net movement of water across a selectively permeable barrier
	Water Potential
		The chemical potential of water represents the free-energy status of water
		Three major factors contribute to cell water potential
		Water potentials can be measured
	Water Potential of Plant Cells
		Water enters the cell along a water potential gradient
		Water can also leave the cell in response to a water potential gradient
	Cell Wall and Membrane Properties
		Small changes in plant cell volume cause large changes in turgor pressure
		Water potential and its components vary with growth conditions and location within the plant
		The rate at which cells gain or lose water is influenced by plasma membrane hydraulic conductivity
		Aquaporins facilitate the movement of water across plasma membranes
	Plant Water Status
		Solute accumulation helps cells maintain turgor and volume
		Physiological processes are affected by plant water status
	Summary
	Web Material
	Suggested Reading
Chapter 4 Water Balance of Plants
	Water in the Soil
		A negative hydrostatic pressure in soil water lowers soil water potential
		Water moves through the soil by bulk flow
	Water Absorption by Roots
		Water moves in the root via the apoplast, symplast, and transmembrane pathways
		Solute accumulation in the xylem can generate “root pressure”
		The xylem consists of two types of transport cells
	Water Transport through the Xylem
		Water moves through the xylem by pressure-driven bulk flow
		Water movement through the xylem requires a smaller pressure gradient than movement through living cells
		What pressure difference is needed to lift water 100 meters to a treetop?
		The cohesion–tension theory explains water transport in the xylem
		Xylem transport of water in trees faces physical challenges
	Water Movement from the Leaf to the Atmosphere
		Plants minimize the consequences of xylem cavitation
		Leaves have a large hydraulic resistance
		The driving force for transpiration is the difference in water vapor concentration
		Water loss is also regulated by the pathway resistances
		Stomatal control couples leaf transpiration to leaf photosynthesis
		The cell walls of guard cells have specialized features
		An increase in guard cell turgor pressure opens the stomata
	Overview: The Soil–Plant– Atmosphere Continuum
		The transpiration ratio measures the relationship between water loss and carbon gain
	Summary
	Web Material
	Suggested Reading
Chapter 5 Mineral Nutrition
	Essential Nutrients, Deficiencies, and Plant Disorders
		Special techniques are used in nutritional studies
		Nutrient solutions can sustain rapid plant growth
		Mineral deficiencies disrupt plant metabolism and function
		Analysis of plant tissues reveals mineral deficiencies
	Treating Nutritional Deficiencies
		Crop yields can be improved by the addition of fertilizers
		Some mineral nutrients can be absorbed by leaves
		Negatively charged soil particles affect the adsorption of mineral nutrients
	Soil, Roots, and Microbes
		Soil pH affects nutrient availability, soil microbes, and root growth
		Some plants develop extensive root systems
		Excess mineral ions in the soil limit plant growth
		Root systems differ in form but are based on common structures
		Different areas of the root absorb different mineral ions
		Nutrient availability influences root growth
		Mycorrhizal symbioses facilitate nutrient uptake by roots
		Nutrients move between mycorrhizal fungi and root cells
	Summary
	Web Material
	Suggested Reading
Chapter 6 Solute Transport
	Passive and Active Transport
	Transport of Ions across Membrane Barriers
		Different diffusion rates for cations and anions produce diffusion potentials
		How does membrane potential relate to ion distribution?
		The Nernst equation distinguishes between active and passive transport
		Proton transport is a major determinant of the membrane potential
	Membrane Transport Processes
		Channels enhance diffusion across membranes
		Carriers bind and transport specific substances
		Primary active transport requires energy
		Secondary active transport uses stored energy
		Kinetic analyses can elucidate transport mechanisms
	Membrane Transport Proteins
		The genes for many transporters have been identified
		Transporters exist for diverse nitrogen-containing compounds
		Cation transporters are diverse
		Anion transporters have been identified
		Aquaporins have diverse functions
		Transporters for metal and metalloid ions transport essential micronutrients
		Plasma membrane H+-ATPases are highly regulated P-type ATPases
		The tonoplast H+-ATPase drives solute accumulation in vacuoles
		H+-pyrophosphatases also pump protons at the tonoplast
	Ion Transport in Roots
		Solutes move through both apoplast and symplast
		Ions cross both symplast and apoplast
		Xylem parenchyma cells participate in xylem loading
	Summary
	Web Material
	Suggested Reading
Chapter 7 Photosynthesis: The Light Reactions
	Photosynthesis in Higher Plants
	General Concepts
		Light has characteristics of both a particle and a wave
		When molecules absorb or emit light, they change their electronic state
		Photosynthetic pigments absorb the light that powers photosynthesis
	Key Experiments in Understanding Photosynthesis
		Photosynthesis takes place in complexes containing light-harvesting antennas and photochemical reaction centers
		Action spectra relate light absorption to photosynthetic activity
		Light drives the reduction of NADP+ and the formation of ATP
		The chemical reaction of photosynthesis is driven by light
		Oxygen-evolving organisms have two photosystems that operate in series
	Organization of the Photosynthetic Apparatus
		The chloroplast is the site of photosynthesis
		Thylakoids contain integral membrane proteins
		Photosystems I and II are spatially separated in the thylakoid membrane
		Anoxygenic photosynthetic bacteria have a single reaction center
		The antenna funnels energy to the reaction center
	Organization of Light-Absorbing Antenna Systems
		Antenna systems contain chlorophyll and are membrane-associated
		Many antenna pigment–protein complexes have a common structural motif
		Electrons from chlorophyll travel through the carriers organized in the Z scheme
	Mechanisms of Electron Transport
		Energy is captured when an excited chlorophyll reduces an electron acceptor molecule
		The reaction center chlorophylls of the two photosystems absorb at different wavelengths
		Water is oxidized to oxygen by PSII
		The PSII reaction center is a multi-subunit pigment–protein complex
		Pheophytin and two quinones accept electrons from PSII
		Electron flow through the cytochrome
		complex also transports protons
		Plastoquinone and plastocyanin carry electrons between photosystems II and I
		The PSI reaction center reduces NADP+
		Cyclic electron flow generates ATP but no NADPH
	Proton Transport and ATP Synthesis in the Chloroplast
		Some herbicides block photosynthetic electron flow
	Repair and Regulation of the Photosynthetic Machinery
		Carotenoids serve as photoprotective agents
		Some xanthophylls also participate in energy dissipation
		The PSII reaction center is easily damaged
		PSI is protected from active oxygen species
	Genetics, Assembly, and Evolution of Photosynthetic Systems
		Thylakoid stacking permits energy partitioning between the photosystems
		Chloroplast genes exhibit non-Mendelian patterns of inheritance
		Most chloroplast proteins are imported from the cytoplasm
		Complex photosynthetic organisms have evolved from simpler forms
		The biosynthesis and breakdown of chlorophyll are complex pathways
		Mechanisms of Electron Transport
	Summary
	Web Material
	Suggested Reading
Chapter 8 Photosynthesis: The Carbon Reactions
	The Calvin–Benson Cycle
		The Calvin–Benson cycle has three phases: carboxylation, reduction, and regeneration
		The fixation of CO2 via carboxylation of ribulose 1,5-bisphosphate and the reduction of the product 3-phosphoglycerate yield triose phosphates
		The regeneration of ribulose 1,5-bisphosphate ensures the continuous assimilation of CO2
		An induction period precedes the steady state of photosynthetic CO2 assimilation
		Many mechanisms regulate the Calvin–Benson cycle
		Rubisco-activase regulates the catalytic activity of rubisco
		Light regulates the Calvin–Benson cycle via the ferredoxin–thioredoxin system
		Light-dependent ion movements modulate enzymes of the Calvin–Benson cycle
		Light controls the assembly of chloroplast enzymes into supramolecular complexes
	The C2 Oxidative Photosynthetic Carbon Cycle
		The oxygenation of ribulose 1,5-bisphosphate sets in motion the C2 oxidative photosynthetic carbon cycle
		Enzymes of the plant C2 oxidative photosynthetic carbon cycle derive from different ancestors
		Photorespiration is linked to the photosynthetic electron transport system
		Cyanobacteria use a proteobacterial pathway for bringing carbon atoms of 2-phosphoglycolate back to the Calvin–Benson cycle
		The C2 oxidative photosynthetic carbon cycle interacts with many metabolic pathways
		Production of biomass may be enhanced by engineering photorespiration
	Inorganic Carbon–Concentrating Mechanisms
	Inorganic Carbon–Concentrating Mechanisms: The C4 Carbon Cycle
		Malate and aspartate are the primary carboxylation products of the C4 cycle
		The C4 cycle assimilates CO2 by the concerted action of two different types of cells
		The C4 cycle uses different mechanisms for decarboxylation of four-carbon acids transported to bundle sheath cells
		Bundle sheath cells and mesophyll cells exhibit anatomical and biochemical differences
		The C4 cycle also concentrates CO2 in single cells
		Light regulates the activity of key C4 enzymes
		Photosynthetic assimilation of CO2 in C4 plants demands more transport processes than in C3 plants
		In hot, dry climates, the C4 cycle reduces photorespiration
	Inorganic Carbon–Concentrating Mechanisms: Crassulacean Acid Metabolism (CAM)
		Different mechanisms regulate C4 PEPCase and CAM PEPCase
		CAM is a versatile mechanism sensitive to environmental stimuli
	Accumulation and Partitioning of Photosynthates—Starch and Sucrose
	Formation and Mobilization of Chloroplast Starch
		Chloroplast stroma accumulates starch as insoluble granules during the day
		Starch degradation at night requires the phosphorylation of amylopectin
		The export of maltose prevails in the nocturnal breakdown of transitory starch
		The synthesis and degradation of the starch granule are regulated by multiple mechanisms
	Sucrose Biosynthesis and Signaling
		Triose phosphates from the Calvin–Benson cycle build up the cytosolic pool of three important hexose phosphates in the light
		Sucrose is continuously synthesized in the cytosol
		Fructose 2,6-bisphosphate regulates the hexose phosphate pool in the light
	Summary
	Web Material
	Suggested Reading
Chapter 9 Photosynthesis: Physiological and Ecological Considerations
	Photosynthesis Is Influenced by Leaf Properties
		Leaf anatomy and canopy structure maximize light absorption
		Leaf angle and leaf movement can control light absorption
		Leaves acclimate to sun and shade environments
	Effects of Light on Photosynthesis in the Intact Leaf
		Light-response curves reveal photosynthetic properties
		Leaves must dissipate excess light energy
		Absorption of too much light can lead to photoinhibition
	Effects of Temperature on Photosynthesis in the Intact Leaf
		Leaves must dissipate vast quantities of heat
		There is an optimal temperature for photosynthesis
		Photosynthesis is sensitive to both high and low temperatures
		Photosynthetic efficiency is temperature-sensitive
	Effects of Carbon Dioxide on Photosynthesis in the Intact Leaf
		Atmospheric CO2 concentration keeps rising
		CO2 diffusion to the chloroplast is essential to photosynthesis
		CO2 imposes limitations on photosynthesis
		How will photosynthesis and respiration change in the future under elevated CO2 conditions?
	Stable Isotopes Record Photosynthetic Properties
		How do we measure the stable carbon isotopes of plants?
		Why are there carbon isotope ratio variations in plants?
	Summary
	Web Material
	Suggested Reading
Chapter 10 Stomatal Biology
	Light-dependent Stomatal Opening
		Guard cells respond to blue light
		Blue light activates a proton pump at the guard cell plasma membrane
		Blue light regulates the osmotic balance of guard cells
		Blue-light responses have characteristic kinetics and lag times
		Sucrose is an osmotically active solute in guard cells
	Mediation of Blue-light Photoreception in Guard Cells by Zeaxanthin
	Reversal of Blue Light–Stimulated Opening by Green Light
		A carotenoid–protein complex senses light intensity
	The Resolving Power of Photophysiology
		Mediation of Blue-light Photoreception in Guard Cells by Zeaxanthin
	Summary
	Web Material
	Suggested Reading
Chapter 11 Translocation in the Phloem
	Pathways of Translocation
		Sugar is translocated in phloem sieve elements
		Mature sieve elements are living cells specialized for translocation
		Large pores in cell walls are the prominent feature of sieve elements
		Damaged sieve elements are sealed off
		Companion cells aid the highly specialized sieve elements
	Patterns of Translocation: Source to Sink
		Phloem sap can be collected and analyzed
	Materials Translocated in the Phloem
		Sugars are translocated in a nonreducing form
		Other solutes are translocated in the phloem
	Rates of Movement
		An osmotically generated pressure gradient drives translocation in the pressure-flow model
	The Pressure-Flow Model, a Passive Mechanism for Phloem Transport
		Some predictions of pressure flow have been confirmed, while others require further experimentation
		The energy requirement for transport through the phloem pathway is small in herbaceous plants
		There is no bidirectional transport in single sieve elements, and solutes and water move at the same velocity
		Sieve plate pores appear to be open channels
		Pressure gradients in the sieve elements may be modest; pressures in herbaceous plants and trees appear to be similar
		Alternative models for translocation by mass flow have been suggested
		Does translocation in gymnosperms involve a different mechanism?
	Phloem Loading
		Phloem loading can occur via the apoplast or symplast
		Abundant data support the existence of apoplastic loading in some species
		Sucrose uptake in the apoplastic pathway requires metabolic energy
		Phloem loading is symplastic in some species
		Phloem loading in the apoplastic pathway involves a sucrose–H+ symporter
		The polymer-trapping model explains symplastic loading in plants with intermediary-type companion cells
		The type of phloem loading is correlated with several significant characteristics
		Phloem loading is passive in several tree species
	Phloem Unloading and Sink-to-Source Transition
		Phloem unloading and short-distance transport can occur via symplastic or apoplastic pathways
		Transport into sink tissues requires metabolic energy
		The transition of a leaf from sink to source is gradual
	Photosynthate Distribution: Allocation and Partitioning
		Various sinks partition transport sugars
		Allocation includes storage, utilization, and transport
		Source leaves regulate allocation
		Sink tissues compete for available translocated photosynthate
		The source adjusts over the long term to changes in the source-to-sink ratio
		Sink strength depends on sink size and activity
	Transport of Signaling Molecules
		Turgor pressure and chemical signals coordinate source and sink activities
		Proteins and RNAs function as signal molecules in the phloem to regulate growth and development
		Plasmodesmata function in phloem signaling
	Summary
	Web Material
	Suggested Reading
Chapter 12 Respiration and Lipid Metabolism
	Overview of Plant Respiration
	Glycolysis
		Glycolysis metabolizes carbohydrates from several sources
		Plants have alternative glycolytic reactions
		The energy-conserving phase of glycolysis extracts usable energy
		In the absence of oxygen, fermentation regenerates the NAD+ needed for glycolysis
		Plant glycolysis is controlled by its products
	The Oxidative Pentose Phosphate Pathway
		The oxidative pentose phosphate pathway is redox-regulated
		The oxidative pentose phosphate pathway produces NADPH and biosynthetic intermediates
	The Citric Acid Cycle
		Mitochondria are semiautonomous organelles
		Pyruvate enters the mitochondrion and is oxidized via the citric acid cycle
	Mitochondrial Electron Transport and ATP Synthesis
		The citric acid cycle of plants has unique features
		The electron transport chain catalyzes a flow of electrons from NADH to O2
		The electron transport chain has supplementary branches
		ATP synthesis in the mitochondrion is coupled to electron transport
		Aerobic respiration yields about 60 molecules of ATP per molecule of sucrose
		Transporters exchange substrates and products
		Several subunits of respiratory complexes are encoded by the mitochondrial genome
		Plants have several mechanisms that lower the ATP yield
		Short-term control of mitochondrial respiration occurs at different levels
		Respiration is tightly coupled to other pathways
		Plants respire roughly half of the daily photosynthetic yield
	Respiration in Intact Plants and Tissues
		Different tissues and organs respire at different rates
		Respiration operates during photosynthesis
		Environmental factors alter respiration rates
		Triacylglycerols are stored in oil bodies
	Lipid Metabolism
		Fats and oils store large amounts of energy
		Polar glycerolipids are the main structural lipids in membranes
		Fatty acid biosynthesis consists of cycles of two-carbon addition
		Glycerolipids are synthesized in the plastids and the ER
		Membrane lipids are precursors of important signaling compounds
		Lipid composition influences membrane function
		Storage lipids are converted into carbohydrates in germinating seeds
	Summary
	Web Material
	Suggested Reading
Chapter 13 Assimilation of Inorganic Nutrients
	Nitrogen in the Environment
		Nitrogen passes through several forms in a biogeochemical cycle
		Unassimilated ammonium or nitrate may be dangerous
	Nitrate Assimilation
		Many factors regulate nitrate reductase
		Nitrite reductase converts nitrite to ammonium
		Both roots and shoots assimilate nitrate
		Converting ammonium to amino acids requires two enzymes
	Ammonium Assimilation
		Ammonium can be assimilated via an alternative pathway
		Transamination reactions transfer nitrogen
	Amino Acid Biosynthesis
		Asparagine and glutamine link carbon and nitrogen metabolism
	Biological Nitrogen Fixation
		Free-living and symbiotic bacteria fix nitrogen
		Nitrogen fixation requires microanaerobic or anaerobic conditions
		Symbiotic nitrogen fixation occurs in specialized structures
		Establishing symbiosis requires an exchange of signals
		Nod factors produced by bacteria act as signals for symbiosis
		Nodule formation involves phytohormones
		The nitrogenase enzyme complex fixes N2
		Amides and ureides are the transported forms of nitrogen
	Sulfur Assimilation
		Sulfate assimilation requires the reduction of sulfate to cysteine
		Sulfate is the form of sulfur transported into plants
		Methionine is synthesized from cysteine
	Phosphate Assimilation
		Sulfate assimilation occurs mostly in leaves
		Cations form noncovalent bonds with carbon compounds
	Cation Assimilation
		Roots modify the rhizosphere to acquire iron
	Oxygen Assimilation
		Iron cations form complexes with carbon and phosphate
	The Energetics of Nutrient Assimilation
	Summary
	Web Material
	Suggested Reading
Chapter 14 Cell Walls: Structure, Formation, and Expansion
	Overview of Plant Cell Wall Functions and Structures
		Plant cell walls vary in structure and function
		Components differ for primary and secondary cell walls
		Cellulose microfibrils have an ordered structure and are synthesized at the plasma membrane
		Matrix polymers are synthesized in the Golgi apparatus and secreted via vesicles
		Pectins are hydrophilic gel-forming components of the primary cell wall
		Hemicelluloses are matrix polysaccharides that bind to cellulose
		New primary cell walls are assembled during cytokinesis and continue to be assembled during growth
	Primary Cell Wall Structure and Function
		The primary cell wall is composed of cellulose microfibrils embedded in a matrix of pectins and hemicelluloses
	Mechanisms of Cell Expansion
		Microfibril orientation influences growth directionality of cells with diffuse growth
		Cortical microtubules influence the orientation of newly deposited microfibrils
	The Extent and Rate of Cell Growth
		Stress relaxation of the cell wall drives water uptake and cell expansion
		Acid-induced growth and wall stress relaxation are mediated by expansins
		Cell wall models are hypotheses about how molecular components fit together to make a functional wall
	Secondary Cell Wall Structure and Function
		Many structural changes accompany the cessation of wall expansion
		Secondary cell walls are rich in cellulose and hemicellulose and often have a hierarchical organization
		Lignification transforms the SCW into a hydrophobic structure resistant to deconstruction
	Summary
	Web Material
	Suggested Reading
Chapter 15 Signals and Signal Transduction
	Temporal and Spatial Aspects of Signaling
	Signal Perception and Amplification
		Receptors are located throughout the cell and are conserved across kingdoms
		Signals must be amplified intracellularly to regulate their target molecules
		The MAP kinase signal amplification cascade is present in all eukaryotes
		Ca2+ is the most ubiquitous second messenger in plants and other eukaryotes
		Changes in the cytosolic or cell wall pH can serve as second messengers for hormonal and stress responses
		Reactive oxygen species act as second messengers mediating both environmental and developmental signals
	Hormones and Plant Development
		Lipid signaling molecules act as second messengers that regulate a variety of cellular processes
		Gibberellins promote stem growth and were discovered in relation to the “foolish seedling disease” of rice
		Auxin was discovered in early studies of coleoptile bending during phototropism
		Cytokinins were discovered as cell division– promoting factors in tissue culture experiments
		Ethylene is a gaseous hormone that promotes fruit ripening and other developmental processes
		Abscisic acid regulates seed maturation and stomatal closure in response to water stress
		Brassinosteroids regulate photomorphogenesis, germination, and other developmental processes
		Strigolactones suppress branching and promote rhizosphere interactions
	Phytohormone Metabolism and Homeostasis
		Indole-3-pyruvate is the primary intermediate in auxin biosynthesis
		Gibberellins are synthesized by oxidation of the diterpene ent-kaurene
		Cytokinins are adenine derivatives with isoprene side chains
		Abscisic acid is synthesized from a carotenoid intermediate
		Ethylene is synthesized from methionine via the intermediate ACC
		Brassinosteroids are derived from the sterol campesterol
	Signal Transmission and Cell–Cell Communication
		Strigolactones are synthesized from beta-carotene
		The cytokinin and ethylene signal transduction pathways are derived from the bacterial two-component regulatory system
	Hormonal Signaling Pathways
		Receptor-like kinases mediate brassinosteroid and certain auxin signaling pathways
		The core ABA signaling components include phosphatases and kinases
		Plant hormone signaling pathways generally employ negative regulation
		Several plant hormone receptors encode components of the ubiquitination machinery and mediate signaling via protein degradation
		Plants have evolved mechanisms for switching off or attenuating signaling responses
		The cellular response output to a signal is often tissue-specific
		Cross-regulation allows signal transduction pathways to be integrated
	Summary
	Suggested Reading
Chapter 16 Signals from Sunlight
	Plant Photoreceptors
		Photoresponses are driven by light quality or spectral properties of the energy absorbed
		Plants responses to light can be distinguished by the amount of light required
		Phytochrome is the primary photoreceptor for red and far-red light
	Phytochromes
		Phytochrome can interconvert between Pr and Pfr forms
		The phytochrome chromophore and protein both undergo conformational changes in response to red light
		Pfr is the physiologically active form of phytochrome
		Pfr is partitioned between the cytosol and the nucleus
	Phytochrome Responses
		Phytochrome responses fall into three main categories based on the amount of light required
		Phytochrome responses vary in lag time and escape time
		Phytochrome A mediates responses to continuous far-red light
		Roles for phytochromes C, D, and E are emerging
	Phytochrome Signaling Pathways
		Phytochrome B mediates responses to continuous red or white light
		Phytochrome regulates membrane potentials and ion fluxes
		Phytochrome interacting factors (PIFs) act early in signaling
		Phytochrome regulates gene expression
		Phytochrome signaling involves protein phosphorylation and dephosphorylation
		Phytochrome-induced photomorphogenesis involves protein degradation
	Blue-Light Responses and Photoreceptors
		Blue-light responses have characteristic kinetics and lag times
	Cryptochromes
		The activated FAD chromophore of cryptochrome causes a conformational change in the protein
		Nuclear cryptochromes inhibit COP1-induced protein degradation
		cry1 and cry2 have different developmental effects
		Cryptochrome can also bind to transcriptional regulators directly
	The Coaction of Cryptochrome, Phytochrome, and Phototropins
		Stem elongation is inhibited by both red and blue photoreceptors
		The circadian clock is regulated by multiple aspects of light
	Phototropins
		Phytochrome interacts with cryptochrome to regulate flowering
		Blue light induces changes in FMN absorption maxima associated with conformation changes
		The LOV2 domain is primarily responsible for kinase activation in response to blue light
		Blue light induces a conformational change that “uncages” the kinase domain of phototropin and leads to autophosphorylation
		Phototropism requires changes in auxin mobilization
		Phototropins regulate chloroplast movements via F-actin filament assembly
		Stomatal opening is regulated by blue light, which activates the plasma membrane H+-ATPase
		The main signal transduction events of phototropin-mediated stomatal opening have been identified
	Responses to Ultraviolet Radiation
	Summary
	Web Material
	Suggested Reading
Chapter 17 Embryogenesis
	Overview of Plant Growth and Development
		Sporophytic development can be divided into three major stages
		Embryogenesis differs between eudicots and monocots, but also features common fundamental processes
	Embryogenesis: The Origins of Polarity
		Apical–basal polarity is established early in embryogenesis
		Position-dependent mechanisms guide embryogenesis
		Intercellular signaling processes play key roles in guiding position-dependent development
		Embryo development features regulated communication between cells
		The analysis of mutants identifies genes for signaling processes that are essential for embryo organization
		Auxin functions as a mobile chemical signal during embryogenesis
		Plant polarity is maintained by polar auxin streams
		Auxin transport is regulated by multiple mechanisms
		The GNOM protein establishes a polar distribution of PIN auxin efflux proteins
		Radial patterning guides formation of tissue layers
		MONOPTEROS encodes a transcription factor that is activated by auxin
		The origin of epidermis: a boundary and interface at the edge of the radial axis
		Procambial precusors for the vascular stele lie at the center of the radial axis
		The differentiation of cortical and endodermal cells involves the intercellular movement of a transcription factor
	Meristematic Tissues: Foundations for Indeterminate Growth
		The root and shoot apical meristems use similar strategies to enable indeterminate growth
	The Root Apical Meristem
		The origin of different root tissues can be traced to specific initial cells
		The root tip has four developmental zones
		Responses to auxin are mediated by several distinct families of transcription factors
		Cell ablation experiments implicate directional signaling processes in determination of cell identity
		Auxin contributes to the formation and maintenance of the RAM
		Cytokinin is required for normal root development
	The Shoot Apical Meristem
		The shoot apical meristem has distinct zones and layers
		Shoot tissues are derived from several discrete sets of apical initials
		Factors involved in auxin movement and responses influence SAM formation
		Embryonic SAM formation requires the coordinated expression of transcription factors
		A combination of positive and negative interactions determines apical meristem size
		class homeodomain genes help maintain the proliferative ability of the SAM through regulation of cytokinin and GA levels
		Localized zones of auxin accumulation promote leaf initiation
	The Vascular Cambium
		The maintenance of undetermined initials in various meristem types depends on similar mechanisms
	Summary
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Chapter 18 Seed Dormancy, Germination, and Seedling Establishment
	Seed Structure
		Seed anatomy varies widely among different plant groups
	Seed Dormancy
		Dormancy can be imposed on the embryo by the surrounding tissues
		Embryo dormancy may be caused by physiological or morphological factors
		Non-dormant seeds can exhibit vivipary and precocious germination
		The ABA:GA ratio is the primary determinant of seed dormancy
	Release from Dormancy
		Some seeds require either chilling or after-ripening to break dormancy
		Light is an important signal that breaks dormancy in small seeds
	Seed Germination
		Germination can be divided into three phases corresponding to the phases of water uptake
		Seed dormancy can by broken by various chemical compounds
		The cereal aleurone layer is a specialized digestive tissue surrounding the starchy endosperm
	Mobilization of Stored Reserves
		Gibberellins enhance the transcription of
		mRNA
		The gibberellin receptor, GID1, promotes the degradation of negative regulators of the gibberellin response
		DELLA repressor proteins are rapidly degraded
		GA-MYB is a positive regulator of
		amylase transcription
		ABA inhibits gibberellin-induced enzyme production
	Seedling Growth and Establishment
		The outer tissues of eudicot stems are the targets of auxin action
		The minimum lag time for auxin-induced elongation is 10 minutes
		Auxin promotes growth in stems and coleoptiles, while inhibiting growth in roots
		Auxin-induced proton extrusion induces cell wall creep and cell elongation
		Gravitropism involves the lateral redistribution of auxin
	Tropisms: Growth in Response to Directional Stimuli
		Polar auxin transport requires energy and is gravity independent
		According to the starch–statolith hypothesis, specialized amyloplasts serve as gravity sensors in root caps
		Auxin movements in the root are regulated by specific transporters
		The gravitropic stimulus perturbs the symmetric movement of auxin from the root tip
		Gravity perception in eudicot stems and stemlike organs occurs in the starch sheath
		Gravity sensing may involve pH and calcium ions (Ca2+) as second messengers
	Phototropism
		Phototropism is mediated by the lateral redistribution of auxin
		Phototropism occurs in a series of posttranslational events
	Photomorphogenesis
		Gibberellins and brassinosteroids both suppress photomorphogenesis in the dark
		Hook opening is regulated by phytochrome and auxin
		Ethylene induces lateral cell expansion
	Shade Avoidance
		Decreasing the R:FR ratio causes elongation in sun plants
		Phytochrome enables plants to adapt to changes in light quality
		Reducing shade avoidance responses can improve crop yields
	Vascular Tissue Differentiation
		Auxin and cytokinin are required for normal vascular development
		Zinnia suspension-cultured cells can be induced to undergo xylogenesis
		Xylogenesis involves chemical signaling between neighboring cells
	Root Growth and Differentiation
		Root epidermal development follows three basic patterns
		Auxin and other hormones regulate root hair development
		Lateral root formation and emergence depend on endogenous and exogenous signals
		Regions of lateral root emergence correspond with regions of auxin maxima
		Lateral roots and shoots have gravitropic setpoint angles
	Summary
	Web Material
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Chapter 19 Vegetative Growth and Organogenesis
	Leaf Development
	The Establishment of Leaf Polarity
		Hormonal signals play key roles in regulating leaf primordia emergence
		A signal from the SAM initiates adaxial–abaxial polarity
		Adaxial leaf development requires HD-ZIP III transcription factors
		ARP genes promote adaxial identity and repress the KNOX1 gene
		The expression of HD-ZIP III genes is antagonized by miR166 in abaxial regions of the leaf
		Interactions between adaxial and abaxial tissues are required for blade outgrowth
		Antagonism between KANADI and HD-ZIP III is a key determinant of adaxial–abaxial leaf polarity
		Blade outgrowth is auxin dependent and regulated by the YABBY and WOX genes
		Leaf proximal–distal polarity also depends on specific gene expression
		In compound leaves, de-repression of the KNOX1 gene promotes leaflet formation
	Differentiation of Epidermal Cell Types
		Guard cell fate is ultimately determined by a specialized epidermal lineage
		Two groups of bHLH transcription factors govern stomatal cell fate transitions
		Peptide signals regulate stomatal patterning by interacting with cell surface receptors
		Genetic screens have led to the identification of positive and negative regulators of trichome initiation
		GLABRA2 acts downstream of the GL1–GL3–TTG1 complex to promote trichome formation
	Venation Patterns in Leaves
		Jasmonic acid regulates Arabidopsis leaf trichome development
		Auxin canalization initiates development of the leaf trace
		The primary leaf vein is initiated discontinuously from the preexisting vascular system
		Basipetal auxin transport from the L1 layer of the leaf primordium initiates development of the leaf trace procambium
		The existing vasculature guides the growth of the leaf trace
		Higher-order leaf veins differentiate in a predictable hierarchical order
		Auxin canalization regulates higher-order vein formation
		Localized auxin biosynthesis is critical for higher-order venation patterns
	Shoot Branching and Architecture
		Axillary meristem initiation involves many of the same genes as leaf initiation and lamina outgrowth
		Auxin, cytokinins, and strigolactones regulate axillary bud outgrowth
		Strigolactones act locally to repress axillary bud growth
		Auxin from the shoot tip maintains apical dominance
		Cytokinins antagonize the effects of strigolactones
		The initial signal for axillary bud growth may be an increase in sucrose availability to the bud
		Integration of environmental and hormonal branching signals is required for plant fitness
		Axillary bud dormancy in woody plants is affected by season, position, and age factors
		Plants can modify their root system architecture to optimize water and nutrient uptake
	Root System Architecture
		Monocots and eudicots differ in their root system architecture
		Root system architecture changes in response to phosphorous deficiencies
		Root system architecture responses to phosphorus deficiency involve both local and systemic regulatory networks
		Mycorrhizal networks augment root system architecture in all major terrestrial ecosystems
	Secondary Growth
		The vascular cambium and cork cambium are the secondary meristems where secondary growth originates
		Phytohormones have important roles in regulating vascular cambium activity and differentiation of secondary xylem and phloem
		Secondary growth evolved early in the evolution of land plants
		Secondary growth from the vascular cambium gives rise to secondary xylem and phloem
		Genes involved in stem cell maintenance, proliferation, and differentiation regulate secondary growth
		Environmental factors influence vascular cambium activity and wood properties
	Summary
	Web Material
	Suggested Reading
Chapter 20 The Control of Flowering and Floral Development
	Floral Evocation: Integrating Environmental Cues
	The Shoot Apex and Phase Changes
		Plant development has three phases
		Juvenile tissues are produced first and are located at the base of the shoot
		Phase changes can be influenced by nutrients, gibberellins, and other signals
	Circadian Rhythms: The Clock Within
		Circadian rhythms exhibit characteristic features
		Phytochromes and cryptochromes entrain the clock
		Phase shifting adjusts circadian rhythms to different day–night cycles
	Photoperiodism: Monitoring Day Length
		Plants can be classified according to their photoperiodic responses
		Night breaks can cancel the effect of the dark period
		The leaf is the site of perception of the photoperiodic signal
		Photoperiodic timekeeping during the night depends on a circadian clock
		Plants monitor day length by measuring the length of the night
		The coincidence model is based on oscillating light sensitivity
		The coincidence of CONSTANS expression and light promotes flowering in LDPs
		Phytochrome is the primary photoreceptor in photoperiodism
		SDPs use a coincidence mechanism to inhibit flowering in long days
		A blue-light photoreceptor regulates flowering in some LDPs
	Vernalization: Promoting Flowering with Cold
		Vernalization results in competence to flower at the shoot apical meristem
		Vernalization can involve epigenetic changes in gene expression
		A range of vernalization pathways may have evolved
	Long-distance Signaling Involved in Flowering
		Grafting studies provided the first evidence for a transmissible floral stimulus
		Florigen is translocated in the phloem
	The Identification of Florigen
		The Arabidopsis protein FLOWERING LOCUS T (FT) is florigen
		Gibberellins and ethylene can induce flowering
		The transition to flowering involves multiple factors and pathways
	Floral Meristems and Floral Organ Development
		The four different types of floral organs are initiated as separate whorls
		The shoot apical meristem in Arabidopsis changes with development
		Two major categories of genes regulate floral development
		Floral meristem identity genes regulate meristem function
		Homeotic mutations led to the identification of floral organ identity genes
		The ABC model partially explains the determination of floral organ identity
		Arabidopsis Class E genes are required for the activities of the A, B, and C genes
		According to the Quartet Model, floral organ identity is regulated by tetrameric complexes of the ABCE proteins
		Class D genes are required for ovule formation
		Floral asymmetry in flowers is regulated by gene expression
	Summary
	Web Material
	Suggested Reading
Chapter 21 Gametophytes, Pollination, Seeds, and Fruits
	Development of the Male and Female Gametophyte Generations
	Formation of Male Gametophytes in the Stamen
		Pollen grain formation occurs in two successive stages
		The multilayered pollen cell wall is surprisingly complex
	Female Gametophyte Development in the Ovule
		The Arabidopsis gynoecium is an important model system for studying ovule development
		The vast majority of angiosperms exhibit Polygonum-type embryo sac development
		Functional megaspores undergo a series of free nuclear mitotic divisions followed by cellularization
		Embryo sac development involves hormonal signaling between sporophytic and gametophytic generations
	Pollination and Fertilization in Flowering Plants
		Delivery of sperm cells to the female gametophyte by the pollen tube occurs in six phases
		Adhesion and hydration of a pollen grain on a compatible flower depend on recognition between pollen and stigma surfaces
		Ca2+-triggered polarization of the pollen grain precedes tube formation
		Pollen tubes grow by tip growth
		Receptor-like kinases are thought to regulate the ROP1 GTPase switch, a master regulator of tip growth
		Style tissue conditions the pollen tube to respond to attractants produced by the synergids of the embryo sac
		Pollen tube tip growth in the pistil is directed by both physical and chemical cues
		Double fertilization occurs in three distinct stages
	Selfing versus Outcrossing
		Hermaphroditic and monoecious species have evolved floral features to ensure outcrossing
		Self-incompatibility (SI) is the primary mechanism that enforces outcrossing in angiosperms
		Cytoplasmic male sterility (CMS) occurs in the wild and is of great utility in agriculture
		The Brassicaceae sporophytic SI system requires two S-locus genes
		Gametophytic self-incompatibility (GSI) is mediated by cytotoxic S-RNases and F-box proteins
	Apomixis: Asexual Reproduction by Seed
		Apomixis is not an evolutionary dead end
	Endosperm Development
		Cellularization of coenocytic endosperm in Arabidopsis progresses from the micropylar to the chalazal region
		Endosperm development and embryogenesis can occur autonomously
		Cellularization of the coenocytic endosperm of cereals progresses centripetally
		Many of the genes that control endosperm development are maternally expressed genes
		The FIS proteins are members of a Polycomb repressive complex (PRC2) that represses endosperm development
		Two genes, DEK1 and CR4, have been implicated in aleurone layer differentiation
		Cells of the starchy endosperm and aleurone layer follow divergent developmental pathways
	Seed Coat Development
		Seed coat development appears to be regulated by the endosperm
	Seed Maturation and Desiccation Tolerance
		Seed filling and desiccation tolerance phases overlap in most species
		LEA proteins and nonreducing sugars have been implicated in seed desiccation tolerance
		The acquisition of desiccation tolerance involves many metabolic pathways
		During the acquisition of desiccation tolerance, the cells of the embryo acquire a glassy state
		Specific LEA proteins have been implicated in desiccation tolerance in
		Coat-imposed dormancy is correlated with longterm seed-viability
		Abscisic acid plays a key role in seed maturation
	Fruit Development and Ripening
		Arabidopsis and tomato are model systems for the study of fruit development
		Fleshy fruits undergo ripening
		Ripening involves changes in the color of fruit
		The causal link between ethylene and ripening was demonstrated in transgenic and mutant tomatoes
		Fruit softening involves the coordinated action of many cell wall–degrading enzymes
		Taste and flavor reflect changes in acids, sugars, and aroma compounds
		Climacteric and non-climacteric fruit differ in their ethylene responses
		Angiosperms share a range of common molecular mechanisms controlling fruit development and ripening
		The ripening process is transcriptionally regulated
		Fruit ripening is under epigenetic control
		A mechanistic understanding of the ripening process has commercial applications
	Summary
	Web Material
	Suggested Reading
Chapter 22 Plant Senescence and Cell Death
	Programmed Cell Death and Autolysis
		PCD during normal development differs from that of the hypersensitive response
		The autophagy pathway captures and degrades cellular constituents within lytic compartments
		A subset of the autophagy-related genes controls the formation of the autophagosome
		The autophagy pathway plays a dual role in plant development
	The Leaf Senescence Syndrome
		The developmental age of a leaf may differ from its chronological age
		Leaf senescence may be sequential, seasonal, or stress-induced
		Developmental leaf senescence consists of three distinct phases
		The earliest cellular changes during leaf senescence occur in the chloroplast
		The autolysis of chloroplast proteins occurs in multiple compartments
		The STAY-GREEN (SGR) protein is required for both LHCP II protein recycling and chlorophyll catabolism
		Leaf senescence is preceded by a massive reprogramming of gene expression
		The NAC and WRKY gene families are the most abundant transcription factors regulating leaf senescence
	Leaf Senescence: The Regulatory Network
		ROS serve as internal signaling agents in leaf senescence
		Sugars accumulate during leaf senescence and may serve as a signal
		Plant hormones interact in the regulation of leaf senescence
	Leaf Abscission
		The timing of leaf abscission is regulated by the interaction of ethylene and auxin
	Whole Plant Senescence
		Angiosperm life cycles may be annual, biennial, or perennial
		Whole plant senescence differs from aging in animals
		The determinacy of shoot apical meristems is developmentally regulated
		Nutrient or hormonal redistribution may trigger senescence in monocarpic plants
		The rate of carbon accumulation in trees increases continuously with tree size
	Summary
	Web Material
	Suggested Reading
Chapter 23 Biotic Interactions
	Beneficial Interactions between Plants and Microorganisms
		Arbuscular mycorrhizal associations and nitrogen-fixing symbioses involve related signaling pathways
		Nod factors are recognized by the Nod factor receptor (NFR) in legumes
		Rhizobacteria can increase nutrient availability, stimulate root branching, and protect against pathogens
	Harmful Interactions between Plants, Pathogens, and Herbivores
		Mechanical barriers provide a first line of defense against insect pests and pathogens
		Plant secondary metabolites can deter insect herbivores
		Plants store constitutive toxic compounds in specialized structures
		Plants often store defensive chemicals as nontoxic water-soluble sugar conjugates in the vacuole
	Inducible Defense Responses to Insect Herbivores
		Constitutive levels of secondary compounds are higher in young developing leaves than in older tissues
		Modified fatty acids secreted by grasshoppers act as elicitors of jasmonic acid accumulation and ethylene emission
		Plants can recognize specific components of insect saliva
		Phloem feeders activate defense signaling pathways similar to those activated by pathogen infections
		Calcium signaling and activation of the MAP kinase pathway are early events associated with insect herbivory
		Jasmonic acid activates defense responses against insect herbivores
		Jasmonic acid acts through a conserved ubiquitin ligase signaling mechanism
		Hormonal interactions contribute to plant–insect herbivore interactions
		JA initiates the production of defense proteins that inhibit herbivore digestion
		Herbivore damage induces systemic defenses
		Glutamate receptor-like (GLR) genes are required for long-distance electrical signaling during herbivory
		Herbivore-induced volatiles can repel herbivores and attract natural enemies
		Herbivore-induced volatiles can serve as longdistance signals between plants
		Defense responses to herbivores and pathogens are regulated by circadian rhythms
		Herbivore-induced volatiles can also act as systemic signals within a plant
	Plant Defenses against Pathogens
		Insects have evolved mechanisms to defeat plant defenses
		Microbial pathogens have evolved various strategies to invade host plants
		Pathogens produce effector molecules that aid in the colonization of their plant host cells
		Pathogen infection can give rise to molecular “danger signals” that are perceived by cell surface pattern recognition receptors
		R genes provide resistance to individual pathogens by recognizing strain-specific effectors
		Effectors released by phloem-feeding insects also activate NBS–LRR receptors
		Exposure to elicitors induces a signal transduction cascade
		The hypersensitive response is a common defense against pathogens
		Phytoalexins with antimicrobial activity accumulate after pathogen attack
		A single encounter with a pathogen may increase resistance to future attacks
		The main components of the salicylic acid signaling pathway for SAR have been identified
		Interactions of plants with nonpathogenic bacteria can trigger systemic resistance through a process called induced systemic res
	Plant Defenses against Other Organisms
		Some plant parasitic nematodes form specific associations through the formation of distinct feeding structures
		Plants compete with other plants by secreting allelopathic secondary metabolites into the soil
		Some plants are biotrophic pathogens of other plants
	Summary
	Web Material
	Suggested Reading
Chapter 24 Abiotic Stress
	Defining Plant Stress
		Physiological adjustment to abiotic stress involves trade-offs between vegetative and reproductive development
		Adaptation to stress involves genetic modification over many generations
		Acclimation allows plants to respond to environmental fluctuations
	Acclimation and Adaptation
	Environmental Factors and Their Biological Impacts on Plants
		Water deficit decreases turgor pressure, increases ion toxicity, and inhibits photosynthesis
		Light stress can occur when shade-adapted or shade-acclimated plants are subjected to full sunlight
		Salinity stress has both osmotic and cytotoxic effects
		Temperature stress affects a broad spectrum of physiological processes
		Heavy metals can both mimic essential mineral nutrients and generate ROS
		Flooding results in anaerobic stress to the root
		Mineral nutrient deficiencies are a cause of stress
		During freezing stress, extracellular ice crystal formation causes cell dehydration
		Ozone and ultraviolet light generate ROS that cause lesions and induce PCD
		Combinations of abiotic stresses can induce unique signaling and metabolic pathways
	Stress-Sensing Mechanisms in Plants
		Sequential exposure to different abiotic stresses sometimes confers cross-protection
	Signaling Pathways Activated in Response to Abiotic Stress
		Early-acting stress sensors provide the initial signal for the stress response
		The signaling intermediates of many stress-response pathways can interact
		Acclimation to stress involves transcriptional regulatory networks called
		Chloroplast genes respond to high-intensity light by sending stress signals to the nucleus
		A self-propagating wave of ROS mediates systemic acquired acclimation
		Hormonal interactions regulate normal development and abiotic stress responses
		Epigenetic mechanisms and small RNAs provide additional protection against stress
	Developmental and Physiological Mechanisms That Protect Plants against Abiotic Stress
		Plants adjust osmotically to drying soil by accumulating solutes
		Submerged organs develop aerenchyma tissue in response to hypoxia
		Antioxidants and ROS-scavenging pathways protect cells from oxidative stress
		Molecular chaperones and molecular shields protect proteins and membranes during abiotic stress
		Plants can alter their membrane lipids in response to temperature and other abiotic stresses
		Exclusion and internal tolerance mechanisms allow plants to cope with toxic ions
		Phytochelatins and other chelators contribute to internal tolerance of toxic metal ions
		Plants use cryoprotectant molecules and antifreeze proteins to prevent ice crystal formation
		ABA signaling during water stress causes the massive efflux of K+ and anions from guard cells
		Plants can alter their morphology in response to abiotic stress
		Metabolic shifts enable plants to cope with a variety of abiotic stresses
		Developing crops with enhanced tolerance to abiotic stress conditions is a major goal of agricultural research
		The process of recovery from stress can be dangerous to the plant and requires a coordinated adjustment of plant metabolism and
	Summary
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