Chapter 35: Vascular Plant Structure, Growth, and Development

35.1: Plants have a hierarchal organization consisting of organs, tissues, and cells

• Cell: Fundamental unit of life

• Tissue: Group of cells consistig of 1+ cell types that perform a specialized function together

• Organ: Several types of tissues that carry out a specialized function together

• Three basic organs, roots, stems, and leaves, part of a root system and a shoot system

• Root: Organ that anchors a vascular plant in soil

  • Primary root is the first root to emerge from the seet. then branches to form lateral roots

• Taproot: Main verticle root which develops from the primary root in taproot systems

  • Enables the plant to grow taller, usually in tall erect plants with large shoot masses

• Fibrous Root System: Thick mat of slender roots spreading out below soil surface

• Root Hairs: Thin fingerlike extensions of root epidermal cells that emerge and increase surface area and absorb water and minerals

• Steam: Plant organ bearing leaves and buds to elongate and orient the shoot in a way to optimize photosynthesis

• Nodes: Points which leaves are attached at

• Internodes: Steam segments between nodes

• Apical Bud: Growing shoot tip, where most of the growth of a young shoot is concentrated

• Auxillary Bud: Upper angle formed by leaf and steam, which can potentially form a lateral branch or thorn or flower

• Leaf: Main photosynthetic organ

  • Has a flattened blade and petiole (stalk) which joins the leaf at a node

  • Veins: Vascular tissue of leaves, differ between monocots and eudicots

    • Monocots have simple leaves, eudicots have compound leaves

      • Compound leaves confine invading pathogens better

• Tissue System: Plants have three types of tissues, dermal, vascular, and ground

  • Together they form three basic vascular plant organs (roots, stems, leaves)

• Dermal Tissue: Outer protective covering of the plant (like skin), first line of defense aganst physical damage and pathogens

  • Epidermis: Tissue in nonwoody plants, layer of tightly packed cells

    • Permiderm: Protecting tissues in woody plants instead of epidermis

  • Cuticle: Waxy epidermal coating that prevents water loss

• Guard Cells: Specialized epidermal cells in shoots involved in gas exchange

• Trichomes: Highly specialized epidermal cells in shoots. Some reduce water loss, reflect excess light, or defend against insects

• Vascular Tissue: Facilitates transport of materials through the plant and provides mechanical support. Two types xylem and phloem

  • Xylem: Conducts water and dissolved minerals upward from roots into shoots

  • Phloem: Transports sugars from where they’re made (leaves) to where they’re needed or stored (roots and sites of growth)

  • Stele: Vascular tissue of root or stem

• Ground Tissue: Tissue that’s not dermal or vascular

  • Pith: Ground tissue internal to vascular tissue

  • Cortex: Ground tissue external to vascular tissue

• Parenchyma Cells: Have thin and flexible primary walls and lack secondary walls

• Collenchyma Cells: Support young parts of plant shoot

• Sclerenchyma Cells: More rigid that collenchyma cells. Secondary cell wall contains lots of lignin (present in all vascular plants)

  • Schlerids: Boxy and irregular in shape with thick second walls, give hardness and gritty texture

  • Fibers: Long, slender, and tapered, used for suppport

• Tracheids: Water conducting cells in xylem of all vascular plants

• Vessel Elements: Wider, shorter, thinner walled, and less tapered than tracheids, water conducing cells

  • Vessels: Long pipes made from vessel elements that are aligned end to end

• Sieve Tube Elements: Cells that make sieve tubes which transport turients

  • No nucleus, ribosomes, distinct vacuole, or cytoskeletal elements

• Sieve Plates: End walls between sieve tube elements with pores to facilitate flow of fluid from cell to cell

• Companion Cell: Nonconducting cell, connected to the sieve tube element

35.2: Different meristems generate new cells for primary and secondary growth

• Intermediate Growth: Growth occurs throughout a plant’s life

  • Meristems: Undiffrentiated tissues that let plants keep growing and leading to new cells that elongate and become diffrentiated

    • Apical Meristems: Located at root and shoot tips, provide cells that enable primary growth (growth in length)

• Determinate Growth: Stop growing after reaching a certain size

• Secondary Growth: Growth in thickness, made possible by lateral meristems

  • Two types of lateral meristems

    • Vascular Cambium: Adds vascular tissue (secondary xylem (wood, responsible form most of the thickening) and secondary phloem)

    • Cork Cambium: Replaces epidermis with thicker, tougher perimderm

• Primary Meristems: Three tissues (protoderm, ground meristem, procambium) that produce the three mature tissues of a shoot or root (dermal, ground, vascular)

• Three categories of plants based on when they die. Annuals complete their life cycle from germination → flowering → seed production → death. Biennials require two growing seasons and flower and fruit only in the second year. Perennials live many years.

35.3: Primary growth lengthens roots and shoots

• Root Cap: Protects delicate apicak meristem as the root pushes through the soil, nade by the root apical meristem. Secretes polysaccharide slime that lubricates soil around the tip of the root

• Zone of Cell Division: Stem cells of the root apical meristem and their immediate products

• Zone of Elogation: A few mm behind the tip of the root, where most of the growth occurs as root cells elongate, pushing the tip further into the soil

• Zone of Differentiation/Maturation: Cells complete diffrentiation and become distinct cell types

• Endodermis: Cylinder one cell thick that forms the boundary with the vascular cylinder

• Pericycle: Cell layer surrounding vascular cylinder (Solid core of xylem and phloem tissues)

  • Xylem is like a star in the cross section, phloem is the space around it

• Apical Dominance: The closer an axillary bud is to an active bud the more inhibited it is

• Leaf Primordia: Projections shaped like a cat’s ear that emerge along sides of shoot. Almost no secondary growth in leaves

• Stomata: Allows exchange of CO₂ and O₂ between surrounding air and leafs photosynthetic cells. Interrupts the leaf epidermis (waxy cuticle that reduces water loss)

• Mesophyll: Leaf’s ground tissue, sandwiched between upper and lower epidermal layers. Two layers

  • Palisade Mesophyll: Underneath upper epidermis, one or more layers of elongated chloroplast rich cells specialized for light capture

  • Spongey Mesophyll: Located inward from lower epidermis, irregularly shaped cells with fewer chloroplasts. Have lots of air spaces for CO₂ and O₂ to circulate

35.4: Secondary growth increases the diameter of stems and roots in woody plants

• Vascular Cambrium: Meristematic cylinder that produces secondary xylem and secondary phloem during secondary growth

  • Older layers of secondary xylem become inactive while younger layers still conduct water

• Bark: All tissues external to the vascular cambium

• Lenticels: Dotting the permiderm, small raised areas with more space between cork cells, letting living cells within to exchange gases with outside air

35.5: Growth, morphogenesis, and cell diffrentiation produce the plant body

• Development: Specific series of changes by cells which form tissues, organs, and organisms

  • Developmental plasticity is ability to alter form in response to local environmental conditions

• Growth: Irreversible increase in size

• Cell Diffrentiation: Process by which cells with the same genes become different from each other

• Cell division happens on a precise plan that halves the cytoplasm of the parent cell, but it’s not always divided equally

  • Asymmetrical cell division generates cells that grow up into different types

• Cell expansion is responsible for plant growth, mostly fromwater uptake (responsible for 90% of expansion)

• Pattern Formation: Development of specific structures in specific locations

• Internal or environmental cues may cause a plant to switch from one developmental stage to another

  • Phase Changes: Changes from one developmental stage to another

• Floral development is used to study pattern formation

  • ABC Hypothesis: Proposes three classes of genes direct the formation of the four types of floral organs

Chapter 36: Resource Acquisition and Transport in Vascular Plants

36.1: Adaptations for acquiring resources were key steps in the evolution of plants

• Earliest plants were nonvascular and produced photosynthetic shoots above shallow freshwater where they lived

• Xylem: Transports water and minerals from roots to shoots

• Phloem: Transports products ofphotosynthesis from where they’re made or stored to where they’re needed

• Mycorrhizae: Evolution of mutualistic associations between roots and fungi

• Leaves function in gathering sunlight and CO₂ for photosynthesis

  • Stems are supporting structures for leaves and conduits for long distance transport of water and nutrients

36.2: Different mechanisms transport substances over short or long distances

• Apoplast: Everything external to the plasma membranes of living cells

  • Including cell walls, extracellular spaces, and the interior of dead cells (vessel elements and tracheids)

• Symplast: Entire mass of cytosol of all living cells in a plasm and the cytoplasmic channels that interconnect them (plasmodesmata)

• Three routs of transport within a plant tissue or organ

  • Apoplastic, water and solutes (dissolved chemicals) move along the continuum of cell walls and extracellular spaces

  • Symplastic, move along the continuum of cytosol

  • Transmembrane, move out of one cell, across the cell wall, and into the neighboring cell

• Hydrogen ions play the primary role in transport processes in plant cells

• Osmosis: Diffusion of free water, controls absorption or loss of water

• Water Potential: Quantity that includes effects of solute concentration and physical pressure, the physical property that predicts the direction water will flow in

• Megapascal: Unit of pressure to measure water potential (Ψ)

• Ψ = Ψ_S + Ψ_p

  • Ψ is water poential

  • Ψ_S is solute potential

    • Solute/Osmotic Potential: Directly proportional to its molarity, number of free water molecules (0 for just water, when solutes are added its negative)

  • Ψ_p is pressure potential

    • Pressure Potential: Physical pressure on a solution

• Plasmolysis: Cell shrinks and pulls away from cell wall (in hypertonic) 😢

• Turgid: Walled cell with greater solute concentration than surroundings (in hypotonic) 🙂

  • Wilting: Turgor loss, everything droops because cells have lost water

• Aquaporins: Transport proteins that facilitate transport of water molecules across plant cell plasma membranes

• Bulk Flow: Movement of liquid in response to a pressure gradient

36.3: Transpiration drives the transport of water and minerals from roots to shoot via the xylem

• Endodermis: Innermost layer of cells in the root cortex, “last checkpoint” for selective passage of minerals from cortex to vascular cylinder

• Casparian Strip: Dead end that blocks passage to the vascular cylinder. Water and minerals can’t cross the endodermis and have to use the apoplast to enter instead

• Xylem Sap: Water and dissolved minerals in the zylem

  • Transport through bulk flow involves the loss of a lot of water through transpiration

• Transpiration: Loss of water vapor from leaves and other aerial parts of the plant

• Root Pressure: A push of xylem sap

  • Guttation: Dew, ooze of water droplets due to root pressure causing too much water to enter leaves, which is transpired

• Cohesion Tension Hypothesis: Transpiration provides the pull for ascent of xylem sap which is usually under negative pressure/tension

  

36.4: The rate of transpiration is regulated by the stomata

• Stomata accounts for ~95% water loss in plants

• Stomata open when guard cells accumulate K⁺ from neighboring epidermal cells. When it opens, H⁺ is transported out of the guard cell. K⁺ is driven into the cell, and water potential becomes more negative so cells become more turgid

• Stomata usually open during the day and are closed at night. Three cues contribute to opening at dawn. Light, CO₂ depletion, and an internal clock in guard cells

  • Light stimulates guard cells to accumulate K amd become turgid

  • As CO₂ concentrations decrease during the day, the stomata opens

  • Circadian rhythms cause the stomata to continue their daily rhythm of opening and closing

• Abascisic Acid (ABA): Hormone produced in roots and leaves in response to water deficiency, signaling guard cells to close stomata

36.5: Sugars are transported from sources to sinks via the phloem

• Translocation: Transport of products of photosynthesis, carried out by the phloem

• Phloem Sap: Aqeous solution that flows through sieve tubes. Most prevalent solute is sugar

• Sugar Source: Plant organ, net producer of sugar by photosynthesis or breakdown of starch

  • Sugar Sink: Organ that is a net consumer or depository of sugar

• Phloem transport is always from sugar source to sugar sink

• Phloem loading depends on active transport of sucrose

  • Sucrose is contransported with H⁺, which diffuses down a gradient generated by proton pumps

  • Loading of sugar at the source and unloading at the sink maintains a pressure difference which keeps phloem sap flowing down the sieve tube

36.6: The symplast is highly dynamic

• Plasmodesmata can change in permeability and number

  • When dilated, they provide a passageway for symplastic transport of proteins, RNAs, and other macromolecules over long distances

• Phloem conducts nerve like electrical signals that help integrate whole plant function

Chapter 37: Soil and Plant Nutrition

37.1: Soil contains a living, complex ecosystem

• Humus: Remains of dead organisms and other organic matter

  • Topsoil: Upper layer of soil mostly humus

• Soil Horizons: Soil layers

• Loams: Topsoils that are the most fertile, composed of equal amounts of sand, silt, and clay

• Cation Exchange: Process in which cations are displaced from soil particles by other cations, particularly H⁺

• Fertilization: Addition of mineral nutrients to the soil, makes soil a renewable resource

• Sustainable Agriculture: Commitment to farming practices that are conservation minded, environmentally safe, and profitable

• No Till Agriculture: Plowing technique, special plow creates narrow furrows for seeds and fertilizer

• Phytoremediation: Nondestructive biotechnology that harnesses the ability of some plants to extract soil pollutants and concentrate them in portions of the plant that can easily be removed for safe disposal

37.2: Plant roots absorb many types of essential elements from the soil

• Essential Element: Chemical element required for a plant to complete its life cycle and reproduce

• Hydroponic Culture: Plants are grown in mineral solutions instead of soil

• Macronutrients: Essential elements required by plants in large amounts

• Micronutrients: Essential elements only needed in tiny quantities by plants

37.3: Plant nutrition often involves relationships with other organisms

• Rhizobacteria: Bacteria that lives either in close association with plant roots or in the rhizosphere

  • Rhizosphere: Soil closely surrounding plant roots

• Endophytes: Rhizobacteria that live between cells within the plants

  • Some rhizobacteria are free, others are endophytes

• Nitrogen Cycle: Series of natural processes by which certain nitrogen containing substances from air and soil are made available to living things, used by them, then returned to air and soil

  • Nitrogen Fixation: Reducing atmospheric N₂ to NH₃ to be used in plants

• Nodules: Swellings along a legume’s roots, composed of plant cells infected by Rhizobium bacteria

  • Bacteroids: Form taken by Rhizobium bacteria in each nodule, contained within vesicles formed in root cells

• Crop Rotation: One crop is planted one year, a different one the next, and another one the next, so on, to help restore concentration of nitrogen in the soil

• Ectomycorrhizae: Form a dense sheath of mycelia over the surface of the root

• Arbuscular Mycorrhizae: Don’t ensheath root, but are embedded within it

Chapter 38: Angiosperm Repdoduction and Biotechnology

38.1: Flowers, double fertilization, and fruits are key features of the angiosperm life cycle

• Flower: Sporophytic structure for sexual reproduction

  • Four organs which form cocentric whorls, carpels, stamens, petals, and sepals (inner to outer)

  • Reptacle: Part of stem attached to all floral organs

• Carpels and stamens are sporophylls

• Carpel has an ovary at its base and a style

  • Style: Slender neck of carpel

  • Stigma: Sticky structure at the top of the style that captures pollen

  • Ovules: Become seeds if fertilized, within the ovaries, number varies between species

• Pistil: 1 carpel or 2+ fused carpels

• Stamen (Microsporophyll) has a filament (stalk) and anther

  • Anther: Terminal structure in stamen with microsporangia that produce pollen

• Complete Flowers: Have all basic floral organs

• Incomplete Flowers: Lacking 1+ floral organs. Sterile ones lack stamens & carpels, unisexual/imperfect lack either one

• Inflorescences: Clusters of flowers

• Pollination: Transfer of pollen to ovule bearing structure of a seed plant

  • Abiotic pollination by wind has no selective pressure, ~20% all angiosperm species are wind pollinated

  • ~65% of flowering plants need insects for pollination, sweet, delicat fragrance flowers with bright colors, mostly yellow and blue

  • Moth and butterfly pollinated flowers are sweetly fragrant and brightly colored

  • Fly pollinated flowers are redish and fleshy and smell like rotting meat

  • Bat pollinated flowers are light colored and aromatic, like moth pollinated flowers

  • Bird pollunated flowers are large and bright red or yellow but have little odor

• Coevolution: Joint evolution of two interacting species responding to selection from each other

• Embryo Sac: Female gametophyte, develops in each ovule deep within its ovary

1. In megasporangium within each ovule, two layers of sporophytic tissue that will develop into the seed coat surround each megasporagium except at a gap (micropyle). Embryo sac development begins when the megasporocyte (one cell in the megasporangium of each ovule) enlarges and undergoes meiosis, producing four haploid megaspores

2. The nucleus of the megaspore divides by mitosis three times without cytokinesis, leaving a large cell with eight haploid nuclei divided by membranes to form the embryo sac. The other two nuclei (polar nuclei) share the cytoplasm of the large central cell of the embryo sac.

3. Anthers develop four microsporangia (pollen sacs) with many microsporocytes (diploid cells), which undergo meiosis and form 4 haploid microspores

4. The microspores give rise to a haploid male gametophyte with only two cells which makes a pollen grain

   1. Pollen Grain: Generative cell, tube cell, and spore wall

5. Microsporangium breaks open and releases pollen, and a grin may be transferred to the surface of a stigma, absorbing water and germinating by producing a pollen tub

   1. Pollen Tube: Long cellular protuberance that delivers sperm to the female gametophyte

6. Two sperm are released from pollen tube in the vicinity of the female gametophyte

   1. Fertilization: Fusion of gametes, occurs after two sperm reach the female gametophyte

   2. Endosperm: Multicellular, food storing tissue of the seed

   3. Double Fertilization: Union of two sperm cells with different nuclei of the female gametophyte

7. Fertilization occurs and one sperm fertilizes he egg to form a zygote, other sperm combines with the two polar nuclei to form a triploid nucleus in the center of the large central cell of the female gametophyte. This will give rise to the endosperm

8. Each ovule develops into a seed

9. When a seed germinates the embryo develops into a new sporophyte

• (Mature) Seed: Formant embryo surrounded by stored food and protective layers

• Dormancy: Seed stops growing and metabolism nearly ceases

• Seed Coat: Encloses the embryo and its food supply , formed from the integuments of the ovule

• Hypocotyl: Embryonic axis, terminates in the radicle

  • Radicle: Embryonic root

• Epicotyl: Portion of embryonic axis above where the cotyledons are attached and below the first pair of miniature leaves

• Coteoptile: Covers the young shoot, encloses the embryo

• Coleorhiza: Covers the young root, encloses the embryo

• Imhibition: Uptake of water due to low water potetial of the dry seed, initiates seed germination

• Fruit: Mature ovary of a flower

  • Simple Fruit: Fruits derived from a single carpel or several fused carpel

  • Aggregate Fruit: Flower with more than one seperate carpel which each forms a small fruit

  • Mutiple Fruit: Develops from an inflorescence, when walls of the ovaries start to thicken they fuse

  • Accesory Fruit: Other floral parts contribute to what we call the fruit

38.2: Flowering plants reproduce sexually, asexually, or both

• Asexual Reproduction: Offspring are derived from a single parent, resulting in a clone

  • Fragmentation: Seperation of parent plant into parts that develop into whole plants, mode of asexual reproduction

  • Apomixis: Diploid cell in ovule gives rise to embryo, and ovules mature into seeds, which the dandelion are dispersed

• Vegetative Reproduction: Asexual reproduction based on vegetative growth of stems, leaves, or roots

  • Vegetative Propogation: Vegetative reproduction facillitated by humans

• Self Incompatibility: Plants can rejects its own pollen and pollen of closely related plants

  • S gene recognizes self pollen

  • Two types, gametophytic and sporophytic

    • In gametophytic, determined by genotype of pollen (ex. S1 from S1S2 can pollinate S2S3)

      • In some plants RNA will be destroyed by enzymes if it’s a “self type”

    • In sporophytic, determined by parental origin (ex. S1 from S1S2 can’t pollinate S2S3), since both the pollen and stigma have the genes

• Totipotent: A cell that can divide and asexually produce a clone of the original in a multicellular organism

• Houseplants are asexually produced from plant fragments, shoot cuttings

  • Callus: A mass of dividing, undiffrentiated totipotent cells at the wounded end of a shoot

• Grafting: A severed shoot from a plant is joined to the truncated (one end cut off) stem of another

  • Stock: Plant that provides the roots in grafting

  • Scion: Twig grafted onto the stock

1. Recognizing self pollen through S genes and destroying the RNA or other stuff

2. Less genetic variation, which is an evolutionary disadvantage

3. Less genetic variation so not good, but also more consistent than having to rely on pollinators

38.3: People modify crops by breeding and genetic engineering

• Transgene: Gene transferred from one organism to another

• Biofuels: Fuels derived from living biomass

  • Biomass: World’s total mass of organic matter in a group of organisms in a particular habitat

Chapter 39: Plant Responses to Inernal and External Signals

39.1: Signal transduction pathways link signal reception to response

• Etoliation: Physical adaptations for growing in darkness

• Deetoliation: When a shoot reaches light, the plant goes through many changes

  • Stem elongation slows, leaves expand, roots elongate, shoot produces chlorophyll

• First step is for signals to be detected by receptors, proteins that undergo changes in shape in response to a specific stimulus

• Second Messengers: Small molecules and ions in the cell that amplify signals detected by receptors and transfor it from the receptor to other proteins to carry out the response

39.2: Plants use chemicals to communicate

• Hormone: Signaling molecule produced in low concentrations by one part of an organism’s body and transported to other parts, where it binds to a specific receptor and triggers responses in target cells and tissues

• Tropism: Growth response that results in plant organs curving toward or away from stimuli

• Phototropism: Growth of a shoot toward or away from light

  • Toward is positive phototropism, away from is negative

• Auxin: Any chemical that promotes coleoptile elongation

  • Produced mostly in shoot tips, transported from cell to cell down the stem at a rate of 1 cm/hr

• Acid Growth Hypothesis says protons play a mjor role in growth response of cells to auxin

  • Auxin stimulates plasma membrane’s proton pumps, which increases voltage and lowers pH of the cell

  • Expansins: Proteins that break cross links (hydrogen bonds) between cellulose microfibrils and other cell wall constituents, loosening the wall’s fabric. Activated by acidifcation of the cell wall

    • Causes osmotic uptake of water and increased turgor, which lets the cell elongate

• Cytokinins: Growth regulator that stimulates cytokinesis. Produced in actively growing tissues such as roots, embryos, and fruits

• Gibberellin: Chemical mostly in young roots and leaves that causes hyperelongation of stems by enhancing cell elongation and division

  • Must be present with auxins for fruit to develop

• Abasic Acid (ABA): Slows growth, antagonizing actions of growth hormones

  • Causes seed dormancy and drought tolerance. Ratio of ABA to Gibberellin determines whether seeds remain dormant or germinate

    • During drought it accumulates in leaves and causes stomata to close rapidly

• Ethylene: Hormone produced in response to stresses and during fruit ripening and programmed cell death in response to high concentrations of externally applied auxin.

  • Triple Response: Growth maneuver. Three parts to avoid growing into obstacles. Stem elongation, stem thickening, and curvature

  • Senescence: Programmed death of certain cells, organs, or the entire plant

  • Change in ratio of ethylene to auxin controls leaf abscission, aging cell produces less auxin

  • Ethylene triggers ripening of fruit which triggers more ethylene production

• Brassinosteroids: Steroids similar to cholesterol and sex hromones of animals, inducing cell elongation and division in stem segments and seedlings, slow leaf abcission

• Jasmonates: Fatty acid derived molecules that play important roles both in plant defense and development

• Strigolactones: Xylem mobile chemicals that stimulate seed germination, suppress adventitious root formation, establish mycorrhizal associations, and control apical dominance

39.3: Responses to light are critical for plant success

• Photomorphogenesis: Light triggers many key events in plant growth and development

• Action Spectrum: Depicts relative effectiveness of different wavelengths of radiation in driving a particular process

• Blue Light Photoreceptors: Initiate a variety of responses in plants, the light induced opening of the stomata, and the light induced slowing of hypocotyl elongation

• Phytochromes: Pigments that absorb mostly red and far red light which regulate plant responses to light

  • Provides plant with information about quality of light and lets plants adapt to changes in light avoidance

• Circadian Rhythms control many plant processes

• Photoperiodism: Phisiological response to specific night or day lengths

  • Short Day Plant: Requires light periods shorter than a critical length to flower

  • Long Day Plants: Flower in late spring or early summer

  • Day Neutral Plants: Unaffected by photoperiod and flower when they reach maturity regardless of photoperiod

• Vernalization: Use of pretreatment with cold to induce flowering

• Florigen: Signaling molecule for flowering

39.4: Plants respond to a wide variety of stimuli other than light

• Gravitropism: Plant’s responses to gravity

• Statoliths: Dense cytoplasmic components that settle under the influence of gravity to lower portions of the cell, how plants may detect gravity

• Thigmomorphogenesis: Changes in form that result from mechanical perturbation (stress)

  • Thigmotropism: Directional growth in response to touch

• Action Potentials: Electrical impulses traveling at the same rate as the signal that produces a response

• Abiotic stresses for plants include drought, flooding, salt, heat, or cold

  • Heat Shock Proteins: Proteins that are synthesized under heat stress which prevent other proteins from it

39.5: Plants respond to attacks by pathogens and herbivores

• Pathogen Associated Molecular Patterns (PAMPs): Molecular sequences specific to certain pathogens

• Effectors: Pathogen encoded proteins that cripple the plant’s innate immune systems, delivered directly into plant cells by pathogens

• Hypersensitive Response: Formation of a ring of local cell death around the infection site

• Systemic Acquired Resistance: Plant wide expression of defense genes

  • Methylsaliylic acid produced around infection site, carried by phloem throughout the plant, then converted to salicylic acid in areas remote from sites of infection

    • Salicylic acid activates a signal transduction pathway that poises defense system to respond rapidly to another infection

• Herbivory: Animals eating plants, a stress for plants