Campbell Unit 6: Plant Form and Function
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
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.
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
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
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
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
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 = ΨS + Ψp
Ψ is water poential
ΨS 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)
Ψp 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
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
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
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
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
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
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
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
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
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
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.
Anthers develop four microsporangia (pollen sacs) with many microsporocytes (diploid cells), which undergo meiosis and form 4 haploid microspores
The microspores give rise to a haploid male gametophyte with only two cells which makes a pollen grain
Pollen Grain: Generative cell, tube cell, and spore wall
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
Pollen Tube: Long cellular protuberance that delivers sperm to the female gametophyte
Two sperm are released from pollen tube in the vicinity of the female gametophyte
Fertilization: Fusion of gametes, occurs after two sperm reach the female gametophyte
Endosperm: Multicellular, food storing tissue of the seed
Double Fertilization: Union of two sperm cells with different nuclei of the female gametophyte
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
Each ovule develops into a seed
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
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
Recognizing self pollen through S genes and destroying the RNA or other stuff
Less genetic variation, which is an evolutionary disadvantage
Less genetic variation so not good, but also more consistent than having to rely on pollinators
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
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
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
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
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
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
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
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.
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
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
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
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
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 = ΨS + Ψp
Ψ is water poential
ΨS 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)
Ψp 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
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
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
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
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
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
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
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
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
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
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.
Anthers develop four microsporangia (pollen sacs) with many microsporocytes (diploid cells), which undergo meiosis and form 4 haploid microspores
The microspores give rise to a haploid male gametophyte with only two cells which makes a pollen grain
Pollen Grain: Generative cell, tube cell, and spore wall
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
Pollen Tube: Long cellular protuberance that delivers sperm to the female gametophyte
Two sperm are released from pollen tube in the vicinity of the female gametophyte
Fertilization: Fusion of gametes, occurs after two sperm reach the female gametophyte
Endosperm: Multicellular, food storing tissue of the seed
Double Fertilization: Union of two sperm cells with different nuclei of the female gametophyte
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
Each ovule develops into a seed
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
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
Recognizing self pollen through S genes and destroying the RNA or other stuff
Less genetic variation, which is an evolutionary disadvantage
Less genetic variation so not good, but also more consistent than having to rely on pollinators
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
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
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
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
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
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
