• Shuffle
    Toggle On
    Toggle Off
  • Alphabetize
    Toggle On
    Toggle Off
  • Front First
    Toggle On
    Toggle Off
  • Both Sides
    Toggle On
    Toggle Off
  • Read
    Toggle On
    Toggle Off
Reading...
Front

Card Range To Study

through

image

Play button

image

Play button

image

Progress

1/107

Click to flip

Use LEFT and RIGHT arrow keys to navigate between flashcards;

Use UP and DOWN arrow keys to flip the card;

H to show hint;

A reads text to speech;

107 Cards in this Set

  • Front
  • Back
Developmental Plasticity
the ability of a plant to alter itself in response to its environment
Roots
Functions:
Anchoring the plant
Absorbing minerals and water
Storing organic nutrients
Taproot
Lateral roots
A taproot system consists of one main vertical root that gives rise to lateral roots, or branch roots - eudicots
Stem
Consisting of :
An alternating system of nodes, the points at which leaves are attached
Internodes, the stem segments between nodes
Axillary Bud


Apical Bud


Apical Dominance
An axillary bud is a structure that has the potential to form a lateral shoot, or branch
An apical bud, or terminal bud, is located near the shoot tip and causes elongation of a young shoot
Apical dominance helps to maintain dormancy in most nonapical buds
Leaf
The leaf is the main photosynthetic organ of most vascular plants
Leaves generally consist of a flattened blade and a stalk called the petiole, which joins the leaf to a node of the stem
Monocots vs. Eudicots: Veins
Most monocots have parallel veins

Most eudicots have branching veins
Modified Roots
prop roots
storage roots
strangling aerial roots
pneumatophores
buttress roots
Modified Stems
rhizomes
bulbs
stolons
tubers
Modified Leaves
tendrils
spines
storage leaves
reproductive leaves
bracts
Dermal Tissue System
epidermis; cuticle - helps prevent water loss from the epidermis; periderm - replace the epidermis in older regions of stems and roots; trichomes - outgrowths of the shoot epidermis and can help with insect defense
Vascular Tissue System
Xylem conveys water and dissolved minerals upward from roots into the shoots
Phloem transports organic nutrients from where they are made to where they are needed
Stele
The vascular tissue of a stem or root is collectively called the stele
In angiosperms the stele of the root is a solid central vascular cylinder
The stele of stems and leaves is divided into vascular bundles, strands of xylem and phloem
Ground Tissue System
Ground tissue internal to the vascular tissue is pith; ground tissue external to the vascular tissue is cortex
Major Types of Plant Cells
Parenchyma
Collenchyma
Sclerenchyma
Water-conducting cells of the xylem
Sugar-conducting cells of the phloem
Parenchyma Cells
Have thin and flexible primary walls
Lack secondary walls
Are the least specialized
Perform the most metabolic functions
Retain the ability to divide and differentiate
Collenchyma Cells
Collenchyma cells are grouped in strands and help support young parts of the plant shoot
They have thicker and uneven cell walls
They lack secondary walls
These cells provide flexible support without restraining growth
Sclerenchyma Cells
Sclerenchyma cells are rigid because of thick secondary walls strengthened with lignin
They are dead at functional maturity

There are two types:
Sclereids are short and irregular in shape and have thick lignified secondary walls
Fibers are long and slender and arranged in threads
Xylem
The two types of water-conducting cells, tracheids and vessel elements, are dead at maturity
Phloem
Sieve-tube elements are alive at functional maturity, though they lack organelles
Sieve plates are the porous end walls that allow fluid to flow between cells along the sieve tube
Each sieve-tube element has a companion cell whose nucleus and ribosomes serve both cells
Meristems

Apical meristems

Lateral meristems
Meristems are perpetually embryonic tissue and allow for indeterminate growth
Apical meristems are located at the tips of roots and shoots and at the axillary buds of shoots
Lateral meristems add thickness to woody plants, a process called secondary growth
Vascular Cambium

(meristems)

Cork Cambium
The vascular cambium adds layers of vascular tissue called secondary xylem (wood) and secondary phloem
The cork cambium replaces the epidermis with periderm, which is thicker and tougher
Root
The root tip is covered by a root cap, which protects the apical meristem as the root pushes through soil
in three zones of cells:
Zone of cell division
Zone of elongation
Zone of maturation
Lenticels
Lenticels in the periderm allow for gas exchange between living stem or root cells and the outside air
Pattern Formation

Positional Information

Polarity
Pattern formation is the development of specific structures in specific locations
It is determined by positional information in the form of signals indicating to each cell its location
Polarity, having structural or chemical differences at opposite ends of an organism, provides one type of positional information
Water potential
Water potential is a measurement that combines the effects of solute concentration and pressure; abbreviated as Ψ and measured in megapascals (MPa). The addition of solutes reduces water potential.Physical pressure increases water potential.Negative pressure decreases water potential.
Solute potential / Osmotic potential



Pressure potential
The solute potential (ΨS) of a solution is proportional to the number of dissolved molecules

Pressure potential (ΨP) is the physical pressure on a solution
Aquaporins
Aquaporins are transport proteins in the cell membrane that allow the passage of water
Symplast; Plasmodesmata



Apoplast
The cytoplasmic continuum is called the symplast
The cytoplasm of neighboring cells is connected by channels called plasmodesmata

The apoplast is the continuum of cell walls and extracellular spaces
Water and minerals can travel through a plant by three routes:
Transmembrane route: out of one cell, across a cell wall, and into another cell
Symplastic route: via the continuum of cytosol
Apoplastic route: via the cell walls and extracellular spaces
Bulk flow
The movement of a fluid driven by pressure, important for long distance transport; possible because mature tracheids and vessel elements have no cytoplasm, and sieve-tube elements have few organelles in their cytoplasm
Endodermis




Casparian strip
The endodermis is the innermost layer of cells in the root cortex; surrounds the vascular cylinder and is the last checkpoint for selective passage of minerals from the cortex into the vascular tissue

The waxy Casparian strip of the endodermal wall blocks apoplastic transfer of minerals from the cortex to the vascular cylinder
Root pressure






Guttation
At night, when transpiration is very low, root cells continue pumping mineral ions into the xylem of the vascular cylinder, lowering the water potential; Water flows in from the root cortex, generating root pressure; water flows in from the root cortex

The exudation of water droplets on tips or edges of leaves that can result from root pressure
Transpirational Pull




Cohesion / Adhesion
Transpiration produces negative pressure (tension) in the leaf, which exerts a pulling force on water in the xylem, pulling water into the leaf

Transpirational pull is facilitated by cohesion of water molecules to each other and adhesion of water molecules to cell walls
Xerophytes
Xerophytes are plants adapted to arid climates
They have leaf modifications that reduce the rate of transpiration
Some plants use a specialized form of photosynthesis called crassulacean acid metabolism (CAM) where stomatal gas exchange occurs at night
Translocation
The products of photosynthesis are transported through phloem by the process of translocation
Xylem sap

Phloem sap
Water and minerals, called xylem sap

Phloem sap is an aqueous solution that is high in sucrose
Sugar source



Sugar sink
A sugar source is an organ that is a net producer of sugar, such as mature leaves

A sugar sink is an organ that is a net consumer or storer of sugar, such as a tuber or bulb
Transfer cells
Transfer cells are modified companion cells that enhance solute movement between the apoplast and symplast
Systemic communication
Systemic communication helps integrate functions of the whole plant
The phloem allows for rapid electrical communication between widely separated organs
Soil horizons
Soil is stratified into layers called soil horizons
Soil particles are classified by size; from largest to smallest they are called sand, silt, and clay
Top soil; Humus







Loams
Topsoil consists of mineral particles, living organisms, and humus, the decaying organic material. Topsoil contains bacteria, fungi, algae, other protists, insects, earthworms, nematodes, and plant roots. Humus builds a crumbly soil that retains water but is still porous. It also increases the soil’s capacity to exchange cations and serves as a reservoir of mineral nutrients


Loams are the most fertile topsoils and contain equal amounts of sand, silt, and clay
Cation exchange
During cation exchange, cations are displaced from soil particles by other cations
Displaced cations enter the soil solution and can be taken up by plant roots
Soil pH affects cation exchange and the chemical form of minerals
Cations are more available in slightly acidic soil, as H+ ions displace mineral cations from clay particles
Fertilization
Fertilization replaces mineral nutrients that have been lost from the soil
Commercial fertilizers are enriched in nitrogen, phosphorus, and potassium
Erosion can be reduced by
Planting trees as windbreaks
Terracing hillside crops
Cultivating in a contour pattern
Practicing no-till agriculture
Phytoremediation
Phytoremediation is a biological, nondestructive technology that reclaims contaminated areas
Essential element
A chemical element is considered an essential element if it is required for a plant to complete its life cycle

Researchers use hydroponic culture to determine which chemical elements are essential
Macronutrients

Micronutrients
C, O, H, N, K, Ca, Mg, P, S

Cl, Fe, Mn, B, Zn, Cu, Ni, Mo
Mineral deficiency
Deficiency of a mobile nutrient usually affects older organs more than young ones
Deficiency of a less mobile nutrient usually affects younger organs more than older ones
The most common deficiencies are those of N, K, P
Plants and soil microbes have a mutualistic relationship
Dead plants provide energy needed by soil-dwelling microorganisms
Secretions from living roots support a wide variety of microbes in the near-root environment
Rhizosphere
The layer of soil bound to the plant’s roots is the rhizosphere
The rhizosphere has high microbial activity because of sugars, amino acids, and organic acids secreted by roots
Rhizobacteria
Free-living rhizobacteria thrive in the rhizosphere, and some can enter roots
Produce hormones that stimulate plant growth
Produce antibiotics that protect roots from disease
Absorb toxic metals or make nutrients more available to roots
The nitrogen cycle
The nitrogen cycle transforms nitrogen and nitrogen-containing compounds
Plants absorb nitrogen as either NO3– or NH4+
Bacteria break down organic compounds or use N2 to produce NH3, which is converted to NH4+
Nitrification is carried out by bacteria that convert NH3 into NO3–
Nitrogen fixation
Nitrogen fixation is the conversion of nitrogen from N2 to NH3
Bacteroids
Inside the root nodule, Rhizobium bacteria assume a form called bacteroids, which are contained within vesicles formed by the root cell
The bacteria of a root nodule obtain sugar from the plant and supply the plant with fixed nitrogen
Mycorrhizae
Mycorrhizae are mutualistic associations of fungi and roots
The fungus benefits from a steady supply of sugar from the host plant
The host plant benefits because the fungus increases for water uptake and mineral absorption the surface area
Ectomycorrhizae
In ectomycorrhizae, the mycelium of the fungus forms a dense sheath over the surface of the root
These hyphae form a network in the apoplast, but do not penetrate the root cells
Arbuscular mycorrhizae
In arbuscular mycorrhizae, microscopic fungal hyphae extend into the root
These mycorrhizae penetrate the cell wall but not the plasma membrane to form branched arbuscules within root cells
Epiphyte
An epiphyte grows on another plant and obtains water and minerals from rain; non-parasitic because Parasitic plants absorb sugars and minerals from their living host plant
ex. of epiphyte: staghorn fern
ex. of parasite: mistletoe, dodder, Indian pipe
Sporophyte / Gametophyte
Diploid (2n) sporophytes produce spores by meiosis; these grow into haploid (n) gametophytes
In angiosperms, the sporophyte is the dominant generation, the large plant that we see
The gametophytes are reduced in size and depend on the sporophyte for nutrients
Flowers consist of four floral organs:


Receptacle
Sepals, petals, stamens, and carpels

Flowers are the reproductive shoots of the angiosperm sporophyte; they attach to a part of the stem called the receptacle
Stamen



Carpal; Pistal
A stamen consists of a filament topped by an anther with pollen sacs that produce pollen

A carpel has a long style with a stigma on which pollen may land
At the base of the style is an ovary containing one or more ovules; A single carpel or group of fused carpels is called a pistil
Complete / Incomplete flowers



Inflorescences
Complete flowers contain all four floral organs; Incomplete flowers lack one or more floral organs

Clusters of flowers are called inflorescences
Microspores



Pollen grain; Pollen tube
Pollen develops from microspores within the microsporangia, or pollen sacs, of anthers
If pollination succeeds, a pollen grain produces a pollen tube that grows down into the ovary and discharges sperm near the embryo sac. The pollen grain consists of the two-celled male gametophyte and the spore wall
Megaspores; Embryo sac
Within an ovule, megaspores are produced by meiosis and develop into embryo sacs, the female gametophytes
Double fertilization



Endosperm
Double fertilization results from the discharge of two sperm from the pollen tube into the embryo sac

One sperm fertilizes the egg, and the other combines with the polar nuclei, giving rise to the triploid (3n) food-storing endosperm
Embryo development
The first mitotic division of the zygote is transverse, splitting the fertilized egg into a basal cell and a terminal cell
Hypocotyl

Radicle

Epicotyl
Below the cotyledons the embryonic axis is called the hypocotyl and terminates in the radicle (embryonic root); above the cotyledons it is called the epicotyl
Coleoptile



Coleorhiza
Two sheathes enclose the embryo of a grass seed: a coleoptile covering the young shoot and a coleorhiza covering the young root
Germination; Imbibition
Germination depends on imbibition, the uptake of water due to low water potential of the dry seed
The radicle (embryonic root) emerges first.Next, the shoot tip breaks through the soil surface.
Fruits are also classified by their development:
Simple, a single or several fused carpels - peas
Aggregate, a single flower with multiple separate carpels - raspberry
Multiple, a group of flowers called an inflorescence - pineapple
Accessory fruit contains other floral parts in addition to ovaries - apple
Fragmentation
Fragmentation, separation of a parent plant into parts that develop into whole plants, is a very common type of asexual reproduction
Vegetative reproduction


Apomixis
Asexual reproduction

Apomixis is the asexual production of seeds from a diploid cell
Dioecious


Self-incompatibility
Dioecious species have staminate and carpellate flowers on separate plants

Self-incompatibility, a plant’s ability to reject its own pollen
Some plants reject pollen that has an S-gene matching an allele in the stigma cells. Recognition of self pollen triggers a signal transduction pathway leading to a block in growth of a pollen tube.
Callus
A callus is a mass of dividing undifferentiated cells that forms where a stem is cut and produces adventitious roots
Grafts; Stock / Scion
The stock provides the root system
The scion is grafted onto the stock
Protoplast fusion
Protoplast fusion is used to create hybrid plants by fusing protoplasts, plant cells with their cell walls removed
Transgenic crops have been developed that:
Produce proteins to defend them against insect pests
Tolerate herbicides
Resist specific diseases
Biofuels
Biofuels are made by the fermentation and distillation of plant materials such as cellulose
Efforts are underway to prevent crop-to-weed hybridization by introducing:
Male sterility
Apomixis
Transgenes into chloroplast DNA (not transferred by pollen)
Strict self-pollination
Etiolation



De-etiolation
Morphological adaptations for growing in darkness, collectively called etiolation. After exposure to light, a plant undergoes changes called de-etiolation, in which shoots and roots grow normally
Cell-signal processing
The stages are reception, transduction, and response
Internal and external signals are detected by receptors, proteins that change in response to specific stimuli. Second messengers transfer and amplify signals from receptors to proteins that cause responses.In most cases, these responses to stimulation involve increased activity of enzymes, which can occur by transcriptional regulation or post-translational modification.
Transcription factors
Specific transcription factors bind directly to specific regions of DNA and control transcription of genes
Positive transcription factors are proteins that increase the transcription of specific genes, while negative transcription factors are proteins that decrease the transcription of specific genes
Hormones



Tropism
Hormones are chemical signals that coordinate different parts of an organism

Any response resulting in curvature of organs toward or away from a stimulus is called a tropism
Charles Darwin


Peter Boysen-Jensen


Frits Went
Darwin observed that a grass seedling could bend toward light only if the tip of the coleoptile was present; postulated that a signal was transmitted from the tip to the elongating region

In 1913, Peter Boysen-Jensen demonstrated that the signal was a mobile chemical substance

In 1926, Frits Went extracted the chemical messenger for phototropism, auxin, by modifying earlier experiments
Auxin
Auxin refers to any chemical that promotes elongation of coleoptiles
Indoleacetic acid (IAA) is a common auxin in plants
Auxin transporter proteins move the hormone from the basal end of one cell into the apical end of the neighboring cell
Auxin is also involved in root formation and branching
Auxin affects secondary growth by inducing cell division in the vascular cambium and influencing differentiation of secondary xylem
Acid growth hypothesis; Expansins
According to the acid growth hypothesis, auxin stimulates proton pumps in the plasma membrane
The proton pumps lower the pH in the cell wall, activating expansins, enzymes that loosen the wall’s fabric. With the cellulose loosened, the cell can elongate
Cytokinins
Cytokinins are so named because they stimulate cytokinesis (cell division). Cytokinins work together with auxin to control cell division and differentiation. Cytokinins, auxin, and other factors interact in the control of apical dominance, a terminal bud’s ability to suppress development of axillary buds.
Cytokinins also retard the aging of some plant organs by inhibiting protein breakdown, stimulating RNA and protein synthesis, and mobilizing nutrients from surrounding tissues
Cytokinins are produced in actively growing tissues such as roots, embryos, and fruits
Gibberellins
Gibberellins have a variety of effects, such as stem elongation, fruit growth, and seed germination
Gibberellins stimulate growth of leaves and stems. In many plants, both auxin and gibberellins must be present for fruit to set. After water is imbibed, release of gibberellins from the embryo signals seeds to germinate
Brassinosteroids
Brassinosteroids are chemically similar to the sex hormones of animals
They induce cell elongation and division in stem segments
Abscisic acid
Abscisic acid (ABA) slows growth
Two of the many effects of ABA:
Seed dormancy - Seed dormancy ensures that the seed will germinate only in optimal conditions
Drought tolerance
Ethylene
Plants produce ethylene in response to stresses such as drought, flooding, mechanical pressure, injury, and infection. The effects of ethylene include response to mechanical stress, senescence, leaf abscission, and fruit ripening

The Triple Response to Mechanical Stress - consists of a slowing of stem elongation, a thickening of the stem, and horizontal growth
Senescence




Leaf Abscission
Senescence is the programmed death of plant cells or organs
A burst of ethylene is associated with apoptosis, the programmed destruction of cells, organs, or whole plants

A change in the balance of auxin and ethylene controls leaf abscission, the process that occurs in autumn when a leaf falls
Photomorphogenesis
Effects of light on plant morphology are called photomorphogenesis
There are two major classes of light receptors:
Blue-light photoreceptors and phytochromes
Various blue-light photoreceptors control hypocotyl elongation, stomatal opening, and phototropism
Phytochromes are pigments that regulate many of a plant’s responses to light throughout its life
including seed germination and shade avoidance
Phytochromes exist in two photoreversible states, with conversion of Pr to Pfr triggering many developmental responses. Phytochrome conversion marks sunrise and sunset, providing the biological clock with environmental cues
Photoperiodism

Short-day / Long-day / Neutral-day plants
Photoperiodism is a physiological response to photoperiod
Plants that flower when a light period is shorter than a critical length are called short-day plants
Plants that flower when a light period is longer than a certain number of hours are called long-day plants
Flowering in day-neutral plants is controlled by plant maturity, not photoperiod
Vernalization


Gravitropism; Statoliths
Vernalization is a pretreatment with cold to induce flowering

Response to gravity is known as gravitropism. Roots show positive gravitropism, while shoots show negative gravitropism.
Plants may detect gravity by the settling of statoliths, specialized plastids containing dense starch grains
Thigmomorphogenesis


Thigmotropism


Action potentials
The term thigmomorphogenesis refers to changes in form that result from mechanical disturbance

Thigmotropism is growth in response to touch.
Rapid leaf movements in response to mechanical stimulation are examples of transmission of electrical impulses called action potentials
Methyljasmonic acid
Methyljasmonic acid can activate the expression of genes involved in plant defenses
Drought
During drought, plants reduce transpiration by closing stomata, slowing leaf growth, and reducing exposed surface area
Growth of shallow roots is inhibited, while deeper roots continue to grow
Flooding
Enzymatic destruction of root cortex cells creates air tubes that help plants survive oxygen deprivation during flooding
Salt stress
Salt can lower the water potential of the soil solution and reduce water uptake
Plants respond to salt stress by producing solutes tolerated at high concentrations
This process keeps the water potential of cells more negative than that of the soil solution
Heat stress




Cold stress
Excessive heat can denature a plant’s enzymes
Heat-shock proteins help protect other proteins from heat stress

Cold temperatures decrease membrane fluidity
Altering lipid composition of membranes is a response to cold stress
Freezing causes ice to form in a plant’s cell walls and intercellular spaces
Virulent / Avirulent pathogens
A virulent pathogen is one that a plant has little specific defense against
An avirulent pathogen is one that may harm but does not kill the host plant
Gene-for-gene recognition
Gene-for-gene recognition involves recognition of pathogen-derived molecules by protein products of specific plant disease resistance (R) genes. R proteins activate plant defenses by triggering signal transduction pathways
The hypersensitive response
Causes cell and tissue death near the infection site
Induces production of phytoalexins and PR proteins, which attack the pathogen
Stimulates changes in the cell wall that confine the pathogen
Systemic acquired resistance



Salicylic acid
Systemic acquired resistance causes systemic expression of defense genes and is a long-lasting response
Salicylic acid is synthesized around the infection site and is likely the signal that triggers systemic acquired resistance