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AP Biology Unit 6

Unit 6 from the textbook Campbell Reece Biology, by chapter, in the order they appear. Unit name: Plant Form and Function Unit pages: 712-817 Chapters: 35-39
STUDY
PLAY
plasticity
an organism's ability to alter or molditself in response to local environmental conditions
tissue
an integrated group of cells with a common function, structure, or both
organ
a specialized center of body function composed of several different types of tissues
root system
all of a plant's roots that anchor it in the soil, absorb and transport minerals and water, and store food
shoot system
the aerial portion of a plant body, consisting of stems, leaves, and (in angiosperms) flowers
root
an organ in vascular plants that anchors the plant and enables it to absorb water and nutrients from the soil
taproot system
a root system common to eudicots, consisting of one large, vertical root (the taproot) that produces many smaller lateral, or branch, roots
lateral root
a root that arises from the outermost layer of the pericycle of an established root
fibrous root system
a root system common to monocots consisting of a mat of thin roots spreading out below the soil surface
adventitious
a term describing any plant organ that grows in an atypical location, such as roots growing from stems
root hair
a tiny extension of a root epidermal cell, growing just behind the root tip and increasing surface area for absorption of water and minerals
stem
a vascular plant organ consisting of an alternating system of nodes and internodes that support the leaves and reproductive structures
node
a point along the stem of a plant at which leaves are attached
internode
a segment of a plant stem between the points where leaves are attached
axillary bud
a structure that has the potential to form a lateral shoot, or branch. The bud appears in the angle formed between a leaf and a stem
terminal bud
embryonic tissue at the tip of a shoot, made up of developing leaves and a compact series of nodes and internodes
leaf
the main photosynthetic organ of vascular plants
blade
(1) A leaflike structure of a seaweed that provides most of the surface area for photosynthesis. (2) The flattened portion of a typical leaf
petiole
the stalk of a leaf, which joins the leaf to a node of the stem
vein
(1) In animals, a vessel that returns blood to the heart. (2) In plants, a vascular bundle in a leaf
tissue system
one or more tissues organized into a functional unit connecting the organs of a plant
dermal tissue system
the outer protective covering of plants
epidermis
(1) The dermal tissue system of nonwoody plants, usually consisting of a single layer of tightly packed cells. (2) The outer covering of animals
periderm
the protective coat that replaces the epidermis in plants during secondary growth, formed of the cork and cork cambium
cuticle
(1) A waxy covering on the surface of stems and leaves that acts as an adaptation to prevent desiccation in terrestrial plants. (2) The exoskeleton of an arthropod, consisting of layers of protein and chitin that are variously modified for different functions. (3) A tough coat that covers the body of a nematode
vascular tissue system
a system formed by xylem and phloem throughout a vascular plant, serving as a transport system for water and nutrients, respectively
xylem
vascular plant tissue consisting mainly of tubular dead cells that conduct most of the water and minerals upward from roots to the rest of the plant
phloem
vascular plant tissue consisting of living cells arranged into elongated tubes that transport sugar and other organic nutrients throughout the plant
stele
the vascular tissue of a stem or root
vascular cylinder
the central cylinder of vascular tissue in a root
vascular bundle
a strand of vascular tissues (both xylem and phloem) in a stem or leaf
ground tissue system
plant tissues that are neither vascular nor dermal, fulfilling a variety of functions, such as storage, photosynthesis, and support
pith
ground tissue that is internal to the vascular tissue in a stem; in many monocot roots, parenchyma cells that form the central core of the vascular cylinder
cortex
ground tissue that is between the vascular tissue and dermal tissue in a root or dicot stem
protoplast
the contents of a plant cell exclusive of the cell wall
parenchyma cell
a relatively unspecialized plant cell type that carries out most of the metabolism, synthesizes and stores organic products, and develops into a more differentiated cell type
collenchyma cell
a flexible plant cell type that occurs in strands or cylinders that support young parts of the plant without restraining growth
sclerenchyma cell
a rigid, supportive plant cell type usually lacking protoplasts and possessing thick secondary walls strengthened by lignin at maturity
sclereid
a short, irregular sclerenchyma cell in nutshells and seed coats and scattered through the parenchyma of some plants
fiber
a lignified cell type that reinforces the xylem of angiosperms and functions in mechanical support; a slender, tapered sclerenchyma cell that usually occurs in bundles
tracheid
a long, tapered water-conducting cell that is dead at maturity and is found in the xylem of all vascular plants
vessel element
a short, wide, water-conducting cell found in the xylem of most angiosperms and a few nonflowering vascular plants. Dead at maturity, vessel elements are aligned end to end to form micropipes called vessels
pit
a thinner region in the walls of tracheids and vessels where only primary wall is present
vessels
continuous water-conducting micropipes found in most angiosperms and a few nonflowering vascular plants
sieve-tube member
a living cell that conducts sugars and other organic nutrients in the phloem of angiosperms. They form chains called sieve tubes
sieve plate
an end wall in a sieve-tube member, which facilitates the flow of phloem sap in angiosperm sieve tubes
companion cell
a type of plant cell that is connected to a sieve-tube member by many plasmodesmata and whose nucleus and ribosomes may serve one or more adjacent sieve-tube members
indeterminate growth
a type of growth characteristic of plants, in which the organism continues to grow as long as it lives
determinate growth
a type of growth characteristic of most animals and some plant organs, in which growth stops after a certain size is reached
annual
a flowering plant that completes its entire life cycle in a single year or growing season
biennial
a flowering plant that requires two years to complete its life cycle
perennial
a flowering plant that lives for many years
meristem
plant tissue that remains embryonic as long as the plant lives, allowing for indeterminate growth
apical meristem
embryonic plant tissue in the tips of roots and in the buds of shoots that supplies cells for the plant to grow in length
primary growth
growth produced by apical meristems, lengthening stems and roots
herbaceous
referring to nonwoody plants
secondary growth
growth produced by lateral meristems, thickening the roots and shoots of woody plants
lateral meristem
a meristem that thickens the roots and shoots of woody plants. The vascular cambium and cork cambium are lateral meristems
vascular cambium
a cylinder of meristematic tissue in woody plants that adds layers of secondary vascular tissue called secondary xylem (wood) and secondary phloem
cork cambium
a cylinder of meristematic tissue in woody plants that replaces the epidermis with thicker, tougher cork cells
initials
cells that remain within an apical meristem as sources of new cells
derivatives
new cells that are displaced from an apical meristem and continue to divide until the cells they produce become specialized
primary plant body
the tissues produced by apical meristems, which lengthen stems and roots
root cap
a cone of cells at the tip of a plant root that protects the apical meristem
zone of cell division
the zone of primary growth in roots consisting of the root apical meristem and its derivatives. New root cells are produced in this region
zone of elongation
the zone of primary growth in roots where new cells elongate, sometimes up to ten times their original length
zone of maturation
the zone of primary growth in roots where cells complete their differentiation and become functionally mature
endodermis
the innermost layer of the cortex in plant roots; a cylinder one cell thick that forms the boundary between the cortex and the vascular cylinder
pericycle
the outermost layer of the vascular cylinder of a root, where lateral roots originate
leaf primordia
fingerlike projections along the flanks of a shoot apical meristem, from which leaves arise
stoma
a microscopic pore surrounded by guard cells in the epidermis of leaves and stems that allows gas exchange between the environment and the interior of the plant
guard cells
the two cells that flank the stomatal pore and regulate the opening and closing of the pore
mesophyll
the ground tissue of a leaf, sandwiched between the upper and lower epidermis and specialized for photosynthesis
palisade mesophyll
one or more layers of elongated photosynthetic cells on the upper part of a leaf; also called palisade parenchyma
spongy mesophyll
loosely arranged photosynthetic cells located below the palisade mesophyll cells in a leaf
leaf trace
a small vascular bundle that extends from the vascular tissue of the stem through the petiole and into a leaf
bundle sheath
a protective covering around a leaf vein, consisting of one or more cell layers, usually parenchyma
secondary plant body
the tissues produced by the vascular cambium and cork cambium, which thicken the stems and roots of woody plants
fusiform initials
cells within the vascular cambrium that produce elongated cells such as tracheids, vessel elements, fibers, and sieve-tube members
ray initials
cells within the vascular cambrium that produce xylem and phloem rays, radial files that consist mostly of parenchyma cells
heartwood
older layers of secondary xylem, closer to the center of a stem or root, that no longer transport xylem sap
sapwood
outer layers of secondary xylem that still transport xylem sap
lenticels
small raised areas in the bark of stems and roots that enable gas exchange between living cells and the outside air
bark
all tissues external to the vascular cambium, consisting mainly of the secondary phloem and layers of periderm
morphogenesis
the development of body shape and organization
systems biology
an approach to studying biology that aims to model the dynamic behavior of whole biological systems
preprophase band
microtubules in the cortex (outer cytoplasm) of a cell that are concentrated into a ring
pattern formation
the ordering of cells into specific three-dimensional structures, an essential part of shaping an organism and its individual parts during development
positional information
signals to which genes regulating development respond, indicating a cell's location relative to other cells in an embryonic structure
polarity
a lack of symmetry. Structural differences in opposite ends of an organism or structure, such as the root end and shoot end of a plant
phase change
a shift from one developmental phase to another
meristem identity gene
a plant gene that promotes the switch from vegetative growth to flowering
organ identity genes
plant homeotic genes that use positional information to determine which emerging leaves develop into which types of floral organs
ABC model
a model of flower formation identifying three classes of organ identity genes that direct formation of the four types of floral organs.
active transport
the movement of a substance across a biological membrane against its concentration or electrochemical gradient with the help of energy input and specific transport proteins
transport protein
a transmembrane protein that helps a certain substance or class of closely related substances to cross the membrane
proton pump
an active transport mechanism in cell membranes that uses ATP to force hydrogen ions out of a cell, generating a membrane potential in the process
membrane potential
the charge difference between a cell's cytoplasm and the extracellular fluid, due to the differential distribution of ions. Membrane potential affects the activity of excitable cells and the transmembrane movement of all charged substances
cotransport
the coupling of the downhilldiffusion of one substance to the uphilltransport of another against its own concentration gradient
chemiosmosis
an energy-coupling mechanism that uses energy stored in the form of a hydrogen ion gradient across a membrane to drive cellular work, such as the synthesis of ATP. Most ATP synthesis in cells occurs by chemiosmosis
osmosis
the diffusion of water across a selectively permeable membrane
water potential
the physical property predicting the direction in which water will flow, governed by solute concentration and applied pressure
megapascal (MPa)
a unit of pressure equivalent to 10 atmospheres of pressure
solute potential (Ψs)
a component of water potential that is proportional to the number of dissolved solute molecules in a solution and measures the effect of solutes on the direction of water movement; also called osmotic potential, it can be either zero or negative
osmotic potential
a component of water potential that is proportional to the number of dissolved solute molecules in a solution and measures the effect of solutes on the direction of water movement; also called solute potential, it can be either zero or negative
pressure potential (Ψp)
a component of water potential that consists of the physical pressure on a solution, which can be positive, zero, or negative
turgor pressure
the force directed against a cell wall after the influx of water and the swelling of a walled cell due to osmosis
flaccid
limp. A walled cell is flaccid in surroundings where there is no tendency for water to enter
plasmolyze
to shrink and pull away from a cell wall, or when a plant cell protoplast pulls away from the cell wall as a result of water loss
turgid
very firm. A walled cell becomes turgid if it has a greater solute concentration than its surroundings, resulting in entry of water
wilting
the drooping of leaves and stems as a result of plant cells becoming flaccid
aquaporin
a transport protein in the plasma membrane of a plant or animal cell that specifically facilitates the diffusion of water across the membrane (osmosis)
vacuolar membrane
a membrane that encloses the central vacuole in a plant cell, separating the cytosol from the vacuolar contents, called cell sap; also known as the tonoplast
tonoplast
a membrane that encloses the central vacuole in a plant cell, separating the cytosol from the vacuolar contents, called cell sap; also known as the vacuolar membrane
symplast
in plants, the continuum of cytoplasm connected by plasmodesmata between cells
apoplast
in plants, the continuum of cell walls plus the extracellular spaces
bulk flow
the movement of water due to a difference in pressure between two locations
mycorrhizae
mutualistic associations of plant roots and fungi
endodermis
the innermost layer of the cortex in plant roots; a cylinder one cell thick that forms the boundary between the cortex and the vascular cylinder
Casparian strip
a water-impermeable ring of wax in the endodermal cells of plants that blocks the passive flow of water and solutes into the stele by way of cell walls
transpiration
the evaporative loss of water from a plant
root pressure
the upward push of xylem sap in the vascular tissue of roots
guttation
the exudation of water droplets, caused by root pressure in certain plants
circadian rhythm
a physiological cycle of about 24 hours that is present in all eukaryotic organisms and that persists even in the absence of external cues
xerophyte
a plant adapted to an arid climate
translocation
(1) An aberration in chromosome structure resulting from attachment of a chromosomal fragment to a nonhomologous chromosome. (2) During protein synthesis, the third stage in the elongation cycle when the RNA carrying the growing polypeptide moves from the A site to the P site on the ribosome. (3) The transport of organic nutrients in the phloem of vascular plants
sugar source
a plant organ in which sugar is being produced by either photosynthesis or the breakdown of starch. Mature leaves are the primary sugar sources of plants
sugar sink
a plant organ that is a net consumer or storer of sugar. Growing roots, shoot tips, stems, and fruits are sugar sinks supplied by phloem
transfer cell
a companion cell with numerous ingrowths of its wall, increasing the cell's surface area and enhancing the transfer of solutes between apoplast and symplast
mineral nutrient
an essential chemical element absorbed from the soil in the form of inorganic ions
essential element
in plants, a chemical element that is required for the plant to grow from a seed and complete the life cycle, producing another generation of seeds
macronutrient
a chemical substance that an organism must obtain in relatively large amounts. See also micronutrient
micronutrient
an element that an organism needs in very small amounts and that functions as a component or cofactor of enzymes. See also macronutrient
topsoil
a mixture of particles derived from rock, living organisms, and humus
humus
decomposing organic material found in topsoil
horizon
a distinct layer of soil, such as topsoil
loam
the most fertile of all soils, made up of roughly equal amounts of sand, silt, and clay
cation exchange
a process in which positively charged minerals are made available to a plant when hydrogen ions in the soil displace mineral ions from the clay particles
sustainable agriculture
long-term productive farming methods that are environmentally safe
phytoremediation
an emerging nondestructive technology that seeks to cheaply reclaim contaminated areas by taking advantage of the remarkable ability of some plant species to extract heavy metals and other pollutants from the soil and to concentrate them in easily harvested portions of the plant
nitrogen-fixing bacteria
microorganisms that restock nitrogenous minerals in the soil by converting nitrogen to ammonia
nitrogen fixation
the assimilation of atmospheric nitrogen by certain prokaryotes into nitrogenous compounds that can be directly used by plants
nitrogenase
an enzyme complex, unique to certain prokaryotes, that reduces N2 to NH3
nodule
a swelling on the root of a legume. Nodules are composed of plant cells that contain nitrogen-fixing bacteria of the genus Rhizobium
bacteroids
a form of Rhizobium contained within the vesicles formed by the root cells of a root nodule
crop rotation
the alternation of planting a nonlegume one year and a legume the next year to restore concentration of fixed nitrogen in the soil
mycorrhizae
mutualistic associations of plant roots and fungi
ectomycorrhizae
a type of mycorrhiza in which the mycelium forms a dense sheath, or mantle, over the surface of the root. Hyphae extend from the mantle into the soil, greatly increasing the surface area for water and mineral absorption
endomycorrhizae
a type of mycorrhiza that, unlike ectomycorrhizae, does not have a dense mantle ensheathing the root. Instead, microscopic fungal hyphae extend from the root into the soil
haustorium
(plural, haustoria) In certain symbiotic fungi, specialized hyphae that can penetrate the tissues of host organisms
epiphyte
a plant that nourishes itself but grows on the surface of another plant for support, usually on the branches or trunks of tropical trees
sepal
a modified leaf in angiosperms that helps enclose and protect a flower bud before it opens
petal
a modified leaf of a flowering plant. Petals are the often colorful parts of a flower that advertise it to insects and other pollinators
stamen
the pollen-producing reproductive organ of a flower, consisting of an anther and filament
carpel
the ovule-producing reproductive organ of a flower, consisting of the stigma, style, and ovary
receptacle
the base of a flower; the part of the stem that is the site of attachment of the floral organs to the stem
anther
in an angiosperm, the terminal pollen sac of a stamen, where pollen grains with male gametes form
ovary
(1) In flowers, the portion of a carpel in which the egg-containing ovules develop. (2) In animals, the structure that produces female gametes and reproductive hormones
style
the stalk of a flower's carpel, with the ovary at the base and the stigma at the top
stigma
(plural, stigmata) The sticky part of a flower's carpel, which traps pollen grains
ovule
a structure that develops within the ovary of a seed plant and contains the female gametophyte
complete flower
a flower that has all four basic floral organs: sepals, petals, stamens, and carpels
incomplete flower
a flower in which one or more of the four basic floral organs (sepals, petals, stamens, or carpels) are either absent or nonfunctional
inflorescence
a group of flowers tightly clustered together
monoecious
a term typically used to describe an angiosperm species in which carpellate and staminate flowers are on the same plant
dioecious
a term typically used to describe an angiosperm species in which carpellate and staminate flowers are on separate plants
microspore
a spore from a heterosporous plant species that develops into a male gametophyte
megaspore
a spore from a heterosporous plant species that develops into a female gametophyte
self-incompatibility
the ability of a seed plant to reject its own pollen and sometimes the pollen of closely related individuals
endosperm
a nutrient-rich tissue formed by the union of a sperm cell with two polar nuclei during double fertilization, which provides nourishment to the developing embryo in angiosperm seeds
double fertilization
a mechanism of fertilization in angiosperms, in which two sperm cells unite with two cells in the embryo sac to form the zygote and endosperm
seed coat
a tough outer covering of a seed, formed from the outer coat of an ovule. In a flowering plant, the seed coat encloses and protects the embryo and endosperm
hypocotyl
in an angiosperm embryo, the embryonic axis below the point of attachment of the cotyledon(s) and above the radicle
radicle
an embryonic root of a plant
epicotyl
in an angiosperm embryo, the embryonic axis above the point of attachment of the cotyledon(s)
scutellum
a specialized type of cotyledon found in the grass family
coleoptile
the covering of the young shoot of the embryo of a grass seed
coleorhiza
the covering of the young root of the embryo of a grass seed
fruit
a mature ovary of a flower that protects dormant seeds and aids in their dispersal
simple fruit
a fruit derived from a single carpel or several fused carpels
aggregate fruit
a fruit derived from a single flower that has more than one carpel
multiple fruit
a fruit derived from an inflorescence, a group of flowers tightly clustered together
dormancy
a condition typified by extremely low metabolic rate and a suspension of growth and development
asexual reproduction
a type of reproduction involving only one parent that produces genetically identical offspring by budding or by the division of a single cell or the entire organism into two or more parts
fragmentation
a means of asexual reproduction whereby a single parent breaks into parts that regenerate into whole new individuals
apomixis
the asexual production of seeds
callus
a mass of dividing, undifferentiated cells at the cut end of a shoot
protoplast fusion
the fusing of two protoplasts from different plant species that would otherwise be reproductively incompatible
stock
the plant that provides the root system when making a graft
scion
the twig grafted onto the stock when making a graft
transgenic
pertaining to an individual plant or animal whose genome contains a gene introduced from another organism, either from the same or a different species
etiolation
plant morphological adaptations for growing in darkness
de-etiolation
the changes a plant shoot undergoes in response to sunlight; also known informally as greening
second messenger
a small, nonprotein, water-soluble molecule or ion, such as calcium ion or cyclic AMP, that relays a signal to a cell's interior in response to a signal received by a signal receptor protein
hormone
in multicellular organisms, one of many types of circulating chemical signals that are formed in specialized cells, travel in body fluids, and act on specific target cells to change their functioning
tropism
a growth response that results in the curvature of whole plant organs toward or away from stimuli owing to differential rates of cell elongation
phototropism
growth of a plant shoot toward or away from light
auxin
a term that primarily refers to indoleacetic acid (IAA), a natural plant hormone that has a variety of effects, including cell elongation, root formation, secondary growth, and fruit growth
expansins
plant enzymes that break the cross-links (hydrogen bonds) between cellulose microfibrils and other cell wall constituents, loosening the wall's fabric
cytokinins
a class of related plant hormones that retard aging and act in concert with auxin to stimulate cell division, influence the pathway of differentiation, and control apical dominance
gibberellins
a class of related plant hormones that stimulate growth in the stem and leaves, trigger the germination of seeds and breaking of bud dormancy, and stimulate fruit development with auxin
brassinosteroids
steroid hormones in plants that have a variety of effects, including cell elongation, retarding leaf abscission, and promoting xylem differentiation
abscisic acid (ABA)
a plant hormone that slows down growth, often antagonizing actions of growth hormones. Two of its many effects are to promote seed dormancy and facilitate drought tolerance
ethylene
the only gaseous plant hormone. Among its many effects are response to mechanical stress, programmed cell death, leaf abscission, and fruit ripening
triple response
a plant growth maneuver in response to mechanical stress, involving slowing of stem elongation, a thickening of the stem, and a curvature that causes the stem to start growing horizontally
apoptosis
the changes that occur within a cell as it undergoes programmed cell death, which is brought about by signals that trigger the activation of a cascade of suicide proteins in the cell destined to die
photomorphogenesis
effects of light on plant morphology
action spectrum
a graph that depicts the relative effectiveness of different wavelengths of radiation in driving a particular process
blue-light photoreceptors
a class of light receptors in plants. Blue light initiates a variety of responses, such as phototropism and slowing of hypocotyl elongation
phytochromes
a class of light receptors in plants. Mostly absorbing red light, these photoreceptors regulate many plant responses, including seed germination and shade avoidance
circadian rhythm
a physiological cycle of about 24 hours that is present in all eukaryotic organisms and that persists even in the absence of external cues
photoperiodism
a physiological response to photoperiod, the relative lengths of night and day. An example of photoperiodism is flowering
short-day plant
a plant that flowers (usually in late summer, fall, or winter) only when the light period is shorter than a critical length
long-day plant
a plant that flowers (usually in late spring or early summer) only when the light period is longer than a critical length
day-neutral plant
a plant whose flowering is not affected by photoperiod
vernalization
the use of cold treatment to induce a plant to flower
florigen
a flowering signal, not yet chemically identified, that may be a hormone or may be a change in relative concentrations of multiple hormones
gravitropism
a response of a plant or animal to gravity
statolith
(1) In plants, a specialized plastid that contains dense starch grains and may play a role in detecting gravity (2) In invertebrates, a grain or other dense granule that settles in response to gravity and is found in sensory organs that function in equilibrium
thigmomorphogenesis
a response in plants to chronic mechanical stimulation, resulting from increased ethylene production. An example is thickening stems in response to strong winds
thigmotropism
a directional growth of a plant in response to touch
action potential
a rapid change in the membrane potential of an excitable cell, caused by stimulus-triggered, selective opening and closing of voltage-sensitive gates in sodium and potassium ion channels
abiotic
nonliving
biotic
pertaining to the living organisms in the environment
heat-shock protein
a protein that helps protect other proteins during heat stress. Heat-shock proteins are found in plants, animals, and microorganisms
jasmonic acid
an important molecule in plant defense against herbivores
virulent
a term describing a pathogen against which a plant has little specific defense
avirulent
a term describing a pathogen that can only mildly harm, but not kill, the host plant
gene-for-gene recognition
a widespread form of plant disease resistance involving recognition of pathogen-derived molecules by the protein products of specific plant disease resistance genes
elicitor
a molecule that induces a broad type of host defense response
oligosaccharin
a type of elicitor (molecule that induces a broad defense response in plants) that is derived from cellulose fragments released by cell wall damage
phytoalexin
an antibiotic, produced by plants, that destroys microorganisms or inhibits their growth
PR protein
a protein involved in plant responses to pathogens (PR = pathogenesis-related)
hypersensitive response (HR)
a plant's localized defense response to a pathogen
systemic acquired resistance (SAR)
a defensive response in infected plants that helps protect healthy tissue from pathogenic invasion
salicylic acid
a plant hormone that may be partially responsible for activating systemic acquired resistance to pathogens