bio exam two

3 Antipodals

Three haploid cells in the mature embryo sac that usually degenerate after fertilization.

Photoperiodism

Plant response to the relative lengths of day and night.

Flowering

Transition to reproductive development that can be controlled by photoperiod and other environmental cues.

Phytochrome

Plant photoreceptor that switches between forms absorbing red and far-red light.

Red Light

Light around 660 nm that converts phytochrome toward its Pfr form.

Far Red Light

Light around 730 nm that converts Pfr toward the Pr form.

Short Day (Long Night)

Plant that flowers when the uninterrupted night is longer than a critical duration.

Long Day (Short Night)

Plant that flowers when the uninterrupted night is shorter than a critical duration.

Dicot Seed

Seed of a traditional dicot/eudicot with two cotyledons.

Seed Coat

Protective outer layer of the seed derived from integuments.

Plumule

Embryonic shoot containing young leaves.

Epicotyl

Embryonic stem region above the cotyledons.

Hypocotyl

Embryonic stem region below the cotyledons and above the radicle.

Radicle

Embryonic root.

Cotyledons

Embryonic seed leaves.

Monocot Seed

Seed with one cotyledon, often called the scutellum in grasses.

Cotyledon/Scutellum

Single monocot cotyledon; in grasses, the scutellum transfers nutrients from endosperm to embryo.

Endosperm

Triploid nutritive tissue produced by fusion of one sperm with the two polar nuclei.

Coleoptile

Protective sheath surrounding the young shoot in grass seedlings.

Hypocotyl

Embryonic stem region below the cotyledons and above the radicl

Egg+2 Synergids

Egg apparatus at one end of the embryo sac: one egg plus two synergids that help receive the pollen tube.

2 Central Cells (Polar Nuclei)

Two haploid nuclei in the central cell that fuse with one sperm to form triploid endosperm.

Immature Seed

Developing seed containing embryo, endosperm, and seed coat tissues.

Micropyle (closed)

Micropyle after fertilization/development when the opening is no longer open to pollen-tube entry.

Female Gametophyte

Haploid embryo sac containing the egg, polar nuclei, synergids, and antipodals.

Zygote+2 Synergids

After fertilization, the embryo sac contains a diploid zygote and the two synergids remain temporarily.

Megasporangium

Structure in which the megasporocyte undergoes meiosis.

Megasporocyte

Diploid cell that undergoes meiosis to produce megaspores.

Megaspore

Haploid product of megasporocyte meiosis; one functional megaspore develops into the female gametophyte.

Ovule

Structure containing the megasporangium and female gametophyte; becomes a seed after fertilization.

Integuments

Protective layers around the ovule that become the seed coat.

Micropyle (open)

Opening in the integuments through which the pollen tube enters the ovule.

Microgametophyte

Male gametophyte of a seed plant, represented by the pollen grain and its cells.

Tube Nucleus

Term listed in the course study guide; definition should be matched to the lecture material for this item.

Pollen Tube

Tube grown from pollen that delivers sperm to the female gametophyte.

Generative Cell

Pollen cell that divides to produce two sperm.

Sperm 1 & 2

Two haploid sperm cells delivered by the pollen tube for double fertilization.

Carpel

Female floral reproductive unit consisting of stigma, style, and ovary.

Stigma

Sticky or receptive surface where pollen lands.

Style

Stalk connecting stigma to ovary.

Ovary

Term listed in the course study guide; definition should be matched to the lecture material for this item.

Ovule

Structure containing the megasporangium and female gametophyte; becomes a seed after fertilization

Response

Cellular or organismal change produced by a signal.

Stimulus

A change in the environment that triggers a response.

Environmental

A signal or stimulus originating outside the organism.

Hormone

Chemical messenger produced in one part of an organism and acting on target cells.

Receptor

Protein that specifically recognizes a signal molecule or stimulus.

Anther

Male reproductive structure containing microsporangia.

Microsporangium

Structure in the anther where microsporocytes undergo meiosis.

Microsporocyte

Diploid cell that undergoes meiosis to produce microspores.

Microspore

Haploid product of microsporocyte meiosis that develops into a male gametophyte.

Pollen

Male gametophyte or the structure carrying it in seed plants.

Guard Cell

Specialized epidermal cell controlling a stoma.

Potassium influx

K+ enters guard cells, water follows osmotically, and the guard cells become turgid to open stomata.

Potassium efflux

K+ leaves guard cells, water follows, turgor decreases, and stomata close.

ABA

Abscisic acid; hormone that promotes stomatal closure during water stress.

Companion Cell

Term listed in the course study guide; definition should be matched to the lecture material for this item.

Bulk Flow

Movement of fluid driven by a pressure gradient, such as mass flow in xylem or phloem.

Source to Sink

Phloem transport from a sugar-producing/exporting source to a sugar-using or storing sink.

Signal Reception

Detection of a stimulus by a receptor.

Signal Transduction

Conversion of a received signal into intracellular steps that produce a response.

Second Messenger

Small intracellular signaling molecule that relays or amplifies a signal, such as Ca2+ or cAMP.

Turgor

Pressure of cell contents against the cell wall.

Wilt

Loss of turgor causing leaves or soft tissues to droop.

Symplast

Continuous cytoplasmic pathway through cells connected by plasmodesmata.

Plasmodesmata

Channels connecting the cytoplasm of adjacent plant cells.

Apoplast

Continuous pathway through cell walls and extracellular spaces.

Endodermis

Innermost layer of root cortex regulating movement into the vascular cylinder.

Casparian Strip

Water-resistant band in the endodermis that blocks apoplastic flow and forces water through membranes.

Transpiration

Loss of water vapor from aerial plant surfaces, mainly through stomata.

Adhesion

Attraction of water to other surfaces, such as xylem walls.

Cohesion

Attraction between water molecules.

Tension

Negative pressure generated by transpiration that pulls water upward through xylem

CAM

Crassulacean acid metabolism; photosynthetic pathway that separates CO2 fixation and the Calvin cycle by time.

Crassulacean Acid Metabolism

CO2 is fixed at night and stored as organic acids; CO2 is released for the Calvin cycle during the day.

Temporal Separation

CAM separates carbon fixation from the Calvin cycle by time of day.

Water Potential

Measure of the tendency of water to move; water moves from higher to lower water potential.

Solute (osmotic) Potential

Water-potential component caused by dissolved solutes; it is zero or negative.

ΨS

Symbol for solute/osmotic potential.

Pressure Potential

Water-potential component produced by physical pressure; positive pressure contributes to turgor.

ΨP

Symbol for pressure potential.

Photorespiration

Process initiated when Rubisco uses O2 instead of CO2, reducing photosynthetic efficiency.

C4 Pathway

Photosynthetic strategy that first fixes CO2 into four-carbon compounds and concentrates CO2 near Rubisco.

PEP Carboxylase

Enzyme that initially fixes CO2 in C4 and CAM plants; it has high affinity for CO2 and does not bind O2.

Mesophyll

Leaf tissue where initial carbon fixation occurs in C4 plants.

Bundle Sheath

Cells surrounding veins where the Calvin cycle occurs in C4 plants.

"Physical Separation"

C4 photosynthesis separates initial CO2 fixation and the Calvin cycle into different cell types.

NADP->NADPH

Reduction of NADP+ to NADPH, an electron carrier used in carbon fixation.

Light Reactions

Photosynthetic reactions using light energy to produce ATP and NADPH and release O2 from water.

O2 from H2O

Oxygen released during photosynthesis comes from splitting water, not from CO2.

H+ from H2O

Water splitting contributes protons to the thylakoid interior.

Synthetic Reactions

Light-independent reactions that use ATP and NADPH to build carbohydrates; includes the Calvin cycle.

Calvin Cycle (C3)

Cycle that fixes CO2 into organic molecules using ATP and NADPH; first stable product is a 3-carbon compound.

RUBISCO

Enzyme that fixes CO2 to RuBP; it can also bind O2, causing photorespiration.

Chloroplast

Photosynthetic organelle where light reactions occur in thylakoid membranes and carbon fixation occurs in the stroma.

Thylakoid

Flattened membrane sac containing photosystems and electron transport components.

Granum/Grana

Stack of thylakoids.

Stroma

Fluid region of the chloroplast surrounding thylakoids; site of the Calvin cycle.

Absorption Spectrum

Graph showing wavelengths of light absorbed by a pigment.

Action Spectrum

Graph showing the effectiveness of different wavelengths in driving a process such as photosynthesis.