HCS 2202 Exam 1

abaxial

refers to the lower surface of a leaf blade.

abscission zone

the region at the base of an organ, such as a leaf or fruit, in which cells die and tear, permitting the organ to fall cleanly away from the stem with a minimum of damage.

actin filament

a helical protein filament that is part of the cellular cytoskeleton. It is involved in cytoplasmic streaming and movement of organelles.

adaxial

refers to the upper surface of a leaf blade.

adventitious roots

roots that do not form from pre-existing roots and are not radicles.

aerial root

adventitious roots that arise from any plant part above the soil surface.

aerial roots

above-ground roots, usually adventitious, that are typical in epiphytes, some rainforest trees (e.g., banyan), tropical swamp trees (e.g., mangrove), and vines (e.g., poison ivy).

algaculture

the farming of algae species to produce biofuels, pharmaceuticals, vegetable oils, or other products of economic importance.

alternate (distichous) phyllotaxy

leaf arrangement in which there is one leaf per node, but the leaves are arranged in two opposite ranks that alternate direction.

amyloplast

a type of leucoplast involved in the synthesis and long-term storage of starch.

anaphase

the third phase of mitosis; at the metaphase-anaphase transition, centromeres divide and the two chromatids of a chromosome become independent chromosomes. During this phase, the two are pulled to opposite poles of the spindle by spindle microtubules.

angiosperm

flowering plant with seeds that develop within a fruit.

annual

herbaceous plant that completes its life cycle and dies within a single growing season.

anthocyanins

water-soluble blue or red pigments found in the cell sap (vacuolar contents).

apical dominance

the suppression of axillary bud development by the shoot apical meristem.

apical meristem

region of actively dividing cells found in shoot tips and root tips that is responsible for primary growth.

apical-basal pattern of growth

direction of development of the plant body in the vertical direction (i.e., increase in length).

apoplast

the nonliving network of cell walls, intercellular spaces, and xylem tissue through which water and minerals are translocated.

Archaea

the kingdom of single-celled, prokaryotic organisms that are unlike bacteria due to genes and metabolic pathways that more closely resemble those of eukaryotes. The archaea includes extremophiles that survive in extreme chemical or physical environments.

ATP

adenosine triphosphate, the major source of usable chemical energy in cellular metabolism.

auricle

a small projection from the base of a grass leaf blade where the blade joins the sheath.

axial growth

cells that are produced with their long axes parallel to the stem axis.

axillary bud

a bud (embryonic shoot enclosed in scale leaves) that arises in the axil of a leaf.

bark

all tissues outside the vascular cambium in a woody stem.

bast fiber

the "soft" fibers of stem tissue derived from the phloem fibers of some dicots (e.g., hemp, jute, and flax).

biennial

herbaceous plant that complete its life cycle over two growing seasons: first season growth produces a rosette of leaves, and the plant 'bolts' (flowers) and produces seeds in the second season.

border cells

rootcap cells that are programmed to separate from the rootcap and that may remain alive in the rhizosphere for several weeks.

bordered pit pair

in adjacent xylem-conducting cells, two opposite pits with thickened rims separated by a pit membrane (primary cell walls).

brace (or prop) roots

adventitious roots extending from the stem above the soil level and helping to support the plant; common in monocots such as maize (corn).

bracts

modified leaves associated with a flower or inflorescence.

bud primordium

a bud (embryonic shoot) in its earliest stages of differentiation.

bud scales

modified leaves, usually waxy or corky, that protect an unopened bud.

bulb

modified leaves that serve as a food storage and vegetative reproductive organ (e.g., onion).

bulliform cells

large epidermal cells present in longitudinal rows in grass leaves; involved in the rolling of grass leaf blades in response to water stress.

buttress roots

roots that grow asymmetrically such that it becomes very tall and thin, extending up the trunk as much as a meter or more and giving the trunk lateral stability.

capillary action

the attraction between contacting surfaces of a liquid and solid that causes the liquid to rise in a narrow tube.

carbohydrates

organic molecules consisting of a carbon, hydrogen, and oxygen in a ratio of approximately 1:2:1 (e.g., sugars, starches).

carotenoids

a group of fat-soluble (water insoluble), orange or yellow pigments found in plant chloroplasts or chromoplasts.

Casparian strip

a layer of impermeable lignin and suberin in the walls of endodermal cells, preventing diffusion of material through that portion of the wall.

cell

the structural unit of organisms; in plants, cells consist of the cell wall and protoplast.

cell cycle

the entire life cycle of a cell involving interphase, mitosis, and cytokinesis.

cell plate

the region where the new cell wall forms at the equator of the spindle in dividing plant cells during early telophase.

cell wall

the outermost layer of a plant cell that is composed mostly of cellulose; it surrounds, supports, and protects the cell protoplasm.

cellulose

a polysaccharide composed only of glucose residues linked by beta-1, 4-glycosidic bonds; it is the major strengthening component of plant cell walls.

centromere

the constricted region of a chromosome that holds the sister chromatids together.

chlorenchyma

parenchyma cells that contain chloroplasts.

chlorophyll

the fat-soluble (water insoluble) green pigment found in plant chloroplasts. Chlorophyll is the receptor of light energy in photosynthesis.

chloroplast

chlorophyll-rich plastid that carries out photosynthesis.

chromatid

one of the two daughter strands of a duplicated chromosome which are joined at the centromere.

chromoplast

a plastid containing pigments other than chlorophyll, usually yellow and orange carotenoid pigments.

chromosome

a structure in the nucleus that carries genes in a linear DNA molecule. It is composed of the nuclear DNA double helix complexed with histone proteins. It consists of one chromatid prior to the S phase or two chromatids plus a centromere after the S phase.

cladophyll

a flattened, modified stem that resembles a leaf (e.g., Christmas cactus).

closed vascular bundle

vascular bundle typical of monocot and some dicot stems in which the vascular tissue is surrounded by a sheath of sclerenchyma fibers.

collenchyma

a tissue composed of living cells that have unevenly thickened primary walls; the walls are thickened at the corners of the cell and thin elsewhere.

companion cell

a specialized parenchyma cell associated with a sieve-tube element in angiosperm phloem; it is responsible for loading and unloading of sugar into the sieve tube element.

complex tissue

tissue that is composed of two or more cell types.

compound leaf

leaf with blade divided into leaflets.

contractile roots

modified adventitious roots that develop from the base of the stem of a bulb or corm and can contract to pull the bulb or corm deeper in the soil for protection.

cork

secondary tissue produced outwardly by the cork cambium and consisting of non-living, suberized cells at maturity.

cork cambium

secondary (lateral) meristem that produces cork cells of the outer bark.

cork cambium

the lateral meristem that forms the periderm, giving rise to the cork cells of bark in woody plants.

corm

modified underground stem that grows upright and has compressed internodes covered with thin papery leaves. It functions for storage and vegetative reproduction.

cortex

ground tissue region of roots or stems located between the epidermis and vascular tissue.

creeping roots

roots that contain adventitious buds capable of generating new plants.

crown growth

growth habit of monocots in which the internodes remain compressed and the apical meristem remains at or below the soil surface.

culm growth

growth habit of monocots in which the internodes elongate and the apical meristem is pushed increasingly higher above the soil surface.

cuticle

a protective layer of cutin + waxes on the outer wall of epidermal cells; it reduces water loss but also restricts the entry of carbon dioxide and water.

cutin

a polymer of fatty acids that is water impermeable; it forms a layer (cuticle) on the epidermis.

cyanobacteria

aquatic, photosynthetic bacteria (prokaryotes) that are the earliest known organisms on earth, appearing as early as 4.1 billion years ago.

cytokinesis

division of the cytoplasm of a cell following nuclear division (mitosis), it concludes in the formation of two new daughter cells.

cytoplasm

the living substance of a cell excluding the nucleus and vacuoles.

cytoplasmic streaming

the movement of cytoplasm within a cell, facilitated by actin filaments.

cytoskeleton

the flexible network of protein strands within cells, consisting of microtubules and actin filaments.

cytosol

the liquid substance of the protoplasm, excluding all organelles such as nuclei, plastids, ribosomes, mitochondria, etc.

dermal tissue system

tissue system that comprises the outer covering of the plant; the epidermis or periderm.

dicots (eudicots)

angiosperms having two cotyledons, flower parts in multiples of 4 or 5, leaves with netted veins, taproot system, and stems with vascular bundles arranged in concentric circles.

differentiation

developmental process in which unspecialized cells or tissues undergo a progressive change into more specialized cells or tissues with a specific function.

ectomycorrhizae

a type of mycorrhizal relationship in which the fungi does not penetrate the root cortex cells but grows between the cells of the epidermis and cortex, and forms a sheath that covers the root surface. Usually found in woody plants.

elaioplast

a type of leucoplast involved in the synthesis and long-term storage of lipids (oils, fats).

endodermis

sheath of cells surrounding the vascular tissue of roots, preventing uncontrolled diffusion between root cortex and root vascular tissue.

endomembrane system

collectively, the cellular membranes that form a continuum in the cytoplasm, including the plasma membrane, tonoplast, endoplasmic reticulum, Golgi bodies, and nuclear envelope.

endomycorrhizae

a type of mycorrhizal relationship in which the fungi invade all cells of the root cortex. Usually found in herbaceous plants.

endoplasmic reticulum

a system of narrow tubes and sheets of membrane that form a network throughout the cytoplasm. If ribosomes are attached, it is rough and is involved in protein synthesis. If no ribosomes are attached, it is smooth and is involved in lipid synthesis.

endosymbiosis

a symbiotic relationship in which one or more organisms live within the cells or body of a host without doing harm.

enzyme

a protein that serves as a biochemical catalyst by lowering the activation energy required for biochemical reactions in the cell.

epicuticular wax

the outermost layer of wax on the surface of the cuticle; its thickness varies depending on the organ (thicker on leaves than on roots), species, and environmental conditions during development.

epidermis

the outermost layer of the plant primary body, covering leaves, flower parts, young stems, and roots.

epiphyte

plant that derives its moisture and nutrients from the air and usually grows on another plant, but is not parasitic (e.g., some orchid species, bromeliads).

etioplast

a plastid of a plant grown in the dark.

eukaryotes

Organisms that have true nuclei and membrane-bounded organelles, including plants, animals, fungi, and protists, but not bacteria or archaea.

extremophile

An organism that thrives in extreme physical or chemical environments that will not sustain most life forms.

fascicular cambium

portion of the vascular cambium that develops within the vascular bundle.

fiber

sclerenchyma cell that is long and tapered and has pointed ends; provides a tissue with strength and flexibility.

flagella

long, threadlike organelles that protrude from the surface of cells, they consist of microtubules that are used for locomotion and are found in some bacteria and algae cells.

fluid mosaic model

biological membranes; two-dimensional fluid membranes in which various types of lipids and intrinsic proteins can diffuse laterally.

fusiform initials

long, meristematic cells with tapered ends that give rise to the axial cells of secondary phloem and secondary xylem.

G1 phase

part of interphase of the cell cycle that is the interval between cell division and the synthesis of DNA in the nucleus. This is often the longest phase, during which the nucleus actively directs cytoplasmic metabolism.

G2 phase

part of interphase of the cell cycle that is the interval between the synthesis of DNA and the beginning of nuclear division.

Golgi complex

(synonyms are Golgi bodies, Golgi apparatus, and dictyosome) - a group of flat, disk-shaped membrane stacks in the cytoplasm that serve as collecting, packaging, and vesicle delivery centers of the cell.

gravitropic

the directed growth of a plant root in response to gravity.