Unit 5 Key Terms (Bio 191)

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apical bud

A bud at the tip of a plant stem; also called a terminal bud.

axillary bud

A structure that has the potential to form a lateral shoot or branch.

bark

All tissues external to the vascular cambium, consisting mainly of the secondary phloem and layers of periderm.

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.

collenchyma cells

A flexible plant cell type that occurs in strands or cylinders that support young parts of the plant without restraining growth.

cuticle

1) A waxy covering on the surface of stems and leaves that prevents desiccation in terrestrial plants.

dermal tissue

The outer protective covering of plants.

determinate growth

A type of growth characteristic of most animals and some plant organs, in which growth stops after a certain size is reached.

endodermis

In plant roots, the innermost layer of the cortex that surrounds the vascular cylinder.

epidermis

1) The dermal tissue of non-woody plants, usually consisting of a single layer of tightly packed cells. 2) The outermost layer of a cells in an animal.

ground tissue

Plant tissue that is neither vascular nor dermal, fulfilling a variety of functions, such as storage, photosynthesis, and support.

guard cells

The two cells that flank the stomatal pore and regulate the opening and closing of the pore.

indeterminate growth

A type of growth characteristic of plants, in which the organism continues to grow as long as it lives.

internode

A segment of a plant stem between the points where leaves are attached.

lateral meristems

A meristem that thickens the roots and shoots of woody plants. The vascular cambium and cork cambium are lateral meristems.

lateral roots

A root that arises from the pericycle of an established root.

leaves

The main photosynthetic organ of vascular plants.

meristems

Plant tissue that remains embryonic as long as the plant lives, allowing for indeterminate growth.

mesophyll

Leaf cells specialized for photosynthesis. In C3 and CAM plants, mesophyll cells are located between the upper and lower epidermis; in C4 plants, they are located between the bundle-sheath cells and the epidermis.

nodes

A point along the stem of a plant at which leaves are attached.

organ

A specialized center of body function composed of several different types of tissues.

parenchyma cells

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.

petiole

The stalk of a leaf, which joins the leaf to a node of the stem.

phloem

Vascular plant tissue consisting of living cells arranged into elongated tubes that transport sugar and other organic nutrients throughout the plant.

primary growth

Growth produced by apical meristems, lengthening stems and roots.

primary meristems

The three meristematic derivatives (protoderm, procambium, and ground meristem) of an apical meristem.

roots

An organ in vascular plants that anchors the plant and enables it to absorb water and minerals from the soil.

root system

All of a plant's roots, which anchor it in the soil, absorb and transport minerals and water, and store food.

root hairs

A tiny extension of a root epidermal cell, growing just behind the root tip and increasing surface area for absorption of water and minerals.

root cap

A cone of cells at the tip of a plant root that protects the apical meristem.

sclerenchyma cells

A rigid, supportive plant cell type usually lacking a protoplast and possessing thick secondary walls strengthened by lignin at maturity.

secondary growth

Growth produced by lateral meristems, thickening the roots and shoots of woody plants.

shoot system

The aerial portion of a plant body, consisting of stems, leaves, and (in angiosperms) flowers.

sieve-tube elements

A living cell that conducts sugars and other organic nutrients in the phloem of angiosperms; also called a sieve-tube member. Connected end to end, they form sieve tubes.

stem

A vascular plant organ consisting of an alternating system of nodes and internodes that support the leaves and reproductive structures.

stoma

(plural stomata) 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.

taproot

A main vertical root that develops from an embryonic root and gives rise to lateral (branch) roots.

tissue

An integrated group of cells with a common structure, function, or both.

tracheids

A long, tapered water-conducting cell found in the xylem of nearly all vascular plants. Functioning tracheids are no longer living.

vascular cambium

A cylinder of meristematic tissue in woody plants that adds layers of secondary vascular tissue called secondary xylem (wood) and secondary phloem.

vascular tissue

Plant tissue consisting of cells joined into tubes that transport water and nutrients throughout the plant body.

veins

1) In animals, a vessel that carries blood toward the heart. 2) In plants, a vascular bundle in a leaf.

vessel elements

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 vessels.

xylem

Vascular plant tissue consisting mainly of tubular dead cells that conduct most of the water and minerals upward from the roots to the rest of the plant.

apoplast

Everything external to the plasma membrane of a plant cell, including cell walls, intercellular spaces, and the space within dead structures such as xylem vessels and tracheids.

bulk flow

The movement of a fluid due to a difference in pressure between two locations.

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.

essential element

A chemical element required for an organism to survive, grow, and reproduce.

flaccid

Lacking turgor (stiffness or firmness), as in a plant cell in surroundings where there is a tendency for water to leave the cell. (A walled cell becomes flaccid if it has a higher water potential than its surroundings, resulting in the loss of water.)

macronutrients

An essential element that an organism must obtain in relatively large amounts.

micronutrients

An essential element that any organism needs in very small amounts. See also macronutrient.

mycorrhiza

(plural mycorrhizae) A mutualistic association of plant roots and fungus.

nitrogen cycle

The natural process by which nitrogen, either from the atmosphere or from decomposed organic material, is converted by soil bacteria to compounds assimilated by plants. The incorporated nitrogen is then taken in by other organisms and subsequently released, acted on by bacteria, and made available again to the nonliving environment.

nitrogen fixation

The conversion of atmospheric nitrogen (N2) to ammonia (NH3). Biological nitrogen fixation is carried out by certain prokaryotes, some of which have mutualistic relationships with plants.

nodules

A swelling on the root of a legume. Nodules are composed of plant cells that contain nitrogen-fixing bacteria of the genus Rhizobium.

osmosis

The diffusion of free water molecules across a selectively permeable membrane.

phloem sap

The sugar-rich solution carried through a plant's sieve tubes.

symplast

In plants, the continuum of cytoplasm connected by plasmodesmata between cells.

transpiration

The evaporative loss of water from a plant.

turgid

Swollen or distended, as in plant cells. (A walled cell becomes turgid if it has a lower water potential than its surroundings, resulting in entry of water.)

water potential

The physical property predicting the direction in which water will flow, governed by solute concentration and applied pressure.

wilting

The drooping of leaves and stems that occurs when plant cells become flaccid.

anther

In an angiosperm, the terminal pollen sac of a stamen, where pollen grains containing sperm-producing male gametophytes form.

asexual reproduction

The generation of offspring from a single parent that occurs without the fusion of gametes, in most cases, the offspring are genetically identical to the parent.

carpels

The ovule-producing reproductive organ of a flower, consisting of the stigma, style, and ovary.

coevolution

The joint evolution of two interacting species, each in response to selection imposed by the other.

complete flowers

A flower that has all four basic floral organs: sepals, petals, stamens, and carpels.

dormancy

A condition typified by extremely low metabolic rate and a suspension of growth and development.

double fertilization

A mechanism of fertilization in angiosperms in which two sperm cells unite with two cells in the female gametophyte (embryo sac) to form the zygote and endosperm.

fertilization

1) The union of haploid gametes to produce a diploid zygote. 2) the addition of mineral nutrients to the soil.

fruit

A mature ovary of a flower. The fruit protects dormant seeds and often aids in their dispersal.

incomplete flowers

A flower in which one or more of the four basic floral organs (sepals, petals, stamens, or carpels) are either absent or nonfunctional.

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.

ovules

A structure that develops within the ovary of a seed plant and contains the female gametophyte.

petals

A modified leaf of a flowering plant. Petals are the often colorful parts of a flower that advertise it to insects and other pollinators.

pistil

A single carpel (a simple pistil) or a group of fused carpels (a compound pistil).

pollen grain

In seed plants, a structure consisting of the male gametophyte enclosed within a pollen wall.

pollen tube

A tube that forms after germination of the pollen grain and that functions in the delivery of sperm to the ovule.

pollination

The transfer of pollen to the part of a seed plant containing the ovules, a process required for fertilization.

radicle

An embryonic root of a plant.

receptacle

The base of a flower; the part of the stem that is the site of attachment of the floral organs.

seed

An adaptation of some terrestrial plants consisting of an embryo packaged along with a store of food within a protective coat.

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.

self-incompatibility

The ability of a seed plant to reject its own pollen and sometimes the pollen of closely related individuals.

sepals

A modified leaf in angiosperms that helps enclose and protect a flower bud before it opens.

stamens

The pollen-producing reproductive organ of a flower, consisting of an anther and a filament.

style

The stalk of a flower's carpel, with the ovary at the base and the stigma at the top.

transgenic

Pertaining to an organism whose genome contains DNA introduced from another organism of the same or a different species.