A Glossary of Terms from Lab 9:

angiosperm
Any plant that is a member of the class Angiospermae, in which the seeds are enclosed in an ovary. Each member of the class is either a monocotyledon (grasses, tulips) or a dicotyledon (apple, primrose).

apical meristem
A group of plant cells that are found at the growing tip of a root or a stem. These cells are capable of dividing indefinitely and their main function is the production of new growth.

bark
The living tissue outside the vascular cambium in a woody stem. It is composed of phloem tissues, which occur as living inner and dead outer zones.

branch primordia
A lateral stem that is in its earliest stage of differentiation.

bud
An immature shoot, which the stems, leaves, or flowers may develop from.

collenchyma
A supporting plant tissue similar to parenchyma cells, but have cellulose wall thickenings.

companion cells
A type of plant cell that is connected to a sieve-tube member, making up the phloem tissue.

cork cambium
A cylinder of meristematic tissue in plants that produces cork cells to replace the epidermis during secondary growth.

cork cell
A secondary tissue produced by the cork cambium, and forms the outer part of the periderm in a woody plant.

cortex
The region of the root between the stele and epidermis filled with ground tissue.

cotyledons
The one (monocot) or two (dicot) seed leaves of an angiosperm embryo.

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.

dicot
A subdivision of flowering plants whose members possess two embryonic seed leaves, or cotyledons.

endodermis
The innermost layer of the plant cortex which surrounds the stele in plants. It functions in controlling the transport of substances within the plant.

endosperm
A nutrient-rich tissue formed by union of a sperm cell with two polar nuclei during double fertilization, which provides nourishment to the developing embryo in angiosperm seeds.

epidermis
(1) the dermal tissue system in plants. (2) the outer covering of animals.

fiber cell
A type of plant cell which has a thickened cell wall that performs a structural role. (e.g. cortex, phloem, and xylem).

gymnosperm
A vascular plant that bears naked seeds not enclosed in any specialized chambers.

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

lateral
At the side of.

lateral meristem
Consisting of the vascular cambium and the cork cambium, it produces the secondary tissues which make up the secondary plant body.

leaf primordia
The early, precursor cells of a leaf.

lenticel
A small pore found on the surface of stems and roots in higher plants through which gas exchange can take place.

lumen
Any cavity enclosed within a cell or structure, such as the lumen of the gut.

meristem
A region of a plant in which active cell division occurs, the cells of the meristem being undifferentiated into a specialized form. Meristematic tissues occur at the root and shoot tips giving growth in length.

mesophyll
The ground tissue of a leaf, sandwiched between the upper and lower epidermis and specialized for photosynthesis.

monocot
A subdivision of flowering plants whose members possess one embryonic seed leaf, or cotyledon.

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

parenchyma cells
A relatively unspecialized plant cell type that carries on most of the metabolism synthesizes and stores organic products, and develops into more differentiated cell types.

pericycle
A layer of cells just inside the endodermis of a root that may become meristematic and begin dividing again.

periderm
The protective coat that replaces the epidermis in plants during secondary growth, formed of the cork and cork cambium.

phloem
The portion of the vascular system in plants consisting of living cells arranged into elongated tubes that transport sugar and other organic nutrients throughout the plant.

pith
The core of a dicotyledon stem, containing parenchyma cells that have a storage function.

primary growth
Growth that takes place relatively close to the tips of roots and stems. It is intiated by the apical meristems, and primarily involves extending the length of the plant body.

respiration
A process by which gaseous exchange -oxygen and carbon dioxide-takes place between an organism and the surrounding medium.

root
The part of a plant that usually grows below ground. The root provides anchorage for aerial parts, absorbs water and mineral salts from the soil, conducts water and nutrients to other parts of the plant, and often stores food materials over winter.

root apical meristem
A group of plant cells found at the growing end of a root which are capable of dividing indefinetly. Their main function is the production of new root.

root cap
A structure found at the apex of roots, except those of many water plants, produced by the apical meristem. As the root pushes its way through the soil, the outer (older) cells of the root cap are sloughed off and replaced by new cells from the meristem.

secondary growth
The increase in girth of the stems and roots of many plants, especially woody, perennial dicots.

secondary root
(Lateral root.) A root that arises from another, older primary root. Initiated by the plant hormone, auxin.

secondary phloem
Tissue produced by vascular cambium and composed of both sieve tubes and companion cells.

secondary xylem
Tissue produced by vascular cambium and composed of both tracheids and vessel elements.

seed coat
A protective coat around the seed, formed from the integuments of the ovule.

sieve tubes
A series of long cells lying end to end and forming a tube, found in the phloem of Angiosperms.

sporophyte
The multicellular diploid form in organisms undergoing alternation of generations that results from a union of gametes and that meiotically produces haploid spores that grow into the gametophyte generation.

stele
The central vascular cylinder in roots where xylem and phloem are located.

suberin
A complex of fatty substances present in the wall of cork tissue that waterproofs it and makes it resistant to decay.

vascular cambium
A continuous cylinder of meristematic cells surrounding the xylem and pith that produces secondary xylem and phloem.

vascular bundle
A structure of vascular plants that runs up through the roots, into the stems, and out into the leaves, and whose function is transport of water, ions and dissolved organic solutes within the plant.

vessel cell
An empty tube formed from longitudinal fusion of several cells with strong walls reinforced with lignin, whose function is mass transport of water for transpiration.

xylem
The tube-shaped, non-living portion of the vascular system in plants that carries water and minerals from the roots to the rest of the plant.