Glossary of Terms

**No new terms are introduced after Photo Unit 12.**

Photo Unit 1 Terms:

Cotyledons: Seed leaves

Embryo: Development from cotyledon appearance to germination

Epicotyl: Stem apex without appendage differentiation

Epigeal: Cotyledons emerge above soil line

Hypocotyl: That portion of the axis intermediate between root and cotyledons in the shoot

Hypogeal: Cotyledons stay submerged below soil line during germination

Organs: Root, leaf, stem, hypocotyl

Plumule: Stem primordium with appendages appearing

Embryo: The development of the organism from the zygote to the time of first appearance of the cotyledons

Radicle: Root primordium

Sporophyte: The vegetative generation of plants

Photo Unit 2 Terms:

Blind pit: A pit on one wall with no corresponding member of the pair.

Cell wall: Cellulosic wall bounding the cells in plants.

Compound middle lamella: Intercellular cement, plus primary walls of two contiguous walls.

Cortex: Outer part of a plant body just under the epidermis.

Cytoplasm: The matrix of cellular organelles.

Differentiation: Change in size or number of cells in a region.

Epidermis: Outermost layer of a primary plant body.

Half-bordered pit pair: Borders of cell wall on one side of a pit pair.

Middle lamella: Cementing substance holding cells together.

Nucleus: Organelle which directs the cell development and function.

Pit aperture: Opening of pit pair.

Pit chamber: The area within a pit pair.

Pit membrane: Middle lamella, plus 2 primary walls within a pit.

Pit: Opening in the secondary wall allowing cytoplasmic continuity.

Plasmodesmata: Cytoplasm located in channels in the cell wall.

Plasmolemma: Cytoplasmic membrane.

Plastid: Cellular organelles which are sites of synthesis of starch, fats, chlorophyll.

Primary pit field: Thin area of primary wall containing plasmodesmata and around which the secondary walls form causing pits to form.

Primary wall: First wall material to be laid down in a cell.

Protoplast: Living unit within a cell.

Simple pit pairs: Borders on either wall of the pit pair.

Tonoplast: Vacuolar membrane.

Vestigal pit: A nonfunctional pit where secondary wall overlays a pit pair.

Photo Unit 3 Terms:

Apex (apices): Growing point or terminal area of the main plant axis or their appendages.

Cambium: A secondary meristem increasing diameter of a plant body usually with increase in vascular tissue.

Derivatives: New cells produced from meristem cells.

Differentiation: Cells that have become different from precursors and from the cells around them.

I Initials: Self perpetuating cells.

I Intercellular Spaces: Spaces between cells.

Longitudinal: A view parallel to the long axis of the plant body.

Transverse: A view taken perpendicular with the long axis of the plant body.

Photo Unit 4 Terms:

Anticlinal: A plane perpendicular to the surface.

Chlorenchyma: A chlorophyll containing parenchyma.

Cuticle: A waxy surface on aerial portions of plants.

Cutin: A wax making up the cuticle.

Cutinized ridge: An overlying ridge of cutin over the stomatal aperture.

Dermal: The outer, protective covering of the plant body.

Epidermal appendages: Uni- and multi-cellular hairs in epidermis.

Guard cells: Specialized epidermal cells comprising the stomatal apparatus.

Multiseriate epidermis: A multi-layered epidermis.

Periclinal: A plane parallel to the surface.

Radial: A plane parallel to the radius of a plant organ axis.

Stoma (Stomate): Pore in the epidermal surface through which gaseous interchange takes place.

Subsidiary (Accessory) cells: Sister cells to guard cells.

Tabular cells: Rectangular cells in regular alignment of which monocot leaves are examples.

Tangential: A plane parallel to the tangent drawn to the circumference of a plant organ axis.

Transverse: A plane cutting across the long axis of a plant organ.

Uniseriate: A single-layered epidermis.

Photo Unit 5 Terms:

Closing cells: Cork cell layer overlaying complementary cells that form during periods of stress.

Complementary cells: Parenchyma cells in a lenticel.

Lenticel: Area of gaseous interchange in the periderm.

Periderm: Secondary protective tissue.

Phelloderm: Secondary cortex.

Phellem: Cork tissue.

Phellogen: Cork generating tissue.

Rhytidome: Outer bark.

Suberin: Waxy substance secreted by some cells (eg., endodermis).

Photo Unit 6 Terms:

Dermal: Covering tissue.

Parenchyma: “Packing” tissue in a stem.

Pith ray: Parenchyma tissue between vascular bundles.

Polyhedral: With many faces.

Secretory: Function of secreting substances by a cell.

Tetrakaidecahedron: 14-sided polyhedron (6 squares, 6 hexagons).

Photo Unit 7 Terms:

Abaxial: Lower surface (away from axis).

Adaxial: Upper surface (toward axis).

Angular collenchyma: Wall thickenings at cell angles.

Bast fiber: Phloem fibers.

Bundle cap: Strengthening tissue capping a vascular bundle.

Bundle sheath: Strengthening tissue surrounding a vascular bundle.

Collenchyma: Strengthening parenchyma with unevenly thickened primary walls.

Extraxylary fibers: Fibers outside xylem associated with cortex and phloem.

Fiber: Elongated, thick-walled, mechanical tissue.

Fiber-tracheids: Transitional wall between a fiber and a tracheid.

Lacunate collenchyma: Wall thickenings into intercellular spaces.

Libriform fibers: Phloem-like fibers in xylem.

Lignification: Deposition of lignin in cell walls.

Pericycle: Tissue found between endodermis and vascular tissue.

Perivascular fibers: Pericycle-originating fibers.

Phloem ray: A radially arranged row of parenchyma traversing phloem.

Plate collenchyma: Collenchyma with tangential wall thickenings.

Sclereid: Hard walled.

Septate fibers: Fibers with cross membranes in lumen.

Sterome: All collenchyma and sclerenchyma tissue in the plant body.

Vestigial pits: Remnants of non-functional pits.

Xylem ray: A radially arranged row of parenchyma traversing xylem.

Photo Unit 8 Terms:

Annular: Ring wall thickenings.

Complex tissue: Tissue of varying cell types originating from a common meristem.

Fiber: Long, thick walled mechanical cells.

Foraminate perforation plate: Thin cross walls across the end of a vessel element.

Helical: Spiral type wall thickening.

Pitted: Circular (more or less) openings in secondary wall.

Reticulate: Helical wall thickenings with some of the helices connected.

Scalariform: Ladder-like wall thickenings in xylem cells.

Scalariform perforation plate: Thick cross walls across the end of a vessel element.

Tracheid: Long, pitted water-conduction cell in xylem.

Vascular: Transporting tissue.

Vessel: A series of vessel elements forming a tube.

Vessel element: Large diameter, water-conducting cell in xylem.

Xylem: Water-conducting vascular tissue.

Photo Unit 9 Terms:

Callose: Amorphous polysaccharide collecting at sieve plates of phloem sieve tube elements.

Companion cell: A sister cell to the sieve tube element in the phloem, believed to closely integrate activities in the sieve tube element.

Compound sieve plate: Several sieve plates conjoined at the end of sieve elements.

Sieve areas: Pores through the walls of phloem food conducting cells.

Sieve cell: Food conducting cell in the phloem.

Sieve plate: A collection of sieve areas at the end walls of sieve cells or sieve tube elements.

Sieve tube: A series of sieve tube elements.

Sieve tube element: Large diameter, thick primary-walled, food-conducting all of the phloem.

Slime plug: Proteinaceous accumulation at the sieve plates appearing during injury.

Slime body: Proteinaceous particle in the cytoplasm of young sieve element.

Photo Unit 10 Terms:

Calyptrogen: Root cap promeristem initials.

Corpus: Central body of promeristem in short apex.

Dermatogen: Dermal promeristem initials.

Histogen: Root tip promeristem initial layer.

Korper-Kappe: Histogen between root apex and root cap indicated by planes of division in the meristem.

Periblem: Cortical promeristem initial.

Plerome: Stelar promeristem initials.

Radicle: Embryonic root, forms the basal continuation of the hypocotyls in an embryo.

Stele: The central vascular network extending from the root to the shoot.

Tunica: The portion of the protoderm that lies within the apical meristem.

Photo Unit 11 Terms:

Casparian strip: A suberized, thickened ribbon on the walls of endodermis.

Cortex: Parenchyma tissue (predominately).

Endodermis: Innermost cortical layer, especially obvious in roots.

Hypodermis: A sub-epidermal layer differentiated from ground meristem and obviously descending to either epidermis or cortex.

Metaxylem: Last xylem to mature in the stele of the primary plant body.

Pericycle: A layer of parenchyma immediately internal to the endodermal cylinder.

Protoxylem: First xylem cells to mature while axis is elongating.

Root hair: Extension of a cell in root epidermis.

Xylem wings: Radial extensions of the xylem core in roots.

Photo Unit 12 Terms:

Supernumerary cylinder: Concentric cylinders of vascular tissue separated by pericycle an originating in pericycle. An example is the beet hypocotyl.

**No new terms are introduced after Unit 12.**