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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:
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.
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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.
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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.
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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).
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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).
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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.
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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.
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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.
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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.
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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.
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Photo Unit 12 Terms:

Supernumerary cylinder:
Concentric cylinders of vascular tissue separated by pericycle an originating in pericycle. An example is the beet hypocotyl.
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**No new terms are introduced after Unit 12.**