Albuminous cell
Annular cell walls
Apical meristems
Boarded pit pairs
Bordered pit
cell wall
Cellulose
Chlorenchyma
chloroplast
Collenchyma
Companion cell
Compound leaf
Cork cambium
Cork cells
Cortex
cytoplasm
Dermal tissue system
endoplasmic reticulum- Lee Williams
Epidermis
Fiber - Sarah Slater
Golgi complex
Ground tissue system
Guard cells
Heartwood
Lateral meristems
Lignin
Lumen-Lumen
Meristematic tissue
mitochondria - Tyler Parnall
Parenchyma - Kevin Christie
Pectin
Perforation plate
Periderm
Phloem
Pith
plasma membrane - Andrea Chapman
plasmodesmata - Morgan Traverse
plastids - Tori Waites
Primary meristems
protoplast
ribosomes
Root hair
Sclereid
Sclerenchyma
Sieve cell
Sieve elements-Lee Williams
Sieve plate
Sieve tube element
Simple pit
Suberin
Subsidiary cell
tonoplast- Conyr Aird
Trachery elements
Trichome
vacuoles - Sarah Slater
Vascular tissue- Conyr Aird
Vascular tissue system
Xylem

DEFINITIONS
Please insert your definitions in alphabetical order
Albuminous cell: A specialized parenchyma cell in a gymnosperm. They are thought to perform the same functions as companion cells, for the sieve cellsthey are associated with. This cell has a nucleus as well as other cytoplasmic parts generally found in living cells. Since they are so closely associated with sieve cells, they die when the sieve cells they are linked to die. (Biology of Plants, 7th edition, Peter H. Raven, 522) (Garden Web) http://glossary.gardenweb.com/glossary/albuminous_cell.html) By Caitlin Deas

Annular cell walls
Annular cell walls are a growth layer formed during a single year, in the secondary xylem or secondary phloem (Biology of Plants 6th Edition). Of or pertaining to a ring or rings; ring-like, ring-formed, ringed. annular space: the space between an inner and an outer ring. (Oxford English Dictionary)-Derek Burdikin

Apical meristems(Daniel Struthers): Are found at the tips of all shoots and roots and are composed of cells that are capable of repeated division. Apical meristems are involved with extension of the plant body(Primary growth).The apical meristems of both shoot and root are of great importance, because these tissues are the source of virtually all the new cells responsible for the development of the seedling and the adult plant.( Biology of Plants, 7th edition, Peter H. Raven, pg. 498). There are three types of apical meristems, including root, shoot, and stem apical meristems. The root apical meristem (RAM) is covered by the root cap which protects the apical meristem from the rocks, dirt and pathogens. Stem apical meristem is multicellular and, unlike the root apical meristem, has no cover. Rudimentary leaves may develop as scales, hardening at the end of the growing season to protect the stem apical meristem.(wikipedia online).



Bordered Pit – A pit in which the secondary wall arches over the pit membrane (Biology of Plants, 7th edition, Peter H. Raven,
Glossary pg G-3). Picture from www.uri.edu/cels/bio/plant_anatomy/images/9A.gif (Jackie Taylor)


Enhancement: "Bordered pits are structures found in the conductive tissues of many plants that allow for fluids to pass from one cell to another. The tracheids, which transport liquids, are dead cells; their contents decomposed, they are essentially empty. Simple pits are areas of the tracheid cell wall so thin that nutrient rich solutions can pass through them, to be dispersed throughout the plant. Bordered pits have the secondary cell wall extending over the pit with a small hole in the secondary cell wall that allows the water to pass through. When looking at a bordered pit under the microscope, it has the appearance of a donut. The hole of the donut is the pore and the outer ring of the donut is the margin of the bordered pit." (http://www.microscopyu.com/galleries/dxm1200/borderedpitssmall.html) (Biology of Plants, Peter H. Raven, pg.56) Krista N
Cell Wall The cell wall is a firm membrane that borders that of plant, some protits and some prokaryotic cells (Raven, G-4) . It is not found in animal cells. The cell wall serves as a protective layer and helps keep the cell rigid. It is often composed of cellulose and also helps to prevent infection. http://dictionary.reference.com/browse/cell%20wall
http://www.sigmaaldrich.com/img/assets/22940/Plant-Cell-Wall.jpg
Enhancement:
The cell wall helps keep the structure of the cell, by not breaking. The amount of pressure applied to the cell wall from the vacuole being filled with water is referred to as the turgor pressure. http://library.thinkquest.org/C004535/media/cell_wall.gif _Nick N
Enhancement: “Think of the cell wall as a wicker basket in which a balloon has been inflated so that it exerts pressure from the inside. Such a basket is very rigid and resistant to mechanical damage. Thus does the plant cell gain strength from a flexible plasma membrane pressing against a rigid cell wall.” (Howland, John L. (2000). The Surprising Archaea: Discovering Another Domain of Life. Oxford: Oxford University Press, 69-71.) (Russ Fountain)






Cellulose: A structural polysaccharide of cell walls consisting of glucose monomers joined by B-1, 4-glycosidic linkages (Biology 7th edition, Campbell Reece, pg. 72). A carbohydrate; the chief component of the cell wall in plants and some protists; an insoluble complex carbohydrate formed of microfibrils of glucose molecules attached end to end (Biology of Plants, 7th edition, Peter H. Raven, Glossary pg. G-4). Matti
Cellulose occurs naturally in such fibrous produstc as, cotton and kapok, and is the raw material of many manufactured goods such as, paper, rayon, and cellophane. It's molecular formula is C6, H12, O5. (Merriam-Webster Online) Lee Williams
A complex carbohydrate consisting of 3000, or more glucose units. Cellulose comprises about 33% of all vegetable matter, and is the most abundant of all naturally occuring natural organic compounds. Nondigestible by man, cellulose is a food for herbivorous animals, because they retain it long enough for digestion by micro-organisms. Other cellulose derivitaves are used as adhesives, explosives, thickening agents for foods, and in moisture proof coatings. (Encyclopedia Britannica Online) Lee Williams

Cellulose Magnified:

Science Source, Photo Researchers, Inc.
Lee Williams




Chloroplast: a complex, discrete green structure, or organelle, contained in the cytoplasm of plant cells. Chloroplasts are responsible for the green color in plants. Chloroplast is where the photosynthesis occurs. (The Columbia Encyclopaedia, Sixth Edition) Chloroplast is the structure within a green plant cell in which photosynthesis occurs. They come as three different shaped plastids; round, oval, or disk-shaped. (Encyclopaedia Britannica online) Travis Unsworth Addition - inside the chloroplast the material is called the stroma. Within this stroma are sacks of thylakoids which is the site where photosynthesis takes place. The actual process occurs in the membrane of the thylakoid where light strikes chlorophyll a in such a way as to excite electrons to a higher energy state. Through a series of protiens (electron transport process) the electrons are brought down in energy level releasing energy to form ATP and NADPH. Another form of this is photophosphorylation where two photosystems are linked by a proton pump. This creates a transmembrane proton gradient which is used to synthesize ATP. (http://www.emc.maricopa.edu/faculty/farabee/BIOBK/BioBookPS.html) (Mike Tomlinson)

This is a photo of a typical chloroplast that can be found in a plant cell.This picture shows the inner and outer membranes, the inner membrane space, stroma lamellae, stroma, thylakoids, and granum.


Photo From: Molecular Expressions, http://micro.magnet.fsu.edu/cells/chloroplasts/images/chloroplastsfigure1.jpg
(Photo added by Jessica W)
Enhancement: There are approximately half a million chloroplasts per square millimeter of leaf surface. Chloroplasts are primarily located in the cells of the mesophyll – tissue in the interior of the leaf. Mesophyll cells usually contain 30 – 40 chloroplasts. (Biology, 6th Edition, Neil A. Campbell, pg 178) - Tori Waites



Chlorenchyma: Parenchyma cells which contain cholorplasts (Biology of Plants, 7th edition, Peter H. Raven, Glossary pg. G-5). Picture from http://www2.mcdaniel.edu/Biology/botf99/tissimages/chlorenchyma.jpg (Jackie Taylor)



Addition: the chlorenchyma are the main photosynthetic cells of the plant and manufacture carbohydrates during photosynthesis. (www.botany.uwc.ac.za) Mark Haywood-Farmer
Enhancement: (Katherine Loewen) The palisade mesophyll in leaves, where photosynthesis takes place, consists of specialized chlorenchyma cells (bugs.bio.usyd.edu.au)
Enhancement Nicole L Plant tissue consisting of parenchyma cells that contain chloroplasts and forming the basic green tissue of plant leaves and stems.
(Dictionary.com http://dictionary.reference.com/browse/chlorenchyma)


Collenchyma: Collenchyma tissues are mainly found under the epidermis in young stems in the large veins of leaves. The cells are composed of living, elongated cells running parallel to the length of organs that it is found in. Collenchyma cells have thick cellulose cell walls which thickened at the corners. Intercellular air spaces ar absent or very small. The cells contain living protoplasm and they sometimes contain chloroplasts. The collenchyma serve as supporting and strengthening tissue and if chloroplasts are present in collenchyma, photosynthesis takes place. (www.botany.uwc.ac.za) A supporting tissue composed of collenchyma cells—elongated living cells with unevenly thickened, non-lignified primary cell wall. (Biology of Plants, 7th edition, Peter H. Raven, Glossary pg. G-6) Mark Farmer

Enhancement by Caitlin Deas:
This is a picture of a transverse section of collenchyma tissue. The dark pink areas in the center of the picture are the unevenly thickened cell walls. (University of Hawaii at Manoa Botany) http://www.botany.hawaii.edu/faculty/webb/BOT410/anatweb/images/ParColSclr/CollenColeusTolBl400.jpg

Companion Cell: Relatively small plant cell, with little or no vacuole, found adjacent to a phloem sieve tube and originating with the latter from a common mother cell. Thought to be involved in translocation of sugars in and out of the sieve tube.(www.mblab.gla.ac.uk) A specialized parenchyma cell associated with a sieve-tube element in angiosperm phloem and arising from the same mother cell as the sieve-tube element.( Biology of Plants, 7th edition, Peter H. Raven, glossary pg. G-6) Mark Haywood-Farmer



Enhancement: The sieve tube elements lack nucleoli, and therefore are dependent of the companion cells to provide important molecules such are proteins and the energy required for maintenance. The cells are connected through cytoplasmic threads called plasdomata. Kirsten.
Enhancement: (Dennis Murengi)-Below is an image of companion cells adjacent to the sieve tube. (www.visit-islay.com) http://www.visit-islay.com/resources/plants_files/image016.gif




Compound leaf:
A compound leaf is a leaf that is divided into several smaller leaves called leaflets, each of which has its own petiole (called a petioule). There are two types of compound leaves, pinnately compound and palmately compound. In palmately compound leaves, the leaflets are attached to the end of the leaf’s petiole. In pinnately compound leaves, the leaflets are attached to either side of the length of the leaf’s petiole. Compound leaves allow a plant to maximize the amout of sunlight a absorbed for photosynthesis. (Everything2: http://everything2.com/index.pl?node_id=1547316) (Raven 7th ed.)
Katherine Loewen


Enhancement (Andrea Chapman) Picture of two types of pinnately compound and one type of palmately
compound leaf ( Glossary - http://www.scarborough.k12.me.us/high/projects/trees/compound.gif)


Cork Cambium: The lateral meristem that forms the periderm, producing cork (phellem) toward the surface (outside) of the plant and phelladerm toward the inside; common in stems and rots of gymnosperms and woody angiosperms. Also called phellogen. ( Biology of Plants, Raven Evert Eichhorn, 525-526 ) .A cylinder of meristematic tissue in woody plants that replaces the epidermis with thicker, tougher cork cells.( Biology, seventh edition, Campbell Reece, 720) Dusite
Enhancement (Derek Burdikin)

http://www.kidsgardening.com/onlinecourse/Diagrams/c3/c3-12bark.gif
Enhancement: Cork cumbium produces secondary tissues from a ring of vascular cambium in stems and roots. Secondary phloem forms along the outer edge of the cambium ring, and secondary xylem (i.e., wood) forms along the inner edge of the cambium ring (Britannica online). Tamiki N

Cork cells: A secondary tissue produced by a cork cambium ; made up of polygonal cell, nonliving at maturity, with suberized cell walls, which are resistant to the passage of gases and water vapor ; the outer part of the peirderm. Also called phellem ( Biology of Plants, Raven Evert Eichhorn, Pg 525 ). A layer of usu. Suberized cells produced outwardly by a phellogen. ( Merriam-Webster's
Collegiate dictionary- Seventh ed.) Dustie

the outer darker part is the cork cambium. Dustie
Enhancement(Sarah Slater): Cork cells are non living, as mentioned above and therefore creates a protecting and insulating layer around the living cells in a stem or trunk. The thickness of the cork cell layers varies from species to species. The cork cells from the cork oak tree are what we commonly know as corks used in bottling wine. The cork oak tree grows in harsh Mediterranean conditions, and therefore produces more cork cells for protection, that is why it is the source of most cork used around the world.
Florida State University and Nikon
<http://www.microscopyu.com/galleries/confocal/corkcells.html>
How Stuff Works (founded by Carolina State University Prof)
<http://science.howstuffworks.com/question550.htm>

Enhancement: Cork is composed of dead cells that accumulate on the outer surface of the cork oak tree. Because of its honeycomb-like structure, cork consists largely of empty space; its density (weight per unit volume) is one-fourth that of water. Unlike a honeycomb, however, cork consists of irregularly shaped and spaced cells having an average of 14 sides. With 625 million of these empty cells per cubic inch (40 million per cubic centimeter), cork is like many layers of microscopic Bubble Wrap, making it an effective cushioning material. Its low density makes cork useful in products like life preservers and buoys. The large amount of dead-air space makes cork an effective insulation material for both temperature and noise. (http://www.madehow.com/Volume-5/Cork.html). (Russ Fountain)

Cortex – Ground-tissue region of a stem or root bounded externally by the epidermis or internally by the vascular system; a primary-tissue region; also used to refer to the peripheral region of a cell protoplast. Biology of Plants 7th ed. Peter H. Raven, Pg. G-6)A complex layer of tissue between the epidermis or the corky layer and the vascular tissue of a stem or root, made up mainly of parenchyma cells. (Gage Canadian Dictionary, Pg. 266). Jessica W.
Enhancement: Cortical cells may contain stored food or other substances, such as resins, latex, essential oils, and tannins. Cortical cells in herbaceous stems, young woody stems, and stems of succulents contain chloroplasts and can therefore make food by photosynthesis. (Encyclopedia Britannica Online) - Nicole H.

Picture from: Botany Basics; http://extension.oregonstate.edu/mg/botany/images/fig3-big.gif
Cytoplasm: The cytoplasm is the living matter of the cell not including the nucleus; it can also be called the protoplasm (Raven G-7). It is full of proteins that control cell functions and contains the vital organelles. It is a jelly like material found in eukaryotic cells. http://dictionary.reference.com/browse/cytoplasm --John
Enhancement: (Dennis Murengi)-Cytoplasm functions as a "molecular soup" that holds together all of the cell's organelles, and divides the organelles within the cell. Cytoplasm is thought to be the "home"of the cytoskeleton; the cytoskeleton provides movement of the cell as well as its shape through the "cytoplasmic streaming", when the cytoskeleton moves to push the cell membrane it is then when the cytoplasm moves and fills the empty space. Proteins that occur in the cytoskeleton help to keep the shape of the cell, for the proteins are known to be used for "intracellular support". Within the cytoplasm there are also "microtubules" which function as cell dividers, they are known for "temporary scaffolding"-for the other organelles. Actin Filaments are also found in cytoplasm and they also contribute to cell division as well as cell motility. (www.sun.menloschool.org)
http://sun.menloschool.org/~birchler/cells/plants/cytoplasm/structureandfunction.html

Dermal Tissue System (Brian France): Makes up the outer protective covering of the plant.(Biology of Plants, Raven) Consisting of the epidermis(Paraenchyma cells) and periderm(Cork cells). The major role of the epidermis is to regulate the size of the stomata, which regulates water loss and the exchange of oxygen and carbon dioxide. The primary function of the Periderm is support and protection.(Plants, Their Biology and Importance.Kaufman)

http://www-plb.ucdavis.edu/labs/rost/Rice/Stems/xsstem1.gifOccurs in all organs of the plant, and is continuous from organ to organ and reveal the basic unity of the plant body (Biology of Plants, Raven, pg 369).

Enhancement: Dermal Tissue system is the outer protective layer of the primary plant body (the roots, stems, leaves, flowers, fruits, and seeds). The epidermis is usually one cell layer thick, and its cells lack chloroplasts (Britannica online). Tamiki N

Endoplasmic Reticulum: A system of interconnected vesicular and lamellar cytoplasmic membranes that functions especially in the transport of materials within the cell and that is studded with ribosomes in some places. (Merriam-Webster Online, http://www.m-w.com/dictionary/endoplasmic%20reticulum ). It's a continuous membrane system that forms a series of flattened sacs within the cytoplasm of a eukaryotic cell and is important in the biosynthesis, processing, and transport of proteins and lipids. The ER usually constitutes more than half of the membranous content of the cell and is continuous with the outer membrane of the nuclear envelope. (Encyclopedia Britannica Online, http://www.britannica.com/eb/article-9032619/endoplasmic-reticulum). Lee Williams

Epidermis: The epidermis is the outermost layer of leaf cells and young roots and stems which plays a key role in protection (Raven, pg. 5). It is composed of a single layer of living cells that are very tightly packed without intracellular space. This layer of cells covers all surfaces of a plant and its outside, waxy layer, the cuticle, plays a role in preventing evaporation of water. Since plants undergo photosynthesis, gas exchange occurs at the epidermis through small openings, stomata, which are generally found on the underside to leaves. As well, epidermal cells are clear so sunlight can pass through its layer into chloroplasts (“leaves”, <scidiv.bcc.ctc.edu>).~Quinn

Enhancement (Kristie Seaborn) Epidermal cells usually do not exactly fit together, but there are small voids between the individual cells. These voids between individual epidermal cells are filled up by cuticle plugs which are termed anticlinal walls.

(http://www.uni-muenster.de/GeoPalaeontologie/Palaeo/Palbot/cuticles.htm)

Fiber (Sarah Slater): Fiber cells are a part of the ground tissue system, more specifically a type of sclerenchyma cell that is found in plants. Sclerenchyma cells have very thick secondary walls, and useful for adding strength and support to the plant. Therefore fiber cells add strength to a plant. They are very slim, lengthy, and found in bundles. Fiber extracted from the leaves is called leaf fiber and used to make useful products such as hemp, twine and rope, and are often woven together to create fabric. Fiber extracted from the stem of a plant is called bast fiber, and is stronger than leaf fiber. It is used in the making of heavy-duty fabrics.

Encyclopaedia Britannica Online <http://www.britannica.com/eb/article-9047504/leaf-fibre>
Biology of Plants. Raven. Pg 515

The fiber cell can be seen in the diagram below.




Portion of a picture from: University of California <http://www.ucmp.berkeley.edu/IB181/VPL/Ana/Ana1.html>


Enhancement: Fiber cells are dead at matuarity. They are associated with the xylem and phloem tissue of monocot and dicot stems and roots, but generally not found in gymnosperms. In fact, the primary reason why gymnosperm woods are generally softer and lighter than angiosperm woods is the presence in angiosperm wood of dense clusters of heavily-lignified, thick-walled fiber cells. The densely-packed fiber cells greatly increase the hardness and density of angiosperm woods (http://waynesword.palomar.edu/traug99.htm) Tamiki N


Guard Cells (R.Swite)
In plants, a specialized cell on the undersurface of leaves for controlling gas exchange and water loss. Guard cells occur in pairs and are shaped so that a pore, or stomata, exists between them. They can change shape with the result that the pore disappears. During warm weather, when a plant is in danger of losing excessive water, the guard cells close, cutting down evaporation. http://www.tiscali.co.uk/reference/encyclopaedia/hutchinson/m0035144.html Guard cells are located in the leaf epidermis and pairwise surround stomatal pores, which allow CO2 influx for photosynthetic carbon fixation and water loss via transpiration to the atmosphere. Signal transduction mechanisms in guard cells integrate a multitude of different stimuli to modulate stomatal aperture. Stomata open in response to light. In response to drought stress, plants synthesize the hormone abscisic acid (ABA) which triggers closing of stomatal pores. Guard cells have become a well-developed system for dissecting early signal transduction mechanisms in plants and for elucidating how individual signaling mechanisms can interact within a network in a single cell. http://www-biology.ucsd.edu/labs/schroeder/clickablegc.html

figure 1 Gaurd cell (RSwite) www.fhsu.edu/biology/thomasson/dicot2.JPG

Enhancement: Guard cells contain nearly always chloroplasts, and subsidiary cells that are usually devoid of chloroplasts http://www.biologie.uni-hamburg.de/b-online/e32/32f.htm Tamiki N









Lateral Meristem(LaceyL): Is a meristem that give rise to secondary tissue. Meristems are embryonic tissue regions capable of adding cells indefinitely to the plant body (Biology of Plants, Raven, pg. 6). The lateral meristem is the meristem that thickens the roots and shoots of woody plants. The vascular cambium and cork cambium are lateral meristems (Biology, 7th Edition, Campbell and Reece, pg. 720). Enhancement and picture by Mike Tomlinson


Epidermis/ Periderm: The epidermis is a thin surface layer of tissue in higher plants formed by growth of a primary meristem. (Merriam-Webster Online, http://www.m-w.com/dictionary/epidermis ). The epidermis and its waxy cuticle provide a protective barrier against mechanical injury, water loss, and infection. Various modified epidermal cells regulate transpiration, increase water absorption, and secrete substances. (Encyclopedia Britannica Online, http://www.britannica.com/eb/topic-543478/sieve-element )
The Periderm isthe outer layer of plant tissue in woody roots and stems (MSN Encarta Encyclopedia, http://encarta.msn.com/dictionary_1861725029/periderm.html ), consisting of the cork cambium and the tissues produced by it, such as cork ( The Free Online Dictionary, http://www.thefreedictionary.com/periderm).
The key difference between epidermis and the periderm is that epidermal tissue is young tissue produced by primary meristem, while the periderm consists of woody cork produced by the lateral meristems. (Lee Williams)

Sieve cell/Albuminous cell
Both the Sieve cells and the Albuminous cells are food conducting cells in the phloem in gymnosperms. They both have primary cell walls, they are generally elongated in shape
Sieve cells are associated with albuminous cells, which lack starch, thus making it possible to differentiate them from phloem parenchyma. Albuminous cells have many plasmodesmatal conections with sieve cells, as they are believed to play a role in the delivery of substances to the sieve cell. Since albuminous cells are so closely associated with sieve cells, they die when the sieve cells they are linked to die.
Generally not derived from the same mother cell. (Biology of Plants 6th Edition)-Derek Burdikin
Perforation plates/ sieve plates

Sieve plate: The part of the wall of sieve-tube elements bearing one or more highly differentiated sieve areas. ( Biology of Plants, Raven Evert Eichhorn Pg 520). An end wall in a sieve-tube member, which facilitates the flow of phloem sap in angiosperm sieve tubes. (Biology, seventh edition, Campbell Reece, 719)
Perforation plates: The part of the wall of a vessel element that is perforated. ( Biology of Plants, Raven Evert Eichhorn Pg 516). End walls of vessel elements that enable water to flow freely through the vessel. (Biology, seventh edition, Campbell Reece, 719) These two definitions are similar, showing that both plates facilitate the flow of xylem or phloem in the cells of trees. The difference is perforation plates are found in water conducting cells of the xylem and sieve plates are found in the sugar-conducting cells of the phloem.
Dustie

Protoplast/Tonoplast: Most of the metabolic activities of the cell—the chemical reactions of living systems—occur within protoplasts(Encyclopedia Britannica Online, http://www.britannica.com/eb/article-73102/angiosperm ). The cell wall are the living contents of the cell, called the protoplast. These contents are bounded by a cell membrane composed of a phospholipid bi-layer. The protoplast contains the cytoplasm, which in turn contains various membrane-bound organelles and vacuoles and the nucleus, which is the hereditary unit of the cell. (MSN Encarta Encyclopedia, http://encarta.msn.com/encyclopedia_761568511_2/Plant.html#p12 ).
A tonoplast is the separating membrane in a plant cell: the semipermeable membrane separating a fluid-filled internal cavity vacuole from the surrounding cytoplasm inside a plant cell (MSN Encarta Encyclopedia, http://encarta.msn.com/dictionary_1861720832/tonoplast.html ). The protoplast functions to contain organelles within the cytoplasm, and the tonoplast contains the vacuole, separating it from the cytoplasm. Lee Williams


Lenticels/Guard cells Lenticels: Small raised areas in the bark of stems and roots that enable gas exchange between living cells and the outside air. (Biology, seventh edition, Campbell Reece, 728) Spongy area in the cork surface of stems, roots, and other plant parts that allow interchange of gases between internal tissues and the atmosphere through the periderm; occur in vascular plants. (Biology of Plants, Raven Evert Eichhorn Pg 586-587) Guard cells: The two cells that flank the stomata pore regulate the opening and closing of the pores (Biology, seventh edition, Campbell Reece, 724). Pairs of specialized epidermal cells surrounding a pore, or stoma; changes in the turgor of a pair of guard cells cause the opening and closing of the pore. (Biology of Plants, Raven Evert Eichhorn Pg 523, 524f) The similarities between lenticels and guard cells is each play the roll in gases exchange and both are hole of gases exchange. The difference is that the lenticels are on the outside of the tree and are like little cuts that allow the exchange to take place between the atmosphere and tree. Guard cells are cells that regulate the flow of gas exchange inside the bark. Dustie
Golgi Body and The Endoplasmic reticulum
The golgi body and the endoplasmic reticulum are very closely related, not in function but in the process of metabolism within the cell. The golgi body's primary function is to process and package macromolecules which are produced by the cell, specifically by the RER and the SER. The golgi specializes in labeling macromolecules with protiens which confirm the macromolecules destination wiether it be exocytosis or for use within the cell. The golgi is directly related to the Endoplasmic reticulum through vessicular transport. This process is what transports macromolecules to the plasma membrane to be released from the cell and transports newly synthesized materials from the ER to the golgi. In the ER, transmembrane receptor protiens bind to the cargo molecules. The adaptin binds to the transmembrane protiens which in turn binds to the vesicle coat which causes the initial curvature of the ER membrane which results in vessicular budding. The vesicle soon buds off the ER and travels through the cytoplasm to the golgi. Vesicle docking takes place when a surface markers called snares finds its complementary snare on the golgi body. V-snares are located on the vessicle and t-snares or target snares are located on the golgi. These to sets of snares wrap around eachother with the help of a rab protien. This process brings the vesicle close to the golgi untll it reaches a distance of 1.5nm. This is the distance when the vessicle will begin to fuse to the membrane of the golgi. After this fusion the vesicle coat releases along with the adaptin and the cargo molecules are released. Lodish; et al. (2004). Molecular Cell Biology, 5th edn, W.H. Freeman and Company. Mike Tomlinson

Enhancement:
Three vesicle coats are related to vesicular transport, clathrin, COPI and COPII. Clathrin coats are involved with golgi transport to the plasma membrane, COPI is for retrograde transport from the golgi backto the ER and COPII coats are used in the anterograde transport from the ER to the golgi. Reference: Pelham, H.R.B. and J.E. Rothman, The Debate about Transport in the Golgi - Two Sides of the Same Coin? Cell, 2000. 102: p. 713-719.
-Nikki Heim

Mitochondria/Chloroplast: (Tyler Parnall) Mitochondrion: An organelle found in plant and animal cells. It is the site of cellular respiration. (Biology of Plants, 7th Edition, Raven, pg 45) Chloroplast: An organelle found primarily in plant cells. The Chloroplast is the sight of photosynthesis. (Biology of Plants, 7th Edition, Raven, pg 41-42) Comparison: Both mitochondria and chloroplasts are concerned with the production of energy. Both these organelles also originated as small bacteria. Both also contain their own DNA. Mitochondria produce energy primarily by breaking down sugars in both plant and animal cells, and are the predominant cells in heterotrophs. While Chloroplasts absorb sunlight to produce sugar and energy, Chloroplasts are responsible for sustaining autotrophs.

Ribosome: The Large and small Subunits The ribosome consists of two units, the large and the small subunit. The two units fit together and work together to translate the mRNA into a polypeptide chain which is the initial product of protein synthesis. The subunits of prokaryotic cells are made up of one or two large rRNA molecules and many small protein molecules. The eukaryotic ribosome is similar but consists of two or three large rRNA molecule. Recent research has shown that no ribosomal proteins are located at the reaction site of protein synthesis. This means that the protein portion of ribosomes act more as a scaffold and molding device that may enhance the rRNA to synthesize protein rather than actually taking part in the process. The eukaryotic Ribosomes are 80s in size consisting of a 60s large subunit and a 40s small subunit. The S units of the subunits cannot simply be added because they represent measures of sedimentation rate rather than of mass. The sedimentation rate of each subunit is affected by its shape, as well as by its mass.The large Ribosomal unit is split into three smaller units that are bound by proteins and the small Ribosomal subunit is one unit made up of 1900 nucleotides and approximately 33 protiens. The small subunit before the initiation of protein synthesis is bound to the tRNA containing the amino acid. This tRNA binds to the complementary codon of the mRNA and then recruits the large subunit afterwards. The two subunits join at the start codon and protein synthesis begins. The Large subunit has three tRNA binding sites which are designated A,P and E. The A site binds to a tRNA which is bound to an amino acid, the P site binds to a peptidyl-tRNA which is a tRNA that is bound to the peptide which is being synthesized, and the E site binds to a free tRNA just before it exits the ribosome. After the Ribosome reaches the stop codon which is bound to the last amino acid the ribosomal units push the tRNA to the exit site and then separate and the polypeptide is synthesized. The Molecular Biology of the Cell, fourth eddition. Brusce Alberts, et al. Garland Science (2002) pg. 342, Cech T (2000). "Structural biology. The ribosome is a ribozyme". Science 289 (5481): 878-9 Mike Tomlinson