Double Dormancy- A combination of seed coat (external dormancy) and internal dormancy. To achieve germination with seeds having double dormancy, the seeds must first be scarifies and then stratifies for the appropriate length of time (Overcoming Seeds Dormancy: Trees and Shrubs, Frank A. Blazich, NC State University). Double dormancy combines two or more kinds of dormancy, which is a period of suspended development in a plants lifecycle. In order to promote germination, all blocking conditions must be removed in the proper sequence. This type of dormancy is characteristic of species of trees and shrubs having seeds with hard seed coats (Plant Growth Substances, Richard N. Arteca, Pg. 150). Tessa J


Embryo (Andrea Chapman) – Is a cell that matures from a fertilized egg or zygote and is where organs and tissues begin to form (Raven et al. 2005). The developing tissue and organ systems divide at later stages into the shoot apical meristem and root apical meristem at opposite ends of the embryo. These meristem tissues expand their respective systems through cell division (Steeves and Sussex 1989).

Raven P.H., Evert R.F. and Eichorn S.E. 2005. Biology of plants. Seventh edition. W.H. Freeman and Company. New York, NY. 686 pp
Steeves T.A. and Sussex I.M. 1989. Patterns in plant development. Cambridge University Press. Pg 1 URL http://books.google.ca/books?hl=en&lr=&id=7GCTLqM3FDcC&oi=fnd&pg=PP15&dq=embryo+plant&ots=QFd3x1FTxJ&sig=DgdcdIWeI97rguifhTNeYlS8VcQ#PPA1,M1


Enhancement (Kristie Seaborn) The image below is from seeds that have been opened after the seedcoat was carefully cracked and the seed then softened in water. The almost crystalline red outer layer of the seedcoat (exocarp), roughly 0.5 mm. thick can easily be distinguished from the more leathery, orangish, inner layers. The small pale embryo is attached to two large 'seed leaves' or cotyledons. The cotyledons store food needed for the growth of the emerging seedling. With Texas Mountain Laurel these remain underground as the embryo grows to the light and begins to produce true green leaves to provide nourishment for its continued growth. The embryo also has an embryonic root (radicle) which will develop downwater in order to supply water and nutrients from the soil.

• Embryo detached from its two cotyledons.

(https://webspace.utexas.edu/harms/SOSE-HTML/SophoraSeed.html)

Endosperm: (Nikki Heim)
Endo- means within, and sperm means seed, so endosperm means “within the seed”. (Botanical Society of America) The endosperm is the tissue that surrounds and nourishes the embryo in the angiosperm seed. It provides storage of starch, fat, and protein that are used during seed development. (Encyclopedia Britannica) The endosperm can also provide nutrition for the human diet and is commonly found in cereal grains and oilseeds. References:
(Encyclopedia Britannica) http://www.britannica.com/eb/article-9032623/endosperm
(Botanical Society of America) http://www.scientific-conference.net/PlantTalkingPoints/Endosperm.php

Enhancement:

This is a picture of the endosperm displaying the large role that it has.



http://www.public.iastate.edu/~becraft/kernel.jpg

--John

Epicotyl: The stem of an embryo or a seedling thats is located between the cotyledon and the next true leaves.(http://www.thefreedictionary.com/epicotyl) Another description is it is the top part of the axis of a seedling or an embyro. It is above the seed leaves (cotyledons) and below the next leaf or leaves. (Raven G-4) - Vanessa V
http://cache.eb.com/eb/image?id=72144&rendTypeId=35

www.apsnet.org/.../PhotosE-H/epicotyl.htm

epicotyl portion of the stem of a plant embryo or seedling above the node where the cotyledons are attached Enhancement: The epicotyl is the embryonic shoot above the cotyledons. In most plants the epicotyl will eventually develop into the stem and the leaves of the plant. In diconts, the hypocotyl is what appears to be the base stem under the spent withered cotyledons, and the shoot just above that is the epicotyl. In sunflower seedlings, the difference between epicotyl and hypocotyl can be seen from the parts of the stem divided by the first pair of leaves. Ref: http://www.geo.arizona.edu/palynology/geos581/embryo.gif -Scott Horley Follicle-Danielle Dornik (L. folliculus, small ball)- A dry, dehiscent simple fruit derived from a single carpel and opening along one side. (Biology Of Plants, Peter H. Raven G-9) ‘A kind of fruit, consisting of a single carpel, dehiscing by the ventral suture only (Lindley); formerly used for any kind of capsular fruit. (Oxford English Dictionary Online) The single carpel of a follicle splits open along one seam. When completely opened, the carpel resembles a thick, dried leaf. It is easy to see that the single carpel of a follicle is a modified, seed-bearing leaf (megasporophyll).http://waynesword.palomar.edu/termfr1.htm Growth Regulators: Growth regulators are chemicals produced by the plant that play a very large part in the development of plants. They can be very helpful to plants and there are several brands of commercial growth regulators on the market for gardeners to buy. Growth regulators were first discovered by Charles Darwin and his son in the 1800’s, when they noticed that when grass was covered it would not bend towards the sun. Growth regulators play a role in cell elongation, cell division, cell and organ enlargement, and even dormancy induction. One use that people have is in the clipping of Christmas trees. Every time a shoot is sheared, it stimulates the growth of more because it increases branch density, therefore resulting in a fuller, thicker tree A picture of a Christmas tree that has been sheared to induce the increase branch density. Liz Foster www.cnr.vt.edu/dendro/forestbiology/htmltext/chapter5.htm, (Virginia Tech) www.umass.edu/umext/floriculture/fact_sheets/greenhouse_management/pgr.html (University of Massachusetts) Hypocotyl:Amanda Last 1880 C&F. Darwin Movem Pl5 With seedlings, the stem has been called by many botanists the hypocotyledonous stem, but for brevity sake we will speak of it merely as the hypoctyl.Ibid 10 The radicles, hypocotyls, and cotyledons of seedling plants. 1882 Nature23 Mar. 482 Buck-wheat plants grow from small seeds containing a small hypocotyl that enlarges afterwards to an exceedingly long part.(Oxford English Dictionary) The hypocotyl (embryonic stem) grows several inches above the ground, carrying the cotyledons into the light, in which they become green and often leaflike. (Britannica online) The portion of an embryo or seedling situated between the cotyledons and the radicle. (Biology of Plants, Raven, G-12). Picture illustrating the hypoctoyl and cotyledons of a sprouting plant. Picture from: http://media.allrefer.com/s1/l/h0365200-hypocotyl.jpg Added by: Amanda Last Megagametophyte (Sarah Slater): A female gametophyte, developed from a megaspore. In gymnosperms it is located within the ovule of the seed and is food supply and support for the embryo. Megagametophytes are made up of mostly carbohydrates and fats. Biology of Plants. Raven. G-14 Henderson’s Dictionary of Biology. Lawrence, Eleanor. Pg 383 Scarification: Some seeds have such hard seed coats that these coats can only be removed by abrasion. This can includes any mechanical action, like digestion or soaking the seed in acid, that wears away the seed coat enough to allow water or oxygen to enter the seed. (Biology of Plants, Peter H. Raven, pg.637). An example of a tree species seed that germinates this way is Robinia pseudoacacia (black locust). This tree’s seeds germinate after being eaten by birds like the northern bobwhite or small mammals like squirrels (http://www.na.fs.fed.us/spfo/pubs/silvics_manual/Volume_2/robinia/pseudoacacia.htm).

Northern bobwhite. (http://www.birdsasart.com/Bobwhite-group-_H2D1498-Los-Colmenas-Ranch,-Hidalgo-County,-TX.jpg) -Morgan Traverse
Enhancement (Scarification): Seed scarification is a technique used to break dormancy. The seed will not germinate until the seed coat is altered physically. Any process of breaking, scratching, or mechanically altering the seed coat to make it permeable to water and gases is known as scarification (NC State University, “Overcoming Seed Dormancy: Trees and Shrubs”, By Frank A. Blazich and Erv Evens). Artificial scarification, such as abrasion using a knife, file, or sandpaper, is commonly used by horticulturists to promote seed germination (Raven, Biology of Plants, 637). Tessa J



Stratification(Sarah Slater): Artificially meeting the chilling requirement of seeds. Stratification is the action of chilling seeds for an amount of time before exposing them to warm temperatures to break their dormancy. The process involves first soaking the seeds for twenty-four hours, then drying them off to prevent mold growth. The seeds are then put into a cold storage, which is slightly above freezing temperatures for 4-12 weeks depending on the species. Some species require less chill time because they naturally grow within warmer climate than other species. Biology of Plants. Raven. G-22
University of Manitoba < http://www.ncrs.fs.fed.us/fmg/nfmg/glos.html#s>


Stratification(enhancement): Is a proccessed used to overcome internal dormancy regulated by inner seed tissues. The are two types of strtification. Cold stratification is when a seed is chilled. Warm stratification is when a seed is kept at a temperature of 68 to 86 degrees F (for a certain time period) depending on the species.(http://www.ces.ncsu.edu/depts/hort/hil/hil-8704.html) - VanessaV

Secondary Seed Dispersal (Nicole L.) Subsequent movements of that seed by a distinctly different mechanism (ex. wind, water, and animals) Dispersal implies movement—movement away from an existing population (population expansion) or away from the parent organism (population maintenance)
http://www.ars.usda.gov/research/publications/publications.htm?SEQ_NO_115=154791 http://en.wikipedia.org/wiki/Biological_dispersal
The pictures are different methods of secondary seed dispersal; bees dispersal of pollen, wind disperses seeds, and seeds getting caught on the fur of animals.


Images from http://en.wikipedia.org/wiki/Biological_dispersal
ENHANCEMENT

Secondary seed dispersal occurs whenever a seed is dispersed in two or more different dispersal events, so that different dispersal agents, mainly birds, contribute to different events. In order for secondary dispersal to occur, primary dispersal must. Any movement of the seed from where it lands from primary dispersal is considered secondary dispersal.

MANUEL NOGALES, DAVID P PADILLA, CONCEPCIÓN NIEVES, JUAN C ILLERA, ANNA TRAVESET (2007)
Secondary seed dispersal systems, frugivorous lizards and predatory birds in insular volcanic badlands
Journal of Ecology 95 (6), 1394–1403.
doi:10.1111/j.1365-2745.2007.01305.x
http://www.blackwell-synergy.com/doi/abs/10.1111/j.1365-2745.2007.01305.x Enhancement: Animals, Water and Wind are the three main secondary dispersal agents. (http://www.zephyrus.co.uk/seeddispersal1.html ) Travis Unsworth
Seed Coat (Russ Fountain)
The seed coat is the outer protective covering of a seed. Seed coat is a structure of considerable importance, because it forms the barrier between the embryo and its immediate environment. The most important property of the seed coat is its permeability to water and to gas. (Seed Coat Structure of Pinus Koraiensis - http://journals.cambridge.org/download.php?file=%2FMAM%2FMAM11_S02%2FS1431927605503635a.pdf&code=dd0d250f059fc8125e74d9e8bd98cb77) The seed coat develops from the integument of the ovule. It is also called the testa.(“seed coat” The Free Dictionary http://www.thefreedictionary.com/seed+coats)
Seed coat dormancy (Kristie Seaborn) is dormancy imposed on the embryo by the seed coat and other enclosing tissues, such as endosperm, pericarp, or extrafloral organs. The embryos of such seeds will germinate readily in the presence of water and oxygen once the seed coat and other surrounding tissues are either removed or damaged. There are five basic mechanisms of coat-imposed dormancy: Prevention of water uptake, Mechanical constraint, Interference with gas exchange, Retention of inhibitors,and Inhibitor production (http://4e.plantphys.net/article.php?ch=t&id=8). Some seeds of desert species will germinate only when inhibitors in their coats are leached away by rainfall; this adaptation ensures that the seed will germinate only during those rare intervals when desert rainfall provides sufficient water for the seedling to mature (Biology of plants, pg. 505).
Seed Coat Impermeability (Stephanie Lauer)– impermeability relates to the structure of something that cannot be pervaded by liquid (WordReference.com), therefore if a seed coat is impermeable it cannot allow liquid through its outside layer. This relates to the seed coat dormancy in the sense that the seed coat needs to have some external, physical, environmental factor to break the seed coat impermeability so that germination can take place (Raven, Biology of Plants, pg 504) http://www.wordreference.com/definition/impermeability




Strobilus - A strobilus (plural strobili) is an organ of many plants that contains the reproductive structures. Strobili are ordinarily called cones in many of these groups. It isthe cone of a coniferous plant, or a similar cone-shaped structure in some lower plants that consists of closely packed fertile leaves bearing spore-producing organs. Strobili are characterized by a central axis (anatomically a stem) surrounded by spirally arranged structures that bear reproductive parts.

(http://en.wikipedia.org/wiki/Strobilus) (http://uk.encarta.msn.com/dictionary_1861759564/strobilus.html)
Image (http://www.biologie.uni-hamburg.de/b-online/earle/cy/cy/media1.jpg)
Krista Neufeld

Monocotyledon – Angiosperms (flowering plants) are divided in two major groups. Monocotyledons are plants that have only one seed leaf in the embryo. Thus the sprouting seed only has one primary leaf or cotyledon. Monocotyledons have some similar traits that include: flower parts in threes or multiples of three, leaves with parallel veins, fibrous root system predominant, and increase in stem diameter as a result of cell enlargement or the production of cells from the inner cells (rather then from the cambium layer as in dicots). Most monocotyledons are small plants such as grasses, lilies and orchids but palms are also monocotyledons. (Encyclopaedia Britannica and Merriam-Webster) www.visit-islay.com/resources/plants.htm
Enhancement: Many of the world's most important agricultural crops are monocots, such as corn, wheat, barley, and other cereal crops. Monocots have played a huge part in human culture through the ages as a food source, and still do today. For example, corn (a monocot) is the most important crop plant in the United States (Raven, pg. 479) where it is used primarily for animal feed.
Amanda M

Compare and Contrast (first word alphabetical)
Afterripening/Dormancy:
Afterripening is a period of dormancy after a seed is shed during which the synthetic machinery of the seed is prepared for germination and growth. This is because the embryo is not mature enough to germinate. It needs to develop more before this can happen.
Dormancy is a state of quiescence during the development of many plants characterized by their inability to grow, though continuing their morphological and physiological activities. This is so the seed will not germinate too soon. If it did germinate too soon, in the winter for example, the embryo would die. There are many factors or triggers that break this state of dormancy, including afterripening. There are several types of dormancy, which can be imposed by factors such as the embryo hormones (growth regulators), low temperatures (quiescence), embryo immaturity, seed coat impermeability or dormancy and closed cones. These are all broken by different factors.
http://www.healthguidance.org/entry/6425/1/Afterripening-Rest-Period-and-Dormancy.html
http://www.answers.com/topic/afterripening?cat=technology
Krista Neufeld

Aril/Seed Coat: Both an aril and seed coat are vital to the success of reproduction of plants and are grown from the ovule of a seed. As well, they both compose the outer covering of a seed providing support and protection to the inner components. An aril is a fleshy envelope and often brightly colored which can help to attract animals that will eat it and disperse the seed elsewhere (Biology of Plants, Raven G-3). One example of a plant that produces arils is the Pacific Yew. A seed coat on the other hand is much more solid and compact and is not digested by birds or broken down by other methods very easily. It is responsible for seed dormancy by: preventing the expansion of the embryo, keeping oxygen from entering, and preventing the inflow of water (www.britannica.com). Overall, the seed coat is much longer lived and more important to the survival of a seed.
~Quinn
Enhancement: (AarenS) Aril of a yew, attracts birds which eat the fleshy berry like aril, and disperse the seed following digestion.
www.answers.com
Seed coat – protects the enclosed embryo and can be pivotal in ensuring that germination occurs during ideal conditions.
www.urbanext.uiuc.edu

Chilling requirement/Dark-imposed dormancy (Daniel Struthers): Both are results from the Dormancy of the embryo. Phytohormones keep the embryo in dormancy until a certain requirement is met. After this requirement is met then the embryo is ready to germinate. Chilling requirement is one of the types of conditions for some types of species to bring the seed out of dormancy. The seed needs a minimum chilling period to shift hormone balance to growth promotion. This is useful so that the seed doesn’t germinate during winter and expire. Dark-imposed dormancy in a type of growth regulator dormancy of the embryo in which seeds that are buried won’t germinate until they are exposed to light. For example, if a seed is dispersed during winter and is covered by snow it will stay in dormancy until the snow melts and sunlight shines on the seed.
Chilling requirement/Stratification: Dormancy that is imposed by hormones often require low temperatures to germinate. Most wildflowers, like Chrysopsis villosa (hairy golden aster) that seed out in the fall and sit in the soil all winter require this (www.growwildflowers.com). Stratification is the artificial method of achieving this by manually chilling the seeds (Biology of Plants, Peter H. Raven, pg.637)
http://www.swcoloradowildflowers.com/Yellow%20Enlarged%20Photos/2hevi4.jpg -Morgan Traverse
Cladoptosis/Layering
Cladoptosis is derived from the Greek words clados, meaning branch, and ptosis, meaning fall (Jim Hole). It is the annual falling of leafy twigs instead of individual leaves. This process takes amongst most of cypress family (Botany.com). After the branch drops off on the ground, it regenerates into a tree.
Layering occurs naturally for drooping stems whose trailing tips root where they come in contact with the soil. They then send up new shoots from the newly rooted portion of the plant (Encyclopedia Britannica online). Since the new rooted portion and parent plant, the parent plant supplies the food until the new plant has an adequate root system and can survive on its own (Plant propagation.com).

Both cladoptosis and layering produces new roots from branches that are in contact with soils. However, the layering branch is attached to the parent plants, whereas cladoptosis branch is completely separated from the parent plants. Tamiki N
Cotyledon/Dicotyledon The Cotyledon is the trees first leaves or needles. In monocotyledons it absorbs food and in other angiosperms it stores food. (Raven, Biology of Plants 7th edition). Dicotyledons refers to all angiosperms other than monocotyledons. In Dicotyledons they have two cotyledons, and monocotyledons have one cotyledon. (http://www.biology-online.org/dictionary/Cotyledons) –Nick N

Cotyledons/Epicotyl: The cotyledons of a plant are the seed leaves (Campbell Reece, 7th Edition, pg. 601) and the epicotyl is the upper portion of the axis of an embryo seedling, directly above the cotyledons, and below the next leaf. (Raven G-8) The epicotyl is the shoot tip, which usually has a pair of miniature leaves, and it is located above the cotyledons.
Amanda M
Epicotyl

Cotyledons/Hypocotyl:
Cotyledons: The first leaves of the plant, enclosed inside the seed, the "seed leaves" (Raven, pg. 500) part of the sporophyte generation of the plant, broken into categories such as dicots, monocots, etc. depending on the number of seed leaves present. (Campbell Reece 7th Edition, pg.600)

Hypocotyl: (embryonic stem) grows several inches above the ground, carrying the cotyledons into the light, in which they become green and often leaflike. (Britannica online) The portion of an embryo or seedling situated between the cotyledons and the radicle. (Biology of Plants, Raven, G-12).

The Cotyledons will form the first photosynthetic leaves of the plant in the sporophyte generation. The hypocotyl carries the cotyledons several inches above the ground after the embryo begins to grow so that photosynthesis can begin.
Mark Haywood-Farmer


Cotyledon/Radicle: Both the cotyledon and the radicle are found in the embryo in a seed. The cotyledon is also known as the seed leaf. It is responsible for storing or absorbing food and turns green after the seed has germinated. The radicle is also known as the embryonic roots. It is found in the lower portion of the embryo and is the first part of the plant to emerge from the embryo to form the first root of the plant. (Biology of Plants, Raven 7th Edition)


http://cache.eb.com/eb/image?id=72144&rendTypeId=35 Morgan Traverse




Dicotyledon/Monocotyledon:
A monocotyledon (monos in latin meaning one or single) is a plant who’s embryo has one cotyledon(the leaf of an embryo of a seed plant, which at germination remains in the seed or emerges, enlarges and becomes green) often abbreviated as monocot.
The term dicotyledonous is now an obsolete term (now usually referred to as Eudicotyledones) that refers to all angiosperms that are not monocots. Dicots unlike monocots have 2 cotyledons instead of one. (Raven G-14, G-6, http://www.thefreedictionary.com/dicotyledon)- VanessaV

http://cache.eb.com/eb/image?id=72144&rendTypeId=35

Enhancement:
Dicots: leaf veins are netted, 4-5 flower parts, there is a vascular cambium in secondary growth. (ex. Red alder)

Monocots: leaf veins are parallel, 3 flower parts, there is no vascular cambium in secondary growth. (ex. Palm trees)
(Biology, 7th ed., Campbell Reece, pg. 602)
~Quinn

Dormancy/Quiescence (Andrea Chapman) – Dormancy is a life stage of the embryo where cell division stops, and metabolic activity of a seed slows to wait for unfavourable conditions to subside (Vleeshouwers et al. 1995). The seed may not actually be asleep, but is continuously sensing the environment and adjusting its metabolic rate. Another way to describe this phenomenon is that the seed is actively sleeping or sleeping awake. Quiescence is a stage of inactivity the embryo goes through that still allows the processes of cell division to take place (Rensing and Samuels 2004). Quiescence is also a function of environmental conditions. Dormancy and quiescence are both states of inactivity practiced by the embryo that are influenced by environmental changes. The difference is that dormancy is a state of inactivity where cell division ceases, and quiescence is a state of inactivity where cell division still takes place.

Vleeshouwers L.M., Bouwmeester H.L., and Karssen C.M. 1995. Redifining seed dormancy: an attempt to integrate physiology and ecology. The Journal of Ecology 83(6): 1031-1037 URL http://www.jstor.org/view/00220477/di985501/98p01064/0?frame=noframe&userID=ce7bb2ca@tru.ca/01c0a80a6b005015fea5&dpi=3&config=jstor
Rensing K.H. and Samuels A.L. 2004. Cellular changes associated with rest and quiescence in winter-dormant vascular cambium of Pinus contorta. Trees 18: 373-380 URL http://www.springerlink.com/content/hq0ctklf8y4dv2nf/fulltext.pdf
Dormancy/Double Dormancy Dormancy is a special condition that seeds and buds require preferable growing environmental condition to initiate growth (Raven Glossary, pg. 7).It is the state of reduced metabolic activities under conditions of environmental stress or in winter, when such stressful conditions are likely to appear (Encyclopedia Britannica online). Double Dormancy is a combination of seed coat: external dormancy and internal dormancy. To achieve germination with seeds having double dormancy, the seeds must first be scarified and then stratified for the appropriate length of time (NC state university). This means that the double dormancy require simply warm (> 15oC) or cold (1-10oC) conditions during which time the embryo develops and then breaks the dormancy. It also requires extended cycle of cold and warm temperature to satisfy the dormancy (Robert L. Geneve). Dormancy is the state at which seeds’ activities are reduced until they meet their preferable environment. Whereas, double dormancy is the state at which seeds’ activities are stopped in and out and they requires specific environmental conditions to break the dormancy. Tamiki N


Endosperm and cotyledonsReserved food for the developing seed of angiosperms is initially stored in the nutrient tissue referred to as endosperm. In many eudicots these tissues are reduced to nothing as the embryo absorbs these nutrients to develop fleshy cotyledons, which stores the nutrients through dormancy and then will nourish the seedling as it resumes growth. An example is the garden pea. Some eudicots maintain the endosperm to be absorbed by the cotyledons until after germination. Seedlings obtain nutrients from the endosperm by way of the cotyledon. (Biology of Plants, Raven, p 503-504, 450) Kirsten Jorgensen