Unit C3-1

Identifying Seed GerminationProcesses and Requirements

Common Core/Next Generation Science StandardsAddressed!

MS‐LS1‐6. Construct a scientific explanation based on evidence forthe role of photosynthesis in the cycling of matter and flow of energyinto and out of organisms.

RST.6‐8.1Cite specific textual evidence to support analysis ofscience and technical texts, attending to the precise details ofexplanations or descriptions (MS‐PS1‐2)

RST.6‐8.3Follow precisely a multistep procedure when carrying outexperiments, taking measurements, or performing technical tasks.(MS‐PS1‐6)

WHST.6‐8.1Write arguments to support claims with clear reasonsand relevant evidence. (MS‐LS2‐4)

Career Cluster Content Standards – Agriculture,Food and Natural Resources.

Pathway Content Standard: The student will demonstratecompetence in the application of scientific principles andtechniques to the production and management of plants.

–PS.03.02. Performance Indicator: Develop and implement a plantmanagement plan for crop production.

•PS.03.02.04.a. Observe and record environmental conditions during the germination, growthand development of a crop.

Interest Approach

Teacher: Fill a clean mayonnaise or pickle jar onehalf full with soybeans. Add fine textured sand andshake the jar until the beans and sand are evenlydistributed and the contents fills the jar to the top.Place the jar on a pan at the front of the class. At thestart of class ask students to present hypotheses asto what will happen when the contents is completelysaturated with water. List the predictions on theboard. Fill the jar with water as you collect thestudent hypotheses. Use warm water to speed theprocess. Within 30 to 45 minutes expect the glass tocrack due to the build up of osmotic pressure causedby the seeds’ imbibition of water.

Bell Work

1.Describe the process of seed germination.

2. Discuss the conditions required for seedgermination.

3. Explain the importance of seed quality.

Terms

Amylase

Germination

Imbibition

Phytochrome

Protease

Scarification

Stratification

Turgid

Viability

Vigor

What is the Process of SeedGermination

I. Germination is the process by which the seedembryo begins growth. A seed is considered to havegerminated when the embryonic root emerges fromthe seed coat. Many important crops are grown fromseed. Corn, soybeans, cotton, and vegetables arestarted from seeds. Seed germination is a complexprocess that begins when conditions are favorable forgrowth.

–A. Some plants produce seeds, which germinateimmediately once they are released. Others produce seedsthat have internal dormancy mechanisms and remaindormant until conditions are favorable before the seed cangerminate.

•1. Stratification is a dormancy mechanism that involvestemperature. Seeds with this mechanism mustexperience a period of cold temperature before the seedcan germinate.

•2. Scarification is a dormancy mechanism that involvesthe breakdown of the seed coat. Some plants have verythick and tough protective seed coats. These seed coatsprevent water and oxygen from entering the seed. Theseed coat must be broken before germination can begin.

–B. There are three major stages in the germination process.

•1. Germination begins with the seed’s absorption or imbibitionof water. Most dormant seeds have 5–10% moisture content.When conditions are right, water is imbibed very rapidly. Mostwater is imbibed through the micropyle. As the cells hydrate,they swell and become turgid or rigid.

•2. In stage two, metabolic activity surges. Proteins aresynthesized. Gibberellins stimulate the production of enzymes.The enzyme amylase converts stored starches to sugars. Theenzyme protease breaks down stored proteins into aminoacids. The sugars and amino acids are directed towards celldivision, growth, and differentiation sites at the root and shootmeristems or tips.

•3. Metabolic processes increase in the third phase ofgermination. The swelling of cells causes the seed coat torupture. The primary root or radicle emerges downward, andthe stem grows upwards. The shoot begins manufacturing foodthrough photosynthesis. The roots absorb water and nutrients.

What Conditions areRequired for SeedGermination?

II. Germination begins when favorableconditions exist for the survival of thedeveloping plant. The conditions forgermination include moisture, air, optimaltemperatures, and possibly light or darkness.

–A. Water triggers germination processes and isnecessary as the embryo grows and develops.

–B. All seeds need oxygen to germinate. Oxygen isrequired for cellular respiration, a processnecessary for converting stored food into energy.Seeds germinate at a wide range oftemperatures,ranging from 32°F to 105°F.However, the optimum temperature for mostseeds lies between 65°F and 80°F. Temperatureinfluences the speed of metabolic activities.Metabolism is faster when temperatures are warmthan when temperatures are cool.

–C. Seeds of some plants need exposure to lightbefore they will germinate. Seeds of other plantsrequire darkness in order to germinate, and thereare those that are not influenced by light ordarkness. Seeds that are light sensitive have aphotoreceptor pigment, called phytochrome,found in the seed coat. This pigment sendsmessages to the seed instructing it to initiate or tostop germination.

Why is Seed QualityImportant?

III. Seed quality and proper storage of seed arecrucial to achieving desired high germinationrates. High quality seeds produce healthyseedlings. Seed quality refers to both viabilityand vigor.

–A. Viability is the ability of seeds to germinate underoptimal conditions.

-B. Vigor is the ability of seeds to germinate underdifferent conditions and still produce healthyplants.

-C. Seed producers test seeds to determine thepercentage of seeds that will germinate.Germination rates from the tests are printed onthe seed container label.

-D. Until the seeds are sold and planted they must bekept in storage. A goal is to maintain seedviability and vigor during the storage period.The best seed storage conditions typicallyconsist of cool temperatures (about 40°F) andlow humidity (approximately 15%).