Germination is the process by which a plant grows from a seed. The most common example of germination is the sprouting of aseedling from a seed of an angiosperm or gymnosperm. However the growth of a sporeling from a spore, for example the growth ofhyphae from fungal spores, is also germination. In a more general sense, germination can be simply anything expanding into greater being from a small existence or germ, a method that is commonly used by many seed germination projects.

Germination is the growth of an embryonic plant contained within a seed; it results in the formation of the seedling. The seed of avascular plant is a small package produced in a fruit or cone after the union of male and female sex cells. All fully developed seeds contain an embryo and, in most plant species some store of food reserves, wrapped in a seed coat. Some plants produce varying numbers of seeds that lack embryos; these are called empty seeds^[1] and never germinate. Most seeds go through a period of dormancy where there is no active growth; during this time the seed can be safely transported to a new location and/or survive adverse climate conditions until circumstances are favorable for growth. Dormant seeds are ripe seeds that do not germinate because they are subject to external environmental conditions that prevent the initiation of metabolic processes and cell growth. Under proper conditions, the seed begins to germinate and the embryonic tissues resume growth, developing towards a seedling.

Seed germination depends on both internal and external conditions. The most important external factors include temperature, water,oxygen and sometimes light or darkness.^[2] Various plants require different variables for successful seed germination. Often this depends on the individual seed variety and is closely linked to the ecological conditions of a plant's natural habitat. For some seeds, their future germination response is affected by environmental conditions during seed formation; most often these responses are types of seed dormancy.

• Water is required for germination. Mature seeds are often extremely dry and need to take in significant amounts of water, relative to the dry weight of the seed, before cellular metabolism and growth can resume. Most seeds need enough water to moisten the seeds but not enough to soak them. The uptake of water by seeds is called imbibition, which leads to the swelling and the breaking of the seed coat. When seeds are formed, most plants store a food reserve with the seed, such as starch, proteins, or oils. This food reserve provides nourishment to the growing embryo. When the seed imbibes water, hydrolytic enzymes are activated which break down these stored food resources into metabolically useful chemicals.^[2] After the seedling emerges from the seed coat and starts growing roots and leaves, the seedling's food reserves are typically exhausted; at this point photosynthesis provides the energy needed for continued growth and the seedling now requires a continuous supply of water, nutrients, and light.

• Oxygen is required by the germinating seed for metabolism.^[3] Oxygen is used in aerobic respiration, the main source of the seedling's energy until it grows leaves.^[2] Oxygen is an atmospheric gas that is found in soil pore spaces; if a seed is buried too deeply within the soil or the soil is waterlogged, the seed can be oxygen starved. Some seeds have impermeable seed coats that prevent oxygen from entering the seed, causing a type of physical dormancy which is broken when the seed coat is worn away enough to allow gas exchange and water uptake from the environment.

• Temperature affects cellular metabolic and growth rates. Seeds from different species and even seeds from the same plant germinate over a wide range of temperatures. Seeds often have a temperature range within which they will germinate, and they will not do so above or below this range. Many seeds germinate at temperatures slightly above 60-75 F (16-24 C) [room-temperature if you live in a centrally heated house], while others germinate just above freezing and others germinate only in response to alternations in temperature between warm and cool. Some seeds germinate when the soil is cool 28-40 F (-2 - 4 C), and some when the soil is warm 76-90 F (24-32 C). Some seeds require exposure to cold temperatures (vernalization) to break dormancy. Seeds in a dormant state will not germinate even if conditions are favorable. Seeds that are dependent on temperature to end dormancy have a type of physiological dormancy. For example, seeds requiring the cold of winter are inhibited from germinating until they take in water in the fall and experience cooler temperatures. Four degrees Celsius is cool enough to end dormancy for most cool dormant seeds, but some groups, especially within the family Ranunculaceae and others, need conditions cooler than -5 C. Some seeds will only germinate after hot temperatures during aforest fire which cracks their seed coats; this is a type of physical dormancy.
• Most common annual vegetables have optimal germination temperatures between 75-90 F (24-32 C), though many species (e.g. radishes or spinach) can germinate at significantly lower temperatures, as low as 40 F (4 C), thus allowing them to be grown from seed in cooler climates. Suboptimal temperatures lead to lower success rates and longer germination periods.
  • Light or darkness can be an environmental trigger for germination and is a type of physiological dormancy. Most seeds are not affected by light or darkness, but many seeds, including species found in forest settings, will not germinate until an opening in the canopy allows sufficient light for growth of the seedling.^[2]
  Scarification mimics natural processes that weaken the seed coat before germination. In nature, some seeds require particular conditions to germinate, such as the heat of a fire (e.g., many Australian native plants), or soaking in a body of water for a long period of time. Others need to be passed through an animal's digestive tract to weaken the seed coat enough to allow the seedling to emerge.^[2]

A seed contains an embryonic plant in a resting condition, and germination is its resumption of growth. Seeds will begin to germinate when the soil temperature is in the appropriate range and when water and oxygen are available. However, most of your wildflower seeds will only germinate between specific soil temperatures. Optimum soil germination temperatures will vary greatly from one species to another. With soil temperatures extremely low or excessively high, growth of the seed is either slow and erratic or germination is entirely prevented. Not all of your seeds will sprout at the same time due to constant temperature fluctuations typically observed in nature.

The most common cause of poor germination associated with wildflowers is the depth at which the seeds are sown. Small seeds should be planted on the soil surface and pressed or rolled in for best results since they contain only enough stored food for a limited period of growth. If the seedling is to survive, it must emerge from the soil and quickly begin to produce its own food. If seeds are too deeply buried beneath the soil surface, the seedling will either exhaust its food reserve prior to reaching the soil surface causing its death, or lack of sufficient oxygen will prohibit germination altogether.

Within the descriptive literature of each species, we have listed the following germination data to assist you in your planting.

GERMINATION DAYS:
The average time period in which a particular variety will germinate given optimum conditions. Please allow a variance of plus or minus 25%.

OPTIMUM SOIL TEMPERATURE FOR GERMINATION:
The optimum temperature in degrees Fahrenheit for rapid germination. A steady temperature between the published limits, based on laboratory data, is recommended for best results.

SOWING DEPTH:
An increment in inches has been included for each variety as a quick reference for optimum sowing depth. A good rule to follow, if in doubt about any variety, is to sow the seed at a shallow depth.

SURFACE SOW:
Due to the extremely small size of the seed, the area should be prepared and the seed sown directly on the surface of the soil, then pressed or rolled in. DO NOT COVER.

Process of Seed Germination

Requirements for Germination

Water: 

The role of wwater in germination is of paramount importance.The  seed  reemains in a ormant condirtion and the initiation of the process og germination takes place by the influx of water molecules.The seed has a tiny pore  in the covering (testa which is called micropyle and water enters into the seed initially by imbibation  adsorption ofwater by substances present inside the seed.Thses incluse proteins, starchand cell wall materials suach as hemicellulose and pectic substances.
The swelling of  tese substances ca lesd tot he strong imbiational forces which are great enough to cause rupturing of the seed.

                                                           

Optimum  temperature  :

 There is a characteristic temperature range needed for proper germination of seeds  in a given soil type. It is about  5 to 40⁰   C.  

Oxygen :

 This is required for aerobic respiration  which can be assisted with anaerobic respiration if needed

Plant growth is well explained with an example of germination of Bambarra Bean seed below.

Germination of Voandzeia (Bambarra Bean)

Plant growth is well explained with an example of germination of Bambarra Bean seed below.

Physiology of Germination:

• A typical seed stores carbohydrates, lipids and proteins  for germination.
• As a result of imbibation  and osmosis the embryo bercomes  hydrated which activates the enzymes for respiration.
• basically the storage centre (food) and the growth centre(embryo) are the main regioons of activity.
• Digestion of food on storage centre osccurs  by hydrolysis  and amino acids, sugars anf fatty acids anf glygerol arte produced
• Soluble products are translocaterd to thegrowing regions of the embryo
• The majority of glucose is used for cellulose synthesis and other cell wall materials.amino acids are used for enzymes and structural components.
• The net loss of mass of the seed occurs due to  change of  sugars to  Co₂  and water where C0₂ is lost as gas than O₂  taken up by aerobic respiration.
• Within the embryo growth  occurs by cell division and amounts of proteins, cellulose,nucleic acids steadily increase in the growing regions of the seed.
• Thev first visible sign of growth is the radicle, that emerges fromthe micropyle andis positively  geotropic in nature.It forms the rooyt system of the plant 
• The next structure that emerges is the plumule, that is positively phototropic  and forms the shoot system of the plant.                            

 Stages of Seed Germination

There are basically three steps of seed germination:

• Step 1-Water imbibation results in rupture of seed coat, uniform imbibation is important   and approximately optimum temperatures are required
• Step 2-The imbibition of the seed coat results in emergence of the radicle and the plumule, the cotyledons get   unfolded. It is important that the temperature and photo period  are required in optimum amounts
• Step 3-This marks the final step in the germination of the seed  where the  cotyledons are expanded which are the true leaves.

For the growth and development of seeds ,different kinds of food like carbohydrates, fat and proteins are required in stored form.Besides the growth promoting substances  like auxins, heteroauxins  are also formed at the time of germination which controls the growth and development of seedlings during germination.

Germination of Voandzeia (Bambarra Bean)

Seed germination is an irreversible process. Germination includes the changes that take place from the time the dry seed is provided with suitable conditions to when the seedling becomes established as an independent plant. Various changes take place during germination.

For non-dormant seeds, germination starts when a seed is provided with water as long as the temperature is appropriate. The uptake of water by dry seed is called imbibition (imbibition means to drink: seeds imbibe water, you do not imbibe seeds). As seeds imbibe water, they expand and enzymes and food supplies become hydrated. Hydrated enzymes become active and the seed increase its metabolic activities to produce energy for the growth process. In addition, the water causes turgor pressure to increase in the cells and they are able to enlarge.

As you will see in the movies of germinating seeds, the first part of the seedling to emerge from the seed coat is the root (also called the radical). The emergence of the root is typically used as the first indication that a seed is viable. Eventually the shoot will also expand and emerge from the seed.

If germination occurs in darkness, root growth slows after the shoot emerges and shoot elongation accelerates. This behavior increases the chance that the seedling will emerge from soil into the light where it will be able to obtain energy from sunlight by photosynthesis. Once a seedling emerges into the light, the plant undergoes dramatic changes such as turning green and producing leaves. This light-dependent developmental transformation is called photomorphogenesis.