germination


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germination

 [jer″mĭ-na´shun]
the sprouting of a seed, spore, or plant embryo.
Germinationclick for a larger image
Fig. 171 Germination . A typical seedling.

germination

the beginning of the growth of a seed, spore or other structure that is dormant. Seed DORMANCY can be broken by several factors, depending on the species:
  1. the removal of a germination inhibitor which can be leached out by water.
  2. a period of cold temperature (STRATIFICATION).
  3. exposure to the correct wavelength of light to stimulate PHYTOCHROMES in the seed, for example, lettuce seeds require red light for germination and are inhibited by far-red light.
  4. rupture of a thick testa by (i) microbial breakdown, (ii) abrasive action of soil (as in desert plants), (iii) heat from bush fires, (iv) the effect of digestive juices (as when eaten by birds), (v) the softening action of water. Once dormancy is broken a regular sequence of events takes place: water is imbibed which hydrates the tissues increasing enzymic action in the ALEURONE layer (when present), a process aided by the release of GIBBERELLIN from the embryo; food stores are mobilized by production of enzymes in the ENDOSPERM or within the COTYLEDONS; AUXINS and CYTOKININS are formed which promote cell division and enlargement, causing the embryo to grow and burst through the testa. See Fig. 171 .

There are two main types of germination, depending on whether the seed cotyledons are carried above the soil (EPIGEAL) or remain below ground (HYPOGEAL).

References in periodicals archive ?
Hypocotyl length (HL, in cm) and primary root length (RL, in cm) was measured in ten normal seedlings randomly obtained after count of the total germination (14th day) using meter scale.
After ageing treatments, standard germination test was performed at 25+-1AdegC in dark condition for 10 days.
The main control mechanism of germination is the hormonal balance between Abscisic acid (ABA) and Gibberellins (GA).
According to Marcos Filho (2005), water is one of the main factors infuencing germination, since it is involved directly and indirectly in all stages, besidesreactivating metabolism.
dunnii seeds, Cetnarski Filho & Carvalho (2009) concluded that the substrates sand or paper and temperature of 20 [degrees]C provided the most favorable conditions for the germination test.
The germination processes occurring in different locations in the understory of an ecosystem may be reflected in different patterns, depending on species' responses to such variables as temperature, light, humidity, among others (Bewley, 1997).
To analyze the germination, farmers should get some
To analyse the germination, farmers should get some seeds and keep them dipped in water for two to four hours.
Germination trials were carried out in 100 mm x 15 mm plastic petri dishes lined with Whatman filter paper (Grade 1) saturated in approximately 7 ml of test NaCl solution.
Treating or priming the seeds with small amounts of nutrients before sowing has been shown to partially overcome nutrient immobilisation problem in soils and to increase nutrient use efficiency (Miraj et al., 2013) as well as ameliorated germination and plant vigour.