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 ?
Despite the fact that the pericarp may not influence the dicarpic seed germination (Souza Filho and Takaki, 2011), there are species in which different mechanical constrains are imposed by the pericarp (Imbert, 2002).
In vitro seed germination and explants preparation: In preliminary studies, seeds were germinated in Petri dishes lined with filter paper under the laboratory condition (22-25 0C).
In the present study, the low exposure time of the seeds to the blender together with the protection of the blades may have contributed to avoid possible damage to seed germination; however, the exposure time seems to be the most important when using this technique.
Seed germination in untreated soil was superior to that in acid-leached soil, revealing that the phytotoxic effect of acid leaching is more serious than that of heavy metals.
First experiment: The germination responses from two seed lots harvested in 2011 and 2012 were evaluated to discriminate the samples with better percentages of seed germination. The experimental design was completely randomized with six replications, and every germination box was an experimental unit.
For germination, seeds was put into the dish in the artificial climate incubator, and light intensity was 1 500 LX for 12 h/day until the end of seed germination. Under the dark condition for seed germination was set: the dish with wrapping black paper put in the dark and constant temperature environment for sprouting, repeated for three times according to the above conditions.
Results prove that rate of seed germination and seedling emergences are higher for magnetized water than the normal water (Figs.
For the salinity treatments (Figure 1), seed germination showed three effects of increasing salinity in the germination medium.
Previous field studies have shown that the rate of natural seed germination is very low and natural recruitment through seed is rare under natural conditions (Yang, 2009).
Results with respect to the effect of different concentrations of extracts on seed germination performance were measured in terms of growth.