Epigeal germination (

Ancient Greek Ancient Greek includes the forms of the Greek language used in ancient Greece and the ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following periods: Mycenaean Greek (), Dark Ages (), the Archaic pe ...

[] 'above ground', from [] 'on' and [] 'earth, ground') is a Glossary of botanical terms, botanical term indicating that the germination of a plant takes place above the ground. An example of a plant with epigeal germination is the common bean (''

Phaseolus vulgaris ''Phaseolus vulgaris'', the common bean, is a herbaceous annual plant grown worldwide for its edible dry seeds or green, unripe pods. Its leaf is also occasionally used as a vegetable and the straw as fodder. Its botanical classification, ...

''). The opposite of epigeal is

hypogeal Hypogeal, hypogean, hypogeic and hypogeous (; ) are biological terms describing an organism's activity below the soil surface. In botany, a seed is described as showing hypogeal germination when the cotyledons of the germinating seed remai ...

(underground germination). , Epi: Above + Geo: Earth , +

Epigeal germination

Epigeal germination implies that the

cotyledon A cotyledon (; ; ; , gen. (), ) is a significant part of the embryo within the seed of a plant, and is defined as "the embryonic leaf in seed-bearing plants, one or more of which are the first to appear from a germinating seed." The numb ...

s are pushed above ground. The

hypocotyl The hypocotyl (short for "hypocotyledonous stem", meaning "below seed leaf") is the stem of a germinating seedling, found below the cotyledons (seed leaves) and above the radicle ( root). Eudicots As the plant embryo grows at germination, it ...

elongates while the

epicotyl An epicotyl is important for the beginning stages of a plant's life. It is the region of a seedling stem above the stalks of the seed leaves of an embryo plant. It grows rapidly, showing hypogeal germination, and extends the stem above the soil surf ...

remains the same in length. In this way, the hypocotyl pushes the cotyledon upward. Normally, the cotyledon itself contains very little nutrients in plants that show this kind of germination. Instead, the first leaflets are already folded up inside it, and

photosynthesis Photosynthesis is a process used by plants and other organisms to convert light energy into chemical energy that, through cellular respiration, can later be released to fuel the organism's activities. Some of this chemical energy is stored in ...

starts to take place in it rather quickly.Parolin, P., Ferreira, L.V., Junk, W.J. (2003
"Germination characteristics and establishment of trees from central Amazonian flood plains"
''Tropical Ecology'' 44(2): 157-169 Because the cotyledon is positioned above the ground it is much more vulnerable to damage like night-frost or

grazing In agriculture, grazing is a method of animal husbandry whereby domestic livestock are allowed outdoors to roam around and consume wild vegetations in order to convert the otherwise indigestible (by human gut) cellulose within grass and ot ...

. The evolutionary strategy is that the plant produces a large number of seeds, of which statistically a number survive. Plants that show epigeal germination need external nutrients rather quickly in order to develop, so they are more frequent on nutrient-rich soils. The plants also need relatively more sunlight for photosynthesis to take place. Therefore they can be found more often in the field, at the border of forests, or as pioneer species. Plants that show epigeal germination grow relatively fast, especially in the first phase when the leaflets unfold. Because of this, they occur frequently in areas that experience regular flooding, for example at the river borders in the Amazon region. The fast germination enables the plant to develop before the next flooding takes place. After the faster first phase, the plant develops more slowly than plants that show hypogeal germination. It is possible that within the same

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nom ...

one species shows epigeal germination while another species shows hypogeal germination. Some genera in which this happens are: *''

Phaseolus ''Phaseolus'' (bean, wild bean) is a genus of herbaceous to woody annual and perennial vines in the family Fabaceae containing about 70 plant species, all native to the Americas, primarily Mesoamerica. It is one of the most economically importan ...

'': the common bean (''

'') shows epigeal germination, whereas the runner bean ('' Phaseolus coccineus'') shows hypogeal germination *''

Lilium ''Lilium'' () is a genus of herbaceous flowering plants growing from bulbs, all with large prominent flowers. They are the true lilies. Lilies are a group of flowering plants which are important in culture and literature in much of the world. M ...

'': see Lily seed germination types *''

Araucaria ''Araucaria'' (; original pronunciation: .ɾawˈka. ɾja is a genus of evergreen coniferous trees in the family Araucariaceae. There are 20 extant species in New Caledonia (where 14 species are endemic, see New Caledonian ''Araucaria ...

'': species in the section ''Eutacta'' show epigeal germination, whereas species in the section ''Araucaria'' show hypogeal germination

Phanerocotylar vs. cryptocotylar

In 1965, botanist

James A. Duke James A. Duke (4 April 1929 – 10 December 2017) was an American botanist. He was the author of numerous publications on botanical medicine, including the '' CRC Handbook of Medicinal Herbs''. He was well known for his 1997 bestseller, ''The Gree ...

introduced the terms phanerocotylar and cryptocotylar as synonyms for epigeal and hypogeal respectively, because he didn't consider these terms etymologically correct. Later, it was discovered that there are rare cases of species where the germination is epigeal and cryptocotylar. Therefore, divisions have been proposed that take both factors into account.Garwood, N.C. (1996) "Functional morphology of tropical tree seedlings", in: ''The ecology of tropical forest tree seedlings'', pp. 59-129. New York: Swaine

References

{{Reflist Plant reproduction