Hypogeal germination (from

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 peri ...

[] 'below ground', from [] 'below' and [] 'earth, ground') is a botanical term indicating that the germination of a plant takes place below the ground. An example of a plant with hypogeal germination is the

pea The pea is most commonly the small spherical seed or the seed-pod of the flowering plant species ''Pisum sativum''. Each pod contains several peas, which can be green or yellow. Botanically, pea pods are fruit, since they contain seeds and d ...

(''Pisum sativum''). The opposite of hypogeal is

epigeal Epigeal, epigean, epigeic and epigeous are biological terms describing an organism's activity above the soil surface. In botany, a seed is described as showing epigeal germination when the cotyledons of the germinating seed expand, throw off the ...

(above-ground germination).

Germination

Hypogeal 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 stay below the ground. 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 ...

(part of the

stem Stem or STEM may refer to: Plant structures * Plant stem, a plant's aboveground axis, made of vascular tissue, off which leaves and flowers hang * Stipe (botany), a stalk to support some other structure * Stipe (mycology), the stem of a mushro ...

above the cotyledon) grows, while 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 send ...

(part of the stem below the cotyledon) remains the same in length. In this way, the epicotyl pushes the

plumule A seedling is a young sporophyte developing out of a plant embryo from a seed. Seedling development starts with germination of the seed. A typical young seedling consists of three main parts: the radicle (embryonic root), the hypocotyl (embr ...

above the ground. Normally, the cotyledon is fleshy, and contains many nutrients that are used for germination. Because the cotyledon stays below the ground, it is much less vulnerable to for example 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 other ...

. The evolutionary strategy is that the plant produces a relatively low number of seeds, but each seed has a bigger chance of surviving. Plants that show hypogeal germination need relatively little in the way of external nutrients to grow, therefore they are more frequent on nutrient-poor soils. The plants also need less sunlight, so they can be found more often in the middle of forests, where there is much competition to reach the sunlight.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 Plants that show hypogeal germination grow relatively slowly, especially in the first phase. In areas that are regularly flooded, they need more time between floodings to develop. On the other hand, they are more resistant when a flooding takes place. After the slower first phase, the plant develops faster than plants that show epigeal germination. It is possible that within the same

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...

one species shows hypogeal germination while another species shows epigeal 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 runner bean (''

Phaseolus coccineus ''Phaseolus coccineus'', known as runner bean, scarlet runner bean, or multiflora bean, is a plant in the legume family, Fabaceae. Another common name is butter bean, which, however, can also refer to the lima bean, a different species. It is ...

'') shows hypogeal germination, whereas 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, alo ...

'') shows epigeal 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 Lilies seed germination is classified as either epigeal or hypogeal. These classifications may be further refined as immediate or delayed. Whether a lily is epigeal or hypogeal may be related to survival strategies developed according to the c ...

*''

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

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

Phanerocotylar vs. cryptocotylar

In 1965, botanist James A. Duke introduced the terms cryptocotylar ("hidden cotyledon") and phanerocotylar ("visible cotyledon") as synonyms for hypogeal and epigeal 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 such as '' Rollinia salicifolia''. 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