Hypogeal germination (from Ancient Greek [] '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 (''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 th ...

(above-ground germination).

Germination

Hypogeal germination implies that the cotyledons stay below the ground. The epicotyl (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 (part of the stem below the cotyledon) remains the same in length. In this way, the epicotyl pushes the plumule 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 living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial n ...

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 import ...

'': the runner bean ('' Phaseolus coccineus'') shows hypogeal germination, whereas the common bean ('' Phaseolus vulgaris'') 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 *'' Araucaria'': 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 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 Green ...

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 ''Rollinia'' is a genus of plants in the family Annonaceae. While it is widely recognised as a distinct genus a monograph published in 2006 advocates its inclusion in ''Annona'',Rainer, H. (2006)Monographic studies in the genus ''Annona'' L. (A ...

''. 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