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Hypogeal, hypogean, hypogeic and hypogeous ( lit.'underground'; from Ancient Greek ὑπό (hupó) 'under', and γῆ () 'earth') [1] 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 remain non-photosynthetic, inside the seed shell, and below ground. [2] The converse, where the cotyledons expand, throw off the seed shell and become photosynthetic above the ground, is epigeal germination.

In water purification works, the hypogeal (or Schmutzdecke) layer is a biological film just below the surface of slow sand filters. It contains microorganisms that remove bacteria and trap contaminant particles.

The terms hypogean and hypogeic are used for fossorial ( burrowing) and troglobitic (or stygobitic) cave-living organisms. The opposite terms are epigean and epigeic.

The term hypogeous is used for fungi with underground fruiting bodies - for example, truffles. The opposite term is epigeous.

References

  1. ^ "hypogeal". Merriam-Webster.com Dictionary.
  2. ^ Adrian D. Bell; Alan Bryan (2008). Plant Form: An Illustrated Guide to Flowering Plant Morphology. Timber Press. p. 200. ISBN  978-0-88192-850-1.