This article needs additional citations for
verification. (March 2011) |
Hypogeal, hypogean, hypogeic and hypogeous ( lit. 'underground'; from Ancient Greek ὑπό (hupó) 'under', and γῆ (gê) '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.