Define Epigeal and Hypogeal GERMINATION

Jim McKenney
Mon, 04 Jan 2010 17:30:36 PST
Jim Shields wrote: “As Jim McK. defined "epigeal germination" and "hypogeal
germination" -- where the seed germinates rather than how -- the terms are
trivial and almost meaningless,”


I’ll agree, Jim, that the terms might seem trivial to some people; but
meaningless they are not. They mean exactly what they say, and in doing so
they violate one of our usual assumptions about words, namely that they do
not mean what they literally say. That’s why we usually observe a
distinction between the denotation and the connotation of a word. That’s why
we often have pairs of words in English, one derived from the Latin and one
derived from the Greek, whose etymology seems to suggest a similar meaning,
but whose usage is another matter altogether; consider the words innocence
(Latin) and ignorance (Greek). 


To someone speaking literally, the word combination “hypogeal germination”
does not mean the same thing it does to someone speaking in any of the
several contexts in which that word combination has specialized meanings. 


I was not trying to “define” these terms; I was simply trying to get to the
source of your uncertainties. 


You went on to write: “They persist in the literature of plant physiology;
and in horticulture and plant physiology, the terms clearly are not intended
to have a trivial meaning, so what do they mean?” I think Tim has already
pointed to the answer here: there is a bit of ellipsis involved here. If you
read the old accounts of the usage of the terms epigeal and hypogeal in the
lily literature, these terms refer to the position of the cotyledon shortly
after germination. Those lilies which produce a cotyledon which appears
above ground (typically with the seed coat dangling from it) are said to
have epigeal germination. Sorry, I didn’t make that up. The term does not
mean, literally, that the germination is epigeal. It simply means that the
germination process produces a cotyledon above ground. 


In the same way, those lilies whose process of germination keeps the
cotyledon underground are said to have hypogeal germination. In this case,
the term hypogeal germination is literally true. But all lilies are capable
of hypogeal germination in the literal sense, but not in the specialized


Lily growers add another qualification: the time of the initiation of the
germination process. They distinguish between lilies which germinate
immediately (or within a period of weeks) and are said to have immediate
germination, and those whose germination is delayed and are said to have
(surprise!) delayed germination. 


Since the position of the seed when it germinates (i.e. if it is above
ground or below ground) is not taken into consideration (in spite of the
terminology), that leaves the four categories mentioned in my earlier post
(immediate epigeal, delayed epigeal, immediate hypogeal and delayed
hypogeal). Here are examples: immediate epigeal – most lilies, in particular
most trumpets, most Asiatic hybrids; delayed epigeal – several uncommonly
grown lilies such as Lilium pomponium and the members of the genus
Cardiocrinum, long considered lilies; immediate hypogeal – Lilium dauricum
and L. philadelphicum; and delayed hypogeal – Lilium speciosum, L. auratum
and their hybrids, most of the North American lilies, Lilium martagon and
its relatives. 


Within each group, when large lots of seed are sown plants which do not
conform to the expected pattern sometimes occur. 


With respect to the uses of the terms epigeal and hypogeal in lilies, those
concepts did not originate with McRae. They have been in common use among
lily growers for over a half century. I’ll bet the terms originated with


Also (sorry to be so nit-picky) when you wrote “while the hypogeal lilies
produce the first leaf only after a period of cold dormancy, so in the
second season of growth”, that’s not quite true. Lilies which show hypogeal
germination are of two types, called delayed hypogeal germinators and
immediate hypogeal germinators. The former is the larger group, and only a
few lilies (such as L. dauricum and L. philadelphicum) show immediate
hypogeal germination. I’m going into detail here because those lilies which
show immediate hypogeal germination produce their first leaves almost
immediately and do not require a cold period for leaf production. 



John Gyer was on to something when he coined the words skotomorphogenesis
(ouch! Where are the orthography police when you need them?) and
photomorphogenesis. I’m skeptical of the utility of these terms because they
are, in effect, red herrings. The presence or absence of light is not what
this phenomenon is all about. So-called skotomorphogenesis is an adaptation
to winter conditions: it allows plants to take advantage of a much longer
growing season and to have ready a much developed embryonic plant by the
time clement growing conditions return. If I’m understanding the term
correctly, it’s common in many plants which are native to areas with severe
winters. Plants as diverse as oaks and blood root show this phenomenon. 


The initial growth observed in some plants which typically germinate in the
dark and the initial growth observed in some plants which typically
germinate  in the light are probably driven by the same factors in both
cases, namely  by food reserves in the seed. In both cases, photosynthesis
comes to play a part later.  The “morphogenesis” observed during the
earliest phases of germination is not in a fundamental sense caused by
either dark or light.


If you germinate bean seeds on a piece of wet towel in full light, and
germinate another lot of bean seeds planted an inch deep in soil, you get
roughly the same results: the seeds grow into bean plants. It’s tempting to
say that the bean seeds which germinated in light are an example of
photomorphogenesis. But does that mean that the bean seeds which germinated
in the dark are exhibiting  skotomorphogenesis until they emerge into the


This topic is growing nicely, isn’t it? 


Jim McKenney

Montgomery County, Maryland, USA, 39.03871º North, 77.09829º West, USDA zone

My Virtual Maryland Garden



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