Byrophyte definition

Bob Makinson rom at ANBG.GOV.AU
Fri Sep 23 12:49:56 CDT 1994


Marc Kodak wrote:

>>Can anyone offer up a definition of byrophyte?



A Byrophyte (correctly Birophyte) is a member of a group of plant
identified by Ladislav Biro (1875-1957) as having a particular system
of photosynthesis involving phytochrome pigments usually in blue or
red wavelengths but also with green, purple, and even black
(all-absorbtive) variants.  Some advanced taxa can actually rotate
between these pigmentation systems.  The plant body is generally
tubular.

 The life-cycle is also peculiar:  for one thing, the operculum of
 the mature propagule dehisces unpredictably (leading to partial or
 total dessication of the fruit (itself called a Biro).  The mode of
 dispersal of propagules and mature organisms is closely adapted to
 human vectors; motility between favoured secluded sites (pockets,
 behind desks, in drawers, etc) is enhanced by intermittent human
 use.

There has been some debate over whether the Biro is threatened with
extinction due to ecological and ergonomic changes that may lead to a
paperless office environment, reducing the need for and possibilities
of the human mediation of biro reproduction and dispersal.  Data from
those human communities which have progressed furthest along this
adaptive pathway however seem to indicate that the paperless office
is a purely theoretical construct and is unlikely to eventuate as an
evolutionary fact.  The general niche-space of birophytes seems
secure.


Bob Makinson
Collections Manager
Australian National Herbarium
rom at anbg.gov.au


Sorry.  The serious answer is that the group of plants known as
BRYOPHYTES is a paraphyletic assemblage made up of three separate
groups:  mosses, hornworts, and liverworts (or hepatics).  The groups
are not particularly closely related in evolutionary terms, but share
certain significant anatomical, reproductive, and ecological
features; they also lack other features characteristic of more
"advanced" (vascular) plants, and the lineages that gave rise to the
bryophyte groups are therefore all assumed to be fairly basal within
the phylogeny of green plants.

Common features of the three groups include:
- dependence of motile sperm on presence of free water as a medium
for moving to the egg, which is housed inside a structure termed an
archegonium;
- common elements to the structure of both archgonia and the male
reproductive structures (antheridia);
- gametophyte generation plants develop filamentous rhizoids (root
analogues, except that they play a mechanical anchoring role only and
do not as far as I know ever absorb water or nutrients).

Differences include:
-Stomata: present in hornworts and mosses, absent in liverworts;
- Water-conducting tisues:  present in mosses, usually lacking in
liverworts, lacking in hornworts.

In summary, the term defines a non-natural assemblage of these three
taxa (in much the same way that "Gymnosperm" is a non-natural term of
convenience covering the distinct groups of cycads, conifers, ginkgo,
and Gnetophytes).


Bob Makinson




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