[pbs] what is the opposite of contractile?
Jane McGary
janemcgary at earthlink.net
Wed Sep 19 13:54:28 EDT 2007
Max asked about Drimia maritima and its tendency to rise to the surface.
Possibly bulbs that "push" themselves out of the soil evolved in situations
of highly mobile soils, such as dunes or repeatedly flooded zones, and this
strategy keeps the bulb at an optimal level where it will not be buried too
deeply and have to expend too much stored energy extending its leaves and
scape to the increasingly distant surface.
This would apply to Drimia maritima in one of its habitats, coastal dunes,
but it also grows in rocky situations that appear quite stable. Because
sheep and goats don't eat it, it probably has spread into habitats that
would have been occupied by other plants before human activity changed the
environment.
Other geophytes found in very mobile situations, such as riverbanks and
scree, often reproduce vegetatively by stolons or very elongated bulbs
(e.g., certain riparian Lilium species).
Jane McGary
Northwestern Oregon, USA
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