Jim McNamara j_mcnamara at envworld.com
Thu Aug 29 14:14:38 EST 1996

Anne Gillen wrote:
> Perry d'Obrenan (perry_dobrenan at darwin.biochem.ualberta.ca) wrote:
> : Can anyone tell me what causes a dwarf plant to remain in dwarf form?  For
> : example, a Nest Spruce?
> I do not know about Nest Spruce but it is common for dwarfing to be
> caused by a mutation in genes involved in giberellin synthesis.
> Giberellin is a plant hormone that among other things causes elongation
> of internodes.  I have been told that this mutation occurs spontaneouly
> and rather frequently in certain evergreen trees and is responsible for
> the "witches broom"  at the top of some trees.

Nanistic plants can also occur because on environmental conditions.
Pinus serotina growing in the poor soils of the New Jersey 
Pine Barrens seldom grow taller than about 6 feet.  Elsewhere seeds
from these dwarf pines will grow into more normal specimens.
It has been suggested that there is a problem in the soils
there - things like aluminum toxicity perhaps.  Switch grass,
Panicum virgatum, also grows "short" in one environment
and tall in another.  There are lots of studies showing 
species will grow short up in the alpine tundra, and tall 
down in the valley meadows, due to differing environmental
responses -- sometimes called phenotypic plasticity.

jim mcnamara csi santa fe nm

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