New Zealand Journal of Botany abstracts
Facing the furious fifties: the contractile stem of the subantarctic megaherb Pleurophyllum hookeri
C. L. Briggs*
P. M. Selkirk
Department of Biological Sciences
Macquarie University
Sydney, NSW 2109, Australia
D. M. Bergstrom†
Australian Antarctic Division
203 Channel Highway
Kingston, Tasmania 7150, Australia
*Present address: School of Science,
Food and Horticulture, University of Western Sydney, Locked Bag 1797,
Penrith South DC, NSW, Australia.
† Author for correspondence.
Abstract On the cool, moist, extremely windy
subantarctic islands, vegetation is treeless and megaherbs, tussock
grasses, and cushion plants are the dominant plant growth forms. In
world terms the subantarctic environment is an unusual one, and
megaherbs are unusual plants which have some unusual anatomical
features. On Macquarie Island the megaherb Pleurophyllum hookeri has
a vertical contractile stem, largely underground, which maintains the
plant’s rosette of large leaves close to the ground surface. Stem
contraction is associated with reduction in cell volume and increase in
wall thickness of pith cells, and greater contraction of inner cortical
than outer cortical cells. The network of vascular tissue adjusts to
the dimensions of the contracted stem without disruption but the outer
surface of the stem becomes wrinkled. We believe this to be the first
record and description of permanent contraction of extensive stem
tissue in an angiosperm.
Keywords Pleurophyllum hookeri; contractile stem; megaherb; subantarctic; stem anatomy
B05043; Received 23 September 2005; accepted 22 February 2006; Online publication date 2 May 2006
New Zealand Journal of Botany, 2006, Vol. 44: 187–197
0028–825X/06/4402–0187 © The Royal Society of New Zealand 2006
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