New Zealand Journal of Botany abstracts

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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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