Developmental and Structural Section
Mocko, Kerri .
Leaf-stem allometric relationships across diverse growth forms of Pelargonium (Geraniaceae).
While leaf-stem allometric relationships have been documented for a variety of perennial species, most of these studies have focused on shrubs and trees. The South African plant genus Pelargonium varies tremendously in growth form, ranging from geophytes and stem succulents to shrubs, which presents a unique opportunity to investigate shifts in leaf-stem allometric relationships that have accompanied the evolution of different growth forms. The nearly 280 species of the genus Pelargonium comprise five major clades based on karyological diversity, growth forms, and habitat. There is also strong support for further resolution of the xerophytic clade into two subclades. Leaf-stem allometry was measured on a total of 89 greenhouse grown plants of 45 species sampled from all six clades. A common allometric slope was found for relationships between individual leaf area and stem cross-sectional area among all clades, but clades differed in slope elevation. The elevational shifts observed were consistent with an interpretation of evolution in an arid environment, as the xerophytic clades had smaller areas of individual leaves per cross-sectional stem area than sister clades. There were no differences among these clades in allometric scaling between specific leaf area (SLA) and stem cross sectional area, however, again, slopes differed in elevation. This finding suggests that both SLA and leaf area scale proportionately with stem diameter among a wide diversity of growth forms.
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1 - University of Connecticut, Ecology and Evolutionary Biology, 36 Hampden Road
, Stafford Springs, CT, 06076, USA
specific leaf area
Presentation Type: Oral Paper:Papers for Sections
Location: PDR 2/Hilton
Date: Monday, July 9th, 2007
Time: 9:15 AM