Niklas, Karl J. , Cobb, Edward D. .
The Ontogenetic Shift Hypothesis and Diminishing Returns of Specific Leaf Area of Acer rubrum L.
Increases in lamina surface area generally fail to keep pace with increasing lamina mass among conspecifics differing in size as well as interspecifically across diverse plant groups (e.g., angiosperms and ferns). Although diminishing returns in specific leaf area (area/mass) has important implications to harvesting light versus lamina carbon costs, a mechanistic explanation for this phenomenon remains elusive. One possible mechanism is posited by the ontogenetic shift hypothesis, i.e., the number of leaves (or entire shoots) differing in allometry changes with increasing plant size. This hypothesis was examined for Red Maple short and long shoots. Compared to long shoots, short shoot leaf area increases less rapidly with increasing leaf mass; the specific leaf area of short shoot leaves is significantly smaller than those of long shoot leaves; short shoots and their leaves rapidly outnumber long shoots and their leaves in the crowns of progressively larger plants; and short shoots occupy the periphery of tree crowns. The ontogenetic shifts evident within shoot types and within whole plants account for the diminishing returns in total specific leaf area, which is argued to reflect adaptive concessions required by the hydraulic, mechanical, and photosynthetic functions of “sun” and “shade” leaves.
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1 - Cornell University, Department of Plant Biology, Ithaca, New York, 14853, (USA)
2 - Cornell University, Department of Plant Biology, 228 Plant Science Building, Ithaca, New York, 14853-5908, USA
specific leaf area.
Presentation Type: Oral Paper:Papers for BSA Sections
Location: Alpine B/Snowbird Center
Date: Tuesday, July 28th, 2009
Time: 8:30 AM