Pasquet Kok, Jessica , Creese, Chris , Sack, Lawren .
Turning over a new “leaf”: multiple functional significances of leaves versus phyllodes in Hawaiian Acacia koa.
Hawaiian endemic tree Acacia koa is a model for heteroblasty with bipinnately compound leaves and phyllodes. Previous studies suggested three hypotheses for their functional differentiation: an advantage of leaves for early growth or shade tolerance, and an advantage of phyllodes for drought tolerance. We tested the ability of these hypotheses to explain differences between leaf types for potted plants in 107 physiological and morphological leaf traits, including gas exchange, structure and composition, hydraulic conductance, responses to varying light, intercellular CO2, vapor pressure deficit (VPD) and drought. Leaf types were notably similar in numerous traits including total stomatal pore area per leaf area, gas exchange rates per area and their responses to light and VPD, and cuticular conductance. However, each hypothesis was directly supported by key differences in function. Leaves had higher mass-based rates of gas exchange, while the water storage tissue in phyllodes contributed to greater capacitance per area; phyllodes also had higher leaf hydraulic conductance per area, with stronger decline during desiccation and recovery with rehydration. The three hypotheses together explained 89% of trait differences between leaf types. These findings indicate that the heteroblasty confers multiple benefits, realized across different developmental stages and environmental contexts.
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1 - University of California, Los Angeles, Department of Ecology and Evolutionary Biology, 621 Charles E. Young Drive South, Los Angeles, CA, 90095, USA
2 - University of California Los Angeles, Ecology and Evolutionary Biology, 621 Charles E. Young Drive South, Box 951606, Los Angeles, CA, 90095-1606, United States
3 - University of California, Los Angeles, Ecology and Evolutionary Biology, 621 Charles E. Young Drive, Los Angeles, CA, 90095, USA
Presentation Type: Oral Paper:Papers for Topics
Location: 551B/Convention Center
Date: Tuesday, August 3rd, 2010
Time: 10:45 AM