PARENT SESSION
Oral Session 10: Physiology I: Temperature, Light, and Growth.
Presiding: C Knight
Monday, August 2, 8:00 AM to 11:30 AM, Meeting Room C 123.
How does leaf shape relate to temperature? A study of leaves in the Proteaceae.
Leigh, Andrea*,1, Nicotra, Adrienne1, 1 Australian National University, Canberra, ACT, Australia
ABSTRACT- While general patterns regarding leaf size have been demonstrated, little is known about why plants should have such a wide range of leaf shapes. Theories predict that temperature regulation plays a role in leaf shape evolution. The rate and extent of convective heat loss decreases with increasing size. Thus, we might expect lobed leaves to cool more efficiently than entire leaves of equivalent area. Although predictive and single-species studies exist, the relationship between leaf shape and temperature is yet to be tested in a rigorous, comparative manner. We are investigating the functional significance of leaf shape in the Proteaceae, a Gondwanan plant family containing species adapted to a range of habitats and climates. We studied 64 species from 10 tribes in the Proteaceae at the Mt Annan Botanic Gardens, NSW. Species were selected to represent a wide range of leaf shapes and sizes. For each species, we measured temperature range within a leaf, temperature difference between the leaf and ambient air, water content, leaf mass per unit area, length and width. Shape complexity was assessed via two methods: dissection index and fractal dimension. Leaf size was found to be a strong predictor of leaf temperature range. Leaf temperature range increased with leaf shape complexity only as leaves became larger, suggesting that small leaves and deeply lobed leaves serve a similar function with respect to heat transfer.
Key words: leaf size, leaf shape, proteaceae, temperature