Bear Oak (Quercus ilicifolia Wang.) presents a unique architecture in which there is a distinct outer set of leaves on the perimeter of the bush and another set of leaves on the inside. In this paper we examine the relationship between plant architecture, leaf-level physiology, and leaf damage patterns by insects. We measured net photosynthesis, stomatal conductance, and leaf water potential in response to different levels of herbivory or leaf-rolling in both outer- and inner-canopy leaves. Leaf-rolling occurred naturally and was mimicked by hand-rolling leaves to different degrees. Net photosynthesis, stomatal conductance, and leaf water potential varied depending upon a combination of leaf position in the crown and degree of rolling, but not herbivory. Outer-canopy leaves had significantly higher rates of net photosynthesis and stomatal conductance, but lower leaf water potentials and leaf areas than inner-canopy leaves. Leaf rolling had an effect upon photosynthesis and stomatal conductance, which varied depending on whether projected areas of rolled leaves or projected areas of the leaves after they had been unrolled were considered. In both canopy layers, using unrolled projected leaf areas, stomatal conductance and net photosynthesis decreased with increasing leaf rolling. In the outer canopy, using projected areas of rolled leaves, photosynthesis decreased while stomatal conductance increased with increasing leaf rolling. In the inner canopy, photosynthesis increased while stomatal conductance was unchanged with increasing leaf rolling. In all cases, leaf water potential increased with increasing leaf rolling. These results suggest (in order of likelihood) that either rolling creates an area of closed stomata (stomatal patchiness) proportional to the amount of rolling, or leaf specific hydraulic conductance increases, or stomata are responding to changes in the boundary layer of the leaf.
|Number of pages||14|
|State||Published - 1 Jan 2004|