Abstract Detail

Paleobotany

Wagner, Jennifer [1], Kouwenberg, Lenny [2].

Light induced changes in leaf shape and epidermal cells in three Quercus species and Platanus occidentalis.

Plants are adapted to the physical conditions of the environments they live in, including temperature, precipitation, atmospheric CO₂ concentrations, and light level. In cooler and drier habitats, leaves tend to be smaller with condensed venation and toothed margins. While under warmer and wetter conditions, leaves tend to be larger, have ‘drip tips’, and entire margins. Atmospheric CO₂ concentration and light regulate leaf size, stomatal patterns, and cell shape in developing leaves. These characteristics are preserved in the plant fossil record—for instance in cuticles, the decay-resistant waxy layer that envelops leaves—and can be used to infer local conditions at the time the plants were alive. This kind of information can be used to better understand Earth’s history, the evolution of ecosystems, and to help predict the effects of global warming. In 2008, an experiment was conducted to study how differences in light level affect leaf size, shape, stomatal and epidermal cell patterning, and other leaf traits. This experiment used growth chambers to maintain controlled settings for growth of Quercus chrysolepis, Quercus kelloggii, Quercus robur, and Platanus occidentalis. For each of the four species, five plants were grown under high light levels and another five plants were grown under low light levels. The growth chambers controlled for water availability, CO₂ levels, low and high light levels, temperature, and day length. The data being collected are leaf length, leaf width, petiole width, smallest polygon area, leaf area, leaf mass per area (LMA), number of teeth, number of major secondary veins, undulation index (UI), stomatal density (SD), stomatal index (SI), cell area, stomatal characteristics (including guard-cell width, guard-cell length, and pore length), and isotope composition (δ¹³C, δ¹⁵N). Preliminary results suggest higher LMA, lower UI, and higher SD values for all species grown under higher light levels. Other trait values varied among the different species, with P. occidentalis having the most plastic response and Q. kelloggii the most conserved. Understanding the response of leaf morphology to light level intensity will help paleobotanists refine proxies that use leaf and cellular morphology from fossil angiosperm leaves to estimate things like canopy structure, mean annual temperature, mean annual precipitation, and CO₂ reconstructions.

1 - University of California Berkeley, Integrative Biology, Valley Life Sciences Building #3140, Berkeley, CA, 94720-3140
2 - Department Of Geology, 1400 South Lake Shore Drive, Chicago, IL, 60605, United States

Keywords:
leaf mass per area
Epidermal morphology
cell morphology
light regulation
stomtal index
undulation index.

Presentation Type: Oral Paper
Number: PB2007
Abstract ID:964
Candidate for Awards:Isabel Cookson Award,Maynard F. Moseley Award