Variability of leaf chlorophyll content in a population of sassafras

We measured leaf chlorophyll content from leaf discs of known area and mass for 820 leaves from eight trees of Sassafras albidum (Nutt.) Nees., growing along the floodplain of the Bronx River, New York. Sassafras displays leaves in a few discrete categories of form. Leaves with entire margins predominate at the proximal and distal nodes of shoots while lobed leaves are most common at the intermediate nodes. In regression analysis for individual trees, leaf nodal position accounted for 30-50% of the variance in chlorophyll content. Leaves of the intermediate nodes 6 through 11 (ca. 46% of all leaves) accounted for 59.3% of total leaf surface area and had the highest chlorophyll content per unit mass and per unit area. Leaf chlorophyll content was statistically significantly greater in shade leaves in 6 of the 8 trees on a per unit mass basis, and lower in shade leaves in 5 of the 8 trees on a per unit area basis. However, there were no significant differences in chlorophyll content with leaf shape in leaves from sun or shade positions. There were also no statistically significant differences in leaf chlorophyll content among trees. These results suggest that leaves of the intermediate nodes possess the greatest capacity to harvest photosynthetically active radiation.