A Comparison of Water Potential and Mechanical Strength of Tip and Base Leaves in Heteromeles arbutifolia

Heteromeles arbutifolia, commonly known as, Hollywood, is a plant that is extremely common in the California Chaparral ecosystem. It was observed that with Hollywood, the leaves grow on the tips of the branches predominantly. However, there are leaves that grow on the base of the branches that appear to be equally as healthy. The purpose of this investigation was to determine whether the leaves that grow at the tips of the branches or at the base of the branches were better suited to benefit the rest of the plant. Our hypothesis was that the leaves at the tips of the branches would be better suited to benefit the rest of the plant due to their better access to sunlight, as the rest of the plant does not overshadow them. We determined which leaves would be better suited to benefit the plant by measuring the water potential and mechanical strength of leaves at the tip and bases of branches on Heteromeles arbutifolia plants across the street from the Pepperdine cross. Samples were collected from Heteromeles arbutifolia specimens that were both in the sun and in the shade. After the results were compared, the plants in the sun showed that leaves at the base were mechanically stronger than those at the tip, while plants in the shade showed leaves at the tip were mechanically stronger. As for water potential, base leaves had higher water potential across the board