Abstract
The relationships between light environment and photosynthesis were studied in two understory herbs growing in a deciduous forest in Hillsdale, Michigan. The purpose of this study was to better understand how understory plants differentially utilize available sunlight based on their light environment. Specifically, photosynthetic capacity and responsiveness to sunflecks were compared between herbs growing in different light environments within a single forest. The species studied were Trillium grandiflorum and Podophyllum peltatum (mayapple). The approximate contribution of sunflecks to the total daily light in the understory was measured at several locations in the forest. To quantify light environment, the average light intensity in PPFD (photosynthetic photon flux density) experienced by each plant was measured. Carboxylation capacity (Amax) was also measured on trillium and mayapples. To compare the relative responsiveness to sunflecks, induction time and lightfleck use efficiency (LUE) were measured on trillium. Plants grown under higher average light intensities were expected to have higher Amax, longer induction times, and lower LUE. No significant relationships were found between Amax, induction time, or LUE and light intensity. The trillium had a mean Amax of 3.91 μmol/m2s and the mayapples had a mean Amax of 5.69 μmol/m2s corroborating previous research on photosynthesis in these species.