An ecophysiological study of the fern Onoclea sensibilis growing in three environmental locations varying in incident light intensity

Onoclea sensibilis L. plants growing in three locations with varying light intensities (dense shade, partial shade, and open sun) at a temperate site in Palisades, New York, were studied to assess net photosynthesis rate, dark respiration rate, leaf micromorphology, and leaf fluorescence in relation to these light conditions. The mean maximum net photosynthesis rate (3.6 µmoles CO? m?² s?¹) was highest for leaves sampled from the open sun location, compared to lower rates for leaves from partial and dense shade (3.0 and 2.5 µmol CO? m?² s?¹, respectively). Mean stomatal densities (stomata cm?²) were higher in leaves from the open sun and partial shade locations (5,661 and 5,252, respectively) compared to leaves from the dense shade location (2,777). Mean stomatal size was approximately the same for O. sensibilis leaves across the three locations, measuring around 40 to 45 µm in length and 24 to 26 µm in width. A specific leaf area (SLA) was highest in leaves from dense shade (641) and lower in leaves from partial shade and open sun locations (429 and 354, respectively). Overall, the data indicate that O. sensibilis can survive across a broad range of light intensities in this temperate location.   Key words: Chlorophyll concentration, dark respiration, leaf micromorphology, photosynthesis rate, specific leaf area, varying light intensities.