Abstract

Onoclea sensibilis L. is a temperate fern species of horticultural importance, and widely distributed in the natural environment of North America, Eastern Europe, and parts of Asia. With increasing climate change, including excessive heat and unpredictable, sometimes severe precipitation events, ferns such as O. sensibilis may come under increasing loss of habitat and possibly survival threat. This is a study of the photophysiology and dark respiration in O. sensibilis growing on the cliffs overlooking the Hudson River in Palisades New York, United States of America (USA), with documentation of changes it incurred after severe heat and drought-like conditions ensued following a moderate spring season. After the extreme summer events, photosynthesis and respiration rates declined, but leaf fluorescence analyses indicated no major change in quantum yield of photosystem II or electron transport per reaction center, suggesting that O. sensibilis may have survival strategies to succeed if climate change is not too severe. Data are also presented on the photosynthesis rate in relation to variations in light intensity expressed as photosynthetic active radiation (PAR) from 20 to 100 µmol photons m^-2 s^-1, and the results are discussed in relation to prior published findings.

Key words: Habitat loss, leaf chlorophyll fluorescence analysis, physiological ecology, plant conservation, plant ecology.