Photosynthesis of an epiphytic resurrection fern Davallia angustata (Wall .ex Hook. & Grev.)

Abstract

Davallia (Pachypleuria) angustata (Wall. ex Hook. & Grev.) is a common epiphytic fern that grows on tree trucks and palm trees in south-east Asia. The plant is a resurrection plant, capable of rapid recovery from desiccation, but is not a CAM plant like some other epiphytic ferns. Under well-watered conditions Davallia shows a diurnal cycle of photosynthesis with maxima in mid-morning ~0900 hours (solar time). Under optimum conditions, the optimum irradiance (Eopt) = 879.3 ± 65.31 μmol photons m–2 s–1 or ~45% of full sunlight qualifying it as a sun plant. The maximum photosynthetic electron transport rate (ETRmax) was 77.77 ± 3.423 μmol e– m–2 s–1 or, on a Chl a basis 350 ± 36.0 μmol g–1 (Chl a) s–1. The photosynthetic efficiency (α0) is α0 = 0.2404 ± 0.02076 e– photon–1 or 1.082 ± 0.137 e– photon m2 g–1 (Chl a). Eopt and maximum photosynthesis (ETRmax) are directly proportional to one another (y = mx, r = 0.8813, P < <0.001). The slope of the line is the average photosynthetic efficiency at optimum irradiance (ETRmax/Eopt or αEopt = 0.07505 ± 0.00262 e– photon–1), equivalent to a mean asymptotic photosynthetic efficiency (α0) of 0.2040 ± 0.00712 e– photon–1. This simple relationship between ETRmax and Eopt does not appear to have been noted before. There is some accumulation of titratable acid in the morning but no accumulation of organic acids at night. Davallia is not a CAM plant. A simple pulse amplitude modulation (PAM) protocol shows that Davallia is a homiochlorophyllous resurrection plant.