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In situ Studies of Crassulacean Acid Metobolism in Drymoglossum piloselloides, an Epiphytic Fern of the Humid Tropics
Authors:KLUGE  M; FRIEMERT  V; ONG  B L; BRULFERT  J; GOH  C J
Abstract:This paper reports autecological field-studies in Singaporeon Drymoglossum piloselloides (L.) Presl., an epiphytic fernof the humid tropics which is capable of performing Crassulaceanacid metabolism (CAM). As indicated by the gas exchange patternsand by the occurrence of a diurnal malic acid rhythm, the plantalso features CAM in situ at its natural sites. Both in well-wateredand in naturally droughted plants external CO2 was taken upsolely during the night. Water stress decreased nocturnal CO2uptake,but left the synthesis and storage of malic acid unaffected.This indicates that CO2 recycling of respiratory CO2 by CAMis ecophysiologically important at the high night temperaturestypical of the tropical habitats of the fern. The plants showeda diel fluctuation of cell-sap osmotic pressure which paralleledthat of malic acid, while the fluctuation of the xylem tensionfollowed the curve of transpiration more closely than it followedthat of the malic acid content. CAM in D. piloselloides wasclearly not limited by natural access to mineral ions and nitrogen.It is concluded that the ecophysiological advantage of CAM forD. piloselloides lies in a better water use efficiency as comparedwith C3 ferns and in the salvaging of carbon by CO2 recycling. Key words: CAM, epiphytic ferns, gas exchange, water relations
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