A preliminary survey for crassulacean acid metabolism (CAM) in submerged aquatic macrophytes in New Zealand

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Abstract
This preliminary survey covered 13 aquatic macrophytes present at two sites in Lake Taupo and two sites in the Auckland region (northern half of the North Island, New Zealand). Three species previously unrecorded as CAM plants, Isoetes kirkii A. Braun, Lilaeopsis lacustris Hill, and Vallisneria spiralis Graeb., exhibited diurnal fluctuations in titratable acidity and malic acid content. The changes in titratable acidity varied seasonally from 97 (Dec. 1985) to 46 (June 1986) microequivalents per gram fresh weight for I. kirkii, and from 40 to 23 and 51 to 26 microequivalents per gram fresh weight for L. lacustris and V. spiralis, respectively. The absence of CAM both in other members of the low mixed community and in other hydrocharitacean species at the same sites suggests that CAM can not be unequivocally regarded as conferring an ecological advantage to a species.