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

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.

Biochemical and biophysical CO2 concentrating mechanisms in two species of freshwater macrophyte within the genus Ottelia (Hydrocharitaceae)

“…The report here of CAM in O. alismoides at low CO 2 contrasts with the data from (Webb et al 1988) where a diel change of only 7 μequiv g -1 FW…”

“…Diel changes in acid contents in other Hydrocharitaceae such as species from the genera Egeria, Elodea and Lagarosiphon are relatively low (Keeley 1998;Webb et al 1988). Earlier studies reported fixation of 14 C into C 4 acids in species of freshwater Hydrocharitaceae within the genera: Egeria, Elodea and Lagarosiphon (Brown et al 1974;Browse et al 1977;Degroote and Kennedy 1977;Salvucci and Bowes 1983) and also in the marine Halophila (Beer 1989) although there is little evidence for turnover in pulse-chase experiments.…”

“…Vallisneria americana and V. spiralis (Clade B) show evidence for CAM with diel changes in acidity of up to 42 and 51 μequiv g -1 FW respectively (Keeley 1998;Webb et al 1988). …”

Light effects on Crassulacean acid metabolism in the submerged aquatic plantIsoetes kirkiiA. Braun

“…It has a rosette of quill-like leaves arising from a conn/ root system and exhibits diurnal acid fluctuations only in the green parts of the "quills" (Webb et al 1988). At the study site, Three Mile Bay, Lake Taupo (38°45'S, 175°50'E), it exists in a well-established, shallow-water (1.0-2.5 m) low mixed community (Brown 1975), often in nearly monospecific stands.…”

“…Crassulacean acid metabolism (CAM), with its marked diel fluctuations in malic acid content, has been reported in several submerged aquatic plant species (Keeley 1981(Keeley ,1982Keeley & Morton 1982;Boston & Adams 1983;Richardson et al 1984;Webb et al 1988;Morton & Keeley 1990;Gacia & Penuelas 1991;Keeley & Sandquist 1991). The magnitudes of the diel fluctuations are influenced by several environmental factors (e.g., photosynthetically active radiation (PAR), temperature, CO2).…”