title: Dark CO2-fixation and diurnal malic acid fluctuations in the submerged-aquatic Isoetes storkii.
abstract: In the leaves (but not corms) of the submerged aquatic Isoetes storkii malic acid concentration fluctuated from 22 μeg g FW-1in the evening to 171 μeg g FW-1in the morning. Associated with this was a change in titratable acidity of 152 μeg g FW-1between morning and evening.14C carbon was fixed in both the light and the dark, though the amount of carbon fixed in the light was more than that fixed in the dark. Autoradiographs show 88% of14CO2fixed in the dark is recovered after 1 h, in malic acid and the remainder in one other unidentified product, whereas these two products contain less than 15% of the14C fixed after 1 h exposure to14CO2in the light. It is suggested that CAM metabolism in this aquatic species may be related to the low availability of CO2for photosynthesis during the day in its aquatic environment and that this metabolic pathway may prove common in the genus Isoetes.
authors.affiliation: Department of Biology, Occidental College, 90041, Los Angeles, USA.
authors.forename: J
authors.initials: J
authors.lastname: Keeley
authors.affiliation: Department of Biology, Occidental College, 90041, Los Angeles, USA.
authors.forename: B
authors.initials: B
authors.lastname: Morton
authors.affiliation: Department of Biology, Occidental College, 90041, Los Angeles, USA.
authors.forename: B
authors.initials: B
authors.lastname: Babcock
authors.affiliation: Department of Biology, Occidental College, 90041, Los Angeles, USA.
authors.forename: P
authors.initials: P
authors.lastname: Castillo
authors.affiliation: Department of Biology, Occidental College, 90041, Los Angeles, USA.
authors.forename: B
authors.initials: B
authors.lastname: Fish
authors.affiliation: Department of Biology, Occidental College, 90041, Los Angeles, USA.
authors.forename: E
authors.initials: E
authors.lastname: Jerauld
authors.affiliation: Department of Biology, Occidental College, 90041, Los Angeles, USA.
authors.forename: B
authors.initials: B
authors.lastname: Johnson
authors.affiliation: Department of Biology, Occidental College, 90041, Los Angeles, USA.
authors.forename: L
authors.initials: L
authors.lastname: Landre
authors.affiliation: Department of Biology, Occidental College, 90041, Los Angeles, USA.
authors.forename: H
authors.initials: H
authors.lastname: Lum
authors.affiliation: Department of Biology, Occidental College, 90041, Los Angeles, USA.
authors.forename: C
authors.initials: C
authors.lastname: Miller
authors.affiliation: Department of Biology, Occidental College, 90041, Los Angeles, USA.
authors.forename: A
authors.initials: A
authors.lastname: Parker
authors.affiliation: Department of Biology, Occidental College, 90041, Los Angeles, USA.
authors.forename: G
authors.initials: G
authors.lastname: Van Steenwyk