Dark CO2-fixation and diurnal malic acid fluctuations in the submerged-aquatic Isoetes storkii

Jon E. Keeley; B. Morton; B. Babcock; P. Castillo; B. Fish; E. Jerauld; B. Johnson; L. Landre; H. Lum; C. Miller; A. Parker; G. Van Steenwyk

doi:10.1007/bf00346490

USGS · 1007518

Dark CO2-fixation and diurnal malic acid fluctuations in the submerged-aquatic Isoetes storkii

Jon E. Keeley·B. Morton·B. Babcock·P. Castillo·B. Fish·E. Jerauld·B. Johnson·L. Landre·H. Lum·C. Miller·A. Parker·G. Van Steenwyk

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Abstract

In the leaves (but not corms) of the submerged aquatic Isoetes storkii malic acid concentration fluctuated from 22 μeg g FW -1 in the evening to 171 μeg g FW -1 in the morning. Associated with this was a change in titratable acidity of 152 μeg g FW -1 between morning and evening. 14 C 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% of 14 CO 2 fixed 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 the 14 C fixed after 1 h exposure to 14 CO 2 in the light. It is suggested that CAM metabolism in this aquatic species may be related to the low availability of CO 2 for photosynthesis during the day in its aquatic environment and that this metabolic pathway may prove common in the genus Isoetes .

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Jon E. Keeley, B. Morton, B. Babcock, P. Castillo, B. Fish, E. Jerauld, B. Johnson, L. Landre, H. Lum, C. Miller, A. Parker, G. Van Steenwyk. 1981. Dark CO2-fixation and diurnal malic acid fluctuations in the submerged-aquatic Isoetes storkii. https://doi.org/10.1007/bf00346490

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