You are not currently logged in.
Access JSTOR through your library or other institution:
If You Use a Screen ReaderThis content is available through Read Online (Free) program, which relies on page scans. Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
Isoetes howellii: A Submerged Aquatic Cam Plant?
Jon E. Keeley
American Journal of Botany
Vol. 68, No. 3 (Mar., 1981), pp. 420-424
Published by: Botanical Society of America, Inc.
Stable URL: http://www.jstor.org/stable/2442779
Page Count: 5
You can always find the topics here!Topics: Plants, Carbon dioxide, Crassulacean acid metabolism, Leaves, Biological rhythms, Acidity, Photosynthesis, pH, Stomata, Product labeling
Were these topics helpful?See somethings inaccurate? Let us know!
Select the topics that are inaccurate.
Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
Preview not available
In the leaves (but not corms) of the submerged aquatic plant Isoetes howellii, malic acid concentration fluctuates from 1-3 mg g-1FW in the evening to 7-13 mg g-1FW in the morning. Associated with this is a change in pH (a.m. pH 3-4 vs. p.m. pH 5-6) and titratable acidity (75-200 μ eq g-1FW change in acidity between morning and evening) of the plant extract. 14CO2-fixation experiments indicate that carbon is fixed in both the light and the dark, though the amount of carbon fixed in the light is more than double that fixed in the dark. Autoradiographs show 89% of dark-fixed CO2 ends up in malic acid and the remainder in citric acid, whereas these two acids constitute less than 5% of the light-fixation products. It is suggested that CAM metabolism in this aquatic species may be related to the lower availability of CO2 for photosynthesis during the day than during the night in its aquatic environment.
American Journal of Botany © 1981 Botanical Society of America, Inc.