01594nas a2200145   4500008004100000245012300041210006900164260001200233300001400245490000700259520102900266100002001295700001701315856011601332       1990                        eng d00aCarbon uptake characteristics in two high elevation populations of the aquatic CAM plant Isoetes bolanderi (Isoetacae)0 aCarbon uptake characteristics in two high elevation populations   c1990///  a682 - 6880 v773 aIn Isoetes bolanderi, a resident of high elevation lakes in which ambient carbon levels are low and fairly constant throughout the day, CO2 uptake by the leaves generally parallels changes in photosynthetic photon flux density as opposed to changes in ambient CO2 levels. Overnight CO2 uptake by the leaves contributed up to 33% of the total daily carbon assimilation from the water column which is typical of aquatic CAM species but low in comparison to the 30-50% seen in the seasonal pool congener Isoetes howellii. Two additional sources of carbon may supplement the 24-hr period for carbon assimilation conferred by CAM in I. bolanderi: refixation of respiratory CO2 and carbon acquisition from the interstitial sediment water via roots. CAM appears to play a significant role in enhancing carbon gain in I. bolanderi which dominates the littoral flora of Siesta and Ellery Lakes (California) despite higher carbon uptakes rates from the water column found in one associated macrophyte Fontinalis antipyretica. -Authors1 aSandquist, D.R.1 aKeeley, J.E.  uhttp://www.scopus.com/inward/record.url?eid=2-s2.0-0025603812&partnerID=40&md5=5a05f6c1d88f964ca446201241fd044601708nas a2200157   4500008004100000245009200041210006900133260001200202300001400214490000700228520114700235100001701382700001801399700001701417856011601434       1983                        eng d00aDiurnal acid metabolism in Isoetes howellii from a temporary pool and a permanent lake.0 aDiurnal acid metabolism in Isoetes howellii from a temporary poo  c1983///  a854 - 8570 v703 aWater chemistry and titratable acidity and malic acid levels in Isoetes howellii leaves were sampled every 6 hr from plants in a seasonal pool and an oligotrophic lake. Plants in the seasonal pool showed a diurnal fluctuation of approx 300 mu equivalents titratable acidity g-1 fresh wt; daytime deacidification was 75% complete by noon and nighttime acidification was 45% complete by midnight. Late in the season after the pool had dried, emergent leaves showed only a very weak tendency to accumulate acid at night. Plants from the oligotrophic lakes had a diurnal change of approx 100 mu eq g-1 fresh wt, daytime deacidification was only 45% complete by noon but nighttime acidification was 80% complete by midnight. In the seasonal pool there were marked diurnal changes in temperature, pH, oxygen and CO2. Free-CO2 levels were an order of magnitude greater in early morning than in late afternoon. Conditions in the oligotrophic lake showed no marked diurnal fluctuation, though total inorganic carbon levels were extremely low relative to other aquatic systems.-from AuthorsBiology Dept., Occidental College, Los Angeles, CA 90041, USA.1 aKeeley, J.E.1 aMathews, R.P.1 aWalker, C.M.  uhttp://www.scopus.com/inward/record.url?eid=2-s2.0-0020869168&partnerID=40&md5=ba962a51da3936c60f6e19e43512052900696nas a2200133   4500008004100000245008400041210006900125260001200194300001400206490000600220520020300226100001700429856011600446       1983                        eng d00aReport of diurnal acid metabolism in two aquatic Australian species of Isoetes.0 aReport of diurnal acid metabolism in two aquatic Australian spec  c1983///  a203 - 2040 v83 aDiurnal changes in titratable acidity and malic acid levels indicate the presence of CAM in 2 Australian species of Isoetes.-from Author Dept Biology, Occidental College, Los Angeles, CA 90041, USA.1 aKeeley, J.E.  uhttp://www.scopus.com/inward/record.url?eid=2-s2.0-0020869234&partnerID=40&md5=695ac76af5861708b830bc2817010d60