01708nas 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=ba962a51da3936c60f6e19e43512052901055nas a2200145   4500008004100000245007600041210006900117260001200186300001600198490000700214520054100221100001300762700001800775856011600793       1983                        eng d00aSpore morphology and taxonomy of Isoetes in northeastern North America.0 aSpore morphology and taxonomy of Isoetes in northeastern North A  c1983///  a3140 - 31630 v613 aTaxonomy of Isoetes largely rests on megaspore and microspore wall ornamentation and spore size. These characters are reevaluated and the range of their variability is described (SEM photographs). Eight species of Isoetes are recognized for NE North America: I. macrospora, I. hieroglyphica, I. tuckermanii, I. riparia, I. acadiensis, I. echinospora, I. eatonii and I. engelmannii. Each species is provided with a revised list of synonyms, description, ecological notes and distribution maps. A key to species is provided. -from Authors1 aKott, L.1 aBritton, D.M.  uhttp://www.scopus.com/inward/record.url?eid=2-s2.0-0020901416&partnerID=40&md5=1639339936055b4de2712b81625e249700696nas 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