03152nas a2200229   4500008004100000245017800041210006900219260001200288300001100300490000700311520232500318653001502643653002702658653001602685653002002701653001902721653001802740100001402758700001902772700001502791856011602806       2003                        eng d00aThe use of pulse amplitude modulated fluorometry to determine fine-scale temporal and spatial variation of in situ photosynthetic activity within an Isoetes-dominated canopy0 ause of pulse amplitude modulated fluorometry to determine finesc  c2003///  a1 - 150 v773 aWe used in situ pulse amplitude modulated (PAM) fluorometry to investigate photosynthetic activity of Isoetes alpinus (Kirk) in submerged meadows of Lake Wanaka, New Zealand. We examined diel and depth-related variability in the quantum yield of photosystem II (PSII) under varying ambient light, as well as variability due to self-shading effects within the I. alpinus canopy and inter-leaf differences. We also determined the utility of short-term (minutes) irradiance versus yield estimates in assessing longer-term responses to fluctuating light. Results showed that under natural lighting, PSII yield was highly variable within the plant canopy for a given irradiance incident to that canopy, ranging from 0.02 to 0.80. This variability could be explained by relating PSII yield to irradiance within the canopy measured using a miniature scalar irradiance sensor. For individual plants, yield and irradiance were closely related, and quantitatively similar yield-irradiance (Y-E) curves were obtained for plants from a given depth by experiments using diel, short-term (seconds) and in-canopy irradiance changes. Maximum fluorescence yield consistently averaged 0.55-0.65 and the light saturation parameter (E k(Y)) at 3 m depth ranged from 189 to 247. There were water depth-related differences between mean responses of the I. alpinus canopy; individual leaves from the maximum and minimum growth depths (7 and 3 m) showed ranges of (Ek(J)) of 159-228 and 109-151 μmol m-2 s-1, respectively. Irradiance alone is the dominant determinant of PSII activity in I. alpinus in Lake Wanaka, and accurate description of light within a canopy is a pre-requisite to estimating community photosynthesis. This, combined with a comprehensive assessment of the variability of individual plant responses to irradiance, by depth, may provide a sound basis for modelling community activity. We conclude that, by its ability to obtain fine-scale activity measurements rapidly, and with no enclosure or disturbance effects, PAM fluorometry offers new insights to the activity of specific plants and parts of plants in complex submerged canopies. It remains to be determined, however, whether PAM-determined quantum yield of PSII in these plants can be directly related to carbon fixation. © 2003 Elsevier B.V. All rights reserved.10aIrradiance10aIsoetes alpinus (Kirk)10aLake Wanaka10aPAM fluorometry10aPhotosynthesis10aQuantum yield1 aHawes, I.1 aSutherland, D.1 aHanelt, D.  uhttp://www.scopus.com/inward/record.url?eid=2-s2.0-0041739174&partnerID=40&md5=95dca62193f6e14eb91681e33c00b52d01223nas a2200157   4500008004100000245007300041210006900114260001200183300001400195490000700209520068400216100001700900700001500917700001700932856011600949       2003                        eng d00aA re-evaluation of Isoetes savatieri franchet in Argentina and Chile0 areevaluation of Isoetes savatieri franchet in Argentina and Chil  c2003///  a126 - 1360 v933 aIsoetes suvutieri has traditionally been interpreted as being a uniform aquatic ranging from the southernmost regions of South America to the central Andes of Chile and Argentina. An examination of herbarium material supports the recognition of two taxa, a southern I. savatieri and a more northern I. chubutiana, from central Chile and Argentina. The latter taxon is hexaploid and described here as a new species. The morphology of these species suggest that they are sister species resulting from divergence following a polyploidy event. These species, and several other species pairs, provide the best and, to date, only examples of allopatric divergence in polyploid Isoetes.1 aHickey, R.J.1 aMacluf, C.1 aTaylor, W.C.  uhttp://www.scopus.com/inward/record.url?eid=2-s2.0-0141676348&partnerID=40&md5=323242638fd59ed4fe04b166c7422ad801300nas a2200217   4500008004100000245013400041210006900175260001200244300001400256490000700270520057000277653001500847653001200862653001400874653001700888653001300905100001600918700001400934700001700948856011700965       2003                        eng d00aIsoetes (isoetaceae), Ophioglossum and Botrychium (ophioglossaceae) in Calabria (S Italy): More karyological and taxonomical data0 aIsoetes isoetaceae Ophioglossum and Botrychium ophioglossaceae i  c2003///  a359 - 3630 v563 aI. subinermis (Durieu) Cesca and Peruzzi, from a newly discovered Calabrian stand, was karyologically studied. Both chromosome number (2n = 22) and karyotype are presented. Systematic distinctiveness of I. subinermis from I. histrix Bory is confirmed. A new chromosome complement (2n = 44) is recorded for I. duriei Bory, confirming the karyological variability of this taxon. Ophioglossum lusitanicum L. (n = 120) and Botrychium lunaria L. (2n = 90) were karyologically studied too. Their chromosome numbers are reported as the first counts on Italian populations.10aBotrychium10aIsoetes10aKaryology10aOphioglossum10ataxonomy1 aPeruzzi, L.1 aCesca, G.1 aPuntillo, D.  uhttp://www.scopus.com/inward/record.url?eid=2-s2.0-77949731523&partnerID=40&md5=40e99c3e1ecb2fbbe5af20ec7f01717700948nas a2200145   4500008004100000245008000041210007100121260001200192300001400204490000700218520042800225100001700653700001600670856011600686       2003                        eng d00aIsoëtes tennesseensis (Isoëtaceae), an Octoploid Quillwort from Tennessee0 aIsoëtes tennesseensis Isoëtaceae an Octoploid Quillwort from Ten  c2003///  a184 - 1900 v933 aIsoëtes tennesseensis, an octoploid species with a chromosome count of 2n = 88, is described. It occurs in the Hiwassee River in Tennessee. Past collections of this species have been misidentified as Isoëtes macrospora (= I. lacustris). Isoëtes tennesseensis differs from I. lacustris in chromosome number, megaspore and microspore morphology and distribution. Speculation on the origin of this new species is presented.1 aLuebke, N.T.1 aBudke, J.M.  uhttp://www.scopus.com/inward/record.url?eid=2-s2.0-0242507449&partnerID=40&md5=5d391ab9dc24130eb1ab9970d4a6dcf301566nas a2200169   4500008004100000245013100041210006900172260001200241300001400253490000700267520094200274100001501216700001601231700001601247700001701263856011601280       2003                        eng d00aRelationship between Water Chemistry and the Distribution of the Endangered Aquatic Quillwort Isoetes sinensis Palmer in China0 aRelationship between Water Chemistry and the Distribution of the  c2003///  a361 - 3670 v183 aThe progressive decline in populations of Isoetes sinensis Palmer in China has been attributed to deteriorating water quality; however, no data have been adduced to support this assumption. In this study we identified locations in China that presently have populations of I. sinensis and locations where the species has been extirpated. We measured various water chemistry parameters at these sites, as well as at similar sites within the distribution range of I. sinensis but from where the species has never been recorded. The results indicate that distribution and occurrence of I. sinensis are closely correlated with water chemistry. Water samples drawn from habitats from where I. sinensis has been extirpated had higher concentrations of heavy metal ions, particularly chromium VI (Cr 6+). In addition, these samples consistently yielded higher readings for dissolved carbon dioxide, water hardness, and concentration of nitrates.1 aWen, M.-Z.1 aPang, X.-A.1 aWang, Q.-F.1 aTaylor, W.C.  uhttp://www.scopus.com/inward/record.url?eid=2-s2.0-0242275988&partnerID=40&md5=c81ad2c1833c6a70e17163c958e43e50