01396nas a2200133   4500008004100000245009500041210006900136260001200205300001400217490000800231520089300239100001401132856011601146       1997                        eng d00aPlant size and fertility of Isoetes lacustris L. in 20 lakes of Scandinavia: A field study0 aPlant size and fertility of Isoetes lacustris L in 20 lakes of S  c1997///  a171 - 1850 v1393 aA relationship between the individual size and fertility of Isoetes lacustris in the habitat centres of different lakes was found. The maximum (mean) rosette size was 202.2 cm2 and the maximum (mean) number of macrospores in a sporangium was 113.4; the minimum (mean) values were 13.8 cm2 and 30.6 spores. Further correlations between vitality and fertility parameters were established. It is suggested that the main ecological factors responsible for the differences found in the lakes are effects of climate (including water temperature and duration of seasonal growth), which cause the differences in rosette size and fertility. The percentage of individuals with fertile sporangia was lowest in the slightly humic lakes with boreal climate and short summers, and highest in the clear lakes with temperate climate and long summers. Isoetes individuals showed increased size with depth.1 aVöge, M.  uhttp://www.scopus.com/inward/record.url?eid=2-s2.0-0343052607&partnerID=40&md5=3be747f4cb73f24bc9d8880018c16bd101895nas a2200133   4500008004100000245013500041210006900176260001200245300001400257490000800271520135200279100001401631856011601645       1997                        eng d00aNumber of leaves per rosette and fertility characters of the quillwort (Isoetes lacustris L.) in 50 lakes of Europe: A field study0 aNumber of leaves per rosette and fertility characters of the qui  c1997///  a415 - 4310 v1393 aIsoetes lacustris L. was studied in 35 lakes in the main area of distribution (N and W Europe), plus some other lakes outside of this area, where the species is present. By using SCUBA equipment fertile plants were selected randomly and several morphological and fertility characters were studied. It was found that there was a relationship between: a) the (mean) number of leaves per rosette, and the (mean) number of spores per macrosporangium, b) the number of leaves, and the number of macrosporangia per plant. The number of spores per macrosporangium is related directly to the percentage of fertile plants in the part of the population studied. A low number of leaves per rosette is a fair indication of a low number of macrospores in a sporangium and also a low number of macrosporangia per plant, anti the low number of spores points to a low percentage of fertile individuals in the part of the population studied. It is suggested that the often rapid decline of quillwort in lakes of Central Europe may be a self-accelerating process. In the N European lakes, numbers of leaves and spores have an inverse relationship to the colour of the water. In the W European lake sites, the height of the rosettes is correlated to the Secchi depth. No relationship between plant features and water characteristics (pH and conductivity) were found.1 aVöge, M.  uhttp://www.scopus.com/inward/record.url?eid=2-s2.0-0342617829&partnerID=40&md5=e5b61ab9a7b00c72dbe6bce9554fbc2f01786nas a2200229   4500008004100000245008300041210006900124260001200193300001400205490000700219520106000226653001201286653001701298653001501315653002201330653001601352653002301368653002101391653001301412100001401425856011701439       2004                        eng d00aNon-destructive assessing and monitoring of populations of Isoetes lacustris L0 aNondestructive assessing and monitoring of populations of Isoete  c2004///  a147 - 1530 v343 aExtensive studies of Isoetes lacustris, performed throughout Europe, resulted in regressions between the number of leaves per rosette and (1) the number of spores per megasporangium, (2) length of seasonal growth, (3) Secchi depth and (4) water colour plus a relationship between pH and the number of spores per megasporangium. The evaluation of Isoetes populations requires measurements of the lake data Secchi depth, water colour, pH and conductivity, the establishment of climate data and leaf counts on 20-30 plants with the aid of SCUBA. The method may be applied to lakes in a range of situations, varying between lowland and highland, and between temperate and subarctic climate regions. The regressions are displayed graphically. The actual mean leaf number and corresponding megaspore number are compared with the numbers referred to in the environmental data. Consistent values point to the parameters which influence growth and vitality of the quillwort and to what extent, in a particular lake. Examples of evaluation and monitoring are given.10aClimate10aConductivity10aEvaluation10aIsoetes lacustris10aLeaf number10aLight availability10aMegaspore number10apH value1 aVöge, M.  uhttp://www.scopus.com/inward/record.url?eid=2-s2.0-17944391690&partnerID=40&md5=bc81c2908849af47d9ff68a2cff5dbc902100nas a2200193   4500008004100000245010300041210006900144260001200213300001400225490000700239520143200246653001201678653002201690653002701712653002401739653001201763100001401775856011701789       2006                        eng d00aThe reproductive phenology of Isoetes lacustris L.: Results of field studies in Scandinavian lakes0 areproductive phenology of Isoetes lacustris L Results of field s  c2006///  a228 - 2330 v363 aThe phenologic change of the leaf rosette structure of Isoetes lacustris L. was studied in 26 lakes of temperate, boreal, or subarctic Scandinavia between 59° and 70° n.l. The investigations were carried out during six defined seasons: late winter, spring, early summer, late summer, autumn, and early winter. From 640 plants, gained with the aid of SCUBA, six leaf types were distinguished: immature megasporophylls, mature megasporophylls, immature microsporophylls, mature microsporophylls, and sporophylls that had released their spores and leaves with undeveloped sporangia. Mean numbers per rosette of each leaf type were established in each study lake and study season, resulting in a common pattern embracing all lakes studied. Megasporophylls are developed throughout the year, whenever the water temperature is about 10 °C. Their share was always more than 30%, excepting winter. Microsporophylls are produced preferentially in spring/early summer when the days are longest; they amount to more than 50% of the rosette leaves during this period, but only to some 10% in the remaining seasons. The spores mature and are released between late summer and early winter. It is concluded that not all spores mature in the year of their birth, and those that do not mature are released in the early summer of the following year, as well as the old empty leaves become detached. © 2006 Elsevier GmbH. All rights reserved.10aClimate10aIsoetes lacustris10aReproductive phenology10aRosette development10aSeasons1 aVöge, M.  uhttp://www.scopus.com/inward/record.url?eid=2-s2.0-33750991320&partnerID=40&md5=43e430d0fc4386c8148a6682853d96ab