02100nas 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