02241nas a2200121   4500008004100000245008400041210007000125300001200195490000700207520185600214100000502070856004402075       2014                        eng d00aThe effect of temperature on the phenology of germination of Isoëtes lacustris0 aeffect of temperature on the phenology of germination of Isoëtes  a279-2920 v863 a<p>Iso&euml;tes lacustris (quillwort) is an aquatic macrophyte commonly dominating oligotrophic softwater lakes in Europe. Reproductive ecology of a relic population of quillwort based on spore germination was studied in an acidified mountain lake in the Czech Republic. In a four-year experiment, we recorded temperature-related temporal changes in micro- and macrospore germination and sporeling establishment in (i) natural in situ conditions in Čern&eacute; jezero lake and (ii) in the laboratory at various temperatures. Germination of both micro- and macrospores increased gradually over four consecutive growth seasons. Several annual cohorts of germinating macrospores born together in a sporangium indicate that spores remain viable for up to several years and the formation of a spore bank. Minimum temperature necessary for germination was lower for microspores (6 &deg;C) than macrospores (12 &deg;C) and this ensured the availability of spermatozoids for the fertilization of the long-living macrogamethophytes whenever they produced archegonia during growing season(s). Macrogametophyte development started between July and October and sporeling development always followed in the next or subsequent springs. Long germination and embryo development may limit reproduction in I. lacustris by making it sensitive to both episodic and chronic changes in the environment. The relatively high minimum temperature for macrospore germination may set general limits for the reproduction of I. lacustris in lakes, by constraining its distribution along latitudinal and altitudinal gradients, and to particular depths. The mean length of time when the temperature ( 12 &deg;C) was high enough for the germination of I. lacustris in Čern&eacute; jezero lake was 119 days and occurred during the period June to September in 2004&ndash;2011.</p>
1 a  uhttps://isoetes.myspecies.info/node/20402262nas a2200253   4500008004100000245009400041210006900135260001200204300001400216490000700230520146900237653001801706653001501724653002501739653001401764653001301778653001701791653001401808100002501822700001301847700001601860700001501876856011701891       2009                        eng d00aEffects of aluminium toxicity and low pH on the early development of isoëtes echinospora0 aEffects of aluminium toxicity and low pH on the early developmen  c2009///  a135 - 1490 v813 aA relict population of Isoëtes echinospora Durieu survived a thirty-year period of severe acidification and high concentrations of phytotoxic aluminium (Al) in Plešné Lake (Bohemian Forest, Czech Republic). The population consisted of only adult plants. Sporeling survival and age structure were examined during the population recovery in 2004-2008. Laboratory experiments were conducted to assess the effect of various pH values (4-8) and Al concentrations (0-1000 μgl -1) on sporeling development. The responses of the sporelings to the experimental treatments were evaluated and compared with those observed in the lake. The experiments showed that an Al concentration higher than 300 μgl- 1 , and high acidity (pH 4), inhibit sporeling growth, in particular resulted in a pronounced reduction in absorptive organs (macrogametophyte rhizoids, roots and root hairs). With increasing concentrations of Al and at pH 4, the ratio of the below-ground to above-ground sporeling biomass decreased to less than 1. The responses of the lake sporelings, rooting in the upper sediment layer, were similar to those exposed to 100-300 μgl -1 of Al in the laboratory, and reflected the Al toxicity of the lake water. The quillworts at Plešné Lake survived because adult plants can tolerate these adverse conditions and are very long-lived. The population recovered when the pH of the water increased to over 5 and the Al concentration decreased to below 300 μgl- 1 .10aAcidification10aDemography10aIsoëtes echinospora10aQuillwort10aRecovery10aReproduction10aSporeling1 atvrtlíková, M., Č1 aVrba, J.1 aZnachor, P.1 aHekera, P.  uhttp://www.scopus.com/inward/record.url?eid=2-s2.0-68249099192&partnerID=40&md5=9b6556ca288bc4b4849c6e259815eaca02378nas a2200169   4500008004100000245008300041210007000124260001200194300001400206490000700220520179500227100002502022700001602047700001502063700001302078856011702091       2012                        eng d00aEffects of temperature on the phenology of germination of Isoëtes echinospora0 aEffects of temperature on the phenology of germination of Isoëte  c2012///  a141 - 1530 v843 aIsoëtes echinospora, a submerged aquatic quillwort, is native in northern latitudes and a rare glacial relict in mountain lakes in temperate Central Europe. A relic population of this quillwort in the Plešné jezero lake has recovered recently from a 30-year period of failure to reproduce caused by acidification. Early ontogenetic stages of the quillwort are considered to be the most vulnerable to environmental changes. Therefore, the objective of this study was to investigate the phenology of germination of I. echinospora. In a two-year experiment, we examined the time course of germination of micro- and macrospores and establishment of sporelings under (i) natural in situ conditions in the Plešné jezero lake and (ii) at various temperatures (6-17 °C) in the laboratory. We developed a mathematical model that describes the temperature-specific temporal changes in the early ontogeny of I. echinospora. Our experiments clearly show that spores do not germinate at once but gradually over time if exposed to favourable temperatures. Generally, percentage germination tended to increase during the course of a season under most temperature regimes but was inhibited at the lowest temperature. With increasing temperature, microspores germinated earlier and more successfully than macrospores, as described by the model. Sporelings also developed faster at the higher temperature. However, the highest temperature used in the experiments (17 °C) desynchronized the phenology of germination in I. echinospora as it resulted in the two types of spore not being available for fertilization at the same time. Thus, climate change might affect interactions between temperature and the phenology of quillwort reproduction and threaten the survival of this species in Central Europe.1 atvrtlíková, M., Č1 aZnachor, P.1 aNedoma, J.1 aVrba, J.  uhttp://www.scopus.com/inward/record.url?eid=2-s2.0-84856654849&partnerID=40&md5=8703fe17900e64b794da47ec2c7950fe