Available online at www.sciencedirect.com Environmental and Experimental Botany 63 (2008) 28–38 Phenology and autumnal accumulation of N reserves in belowground organs of wetland helophytes Phragmites australis and Glyceria maxima affected by nutrient surplus Edita Tylov´ a a,∗ , Lenka Steinbachov´ a a , Olga Votrubov´ a a , V´ ıt Gloser b a Department of Plant Physiology, Faculty of Science, Charles University in Prague, Viniˇ cn´ a 5, 128 44 Prague 2, Czech Republic b Department of Plant Physiology and Anatomy, Faculty of Science, Masaryk University, Kotl´ aˇ rsk´ a 2, 611 37 Brno, Czech Republic Received 6 November 2006; received in revised form 9 August 2007; accepted 6 October 2007 Abstract Two co-occurring dominant wetland helophytes and potential competitors, Phragmites australis and Glyceria maxima, were cultivated under N, P availabilities simulating the trophic status of wetlands with different fertility (oligo- and eutrophic). The long-term outdoor cultivation was performed with the goal to characterise the extent to which the nutrient enrichment affects plant growth, phenology, and particularly, the accumulation of N storage compounds in belowground organs of wetland rhizomatous plants prior to the onset of winter dormancy. In the present study, both species responded similarly to nutrient surplus. The enhanced growth, delayed shoot senescence, and delayed retranslocation of N into belowground organs were found in both species in eutrophic treatment. Furthermore, N levels remaining in dry leaves were proportionally related to those in living ones, being significantly higher in eutrophic treatment. The efficiency of N retranslocation from senescing leaves varied around 60% in both species and treatments. The formation of N reserves was, however, not disrupted in either species. Although plants in eutrophic treatments accumulated N in their belowground organs significantly later in the season (in the September–December period), the amount of accumulated N was sufficient to reach high belowground N standing stock. Considering formation of N reserves, the differences in species response to treatments were negligible. Phragmites and Glyceria accumulated similar belowground N standing stock prior to the winter. Glyceria may, however, additionally profit from N standing stock of over-wintering green leaves and from the potential of growth and N assimilation during a mild winter period, which is not possible in fully dormant Phragmites. © 2007 Elsevier B.V. All rights reserved. Keywords: Phragmites; Glyceria; Eutrophication; Wetlands; Phenology; Reserve formation; Rhizome; Free amino acids; Retranslocation; Storages 1. Introduction Wetlands, habitats serving irreplaceable ecological func- tions, are constantly exposed to anthropogenic pressures and undergo changes in species occurrence worldwide. Even dom- inant species are affected; common reed (Phragmites australis (Cav.) Trin. ex Steudel) declined in many European water bod- ies during the last decades (for summary see e.g. Ostendorp, 1989; Van der Putten, 1997; Brix, 1999). Although the indirect effects of eutrophication (litter accumulation and phytotoxic- ity of its degradation products) are apparently main reasons of reed die-back (Brix, 1999), direct impacts of nutrient enrich- ∗ Corresponding author. Tel.: +420 22195 1697; fax: +420 22195 1704. E-mail address: edmunz@natur.cuni.cz (E. Tylov´ a). ment on plant phenology and storage formation are also causes of die-back ( ˇ C´ ıˇ zkov´ a-Konˇ calov´ a et al., 1992; K¨ uhl and Kohl, 1993; Woitke et al., 1997). In perennial helophytes, the amount of reserves in belowground organs is one of the critical factors that determines the success of over-wintering, spring outgrowth and affects plant susceptibility to different stresses, e.g. floods or mechanical disturbances ( ˇ C´ ıˇ zkov´ a-Konˇ calov´ a et al., 1992). Several studies dealing with Phragmites showed thinned C reserves in eutrophic habitats (Kub´ ın et al., 1994; ˇ C´ ıˇ zkov´ a et al., 1996, 2001), caused by the decrease of actual carbo- hydrate levels in response to N surplus ( ˇ C´ ıˇ zkov´ a-Konˇ calov´ a et al., 1996; Kohl et al., 1998), as well as by the delayed autumnal translocation to belowground organs (Kohl et al., 1998). Similarly to C reserves, the delayed translocation of N rich compounds into rhizomes was observed in unstable Phragmites 0098-8472/$ – see front matter © 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.envexpbot.2007.10.011