Author's personal copy Environmental and Experimental Botany 77 (2012) 283–287 Contents lists available at SciVerse ScienceDirect Environmental and Experimental Botany journa l h omepa g e: www.elsevier.com/locate/envexpbot Silicon availability changes structural carbon ratio and phenol content of grasses Jörg Schaller ∗ , Carsten Brackhage, E. Gert Dudel Institute of General Ecology and Environmental Protection, University of Technology Dresden, PF 1117, 01737 Tharandt, Germany a r t i c l e i n f o Article history: Received 23 February 2011 Received in revised form 11 November 2011 Accepted 10 December 2011 Keywords: Cellulose Lignin Macrophytes Poaceae Secondary metabolism Silica a b s t r a c t Silicon is not an essential element in sensu stricto but affects the productivity of Poaceae. Recent field stud- ies has shown the effect of silicon on cellulose and lignin content in bulk analyses of green compartments of different species, sampled before matter translocation in the course of senescence. Nevertheless, there is a gap in information about silicon availability and its effect on cellulose, lignin and phenol content in different plant tissues after nutrient resorption. In order to prove the effect of controlled silica supply on functional relevant carbon compounds Phrag- mites australis Trin. was grown in pot trials under three different levels of silicon surplus. After resorption of nutrients into rhizomes the content of silicon, lignin, cellulose and phenol were measured in different plant tissues. The results show that different levels of silicon surplus changed the plant cellulose, lignin and phenol content depending on plant tissue function. Cellulose content in tissues with stabilization function is reduced contrasting enhanced cellulose content in tissues without stabilization function. Furthermore, higher silicon surplus decreased the phenol content in photosynthetic active tissues and increased the phenol content in culm. Only weak silicon to lignin interaction was found. It is concluded that silicon affects the cellulose and phenol metabolism and the tradeoff between pro- ductivity and stabilization/defense. Considering these compounds as crucial factors in decay processes, silicon may be very important for the terrestrial and semi-terrestrial carbon turnover © 2011 Published by Elsevier B.V. 1. Introduction Silica rich grasses dominate a relevant share of terrestrial and semiterrestrial ecosystems. Littoral zones, inland water and estu- aries are very productive due to the abundance of macrophytes. Macrophytes contribute crucially to lake metabolism (Gessner et al., 1996) by forming a quantitatively important part of organic matter. The decay of litter from plant material (macrophytes) depends mainly on elemental stoichiometry (C:N:P) and their lignin, cellulose and phenol content (Taylor et al., 1989; Fioretto et al., 2005; Hättenschwiler and Jorgensen, 2010). Silicon is a ubiq- uitous element and existing in sediments and soils. It was shown that silicon has positive effects on biomass production in plants like Poaceae (Eneji et al., 2008). Furthermore, silicon is beneficial in pathogen resistance (Fawe et al., 1998), drought resistance (Ma, 2004), pest resistance (Lanning, 1966; Cookson et al., 2007) and metal tolerance (Liang et al., 2007). The uptake and transport of sil- icon by Poaceae can take place within a few minutes (Casey et al., 2004) and is under metabolic control(Tamai and Ma, 2003; Ma et al., ∗ Corresponding author. Tel.: +49 351 463 31375; fax: +49 351 463 31399. E-mail address: Schaller@forst.tu-dresden.de (J. Schaller). 2006; Rains et al., 2006). Silicon may be immobilized as plant opals (phytoliths) in cell walls (Sangster, 1970; Epstein, 1999). Silicon could be an energetically cheap alternative (Raven, 1983) to the energetically expensive structural compounds like cellulose and lignin (Jung et al., 1999). Hence silicon may change the ratios of plant compounds like cellulose and lignin. As a result of this change, the decomposition of Poaceae litter may have an important impact on silicon and carbon cycling in freshwater ecosystems (Conley, 2002; Struyf et al., 2007). Schoelynck et al. (2010) found an antago- nistic correlation between biogenic silicon content (BSi) and lignin and cellulose from bulk field samples of the whole plant of differ- ent species (aquatic and wetland plants) from an area in Biebrza National Park (Poland). In contrast nothing is known about the effect of defined silicon availability on lignin, cellulose and phe- nol content in different plant tissues, especially for macrophytes. Phragmites australis, one of the most abundant wetland macro- phytes in the world, is long described as highly productive (Allen and Pearsall, 1963; Gessner et al., 1996) and represents a main type of macrophytes. The working hypothesis for this investigation is therefore that silicon alters the lignin, phenol and cellulose content in different tissues of P. australis. This was tested with different amounts of silicon surplus in an experiment under nature like but controlled conditions. 0098-8472/$ – see front matter © 2011 Published by Elsevier B.V. doi:10.1016/j.envexpbot.2011.12.009