RESEARCH PAPER Altered allocation to roots and shoots in the endophyte-infected seedlings of Puccinellia distans (Poaceae) M. Czarnoleski 1 , P. Olejniczak 2 , K. Go ´ rzyn ´ ska 3 , J. Kozlowski 1 & M. Lembicz 3 1 Institute of Environmental Sciences, Jagiellonian University, Krako ´ w, Poland 2 Institute of Nature Conservation, Polish Academy of Sciences, Krako ´ w, Poland 3 Department of Plant Taxonomy, A. Mickiewicz University, Poznan ´ , Poland INTRODUCTION Endophytic fungi inhabit the tissue of most grass species on Earth, and they are expected to play a major role in ecological and evolutionary processes in plant communities (Clay & Schardl 2002; Saikkonen et al. 2004; Cheplick & Faeth 2009; Rodriguez et al. 2009). Their presence raises a question about the nature of this ubiquitous relationship. The fungal endo- phytes may suppress the development of mycorrhizal fungi (Guo et al. 1992), reduce grass resistance to herbivores and pathogens (e.g. Tibbets & Faeth 1999), or decrease the compet- itive ability (Saikkonen et al. 2004), growth and reproduction of the hosts (Faeth & Hamilton 2006). In contrast, a conven- tional picture of a fungal endophyte has portrayed a symbiont that benefits from enhancing the fitness of its host (Clay 1987; Wilkinson & Schardl 1997). In support of this mutualistic view, endophytes have been reported to increase the growth, reproduction and anti-herbivore protection of their hosts (e.g. Brem & Leuchtman 2001; Novas et al. 2003, 2008; Clay 2004; Jallow et al. 2004; Wang et al. 2004; Jensen 2005; Spiering et al. 2005; Meister et al. 2006; Zhang et al. 2009). The generality of the mutualistic view of endophytes can be questioned on different grounds (Saikkonen et al. 2004, 2006; Cheplick & Faeth 2009). First, the vast majority of studies on endophyte–grass interactions concern a small group of agro- nomically important forage grasses (Lolium and Festuca) and their Neotyphodium endophytes. The endophyte–grass interac- tions in other systems remain seriously understudied. Second, the assessment of the fitness consequences of endophytes requires an adequate time frame (Olejniczak & Lembicz 2007; Faeth 2009), whereas most studies have focused on the short- term effects of endophytic infections and considered a limited number of fitness components. Finally, the costs and benefits of harbouring endophytes may vary with environmental con- ditions and gene–environment interactions. These consider- ations indicate that it is fruitless to attempt to draw firm conclusions about the nature of endophytes (Saikkonen et al. 2004, 2006; Faeth 2009). The recent discoveries in weeping alkaligrass (Puccinellia distans L. (Parl.)) and its Epichloe¨typhina endophyte offer a good example of the possible impacts of a changing time per- spective on conclusions about the nature of endophyte–grass interactions. Olejniczak & Lembicz (2007) observed increased growth and seed production over the course of the first years of life of Epichloe¨ -infected weeping alkaligrass. However, what initially seemed beneficial for the grass eventually appeared to be the source of its fitness losses. The initial supe- riority of the endophyte-infected individuals was achieved at Keywords Endophyte; Epichloe ¨ typhina; germination; grass; seeds; shoot:root ratio; resource allocation. Correspondence M. Lembicz, Department of Plant Taxonomy, A. Mickiewicz University, ul. Umultowska 89, 61-614 Poznan ´ , Poland. E-mail: lembicz@amu.edu.pl Editor P. Franken Received: 10 April 2012; Accepted: 28 April 2012 doi:10.1111/j.1438-8677.2012.00633.x ABSTRACT Endophytes play an important role in ecological and evolutionary processes in plants and have marked economic value. Seed-transmitted fungal endophytes are conventionally regarded as mutualistic symbionts, but their fitness consequences for the offspring of the host are not clear. Puccinellia distans infected with the fungus Epichloe ¨ typhina (E+) produces seeds that are several times smaller than normal (E)). This observation suggests that the E+ seedlings face a developmental disad- vantage. Our growth chamber experiments compared the germination rates of the small E+ and large E) seeds of P. distans and examined the biomass allocation of seedlings to roots and shoots. The E+ seedlings germinated more slowly and main- tained shorter shoots and a smaller root biomass for 30–50 days after sowing. Despite this disadvantage, the E+ plants more quickly increased their total size, attaining a larger shoot and whole-plant biomass. The shoot:root biomass ratio increased more rapidly through time in the E+ seedlings, attaining a value nine times higher in the E+ than the E) group 50 days after sowing. Such differences between the E+ and E) seedlings were not explained by the growth allometry between shoots and roots. The seedlings of P. distans infected with the Epichloe ¨ endophyte were initially handicapped by their postponed emergence, but this disad- vantage was quickly overcome by their superior growth capacity. The decrease in the relative allocation to roots may indicate that endophytes increase the perfor- mance of roots as resource-acquiring organs and ⁄ or reduce the role of roots in pro- tection against herbivores. Plant Biology ISSN 1435-8603 Plant Biology ª 2012 German Botanical Society and The Royal Botanical Society of the Netherlands 1