Original article Biomass allocation and photosynthetic responses of lianas and pioneer tree seedlings to light Tarin Toledo-Aceves*, Michael D. Swaine School of Biological Sciences, University of Aberdeen, Aberdeen AB24 3UU, UK article info Article history: Received 18 October 2007 Accepted 21 March 2008 Published online 27 May 2008 Keywords: Acclimation Biomass allocation Growth Photosynthesis Plasticity Shade tolerance Woody climber abstract Lianas are frequently considered as light demanding plants due to their proliferation in gaps and forest edges. Since lianas are exposed to a very heterogeneous light environment, they could be expected to express morphological and physiological plasticity in response to changes in the light environment, as high as that found in pioneer trees. We compared the biomass allocation and photosynthetic responses of seedlings of three species of lianas and two species of pioneer trees to increased light availability. Seedlings were transferred from medium (4–5 mol m 2 d 1 ) to high irradiance (12–15 mol m 2 d 1 ) in a controlled environment. In general the three liana species allocated fewer resources to the stem in comparison with the trees. The difference in the response between irradiance regimes was similar among the species, with no strong differences between trees and lianas prob- ably due the early stage of the plants. With increase in irradiance plants accumulated more biomass, allocated more resources to the roots and less to the leaves, reduced the leaf area ratio (LAR) and specific leaf area (SLA). The photosynthetic rates recorded were not related to the rates of growth as measured by the increase in dry biomass (RGRm). Regardless of the life form, plants under higher irradiance increased their light compensation point (Lcp) and attained light saturation (Lsp) at higher levels of irradiance, while the saturated photosynthetic rate (A max ) did not show a clear pattern, and dark respiration (R d ) and quan- tum yield (Q) were not affected by the transference. The understanding of liana and tree seedlings responses to the light environment may have important implications in the dynamics of tropical forest regeneration. ª 2008 Elsevier Masson SAS. All rights reserved. 1. Introduction Lianas (woody climbers) are a conspicuous component of tropical forests (Gentry, 1991). They can represent about 30% of all woody stems in gaps after 4 years of gap succession (Uhl et al., 1988). Since their abundance is higher in gaps and in forest edges than in the forest understorey (Putz, 1984; Schnitzer and Carson, 2001), lianas are generally considered gap-dependant pioneer species (Schnitzer and Bongers, 2002). However, there is a wide range of shade tolerance within the group (Sa ´ nches and Valio, 2002). Lianas are exposed to a very heterogeneous light environ- ment, both spatially and temporally. At an early stage, many must maximize their carbon gain under the low light condi- tions of the forest understorey. Further growth will normally lead to higher irradiance, but because of their ability to grow * Corresponding author. CONABIO, Bioinformatics, Avenida Liga Perife ´ rico-Insurgentes Sur 4903, 14010 Me ´ xico DF, Mexico. Tel.: þ52 55 5004 4947; fax: þ52 55 5004 4931. E-mail address: t.tarin@lycos.com (T. Toledo-Aceves). available at www.sciencedirect.com journal homepage: www.elsevier.com/locate/actoec 1146-609X/$ – see front matter ª 2008 Elsevier Masson SAS. All rights reserved. doi:10.1016/j.actao.2008.03.003 acta oecologica 34 (2008) 38–49