Aquatic Botany 96 (2012) 7–13 Contents lists available at SciVerse ScienceDirect Aquatic Botany j ourna l ho me page: www.elsevier.com/locate/aquabot Physiological responses to flooding and light in two tree species native to the Amazonian floodplains Daniel Maurenza a,∗ , Ricardo A. Marenco b , Pia Parolin c , Maria Teresa F. Piedade d,1 a INPA/Max-Planck, Instituto Nacional de Pesquisas da Amazônia, Manaus, Brazil b Instituto Nacional de Pesquisas da Amazônia, Coordenac ¸ ão de Pesquisas em Silvicultura Tropical/Laboratório de Ecofisiologia de Árvores, Manaus, P.O. Box 478, 69060-001, Brazil c University of Hamburg, Biocentre Klein Flottbek, Plant Biodiversity, Germany d Instituto Nacional de Pesquisas da Amazônia, Coordenac ¸ ão de Dinâmica Ambiental, Grupo MAUA, Pesquisas em Biologia Aquática, Manaus, Brazil a r t i c l e i n f o Article history: Received 8 February 2011 Received in revised form 3 September 2011 Accepted 8 September 2011 Available online 16 September 2011 Keywords: Cecropia latiloba Chlorophyll a fluorescence Gas exchange Growth parameters Nutrient rich várzea floodplains Pouteria glomerata Seedling establishment Submergence Waterlogging a b s t r a c t In Amazonian floodplains, plant survival is determined by adaptations and growth strategies to effectively capture sunlight and endure extended periods of waterlogging. By measuring gas exchange, quantum efficiency of photosystem 2 (PSII), and growth parameters, we investigated the combined effects of flood- ing gradients and light on two common evergreen floodplain tree species, the light-tolerant Cecropia latiloba and the shade-tolerant Pouteria glomerata. Individual plants were subjected to different com- binations of light and flooding intensity in short-term and long-term experiments. Plants of C. latiloba lost all their leaves under total submersion treatments (plants flooded to apex and with reduced irra- diance) and showed highest maximum assimilation rates (A max ) in not flooded, high light treatments (6.1 mol CO 2 m -2 s -1 ). Individuals of P. glomerata showed similar patterns, with A max increasing from 1.9 mol CO 2 m -2 s -1 under total flooding to 7.1 mol CO 2 m -2 s -1 in not flooded, high light treatments. During the long-term flooding experiment, quantum efficiency of PSII (F v /F m ) of C. latiloba was not affected by partial flooding. In contrast, in P. glomerata F v /F m decreased to values below 0.73 after 120 days of total flooding. Moreover, total submergence led P. glomerata to reduce significantly light saturation point (LSP), as compared to C. latiloba. For both species morphological adjustments to long-term flooding, such as the production of adventitious roots, resulted in reduced total biomass, relative growth rate (RGR) and leaf mass ratio (LMR). Growth increase in C. latiloba seemed to be more limited by low-light than by flooding. Therefore, the predominant occurrence of this species is in open areas with high light intensities and high levels of inundation. In P. glomerata flooding induced high reductions of growth and photosynthesis, whereas light was not limiting. This species is more abundant in positions where irradiance is reduced and periods of submergence are slightly modest. We could show that the physiological requirements are directly responsible for the flooding (C. latiloba) and shade (P. glomerata) tolerance of the two species, which explains their local distribution in Amazonian floodplain forests. © 2011 Elsevier B.V. All rights reserved. 1. Introduction Inundation is the main abiotic factor influencing the distribu- tion and occurrence of floodplain tree species in Amazonian forests (Junk et al., 1989). Owing to the seasonal variation of precipitation in the Amazon Basin, changes in water level may reach amplitudes of 10 m in central Amazonia. This leads to waterlogging and often ∗ Corresponding author at: Av. André Araújo, 2936, Aleixo, Code 69060-001, Man- aus, Amazonas, Brazil. Tel.: +55 11 43686255; fax: +55 92 36421503. E-mail addresses: dmaurenza@yahoo.com.br, dmaurenza@gmail.com (D. Maurenza), rmarenco@inpa.gov.br (R.A. Marenco), pparolin@botanik.uni-hamburg.de (P. Parolin), maitepp@inpa.gov.br (M.T.F. Piedade). 1 Present address: Dr. Fausto Ribeiro de Carvalho, 135, Vila Orlandina, CEP 09632- 030, São Bernardo do Campo, São Paulo, Brazil. complete submersion of trees for up to 210 days per year (Junk, 1997). During flooding, oxygen in the rhizosphere is scarce so that physiological and morphological adjustments are required for growth and maintenance (Crawford and Braendle, 1996; Pezeshki, 2001). Waterlogging and plant submergence induce a significant reduction in photosynthesis, a process thought to be related to stomatal closure (Waldhoff et al., 1998; Piedade et al., 2000; Armbrüster et al., 2004). Flooding responses may also induce changes in biomass allocation, and allometric traits, reduce rates of respiration and metabolism, and stimulate leaf shedding (Maia and Piedade, 2002; Schöngart et al., 2002; Mommer and Visser, 2005). Other studies suggest that chlorophyll a fluorescence, a robust parameter that measures the efficiency of the photosyn- thetic apparatus (Maxwell and Johnson, 2000), may decrease during inundation (Waldhoff et al., 2002; Rengifo et al., 2005; Oliveira-Wittmann, 2007). 0304-3770/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.aquabot.2011.09.003