Aquatic Botany 112 (2014) 33–40 Contents lists available at ScienceDirect Aquatic Botany journa l h om epage: www.elsevier.com/locate/aquabot Early responses of Avicennia marina (Forsk.) Vierh. to intertidal elevation and light level Ya-Ping Chen, Yong Ye ∗ Key Laboratory of the Ministry of Education for Coastal and Wetland Ecosystem, College of the Environment and Ecology, Xiamen University, Xiamen, Fujian, China a r t i c l e i n f o Article history: Received 10 August 2012 Received in revised form 12 July 2013 Accepted 14 July 2013 Available online 22 July 2013 Keywords: Mangrove Avicennia marina Elevation Light level a b s t r a c t Combined effects of intertidal elevation and light level on two-month-old seedlings of Avicennia marina were studied at Zengying, Xiamen of China. Leaf number, area and thickness were promoted by decreasing elevation or elevating light level. Stem height differed little between light levels but was significantly stimulated by moderate waterlogging. Expansion of stem basal diameter was promoted by high light level but not affected by elevation. Total biomass showed highest at the middle elevation and was promoted by high light level. Seedlings in the gaps generally had higher root weight ratio (RWR) and stem weight ratio (SWR) but lower leaf weight ratio (LWR) than those under the canopy. Leaf pigment contents in the gaps were significantly stimulated by low elevations, while a reverse tendency occurred under the canopy. Both roots and leaves increased superoxide dismutase (SOD) and peroxidase (POD) activities to defend prolonged waterlogging. High light level resulted in high SOD and POD activities in roots but not in leaves. Malonaldehyde (MDA) contents changed little between light levels but were significantly promoted by prolonged waterlogging. These growth and physiological responses suggested that A. marina seedlings had strong tolerance to prolonged waterlogging but not to canopy shade. © 2013 Elsevier B.V. All rights reserved. 1. Introduction Mangrove forests have unique ecological and economic val- ues in protecting shore, sustaining biodiversity and providing food and wood (Danielsen et al., 2005; Ahmed et al., 2012). However, mangroves all over the world have for a long time suffered vari- ous disturbances from natural disasters and human activities, such as hydrologic modifications, agricultural reclamation and uncon- trolled deforestation for fuel wood (Allen et al., 2001; Krauss and Allen, 2003; Prasad et al., 2012). More than 90% of mangrove forests in Xiamen of China are deforested for construction of fishponds, ports and bridges (Lin et al., 2005), which fragmented mangrove habitats and made the remaining mangroves rather vulnerable to interior and external changes. Therefore, it is urgent to improve growth conditions for restoring the degraded mangrove forests in this region. For successful mangrove reforestation, it is of great importance to find out suitable planting sites. Soil texture (e.g. McKee, 1995b; Ye et al., 2005), salinity (e.g. Clarke and Allaway, 1993; Krauss et al., 2008), propagule predation (e.g. Sousa and Mitchell, 1999; Krauss and Allen, 2003), canopy shade (e.g. Clarke and Allaway, 1993; ∗ Corresponding author. Tel.: +86 592 2185622; fax: +86 592 2185622. E-mail address: yeyong@xmu.edu.cn (Y. Ye). Ye et al., 2005) and tidal inundation (e.g. Ellison and Farnsworth, 1997; Chen et al., 2005) are considered as the main factors affecting early development of mangroves. In Xiamen, a significant fac- tor limiting mangrove development is intertidal elevation, since most intertidal zones with mid-to-high elevations which were once occupied by mangroves are now used for economical develop- ments. There have been many studies dealing with effects of intertidal elevation or its related factors such as tidal inundation and water- logging on mangroves. Kitaya et al. (2002) found that survival and growth of mangrove seedlings could be affected by even a slight ele- vation difference of 20 cm. Seedlings of Avicennia marina, Bruguiera gymnorrhiza, Ceriops tagal and Rhizophora stylosa had low survival rates at low intertidal elevations (Smith, 1987). Prolonged water- logging leads to an alteration of biomass partitioning among plant parts in B. gymnorrhiza and K. obovata and results in low stomatal conductance in B. gymnorrhiza and R. stylosa (Naidoo, 1983; Kitaya et al., 2002; Ye et al., 2004). A very striking observation under waterlogging stress is the production of various reactive oxygen species (ROS), especially superoxide radical and hydrogen perox- ide, leading to an increase in lipid peroxidation (Bowler et al., 1992). Significant increases in activities of antioxidant enzymes superox- ide dismutase (SOD) and peroxidase (POD) were recorded in K. obovata and B. gymnorrhiza to protect plants against lipid perox- idation (Ye et al., 2003). 0304-3770/$ – see front matter © 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.aquabot.2013.07.006