Trees (2004) 18:167–174 DOI 10.1007/s00468-003-0293-8 ORIGINAL ARTICLE Asish Kumar Parida · A. B. Das · B. Mittra Effects of salt on growth, ion accumulation, photosynthesis and leaf anatomy of the mangrove, Bruguiera parviflora Received: 15 October 2002 / Revised: 25 June 2003 / Accepted: 21 August 2003 / Published online: 1 November 2003  Springer-Verlag 2003 Abstract The effects of a range of salinity (0, 100, 200 and 400 mM NaCl) on growth, ion accumulation, photosynthesis and anatomical changes of leaves were studied in the mangrove, Bruguiera parviflora of the family Rhizophoraceae under hydroponically cultured conditions. The growth rates measured in terms of plant height, fresh and dry weight and leaf area were maximal in culture treated with 100 mM NaCl and decreased at higher concentrations. A significant increase of Na + content of leaves from 46.01 mmol m -2 in the absence of NaCl to 140.55 mmol m -2 in plants treated with 400 mM NaCl was recorded. The corresponding Cl - contents were 26.92 mmol m -2 and 97.89 mmol m -2 . There was no significant alteration of the endogenous level of K + and Fe 2+ in leaves. A drop of Ca 2+ and Mg 2+ content of leaves upon salt accumulation suggests increasing membrane stability and decreased chlorophyll content respectively. Total chlorophyll content decreased from 83.44 mg cm -2 in untreated plants to 46.56 mg cm -2 in plants treated with 400 mM NaCl, suggesting that NaCl has a limiting effect on photochemistry that ultimately affects photosynthesis by inhibiting chlorophyll synthesis (ca. 50% loss in chlorophyll). Light-saturated rates of photosynthesis decreased by 22% in plants treated with 400 mM NaCl compared with untreated plants. Both mesophyll and stomatal conductance by CO 2 diffusion decreased linearly in leaves with increasing salt concen- tration. Stomatal and mesophyll conductance decreased by 49% and 52% respectively after 45 days in 400 mM NaCl compared with conductance in the absence of NaCl. Scanning electron microscope study revealed a decreased stomatal pore area (63%) in plants treated with 400 mM NaCl compared with untreated plants, which might be responsible for decreased stomatal conductance. Epider- mal and mesophyll thickness and intercellular spaces decreased significantly in leaves after treatment with 400 mM NaCl compared with untreated leaves. These changes in mesophyll anatomy might have accounted for the decreased mesophyll conductance. We conclude that high salinity reduces photosynthesis in leaves of B. parviflora, primarily by reducing diffusion of CO 2 to the chloroplast, both by stomatal closure and by changes in mesophyll structure, which decreased the conductance to CO 2 within the leaf, as well as by affecting the photo- chemistry of the leaves. Keywords Bruguiera parviflora · Leaf succulence · Mangrove · Mesophyll · Photosynthesis Introduction Mangroves are constituent plants of tropical inter-tidal forest communities. They include woody trees and shrubs that flourish in the zone between land and sea along the tropical coastlines of the globe. True mangroves occur only in mangrove habitats. Mangroves are taxonomically diverse; true mangroves include about 54 species in 20 genera belonging to 16 families (Das et al. 2002). The most striking feature of mangroves is their ability to tolerate NaCl up to and above the concentration in seawater (500 mM). Mangroves are divided into the ‘secretors’ and ‘non-secretors’ on the basis of their salt management strategies (Sugihara et al. 2000). The ‘secretors’ have salt glands or salt hairs; the ‘non- secretors’ lack such morphological features for the excretion of excess salt. Bruguiera parviflora is a ‘non- secretor’ that grows in a range of salinities from fresh A. K. Parida · A. B. Das ( ) ) National Institute for Plant Biodiversity Conservation and Research, Nayapalli, 751015 Bhubaneswar, Orissa, India e-mail: a_b_das@hotmail.com Fax: +91-674-550274 A. B. Das Regional Plant Resource Centre, 751015 Bhubaneswar, Orissa, India B. Mittra Centre for Environmental Management of Degraded Ecosystems, School of Environmental Studies, University of Delhi, North Campus, 110 007 Delhi, India