Salt uptake and shoot water relations in mangroves |
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| Institution: | 1. Department of Botany, Faculty of Science, Chulalongkorn University, Bangkok 10330, Thailand;2. Australian Institute of Marine Science, Townsville MC, Qld 4810, Australia;1. College of Environment and Resource, Shanxi University, Taiyuan 030006, China;2. State Key Laboratory of Marine Environmental Science (Xiamen University), College of the Environment and Ecology, Xiamen University, Xiamen 361102, China;3. Zhangzhou Institute of Technology, Zhangzhou 363000, China;1. Micro-Element Research Center, Huazhong Agricultural University, Wuhan, China;2. Hubei Provincial Engineering Laboratory for New-Type Fertilizer, Wuhan, China;3. Key Laboratory of Arable Land Conservation (Middle and Lower Reaches of Yangtze River), Ministry of Agriculture, China;1. Organization of Advanced Science and Technology, Kobe University, 1-1 Rokkodai, Nada, Kobe 657-8501, Japan;2. Department of Chemical Science and Engineering, Graduate School of Engineering, Kobe University, 1-1 Rokkodaicho, Nada, Kobe 657-8501, Japan;3. Department of Chemistry and Biotechnology, School of Engineering, The University of Tokyo, Tokyo, Japan |
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| Abstract: | The effects of salinity on water relations and ion concentrations were investigated in seedlings of the mangroves Avicennia alba, Bruguiera gymnorrhiza, Heritiera littoralis and Xylocarpus granatum grown at salinities of 0, 10, 20, 30, 40 and 60‰. All four species survived and grew at salinities ranging from 0 to 40‰, but none survived at a salinity of 60‰. The concentration of sodium and chloride in the xylem sap increased with increasing salinity in both A. alba and B. gymnorrhiza. Sodium and chloride concentrations in the xylem sap of A. alba grown at 40‰ salinity both reached 114 mol m?3, about 15% of the external concentration around the roots. The xylem sap of B. gymnorrhiza grown at 40‰ salinity, by contrast, contained only 7.0 mol m?3 sodium and 4.1 mol m?3 chloride, about 1% of their concentrations in the external solution around the roots. The results indicated that B. gymnorrhiza, which does not have salt-secreting glands, was more effective at excluding salt than A. alba, which has salt-secreting glands.Analysis of pressure–volume curves showed that the bulk modulus of elasticity increased with increasing salinity. This was accompanied by a decrease in shoot water potential, mainly associated with a reduction in shoot osmotic potentials with increasing salinity. The decrease in osmotic potential was attributed to increasing solute concentrations, particularly sodium and chloride, in the leaves of all species except H. littoralis, which had little sodium and chloride in the leaves. |
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