Osmoregulation Mechanisms of Inorganic Ions in Mangroves during Different Seasons:a Case Study of Avicennia Marina in Mbweni Mangrove Forests

【摘要】：In order to understand osmoregulatory mechanism of the inorganic ions found in mangroves which are halophytes plants, a study was carried out at Mbweni Mangrove Forests on Avicennia marina species. The study involved collection of litter falls monthly in the year2009by setting nine litter traps and different standard methods, and procedures were implemented. Inorganic cations were analyzed using Kjeldahl method for nitrogen (N), optical density method for phosphorus (P), and atomic absorption spectrophotometry method for potassium (K+), calcium (Ca2+), magnesium (Mg2+) and sodium (Na+). Ion Chromatography method was employed to analyze the contents of chlorine (Cl-), sulfate (SO42-) and oxalate (C2O42-). In leaf litter, the highest production was found in September that weighed of5.98g. and the lowest one was detected in April with the weight of0.53g. The results indicated that the vegetative season was from September, and shedding of leaves due to excessive salts and the strong wind that would finally bring short rains. The lowest production accumulated in April indicated that it was a season for production of propagation organs, and also prevalence of heavy rains. In wet season, most of the ions concentrations were low probably due to the salty residues splash and spray, thus easily rinsed away by the rain or rising tide, by leaching and ionization. In the dry season (from June to August), the salinity level of soil environment was high. Thus most of the ions were accumulated in order to maintain the homeostatic control, turgor pressure and osmotic adjustment. It was concluded that varying effects of the inorganic ions to A. marina at different seasons contributed to its survival in the salt stressed environment. Some ions varied independently as it reflected their different roles in the plant, thus mangrove was regard as a salt tolerant plant. Salinity affected the dynamic presence of the inorganic ions and the inorganic ions affected the growth and osmoregulation in A. marina.