Studies Of Eco-physiological Characteristics Of Three Mangrove Species In Constructed Wetland

Mangrove ecosystem is diverse communities of tropical to subtropical trees and shrubs growing in the intertidal zone.Many studies have been done on pollution eco-physiology and purifying effect of mangrove,but these works were conducted under seawater condition.So far,few research has been published related to mangrove wetland under freshwater condition. In this study,under freshwater condition,eco-physiological characteristics of three mangrove species,Sonneratia caseolaris{Sc)Aiegicerascorniculatum(Ac),Bruguiera gymnorrhiza(Bg) in subsurface flow constructed wetland sewage treatment system were studied.The experiment had been performed in South China Normal University, Guangdong Province of China for one year,from January to December 2004. The three mangrove species were one-year seedlings,and they were obtained from Futian Nature Reserve,Shenzhen Bay.The constructed wetland with 2m length,2m width and 0.6m depth was planted with rows of mangrove at a density of 30 plants per wetland bed,and wetland system had been receiving sewage once every week for one year,all the treatments had three replicates. The three mangrove species were measured for height,basal diameter and biomass once every month and chlorophyll content,photosynthetic rate, transpiration rat,stomatal conductance,electrolyte leakage,SOD CAI POD activity and the content of MDA and dissociative proline once every week.The results were obtained after the one year experimentation as follows:1. After one year,stem height increment of Sc,Ac and Bg were 134,32 and 21cm,respectively,and basal diameter increment were18.2,14.3,12.9mm,and biomass increment were 747,113,55g^-1 plant whichindicated that growth rate was in the order as: Sc>Ac>Bg;2. Average value of physiological characteristics of three mangrove species were obtain according to the values of 1-12 month.Total chlorophyll content of Sc,Ac and Bg werel.91,1.26, 0.91 mgg^-1FW,respectively,and chlorophyll a content were 1.44, 0.93, 0.64mgg^-1 FW,and chlorophyll b content were 0.5,0.34,0.17 mgg^FW.and net photosynthetic rate were 9.67,6.39,3.57 μmolCO₂m^-2s^-1,and transpiration rate were 54,38, 24mmolH2Om^-2s^-1,and stomatal conductance were 285,222,110 mmolH2Om^-2s^-1,and electrolyte leakage were 10:2%, ¹2.9%, 13.5%,and SOD activities were 447,396,386Ug^-1FW,and CAT activities were 370.5, 188.53, 417.45 Ug^-1 FW.and POD activities were 310.4, 284.78, 384.77 Ug^-1FW.and the content of MDA were 42.92, 65.36, 52.22 nmolg^-1 FW,and the content of dissociative praline were 58.82 , 80.92 , 59.87μgg^-1FW.These results indicated that photosynthesis and water metabolism showed a sequence as follows: Sc>Ac>Bg, and Sc had a better resistance to environment stress;3. The changes of eco-physiological characteristics of three mangrove species during one year were very similar.Three mangrove species maintained higher growth rate and physiological characteristics from April to October,but they kept lower growth rate and physiological characteristics from January to March and from November to December..Comparing eco-physiological characteristics of three mangrove species in constructed wetlands,the result indicated: Sc was better than Ac, and Ac was better than Bg.4. The daily course of net photosynthetic rate of S. caseolaris showed a curve of single peak,and that of A. corniculatum and B-gymnorrhiza showed a curve of double peaks.5. Comparing the three mangrove species, S. caseolaris, A. corniculatum and B-gymnorrhiza in constructed wetland with that in Futian Nature Reserve,respectively,the content of chlorophyll a,chlorophyll b, chlorophyll a/b and total chlorophyll had no significant differences, and the activities of SOD,CAT had significant differences, and electrolyte leakage,MDA content had no significant differences, and dissociative praline had significant differences.Generally,the physiological characteristics of three mangrove species in constructed wetland were similar with that in Futian Nature Reserve.