A Comparison of the Physioecological Characteristics of Four Kinds of Plants between A Constructed Wetland and Xixi Wetland

Constructed wetland has been proven efficient technology for both wastewater treatment and rescue of water resources.Compared with conventional treatment systems,it is economical,and easily operated and maintained.An integrated vertical flow constructed wetland was built in Hangzhou Botanical Garden,Zhejiang province,P.R.China,to purify eutrophic water from Jade fish-seeing pond.In order to assess the growth state of the plant in the constructed wetland,we studied the differences of physioecological characteristics of plants between a constructed wetland and Xixi wetland.Four species were growing both in both sites,including Iris tectorum,Acorus calamus,Canna indica,Salix matsudana.The plant physiological indices,such as photosynthetic curves,the transpiration rate(Tr) and the photosynthetic rate(P_(n)) under photo synthetically active radiation(PAR) 1 000 μmol/(m~(2)·s) were tested.Through the photosynthetic curves,the light compensation point(LCP),light saturation point(LSP),dark respiration rate(Rd),apparent quantum yield(AQY) and the maximum photosynthetic rate(P_(max))were calculated.Through the Tr and P_(n),the water-use-efficiency(WUE) was calculated.The photosynthesis of the plants in the constructed wetland was better than that in the Xixi wetland.The LSP values of the plants were ones of constructed wetland more than those of Xixi wetland,implicated that the plants in Xixi wetland need more light to achieve the optimal photosynthetic point.The P_(max) of plants in the constructed wetland was higher than those in the Xixi wetland.It is because(a) the constructed wetland with the sand base structure was draftier than the Xixi wetland(b) the intermittent water supply compensated the water loss defect,especially during the droughty season.Those two features kept the plant growing well.The results showed that Rd values of plants in Xixi wetland were more than those in constructed wetland plants,implicating that the plants in Xixi wetland need to consume more energy to maintain their normal physioecological state.The temperature of the environment can be a possible reason for the Rd difference as the temperature in constructed wetland is higher than the Xixi wetland.To some extent having low Rd is benefit for biomass accumulation.The WUE of Acorus calamu and Canna indica in constructed wetland was more than that in Xixi wetland,while the Iris tectorum andSalix matsudana had complicated cases.The plants in the constructed wetland didn't show lower WUE than those inXixi wetland,implying that the environment of the constructed wetland was suitable for the plants keeping a high WUE.This is benefit for the water circulation in the constructed wetland-Jade-fish-seeing-pond system.The order of the fourspecies of P_(max)and AQY were similar,that is,Salix matsudana Canna indica Acorus calamu Iris tectorum.This phenomenon implied that the plant with the high photosynthetic capacity had the high transpiration rate.Furthermore,those kindsof plants had the better capacity of purify the wastewater,and can be appropriate plants planted in the constructed wetland.It isfound that the water supply system with sand base and the shade environment are suitable for plants growing.Especially in July,plants′ growing would be affected negatively by the strong sum radiations,and the declining of the soil and air moisture.The plants can conquer the water deficiency in the constructed wetland system.