Comparison of photosynthetic eco-functions of water hyacinth and their environmental factors in different areas

Abstract

Eichhornia crassipes Solms,commonly known as water hyacinth,is a bundler aquatic plant.It is widely used in sewage purification due to its well developed root system,strong reproductive ability and ultra-strong absorbency.Introduced into China as feed,it is recently moderately consumed as cultivation substrate of edible fungus and methane fermentation materials.In fact,it is now an importantly modern,low-carbon eco-agricultural resource.An experiment was therefore conducted to determine the physiological and ecological characteristics of different types of water hyacinth in different ecological environments.The experiment was carried out at the Jiangsu Academy of Agricultural Sciences experimental sites in Xueyan of Taihu Lake,Nanjing and Dianchi Lake in 2009.Different plant indices such as plant height,root length and dry weight were measured.Also photosynthetic parameters of leaves at different sits were measured using LI-6400 portable photosynthetic system.The related environmental factors such as light intensity,air temperature and relative humid were recorded as well.Different water hyacinth phenotypes were noted in different areas.Short shoot with long root water hyacinths were noted in Dianchi Lake(with shoot/root height ratio of 0.4±0.1).Then medium-long shoot with short root water hyacinths were observed in Nanjing(with shoot/root height ratio of 7.1±0.3).Also long shoot with medium-long root water hyacinths existed in Taihu Lake(with shoot/root height ratio of 2.0±0.2).Compared with those in Nanjing and Dianchi Lake,Pn(25.9～35.3 μmol·m 2·s 1) of water hyacinth at Taihu Lake was the highest for different leaf positions.The correlation coefficients between Pn and relative humidity in Nanjing,Pn and stomatal conductance(Gs) in Dianchi Lake,and relative humidity and transpiration rate(Tr) in Taihu Lake were 0.831**,0.769* and 0.818*(n=6),respectively.Correlation analysis showed that after light intensity,relative humidity was the next most important ecological driving factor of Pn.Difference in phenotype of water hyacinth in different areas had affected maximum photosynthetic potentials of water hyacinth.The strongest plant growth of water hyacinth in Taihu Lake was related with high photosynthetic capacity(Pmax=36.29±1.21 μmol·m 2·s 1) and light saturation point(LSP=2 350.0±69.0 μmol·m 2·s 1).Plant height and light compensation point(LCP),as well as shoot length and LSP were all positively correlated with correlation coefficients of 0.998* and 0.997*(n=10),respectively.The findings of the study were critical for high yield artificial stocking of water hyacinth.It was recommended that future breeding should focus on extensive adaptability of E.crassipes to light and temperature conditions.