STUDY OF ARTIFICIAL SEEDS OF SUBMERGED MACROPHYTE <I>POTAMOGETON CRISPUS</I> L.

Abstract

Restoration of submerged vegetation is the key step of restoration of aquatic ecosystem in eutrophic lakes. The seed bank was strongly destroyed in many eutrophic lakes of China,it is necessary to get plenty of seedlings for restoration of submerged vegetation because of the difficulty of getting enough macrophyte seeds. Usually,seedlings of submerged macrophytes have to be obtained from other water bodies. Transplantation may destroy the source vegetation and encounter shortage of seedlings in case of lack of vegetation in nearby water bodies. The technique of artificial seeds is a promising method to provide a large number of seedlings in a short time without limitation of season,long distant transportation and harm to the natural macrophyte community.In order to establish the method for the preparation of artificial seeds of submerged macrophytes,a common submerged macrophte Potamogeton crispus L. was selected as experimental material. In this study,the artificial seed of P. crispus was obtained by using node segments as explant,buds were induced in induction medium. The node segments with buds of P. crispus were encapsulated with sodium alginate and calcium chloride to form artificial seeds. The effects of hormone types and concentration in capsule,temperature,light intensity,concentration of nitrogen and phosphorus,sediment types on the germination and conversion of artificial seeds of P. crispus were investigated. An experiment of germination and conversion of the artificial seeds in lake was also conducted. The hormones supplemented in the capsules could promote the germination of artificial seeds. The result showed that the germination and conversion rates of artificial seeds,which embedded in IBA 1.0 mg/L and 6-BA 0.5 mg/L,were 80% and 20% respectively in autoclaved tap water. No significant effect of temperature was found on the germination and conversion in range of 15—25℃. Similarly nitrogen and phosphorus caused no significant change on the germination and conversion of artificial seeds of P. crispus. Light intensity affected the germination and conversion significantly. Higher light intensity favored the germination of artificial seeds. The germination and conversion rates of the artificial seeds reached to 67.8% and 35.6% respectively at light intensity of 40μmol/m2·s. Sediment types also affected the germination significantly. Sandy soil was better than sandstone and silt to support the germination. The germination rate of artificial seeds of P. crispus was 60% on the sandy soil,which was higher than that in sandstone and silt sediments. To test the feasibility of artificial seeds of P. crispus in eutrophic lakes,a trial experiment was carried out in the East Lake which is a hyper-eutrophic lake in Wuhan,Hubei the germination and conversion rates of artificial seeds of P. crispus were 28% and 15% under water depth of 0.6 m,and 27% and 12% under water depth of 1.2 m,respectively. The results showed that the artificial seed of P. crispus was applicable in restoration of aquatic vegetation in place of plant transplantation.