论文部分内容阅读
Submerged macrophytes play multiple roles to keep the structure of shallow lake ecosystem to ensure its good performance and well balance,but they usually have been destroyed by blooming cyanobacteria in eutrophicated water bodies.As one of cyanobacterias competing methods,chemical weapon is regarded as an efficient tool to win over aquatic higher plants,and also a restriction of vegetation recovery in cyanobacteria-riched aquatic ecosystem.Dianchi Lake is the most serious eutrophicated lake in China,leading to continuous large-scale outbreak of cyanobacteria bloom every year and submerged macrophytes almost disappeared since last decade.Is the allelopathic effect one of reasons for cyanobacteria to affect higher plants? How does it happen? To answer these questions,we employed the dominant phytoplankton species in Dianchi Lake,Microcystis aeruginosa,and one of the common submerged plants,Potamogeton malaianus,to research the allelopathic effects of M.aeruginosa exudates and extracts on submerged higher plants.We found that: (1) lower concentration of exudates significantly promoted P malaianus germination while higher levels inhibited it,but the extracts didnt affect the germination; (2) both lower levels of exudates and the medium level of extracts significantly increased the biomass of P.malaianus seedlings,on the contrary,higher levels of both exudates and extracts significantly decreased the biomass; (3) both chlorophyll content and Fv/Fm value of the seedlings were decreased by all levels of exudates; (4) Fv/Fm value of seedling leaves is the most sensitive index to indicate the damage of M.aeruginosa allelopathy on P malaianus; (5) the allelopathic effects of M.aeruginosa exudates were obviously stronger than those of extracts.The results indicated that cyanobacteria could inhibitor submerged macrophytes actively by allelopathic effect in algae-dominant water,and significantly restrict the recovery of aquatic vegetation.The early growth of seedling is the most sensitive phase under cyanobactetial allelopathy stress.So,even though there is abundant seed-bank and superior germination,the damaged seedlings would lead to aquatic vegetation unrecoverable.