Study On The Allelopathic Inhibition Effect Of Phragmites Communis On Phalaris Arundinacea And Its Characteristics Of Response To Water Environment

Phragmites communis and Phalaris arundinacea in Riverside wetlands in Zhenjiang were taken as experimental materials in this paper. Allelopathy of Phragmites communis on Phalaris arundinacea was studied from three pathes: allelopathy resulted from aqueous extract of Phragmites communis, decaying substance of Phragmites communis, and under the co-existence of Phragmites communis and Phalaris arundinacea in the natural wetland with different moisture gradients, and the allelopathic chemicals from Phragmites communis were separated, identified and measured, and then the allelopathy mechanism of Phragmites communis on Phalaris arundinacea and its characteristics of response to water environment are revealed. The research results of this paper not only can theoretically reveal the maintenance mechanism of competitive coexistence of Phragmites communis and Phalaris arundinacea population in some certain environments, but also can provide technically guidance for maintaining the stability of the Phragmites communis-Phalaris arundinacea community in the construction wetland. Here are the main results of this study.(l)Under the designed concentration gradients, with the increase in the concentration of aqueous extract from Phragmites communis, most of seed germination rate, seed germination index, seedling height, seedling taproot length, and chlorophyll content in leaf of Phalaris arundinacea show significant or extremely significant reduction, while allelopathic effect indices show significant or extremely significant ascension; activity of antioxidant enzymes of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) show a significant trend of first rise and then decline, while malondialdehyde (MDA) show varying degrees of continuous upward trend. The above results indicate that allelopathic inhibition effects of the aqueous extract of Phragmites communis on seed germination and seedling growth of Phalaris arundinace are very obvious.(2) Within the designed the range of proportion, with an increase in content of Phragmites communis decaying substance, biomass, plant height, tiller number, chlorophyll content, and chlorophyll a/b of mature Phalaris arundinacea mostly continue to significantly decrease; antioxidant enzymes such as SOD, POD, and CAT mostly first rise and then decline significantly, while MDAs mostly continue to significantly increase; photosynthetic gas exchange parameters such as Pn, Cond, and Tr continue to decrease, while Ci continue to rise; chlorophyll fluorescence parameters such as Fo and NPQ mostly continue to significantly increase, while Fv/Fm, qP, ΦPSII, and ETR mostly continue to significantly decrease. The above results indicate that allelopathic inhibition effects of decaying substance of Phragmites communis on growth of mature Phalaris arundinace are very obvious. Research results on Phragmites communis-Phalaris arundinacea coexistence community in the natural wetland show that, under the measured soil moisture gradients, with a decline in the soil moisture, growth indices (biomass and plant height), activities of antioxidant enzymes (SOD, POD, CAT, and MDA), and photosynthetic gas exchange parameters (chlorophyll content, Pn, Cond, Tr, and Ci) all appear a change characteristics similar to above results. This result also shows that the response to water environment of allelopathic inhibition effects of Phragmites communis on Phalaris arundinacea is very obvious.(3)Correlation analysis shows that there is an obvious correlation between allelopathic inhibition effects of Phragmites communis on Phalaris arundinacea and the total phenolic acids content in reed root and soil nearby reed root. It shows that Phenolic acids are the main substance which results in allelopathic inhibition effects of Phragmites communis on Phalaris arundinacea. The outcome of separation,identification and measurement to allelopathy materials under different soil moisture gradients furtherly indicates that the total phenolic acids content and total amount of seven identified phenolic acids(coumaric acid, gallic acid, vanillic acid, clove acid, benzoic acid, ferulic acid,and salicylic acid.) also show a significant response to water environment.