Preliminary Studies On Allelopathic Effects Of Exotic Coreopsis Grandiflora

To explore the allelopathy of the exotic Coreopsis grandiflora, the study analyzed the chemical components of aquatic leaf, root and flower extracts of C. grandiflora with the gas chromatography/mass spectrum (GC/MS). Altogether, the study measured the effects from aqueous leaf and root extracts of C. grandiflora on seed germination of 6 species (Cynodon dactylon, Agrostis matsumurae, Zoysia japonica, Orychophragmus violaceus, Dianthus chinensis, and Celosia cristata) and the effects of aquatic leaf extracts in seedlings of 5 species (Cynodon dactylon, Agrostis matsumurae, Orychophragmus violaceus, Dianthus chinensis and Celosia cristat) using the bioassay. The results as follows:1. There were fifty-six compounds in different organs of the aquatic extracts of C. grandiflora and phenols and terpenes were their main components. Thirty-seven compounds were identified in the aquatic leaf extracts of C. grandiflora and its main compounds were 2-Tolualdehyde (13.00%), aromadendrene oxide (10.08%), etc.. Thirty-eight compounds were identified in the aquatic root extracts of C. grandiflora and its main compounds were homovanillic acid methyl ester (13.59%), Gingerol (7.99%), etc.. Thirty-five compounds were identified in the aquatic flower extracts of C. grandiflora and its main compounds were aromadendrene oxide (13.61%), Longifolenaldehyde(9.43%), and so on.2. The aquatic leaf extract of C. grandiflora had significant allelopathic effects on seed germination of the six plant species, with the effects varying with the concentration of the extract. Foliar extracts at a concentration of 50 g·L^-1 were found to be inhibitory (P < 0.01) to seed germination for C. dactylon, Agrostis matsumurae, Z. japonica and O. violaceus, with inhibition rates of 39.33%,56.0%,53.33%, and 46.22%, respectively, compared with the control. In addition, the seed germination index was more sensitive to leaf extract application than the germination percent, and the inhibition of the aquatic leaf extract was stronger than the aquatic root extract.3. The aquatic leaf extracts of C. grandiflora had significant allelopathic effects on seedling growth, with the effects varying with the type of plants and the concentration of extracts. Foliar extracts at a concentration of 50 g·L^-1 were found to be inhibitory (P < 0.01) to shoot length, root length and fresh mass for C. dactylon, Agrostis matsumurae, O. violaceus and D. chinensis; the chlorophyll content in C. dactylon, Agrostis matsumurae and D. chinensis were reduced by 43.6%, 44.3%, 41.4% (P<0.01), respectively; and the activities of superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT) were significantly reduced (P<0.01) in the three plants; the content of malondialdehyde (MDA) in the seedlings of 5 species was significantly increased (P<0.01), respectively, compared with the control. And the order of allelopathic sensitivity is Agrostis matsumurae and C. dactylon > O. violaceus and D. chinensis > C. cristata.The results of this study firstly proved that there were allelopathy effect in C. grandiflora and provided the basic theory for the mechanism of the formation of mono-dominant community of C. grandiflora. And then it will help the selection and design of landscape plants.