| Plant allelopathy is a common phenomenon in nature. It embodies the biochemical relationship between plant individual and group, constitutes the competition interaction between plants and other creatures to nutrient, moisture, light and space. Nowadays with the rapid development of economy, sustainable development of agriculture and the ecological environment protection become the focus internationally. So the research on allelopathy can help more reasonable to explain the plant composition and distribution, community succession, co-evolution and biological invasion in the agro-ecosystem. Therefore, investigating and clarifying the mechanism of plant (Commelina benghalensis) allelopathy, may provide a basis for further study on the influence of secondary substances in Commelina benghalensis on other crops.In this paper, based on the review of the background, function characteristics, biological determination method, application prospect, allelochemicals’species, release methods and the effect forms of allelopathy in plants, the seed germination and seedling growth of four crops were also discussed.The Commelina benghalensis was used as material, and four crops, Sorghum vulgare, Zea mays, Vigna radiate, and Brassica napus as acceptors, to study the allelopathic effects of aqueous extracts from overground parts and underground parts of C. benghalensis on germination and seedling growth of four crops. Additionally, the effects of allelochemical in C. benghalensis on growth and development of crop in agro-ecosystem.The study was conducted using petri-dish cultivation, and seed germination rate, allelopathic index (RI), antioxidant activity (SOD, POD), MDA content, root vigor, shoot/root biomass, chlorophyll content as well as chlorophyll fluorescence of acceptors were determined. The results were as follows:1. The effects of aqueous extracts of Commelina benghalensis on seed germination of four crops were investigated, the results showed thatlow concentration (<0.025g/mL) aqueous extracts from C. benghalensis had a promoting effect on seed germination of four crops. With the increasing of the concentration of extract, the inhibition effects were gradually strengthened. Except Vigna radiate, the inhibition effects of aqueous extracts from overground parts on seed germination rate was higher than that from underground parts. The seed germination RJ of four acceptors was positive The effects of aqueous extracts of Commelina benghalensis on the malondialdehyde (MDA) contents of Zea mays and Vigna radiata Were investigated, the results show that:under low concentration, while under higher concentration the RI was negative, and the higher the concentration, the lower the RI.2. The aqueous extracts of C. benghalensis had promoting effects on shoot length and root length of four seedlings under low concentration. With the increase of the concentration of extract, the inhibition effects had gradually strengthened, and the inhibition to root growth was stronger than the shoot.3. The synthetic effects of aqueous extract from C. benghalensis on seed germination of four crops were:Brassica napus> Zea mays> Vigna radiata> Sorghum vulgare.4. The effects of aqueous extracts on the superoxide(SOD) and peroxidase (POD) activity of leaves in Zea mays and Vigna radiate seedlings were investigated, the results showed that SOD activity greatly incresed while POD activity decreased under low concentration of aqueous extracts. With the increase of extract concentration, SOD activity gradually decreased and POD activity increased. The inhibition effect of aqueous extracts from underground parts on SOD acbitiry was higher than that from overground parts.5. Under low concentration of aqueous extracts, the malondialdehyde (MDA) contents in leaves of Zea mays and Vigna radiata decreased, while with the increase of extract concentration, the MDA contents increased gradually, and the effect of aqueous extract from underground parts on MDA content was stronger than that from overground parts.6. The root vigor of Zea mays and Vigna radiata seedlings increased under low concentration of aqueous extracts. With the increase of the concentration of extract, the root vigor decreased gradually, In addition, the inhibition effect of aqueous extracts from underground parts was stronger than that from overground parts.7. Under low concentration of aqueous extracts, the dry weight of root and shoot of Zea mays and Vigna radiata seedlings increased greatly, while with the increase of the concentration of extract, the dry weight decreased remarkably.8. The contents of chlorophyll a and b in leaves of Zea mays and Vigna radiata seedlings increased after treated by low concentration of aqueous extracts from overground parts of C. benghalensis. While with the increase of the concentration of extract, the total chlorophyll decreased. The inhibition effect under high concentration of aqueous extracts from underground parts was stronger than that from overground parts.9. Under low concentration of aqueous extracts, Fv/Fm and Fv/Fo in leaves of Zea mays and Vigna radiata seedlings increased a little, while decreased under high concentration. This indicated that the aqueous extracts from C. benghalensis inhibited the PS II primary light transforming efficiency as well as the primary reaction of photosynthesis in receptor crops. In addition, the photochemical quenching (qP) and non-photochemical quenching (NPQ) were also inhibited, which decreased the light transforming efficiency and the heat dissipating efficiency of chlorophyll, finally the photosynthetic organ was damaged under this kind of stress. |
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