Allelopathic Herbicidal Activity And Their Mechanism Of Common Weeds

Weed is the formidable enemy for the production of agriculture and animal husbandry, not only being harmful to agriculture and other related industry but also threatening the native environment, especially the biology diversity. Bio-herbicides with the advantages such as rich resources, low toxicity, little residues, security for non-target organisms and good compatibility of environment etc, have being emphasized step by step. In recent years, effective weed control by allelopathy characteristics of plants in agricultural and animal husbandry ecosystem has been studied and applied widely.In this thesis, the plants of allelopathic herbicidal activities on the common weed Ipomoea cairica in southern china were screened. Thermopsis lanceolata and Aconitum sinomontanum were selected at last. A series of physiological indexes of Ipomoea cairica, Raphanus sativus and Cucumis sativus treated by the whole plant, alkaloids, monomer of Thermopsis lanceolata and Aconitum sinomontanum were studied. The mechanism and target sites of different allelopathic active components of Thermopsis lanceolata and Aconitum sinomontanum were investigated. We hope the results will provide valuable information for the development of botanical herbicide. The main results are as follows:1. The seed germination speed and rate of Ipomoea cairica were inhibited by aqueous extracts from 32 species. 12 plants inhibited more strongly the seed comprehensive germination of Ipomoea cairica.2. Both seed germination and seedling growth of Ipomoea cairica were inhibited by aqueous extracts from 12 species primarily selected. The allelopathy of donor plants on the stem and leaf were stronger than on the root at the same concentration. Ligularia sagitta, Thermopsis lanceolata, Stellera chamaejasme, Ajania tenuifolia, Wedelia trilobata, Setaria viridis, Aconitum sinomontanum, Euphorbia helioscopia and L. virgaurea inhibited more strongly (M←0.50) the seed germination stage of Ipomoea cairica. Thermopsis lanceolata, Aconitum sinomontanum and Stellera chamaejasme inhibited more strongly (M←0.50) the seedling growth stage of Ipomoea cairica.3. Combined the seed germination and seedling growth, Thermopsis lanceolata(-0.73), Aconitum sinomontanum(-0.64), Stellera chamaejasme(0.63) and Ligularia sagitta (-0.62) showed better result. Therefore, Thermopsis lanceolata and Aconitum sinomontanum were selected to study their mechanisms.4. 131.1g alkaloids were extracted by alcohol extraction from 3 kg hay meal of Thermopsis lanceolata and the extraction rate of alkaloid was 4.37 %. 25.62 g alkaloids were extracted by alcohol extraction from 6 kg hay meal of Aconitum sinomontanum and the extraction rate of alkaloid was 0.43 %.5. The allelopathy of alkaloids and non-alkaloid of alcohol extract of Thermopsis lanceolata and Aconitum sinomontanum on Ipomoea cairica, Raphanus sativus and Cucumis sativus were studied. Alkaloids inhibited more strongly than non-alkaloid of alcohol extract both seed germination and seedling growth of those three acceptors. Alkaloids were the main allelochemicals of the two plants.6. The whole plant, alkaloids, thermopsine of Thermopsis lanceolata all inhibited significantly the chlorophyll content, photosynthetic rate, and the activities of Rubisco and pyruvate kinase and anabolism of soluble sugars. The inhibition of thermopsine was the most. Alkaloids of Aconitum sinomontanum inhibited strongly the activities of pyruvate kinase and anabolism of soluble sugars and soluble protein.7. The whole plant of Thermopsis lanceolata and Aconitum sinomontanum inhibited more strongly the activities of root dehydrogenase of Ipomoea cairica, Raphanus sativus and Cucumis sativus than alkaloids.8. According general change of the activities of PAL, SOD and MDA content of Ipomoea cairica, Raphanus sativus and Cucumis sativus which suffered from allilopathic stress, the whole plant, alkaloids, thermopsine of Thermopsis lanceolata all inhibited significantly those indexes, and the inhibition of thermopsine was the most. The inhibition of alkaloids of Aconitum sinomontanum was stronger than the whole plant.9. Thermopsinewhich was the important allelochemical of alkaloids of Thermopsis lanceolata inhibited strongly the activities of key enzymes of photosynthetic system and substance metabolism, such as Rubisco, the key enzyme of photosynthetic system and pyruvate kinase, the key enzyme of Glycolysis. Thermopsine can be deeply researched and developed into botanical herbicide. Alkaloids of Aconitum sinomontanum also can be developed into botanical herbicide as target active components and found allelopathic monomers whose activities are stronger.