| Indoor bioassay was adopted to study allelopathy of the several kinds of extracts of different parts of Dicranopteris pedata on tested materials and bacteriostasis mechanism on four bacteria. Different extracts from different parts or with different concentration were compared to find out their difference in different crops. For further studies, we discussed allelochemicals and its mechanisms of Dicranopteris pedata. The purpose of the research was using the allelopathy among plants to control farmland weed, exploit natural weedicide, reasonbly and effective use resources, provide the theory basis for developing the sustainable agriculture. The main results were as follows.1.The allelopathic effects of several kinds of extracts from Dicranopteris pedata on four receptor plants were bioassayed in lab. The results indicated that seed germination and seedling growth of the receptors showed specific response to allelochemicals and they were inhibited incoordinately with 0.02 gDW/mL extracts. The inhibition extent of these extracts to receptor seedlings were stronger than their seeds germination. The influence to the seeds had two forms, inhibiting and delaying germination. The length of shoots and roots was inhibited and the seedling had malformed symptom.Allelopathy of the same extract of the above-ground part was stronger than the under-ground part. To the same parts, allelopathy of ethanol extracts of Dicranopteris pedata was stronger than those of other extracts. The allelopathic effect on the shoots of receptor plants was stronger than that of roots. It was considered that allelopathy effect of Dicranopteris pedata to lettuce was more sensitive than on others.2.The ethanol extract from Dicranopteris pedata showed different allelopathic effects on seed germination and seedling growth of lettuce. In bioassay, 0.005 gDW·ml-1 ethanol extracts from Dicranopteris pedata inhibitory effects on the germination, seedling growth and roots growth of receptor plants, but 0.001 gDW·ml-1 ethanol extracts showed someway stimulating effects on lettuce growths. This results displayed that the concerntration depending effect with low stimulating and high-inhibitory.3.The activities of CAT,SOD,POD and the content of MDA of lettuce treated with ethanol extracts from leaf were determined during the Lactuca sativa seedling growth courses. The results showed that the influence of ethanol extracts on activities of CAT,SOD and POD in lettuce were significant, and the activity of SOD,POD and CAT in vivo first increased and then decreased. The balance of activate oxygen metabolism was broken. The cell membrane was destroyed, and the content of MDA increased. The growth and development of plants were effected seriously. Activity of root decreased with the extracts concentration increasing. The mechanism of the allelopathy is affecting the activity of protective-enzyme of lettuce and breaks the structure and function of embrane.4.The allelochemical in the three parts of Dicranopteris pedata were analysed primarily. The results showed that Allelopathic activity did not positively correlated with level of polyphenol in different parts. Different substance was observed from the three parts by HPLC.5.Using leaf, above-ground stem and under-ground stem as tested materials, with DW, 95% ethanol, acetone and petroleum ether as extracts, with E. coli,S. aureus, P. vulgaris and B. subtilis as tested bacteria, the method of bacteriostasis circle was used to test the antibacterial effects of different extracts to different bacteria. The results showed that the inhibiting zones diameter of four bacteria caused by leaf extracts from Dicranopteris pedata was biggest. The antibacterial activities of above-ground stems were stronger than the underground parts. Suppression manufacture of S. aureus was the best among the four kinds of bacterium,ethanolic extract and acetone extracts is stronger than aqueous extracts, while petroleum ether extracts has no obvious suppression effects.That is to say that, by different extraction methods and different bacterial, it would cause different suppression effects and antibacterial substances could be extracted compeletly by ethanol.
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