| Summary: | 碩士 === 國立屏東科技大學 === 生物科技研究所 === 96 === Litchi chinensis Sonn., a family of Sapindaceae, is a subtropical commercial orchard crop. Our field observations revealed that the leaf residues of L. chinensis could retard the growth of plants in its surroundings. The objective of this research is to evaluate the allelopathic potential of leaf residues from L. chinensis. The aqueous and methanol extracts were examined against Lactuca sativa L., Brassica chinensis L., Raphannus sativus L. and Medicago sativa L. by standard sponge bioassay and pot experiments. Compared with the aqueous extract from leaf and shoot, the aqueous extract of leaf significantly suppressed the radicle growth of all tested seeds. The highest inhibitory effect on radicle growth was observed on lettuce (L. sativa). The inhibitory effect was increased as the concentration increased. The seasonal variation of allelopathic potential was also investigated, and results showed that leaves residues collected in June exhibited highest allelopathic potential. Meanwhile, the ethyl acetate and dichloromethane fractions of methanol extract of leaves also revealed significant phytotoxic effects on the radicle growth of test plants. In addition, the growth of Bidens pilosa and Ageratum houstonianum in soil (vermiculite-perlite-peat moss, 3:1:1, v/v/v) mixed with the leaf powder of L. chinensis (1g leaves/30g soil) was also markedly suppressed but the growth of Amaranthus tricolor was not affected. Furthermore, the proanthocyanidin A1 (500µg/ml) isolated from L. chinensis leaves has significant inhibition on the radicle growth of Brassica chinensis L. Raphanus sativus L. and Medicago sativa L. These results indicated that the L. chinensis has distinguished allelopathic potential and could be used as natural herbicide for weed control.
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