窿缘桉和尾叶桉的化感作用研究

ALLELOPATHIC EFFECTS OF Eucalytus exserta AND E.urophylla

窿缘桉和尾叶桉是华南地区重要的人工林树种。研究表明，两种桉树叶片在密闭容器中产生的挥发性物质对萝卜、莴苣、新银合欢和马占相思的幼苗生长有显著抑制作用，而对种子萌发无显著影响。水蒸汽蒸馏法所得３个组分中，水溶性非挥发性物质的化感作用最强。当挥发油浓度达到０２ｍＬ／皿时，可完全抑制马占相思的幼苗生长。挥发油在土壤中前１５ｄ分解较快，以后分解较慢。窿缘桉和尾叶桉水抽提物对萝卜、莴苣幼苗生长有显著抑制作用，窿缘桉水提物对马占相思苗高有显著抑制作用。

Eucalytus exserta and E. urophylla are two important tree species of man-made forests in South China. Leaf volatiles of them had significant inhibitions on seedling growth of Raphanus sativa, Lactuca sativa,Leucaena leucocephala and Acaia mangium. In comparsion of allelopathic effects of the three fractions from the distillation of fresh leaves, the declining order was: water soluble unvolatile chemicals > volatile oil > water soluble volatile chemicals. Volatile oils of the two Eucalytus could completely inhibite the seedling growth of A. mangium when volatile oil concentrations are 0.2 milliliter per culture dish. Allelopathic effects of volatile oil decompositing in soil would decline very quickly within 15 days. After that, it would maintain a certain level with significant inhibition. The aqueous extracts of fresh leaves of the two plants showed inhibitory effects on seedling growth of radish and luttuce. The aqueous extracts of E. exserta also inhibited the seedling growthg of A. mangium. The aqueous extracts of E. urophylla inhibited the seedling growth of L. leucocephala.