Allelopathy of the volatiles from isolated leaves and branches of C. deodara to seed germination of Brassica pekinensis, Raphanus sativus and Lactuca sativa were studied in a semi-closed container. The componenets of llelochemicals were determined by GC-MS. The results indicated that germination rate and dry weight of B. pekinensis, R. sativus and L. sativa were not significantly affected by the natural volatiles released by the leaves and branches of C. deodara, but seedling growth was significantly inhibited. The volatile oil from leaves and branches of C. deodara had significant inhibitory effects on the germination rate, germination index, root length and seedling length of seeds of these three vegetables. Germination rate and germination index of L. sativa were inhibited by 92.85%and 96.43%, respectively, while root length of B. pekinensis were inhibited by 51.3%, suggesting that there were potential allelochemicals in the natural volatiles released by the leaves and branches of C. deodara that inhibited seed germination, and that the allelopathic effect of volatile oil was stronger than natural volatile compounds. The chemical components of volatile oil and natural volatile were analyzed. In particular, 37 volatile chemical compounds were identified in volatile oil and 84.64%of these volatiles were α-pinene(24.72%), β-pinene(21.04%) and Caryophyllene(12.42%). 22 volatile chemical compounds were identified in the natural volatile and 52.81% of them were terpenes. The main components were α-pinene(17.16%), β-pinene(11.53%) and Bicyclo[3.1.0]hex-2-ene, 4-methyl-1-(1-methylethyl)-(13.06%). Both the volatile oil and natural volatile shared, but the volatile oil had relatively high terpene content. The components and chemical profile of volatile oil were both more than that of natural volatile, which might be a reason for the stronger allelopathic effect of volatile oil than than that of natural volatile. Seen from the results of analysis, terpenes were the main components of C. deodara that may be associated with the allelopathic effects.%采用半密闭容器测定法，研究了离体雪松（Cedrus deodara）枝叶挥发性物质对白菜（Brassica pekinensis）、萝卜(Raphanus sativus)、莴苣（Lactuca sativa）种子萌发的化感作用，并对其成分进行了GC-MS分析。结果表明：雪松枝叶的自然挥发物对白菜、萝卜和莴苣的发芽率和干质量影响不显著，但对萌发的芽长产生显著的影响，而挥发油对受体种子的发芽率、发芽指数、萌发的根长以及芽长均产生显著的抑制作用，其中对莴苣的发芽率和发芽指数的抑制效应达到92.85%和96.43%，对白菜种子萌发的根长的抑制效应达到51.3%，表明雪松枝叶的挥发物中存在潜在的化感物质，抑制种子的萌发，且挥发油的化感作用大于自然挥发物。对挥发油和自然挥发性成分分析结果表明，两种方法收集的挥发性气体中均鉴定出大量的萜烯类化合物，其中挥发油中鉴定出37种化合物，84.68%为萜烯类化合物，主要成分为α-蒎烯（24.72%）、β-蒎烯（21.04%）、1-石竹烯（12.42%）；自然挥发物中鉴定出22种化合物，52.81%也都是萜烯类化合物，主要成分为α-蒎烯（17.16%）、β-蒎烯（11.53%）、b-侧柏烯（13.06%），两者共有成分15种，均为萜烯类化合物，其中挥发油中的成分含量较高，挥发油中化学成分的种类以及成分含量均大于自然挥发物，这可能是导致挥发油的化感作用大于自然挥发物的一个原因。从成分的分析结果可以看出，萜烯类化合物是雪松挥发性物质的主要成分，因此雪松枝叶挥发物的化感作用可能与其中的萜烯类物质有关。
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