Allelopathic Effects and Chemincal Components of the Volatiles from Cedrus deodara Leaves and Branches

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.