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The Journal of the Royal Institute of Thailand Vol. 30 No. 2 Apr.-Jun. 2005 404 The Influence of Stages of Floral Development on Essential Oil Composition in Cananga odorata (Lam.) Hook.f. & Thomson var. fruticosa (Craib) J. Sinclair cuttings which flowers readily as compared to the woody Kradang-nga Thai. Materials and Methods Plant Material Sixty out of 100 potted plants grown in 10 inches pot for 2 months were selected for experimental ma- terial. Plant cuttings were obtain- able at Chatuchak market. Experimental Design Completely randomized design was used by lottery technique. Determination of flower num- ber and fresh weight were done by tagging every flower to be counted and recorded on the first day of the month. At the end of the season, total number of flowers and fresh weight were calculated. Seasons were determined as summer (March-June), rainy season (July-October) and winter (Novem- ber-February) Essential oil study Flowers were collected in the summer, rainy and winter for essential oil extraction which will be analysed by GC and GC-MS. Extraction was done by steam distillation, solvent extraction with dichloromethane, reagent grade. GC used in this experiment is CP- 9001 (Chrompack) GC column was HP-5 fused silica capillary column (30 m Ó 0.25 mm. Ó 0.25 micromill.) produced by J and W Scientific Co, ltd. FID detector was used. Tempera- ture program was set at 45 degree celsius increasing at the rate of 3 degree C/min from 40-220 degree celsius and maintain temperature at 220 for 10 minutes. Injector tem- perature was set at 230 degree celsius while the detector was set at 240. Helium was the carrier gasat the rate of 2 ml/min. working on split mode at the ratio of 1:100. Injection volume was 1 ul. GC-MS used is the product of Varian model STAR 3400 Cx. with column HP-5 with the same temperature program as the one used in GC. Injector temperature was 230 and 270 for interface line. Carrier gas is helium at the rate of 2 ml/min., working as split mode in the ratio of 1:100. Injection volume was 0.3 ul. MS is SATURN 4 Dmade by varian directly coupled with GC. lon source was set at 230 and aver- age electron energy was 70 eV. Identification of each compound of the essential oil was done by com- paring the retention indices and mass spectra compared with NIST library computerized in the GC-MS set up. Determination of the quantity of the component was done by calculating percentage of peak area in GC chromatograms, computerized by normalization method from the equation. % A = area under peak Ó 100 total peak area Experimental Site Analysis was done in KU labor- atory both at Kamphaeng Saen and Bang Khen Campus. Field work was done in Kanchanaburi. Result and Discussion The floral development in Cananga odorata or Kradang-nga Thai was first observed from floral bud to green stage in 14-21 days and then from green to greennish yellow and finally yellow in about 20-25 days, when the petal base developed a reddish spots. This is the stage ready for flower harvest (Weiss 1997), but the situation is different in Cananga odorata var. fruticosa which last 38 - 46 days for full maturity ready to harvest. This dif- ferences may be due to genetics and/ or environmental factors. (Figure 13) Essential oil composition of Kradang-nga Songkhla seemed to exhibit little degree of differences, during stages of floral development. At the floral green, yellowish green, greenish yellow and yellow stages, the most abundant compound of the essential oils were mainly the same. The most abundant was α -farnesene. Other compounds with high amount are N-amylpyrrole, β - caryophyllene and germacrene D. Ding, et al (1988) also found similar essential oil composition. The highest one was β -caryophyllene followed by r-muurole, α -farnesene and α - humulene respectively. Hudaib, et al (2002) studied essential oil harvested from 2 year and 5 year old thyme in the same season, both yielded thymol at the highest level in June and July. Overton and Manura (2002) found that essential oil of chrysanthemum increased as flowers became more mature, perhaps due to increasing growth rate and as a consequence, increasing metabolism.