落叶松(Larix gemelinii)苗挥发物两种收集方法的对比分析

Comparison of two collecting methods for analysis of volatiles of Larix gemelinii seedings

采用预浓缩和固相微萃取(SPME)2种方法对2年生兴安落叶松苗挥发物成分进行采集并做GC-MS分析。结果表明,落叶松苗挥发物主要成分为萜烯类化合物,其中α-蒎烯、4(10)-侧柏烯、莰烯、β-蒎烯、D-柠檬烯和β-水芹烯所占比例较高;整株、针叶和树皮挥发物的组成和含量存在差异,针叶中饱和烷烃含量较高,树皮中倍半萜烯、醇、酮和酯类挥发物含量较高,并且这2种组织经SPME采集检测的挥发物中石竹烯和α-蛇麻烯含量增加幅度较大,它们可能在昆虫近距离寄主定位中起作用。对2种气体收集方法的分析比较,认为预浓缩结果接近落叶松挥发物组分和含量的自然特征,SPME受萃取头纤维特性的影响,对倍半萜稀类化合物吸附作用强,对烷烃吸附差,并且不同化合物的同时存在可能影响其吸附效率,导致检测量准确度下降,因此预浓缩法更适合植物挥发物定性和定量分析。

Plant volatiles play an important role in host recognition and selection by insects. We used GC-MS analysis to determine the composition and concentration of volatiles from two year old Larix gmelinii seedlings using two collecting methods： cryogenic trapping pre-concentration and solid-phase microextraction （SPME）. Larix gmelinii seedlings contained 70 compounds including terpenes, hydrocarbons, alcohols, ketones, and esters. The major compounds were terpenes including α-pinene, 4（10）-thujene, camphene, β-pinene, D-limonene and β-phellandrene, together comprising more than 75% of total volatiles. The compositions and concentrations of volatiles differed among stem, needle and bark tissues. Needles contained higher levels of saturated hydrocarbons, while more sesuiterpene, alcohol, ketone and ester were found in bark than in stem tissues. The presence of caryophyllene and α-humulene was readily detected in bark by using SPME. These compounds probably facilitate short-distance location of host plants by insects. Of two pre-treatment methods, we found the results from cryogenic trapping pre-concentration were most similar to the natural characteristics of Larix gmelinii volatiles. In the experiments with SPME, the characteristics of adsorbent fiber could affect the absorption of some compounds. More sesuiterpene and less hydrocarbon were detected with SPME than with cryogenic trapping pre-concentration. We hypothesize that the various co-existing volatiles differentially affected the effect of adsorbent fiber, further reducing the accuracy of detection by SPME. We found cryogenic trapping pre-concentration to be useful for qualitative and quantitative analyses of volatiles.