湖北清江和尚洞洞顶植物叶片和土壤的类脂物对比及其意义

用GC-MS对湖北清江岩溶地区和尚洞洞顶植物叶片与该洞上覆土壤层中的类脂物进行了分析和对比。在植物叶片中检测出了一系列直链烷烃、脂肪酸、以及丙三醇、植醇和甾醇等类脂物,其中直链烷烃的碳数分布范围大体在C21～C36之间,以C29或C31为主峰且具有奇偶优势;脂肪酸的分布主要集中在中、短链脂肪酸内（C数<23）,以C16为主峰呈单峰型分布且具有偶奇优势;醇的分布很不规则,仅检测出丙三醇,植醇和三种甾醇,没有检测到脂肪酮类化合物。与之相比,洞顶上覆土壤层中检测出更加丰富的类脂物。类脂物具有如下特征:正构烷烃以C31为主峰,还存在低碳数正构烷烃和异构烷烃,如2-甲基、3-甲基、4-甲基、5-甲基、6-甲基、7-甲基、8-甲基等一系列的单甲基支链烷烃,这些支链烷烃显示了微生物的贡献;脂肪酸分布也以低碳数的C16为主峰,且低碳数脂肪酸的含量较植物叶片中明显的增加,同时一些异构和反异构脂肪酸（C14∶0,C15∶0和C17∶0）以及一些单不饱和脂肪酸（C16∶1,C17∶1,C18∶1和C20∶1）也被检测到,也表明土壤中的脂肪酸不仅存在高等植物的贡献,还存在微生物的来源;没有植醇,但出现姥鲛烷和植烷并检测到了一系列脂肪醇化合物,碳数分布在C21～C36之间;检测到一系列的酮,具有奇偶优势,碳数分布范围在C23～C30和C33。高等植物叶片和土壤的差异反映了微生物对高等植物类脂物输入到土壤过程的重要贡献。本研究工作不仅提供了该岩溶地区植物叶片的类脂物信息,还为研究土壤有机质的来源和植物叶片中类脂物在地质过程中的转变提供信息,更为研究岩溶地区滴水和石笋中类脂物的来源提供一定的参考。

COMPARISON OF LIPID COMPOSITIONS BETWEEN PLANT LEAVES AND OVERLYING SOIL IN HESHANG CAVE,QINGJIANG,HUBEI PROVINCE AND ITS SIGNIFICANCE

Using the studied the Lipids from plant leaves and overlying soil in the Heshang Cave in Qingjiang,Hubei Province have been analyzed by GC-MS.In plant leaves we detected a series of n-alkanes,fatty acids,Glycerol,phytol,and some phytosterols.N-alkanes have odd prominence than even and their carbon number distribution ranges from C21 to C36 with the dominance of C29 or C31.Fatty acids have even prominence and show a single model with the dominance of C16 which belongs to the middle and short range（<23）.Some polyunsaturated fatty acids such as C18 ∶2 also exist.The distribution of n-alkanols was irregular with only Glycerol,phytol,and some types of phytosterols detected.No n-alkan-2-ones was found.In the overlying soil,n-alkanes generally have odd prominence and their carbon number distribution ranges from C15 to C34 with the dominance of high number carbon,C31.These characters are similar to plant leaves.However some low carbon length n-alkanes and branched alkanes such as the monomethylalkanes series of 2-methylalkanes,3-methylalkanes,4-methylalkanes,5-methylalkanes,6-methylalkanes,7-methylalkanes,and 8-methylalkanes suggesting not only plant but also microorganism origins are also detected from the overlying soil.For fatty acids,the soil has more content of low carbon length fatty acids than plant leaves.For example it has C14 ∶0,C15 ∶0,and C17 ∶0 even though they all with the C16 dominance.In addition,we also detect some branched and anti-branched fatty acids（C14 ∶0,C15 ∶0,and C17 ∶0）and some monounsaturated fatty acids（C16 ∶1,C17 ∶1,C18 ∶1,and C20 ∶1）,which also show microorganism origin.In soil we also detect high content of long length fatty acids that were not detected in plant leaves.They may also come from microorganism as microorganism is reported to be able to synthesize some long carbon length fatty acids.Phytol is not detected from soil but pristane,phytane,and a series of n-alkanols have been found,which have even carbon prominence and with the range from C12 to C30.We also detected a series of n-alkan-2-ones with odd carbon prominence and carbon number distribution ranges from C23 to C30 and C33.The result of comparison between plant leaves and soil not only gives some information about plant leaf lipid features but also provides some information about the origin of organic matters in soil.For example,n-alkan-2-ones may from n-alkanes β-oxidation by microorganism.