小麦和苜蓿根系分泌物中饱和烃馏分

为深入研究根系分泌物对根际土中有机物贡献的特点，用柱色层族组成分离方法， 对小麦和苜蓿根际土及二者交界地中提出的可溶有机物采用了GC/MS分析测定。从样品的非极性馏分中分析检测出正构烷烃、类异戊二烯烷烃及酯类3个系列的生物标志化合物，并对小麦地、苜蓿地及二者的交界地中的正构烷烃的奇偶优势比（OEP）、∑C₂₂^-/∑C₂₃⁺比值和姥植比（Pr/Ph）进行了分析比较。小麦和苜蓿的GC/MS的主峰均为nC₃₁，正构烷烃奇偶优势比OEP值大小顺序为苜蓿地>交界地>小麦地，且三者数值均>1.4。正构烷烃∑C₂₂^-/∑C₂₃⁺比值大小顺序为小麦地>交界地>苜蓿地。姥植比（Pr/Ph）的比较结果为苜蓿地>交界地>小麦地。这表明小麦和苜蓿根系分泌物进入土壤后演化程度不一样，小麦地有机质演化程度高于苜蓿地。

Saturated Hydrocarbon Fractions Root Exudates of Wheat and Alfalfa

For studying on the characteristics of organic substances in rhizospheric soil of advanced plants,the dissoluble organic substances in rhizospheric soil from wheat land and alfalfa (Medicago sativa) field were analyzed by the pole chromatographic composition separation(GC/MS). Three series of biomarkers (n-alkanes, isoprenoid alkanes and esters) were detected in the non-polar distillate. The odd-even preference (OEP) of n-alkane, the ratio of n-alkanes ∑C₂₂^-/∑C₂₃⁺ and pristane/phytane ratio (Pr/Ph) of biomarkers in the three fields (wheat land, alfalfa field and the border region) were analyzed. The main peak of n-alkane in wheat land and alfalfa field samples were both nC₃₁, and the order of OEP value of n-alkane was the alfalfa>the border region>the wheat >1.4, and then the order of the n-alkanes ∑C₂₂^-/∑C₂₃⁺ was the wheat>the border region>the alfalfa. Lastly, the sequence of the pristane/phytane ratio was the alfalfa>the border region>the wheat. The results showed that the evolution degree of organic substance from wheatland and alfalfa field was different and the former was higher than the latter.