Extraction, Separation And Identification Of Thepolar Metabolites In Cassava Leaves And The Study Of Drought Resistance

Cassava (Manihot esculenta Crantz) belongs to the Euphorbiaceae. It is an important food crop, and also provides feed stock for starch and bioethanol industry. Cassava has high productivity, barren and drought resistance. Its drought resistant mechanism has been a hot research topic, and the physiological and molecular mechanism has been reported. However, little information is、available on the metabolic mechanism. In this research we established the methods to extract and identify metabolites in cassava, and studied the metabolic mechanism of drought resistance on the metabonomics level.In the research of metabonomics, the very important step is to prepare the sample, which was easily degraded by enzymes when it was extracted. Therefore it is very important to avoid the metabolite’s degradation. The conventional methods include temperature and pH control. The temperature control is easy to perform. In order to get a great quantity of metabolites, we tested different temperature and derivatization reagents to make sure that there are enough metabolites and the derivative reaction was complete. We investigated three varieties of cassava that have different drought resistance. The photosynthesis and proline content was measured as indicators to make sure that the cassava was in drought stress. We found the change of Fv/Fm in photosynthesis under drought stress. The main results of this investigation were listed below:(1)The GC analyses showed that most abundant metabolites were extracted when the temperature was70℃. MSTFA was the best derivatization reagent. The best analysis conditions were obtained with injection volume of lμL, and injection pattern splitting with a rate of10:1, the smooth baseline was obtained.(2)The data processing method was Principal Component Analysis (PCA). The changed metabolites under drought stress can divide into eight kinds.(3) Through GC/MS analysis and database comparison, about36metabolites were identified from the extracted metabolites. Most of them were primary metabolites and the rest were secondary metabolites. The secondary metabolites accounted for most of the metabolic differences between varieties, while most of the primary metabolites were consistent in varieties. The metabolite that displayed the largest difference between varieties was not identified, which was very possible to be related to drought resistance.(4) We analyzed various saccarides with HPLC-ELSD method in different species of plants. We found that trehalose is the saccharide that present only in cassava but not in other species. The trehalose was proved to be related to drought resistance.