Studies On Content, Activity And Inducing Effects Of DIMBOA In Wheat Seedlings

DIMBOA (2,4-dihydroxy- 7- methoxy -2H-l,4-benzoxazin-3 (4H)-one) was an important secondary metabolite in wheat seedlings. It has been paid much attention to because it was closely associated with wheat resistance to insects and pathogens. In this thesis, the content and activity of DIMBOA in wheat seedlings and its biological and chemical induction effects were studied.1- The systemic sum-up was done on the study development of allelopathic effects and DIMBOA in gramineous crops, and the development on plant chemical induction of anti-adversity was also been summarized.2. The pure DIMBOA was obtained by isolation and purification, and detection methods were made. Crystallised DIMBOA was obtained from corn seedlings (NONGDA108 and MZ37) after extraction, isolation and purification. Its structure was determined to be the same as reported in literatures. DIMBOA crystals were analysed with HPLC mounted with ODS C-18 reverse phase column employing an external standard quantitative method. The mobile phase of MeOH:H2O (50:50, V/V) was pumped at 1.0 ml/min and monitored at 220nm wavelength. The HPLC condition was optimized to giving satisfactory separation, high sensitivity and good repetition (RSD for peak area 1.18% and retention time 0.319%) .The formula of DIMBOA external standard curve: Area = 9.96212164*Amt + 0.3635223; R=0.999995. The analysis methods for wheat seedlings tissues and hydroponic solution have the advantages of high accuracy (recoveries > 90%) and good precision (CV < 5% ), all complying with the requirement of micro-analysis. DIMBOA was unstable in methanol solution, so sample solution must be finished analying with HPLC within 16 hours after preparation.3. It was firstly studied on the dynamic change of DIMBOA content everyday. After wheat seedlings were transplanted in hydroponic solution, the content of DIMBOA in the hydroponic solution increased gradually, peaked on the 8th day, and then decreased. The most rapid increasing phase was in the 6th day. So the best time to analyze DIMBOA content in hydroponic solution was determined to be the 6-8th day after being transplanted when studying DIMBOA exudated by roots of wheat seedlings4. HPLC quantitative analyses were carried out on DIMBOA contents in aerial parts and root parts of wheat seedlings of 32 test wheat cultivars as well as in the hydroponic solution. DIMBOA contents: for test wheat cultivars , aerial parts(55.6786ug/fwg)>root parts (42.005l g/fwg); for different wheat cultivars, resistant wheat cultivars > sensitive wheat cultivars. The ranks of all tested wheat cultivars in terms of DIMBOA content was followed such an order : High-resistance Group (Zhengzhou 90629, Dongfeng 611, Zhongfu 9507) > Medium-resistance Group (Zhongbeizhong 39, Baofeng 104,chul1497) > Low-resistance Group (Shuiyuan 11, LOVN10) > Sensitive Group (Beijing 837, Jing 411, Hongmanghong, Shaan 7895, Chancellor).The average DIMBOA content in each group was 62.75,23.28,13.98,7.66 g/fwg individually. The higher the DIMBOA content of wheat cultivar was, the stronger its resistance to insects and pathogens. A positive correlation exists between DIMBOA content and the resistance to insects and pathogens of wheat seedlingsDIMBOA contents were quantitatively analysed for the hydroponic solution of 157 wheat cultivars from 4 different kinds of wheat. The order of DIMBOA content exudated by roots of different wheat cultivars was as follows ,Trit\cum spelta wheat (44.23) > Triticum durum wheat (32.08) > Triticum aestivum L, spring wheat (24.19) > Triticum aestivum L, winter wheat (21.85) (the number in brackets denotes the average content of DIMBOA in test wheat cultivars, unit:ug/30 plants). DIMBOA content exudated by most of wheat cultivars fell below 25 ug/30 plants.5. The allelopathic effects of wheat remnants aqueous extracts were also studied. According to inhibitory ICso, the root-length inhibitory effects of aqueous extracts of Zhong fu 9507 wheat remnant to different young target plants: Digitaria sanguinalis (L) Scop> Poa annua L. >...