导　　师： 陈佩琼;黎晓峰

学科专业： 090302

授予学位： 硕士

作　　者： ;

机构地区： 广西大学

摘　　要： 苜蓿/(Medicago sativa L．/)是豆科“牧草之王”，但它难以适应低pH的土壤条件。为阐明低pH和铝对苜蓿的毒害机理，本文以艾菲尼特品种为试验材料，研究低pH和铝胁迫下苜蓿的生长及其对苜蓿共生结瘤信号传递的影响。研究结果表明： 1．低pH和铝胁迫抑制苜蓿根的伸长 苜蓿在pH 4.5条件下生长12 h和24 h后，根伸长仅为对照/(pH6.5/)的73.9％和72.4％，而3、6、9 μmol／L的AlCL/_3处理24 h，根伸长分别被抑制25.2％、57.0％和73.2％。可见，低pH以及在低pH下的铝都能抑制苜蓿根的伸长。 2．低pH和铝胁迫抑制苜蓿根瘤菌/(R．meliloti/)的生长 在pH 5.0、4.7和4.5的YM液体培养基培养24 h后，R．meliloti菌悬液的OD/_/(600/)值仅为对照/(pH 7.0/)的4.8％、3.2％和3.0％，而3、6和9 μmol／L的AlCl/_3处理24 h后，活菌数分别减少47.4％、63.2％和84.2％，这说明低pH和铝胁迫抑制R．meliloti的生长。因而在接种R．meliloti条件下，随着pH的降低和铝浓度的升高，苜蓿根毛变形率降低。 广肠大学硕士学位掩文低pH和招赫透对首粉共生结劝佗号传邀的形响研究 3.低pH和铝胁迫阻碍结瘤信号的传递 在不接种R.meliloti也不加入结瘤因子/(NF/)的情况下，pH4，5 和9林mol几的AICI:处理对根毛变形无显著影响，而在NF存在但不 接种尺.meliloti条件下，pH4.5和3、6、9林mol几的AIC13使首蓓根 毛变形率分别减少45.92/%、44.59/%、71.43/%和80.09/%，说明低 pH 和铝胁迫条件抑制结瘤信号的传递。 4.低pH和铝胁迫抑制首蓓的结瘤和生长 低pH抑制首蓓的结瘤和生长。在pH 4 .5条件下，接种R.meliloti 3Od后，总根瘤数、有效根瘤数、地上部鲜重和干重分别比对照减少 11.8/%、23.2/%、16.74/%和16.23/%;铝胁迫� To elucidate the mechanisms responsible for the transduction of nodulation signal in symbiotic nitrogen-fixation system, the effects of low-pH and aluminum /(Al/) on the root hair deformation in Medicago sativa L. /(alfalfa/), which is sensitive to Al, was investigated in this study. After the roots had been exposed to 3, 6 or 9 mol//L A1Cl3 solution /(pH 4.5/) for 24 h, primary root elongation was notably inhibited. Similarly, the rate of root hair deformation decreased significantly with decreased pH or elevated Al concentrations. After the roots had been exposed to 4, 5 and 6 mol//L A1C13 in the presence of R. meliloti for 24 h, root hair deformation was depressed by 44.59/%, 71.43/% and 80.09/%, respectively. Although the growth of Rhizobia was restricted by low-pH and Al, the depressing effect of low-pH and Al on the deformation could also be observed after exposing the roots to the low-pH /(pH 4.5/) solution with sterilized Nod factor /(NF, isolated from the medium with R. meliloti and the exudates of alfalfa seeds /) or to which combined Al /(3, 6 or 9 mol//L AlCl3/) with sterilized NF for 24 h. The rate of root hair deformation was depressed by 45.92/%, 44.59/%, 71.43/% and 80.09/%, respectively. These results suggested that low-pH and Al would inhibit the transduction of nodulation signal in symbiotic nitrogen-fixation system. Primary root elongation, root hair deformation and nodulation in alfalfa were suppressed by low-pH and Al, depressing effect of low-pH and Al was strengthened with decreased pH or elevated Al concentrations. One hand, low-pH and Al inhibited the growth of alfalfa and R. meliloti. On the other hand, nodulation signal transduction in symbiotic nitrogen-fixation system was depressed by low-pH and Al. Therefore, the nodulation and the growth of alfalfa in low-nitrogen soils were inhibited by low-pH and Al.

关 键 词： 低 铝胁迫 结瘤 信号 传递 根毛变形 结瘤因子 苜蓿

领　　域： [农业科学]