【作者】 王卫卫；

【导师】 胡正海；

【作者基本信息】 西北大学 ， 植物学， 2003， 博士

【摘要】 对陕西、甘肃黄土高原地区的豆科29属63种野生及栽培豆科植物结瘤及固氮状况进行了野外调查和室内分析，新发现10种结瘤豆科植物，他们是山合欢(Albizzia kalkora)、扁茎黄芪(Astragalus complanatus)、胀萼黄芪(A.ellipsoideus)、糙叶黄芪(A.scaberrimus)、小花香槐(Cladrastis sinensis)、银豆(Falcata japonica)、野大豆(Glycine soja)、多花木蓝(Indigofera amblyantha)、百脉根(Lotus corniculatus)、黄花木(Piptanthus concolor)。采集根瘤的过程中发现在水分充足地带如河滩、田埂、树林等处的豆科植物容易结瘤且长势较好，而荒坡、沙地等缺水处的豆科植物结瘤较少并且形状较小。另外，同种豆科植物在湿润条件下容易结瘤，在干旱条件下不易结瘤。表明豆科植物的结瘤情况与环境关系密切，受环境条件的影响较大。 比较研究表明，由于生态条件不同，豆科植物生活习性多样，从而使根瘤形态具有多种特征。根瘤形态大体可以分为两类：一类以苜蓿、草木樨、三叶草、红豆草等为代表，这种根瘤是长圆形的，较小，分生组织在顶端皮层以内，长圆形的根瘤可以是单个的，也可以聚集在一起，如此则形如掌状或生姜状，多呈不规则形态。另一类以大豆、国槐、菜豆的根瘤为代表，它们是圆形的，分生组织带状，在皮层内，根瘤大都单个存在。一般来说，生于山地草原，天然草场和林间湿地的豆科植物一年生草本居多，其根瘤也是一年生，在形态上较为规则，一般为圆形、长圆形，并带有粉红色，而分布于阳坡地带的多年生豆科乔木、灌木，其根瘤形态多为长柱状，且多具分叉，其颜色以白色、褐色、黄色者居多，着生部位多居于侧根、须根上，主根上很少有瘤。根瘤的直径大小也不一样，其中最小的是百脉根的根瘤，直径为0.8mm；较大的根瘤，如紫荆根瘤直径可达18mm。豆科植物的根瘤形态主要与植物种类有关，同属不同种的豆科植物根瘤形态往往是相似的。 从豆科的牧草、沙生植物、灌木、乔木及豆科作物共计25属46种51份根瘤样品中，分离、纯化，获得根瘤菌47株，将获得根瘤菌菌株部分回接于原寄主植物，27d以后可以结瘤。这些菌株大都在酵母—甘露醇培养基上生长良好，并能分泌大t的粘多糖。一般3d形成菌落，菌落为圆形，边缘整齐，无色透明或乳白色，具有光泽。对其中的14株根瘤菌在个体形态特征方面进行了观察及生理生化试验，所得结果表明，来自不同植物根瘤的分离物其菌体形状有差异，但革兰氏染色均呈G-，在光学显微镜、电子显微镜下观察，有明显的异染颗粒区，可见菌体内有苏丹黑染色类脂颗粒存在.菌株3一酮基乳糖试验均为阴性.菌株在石蕊牛奶培养小5d后，石蕊变红，牛奶开始凝固.部分菌株发酵乳糖产酸l较高，能很快使牛奶凝固. 菌株的氢离子浓度实验结果表明，供试菌株90%能在pH6.0~6.5Y侧叭培养基上生长，85%能在pH6.o一7.5条件下生长，15%能在pH7.0~7.5条件下生长良好.分离自首楷的根瘤菌株对pH适应范围较宽，为pHS.)7.5，其它大部分在pH 5 .5一7.5范围内生长良好。供试菌株大多在NaCI浓度为50/007%范围内生长良好，分离自首楷的根瘤菌株表现出较强的耐受性，在NaCI浓度为10%~15%范围内也能生长或生长良好。表明该地区根瘤菌对盐有较强的忍耐性.供试菌株在60℃条件下处理IOmin，仍然有50%的菌株能正常生长。可见，分离于此区域内的菌株有较强的温度适应能力和对高温有较强的耐性。 对黄土高原地区以及新疆、甘肃、宁夏等不同生态环境中所采集的500余个根瘤样品进行了乙炔还原活性比较，测定结果表明，陕西、甘肃黄土高原地区采集的根瘤样品中85%以上的根瘤为有效根瘤，不同种根瘤的固氮活性差异比较大，一般活性都比较低，小于l林molCZ困gFwh的占46.6%，大于10林molCZ执/gFWh的仅占6.8%，最高者仅37.73脚olCZH斌gFWll。在西北广大地区栽培历史悠久，面积较大的紫花首稽(MediC口90 sativa)、长柔毛野豌豆(巧cia viltosa)、大豆(Glycine max)、白花三叶草(Meditotus albus)以及豌豆(P sativum)等固氮活性都较高。 影响豆科植物结瘤固氮的主要因素和影响豆科植物根瘤固氮活性的因子是十分复杂的。研究分布于西北地区沙漠、戈壁、荒地的野生豆科植物的结瘤状况，发现在高温、干旱季节并非所有的豆科植物都能结瘤，就是结瘤的豆科植物并非都有固氮能力。一般分布于农田田埂、河滩水分比较好的区域根瘤均具有固氮活性或固氮活性较高，而分布于戈壁、沙漠或沙丘豆科植物根瘤，一般固氮活性较低或没有固氮活性。 在自然条件下，植物的生活习性不同，其根瘤活力也不一致，但是生活习性相同的同一种植物其根瘤的固氮活力也有差异，通常是随分布地点不同而异。因此，根瘤的固氮活性的表现与植物的生活习性关系较小，而环境条件对根瘤活性的影响较大。 在早春冬雪融化，土壤湿度大，有利于植物根系的生长发育及土壤中根瘤菌的活动，从而促进根瘤菌对植物根系的侵染和结瘤共生.当土壤湿度不同时，根瘤在不同生育期表现出不同的固氮活性，因此，土壤水分是影响根瘤生长和固氮活性表达的重要因子。 西北干早地区根瘤，对更多还原

【Abstract】 The condition of nodulation and nitrogen fixation of wild and cultural leguminous plants belong to 63 species, 29 genera were field surveyed and indoor analysed. 10 species not reported previously were found nodulated, they were Albizzia kalkora, Astragalus complanatus, A. ellipsoideus, A. scaberrimus, Argyrolobiu argenteum, Glycine soja, Indigofera amblyantha, Lotus orniculatus, Piptanthus nepalensis. During the period of collecting nodules, it was observed that Leguminous plants distributed in region where water is enough, such as beach, field border, woodlot and so on, nodulated easily and nodules grew well, on the contrary, Leguminous plants grown on bareness and sand nodulated less and size of nodules were little. On the other hand, the same leguminous plant nodulated easily under the condition of moist, and nodulated difficultly under the condition of drought. It showed that nodulation condition was related with environment closely and was affected by the environment condition.Comparative studies suggested that with the difference of ecological condition, the life habits of leguminous plants were varied, and there were all kinds of characteristics in the morphology of the nodules. The nodules were divided into two sorts according to the different morphology: one sort was represented by the nodules of Medicago sativa , Melilotus suaveolens, Trifolium repens, Onobrychis viciifolia, which was long round, the size was little, meristem was in the tip cortex, and grew signally or aggregated together to form a palmate or a ginger structure; the other sort was presented by Glycine max, Phaseolus vulgaris, which was round, meristem was barred and in cortex, grew signally. In general, leguminous plants distributed inmountain grassland, native grassland and wet land were mainly annual herb, their nodules were also annual, the form of the nodules was regular, such as round and long round, the color was pink. While, leguminous plants grown in heliophilic area were perennial tree and shrub, their nodules mainly were long round, branched and white, brown or yellow, grew from lateral roots and fibrous root. The diameter of nodules were different, the smallest was the nodule of Lotus orniculatus, about 0.8mm; bigger nodule was one of Cercis chinensis, about 18mm. The morphology of nodules were mainly related with the plant, the nodule morphology of different species belong to the same genera was always similar.From the sample of 25 genera, 46 species, 51 nodules including leguminous pasturage, psammophyte, shrub, tree and field crops, 47 rhizobia were isolated and purified. Then part of them were inoculated to host plants, they nodulated after 27 days. These strains were able to grow in YMA medium well, and secreted glycosaminoglycan. In general, they could form bacterial colonies after 3 days. Colonies were round with luster, the edge were regular, transparent or lacte. The morphology characteristics of 14 strains purified were observed and at the same time physiological and biochemical tests were performed. The results showed there were differences in the morphology of bacteria from different nodules, the Gram staining showed G", An apparent metachromatic granular region was observed under microscope and electron microscope, which indicated there were lipid granular stained with Sudan black in rhizobia.The results of hydrogen ion concentraion experiment of strain showed that 95% of the rhizobia grew on YMA at pH 6.0-6.5, 85% at pH 6.0-7.5,15% at 7.0-7.5. The optimum pH range for rhizobia from Medicago sativa was 5.0-7.5, but most of them could grew at 5.5-7.5. Results above showed that the range of pH for rhizobia collected from the Loess Plateaus were wide. Most of rhizobia for experiment could grow well at the range of 5%~7% NaCl, and the rhizobia from Medicago sativa showed high tolerance, they could grew or grew well at the range of 10%-15% NaCl, which indicated that the tolerance of rhizobia to salt was related with the concentration of salt of soil where the rhizobia were collected. When they were treated for 10更多还原