植物内生菌Pantoea sp. PP04促进杂交狼尾草生长及提高其耐盐能力的作用机制研究

发布时间：2019-03-09 14:50

【摘要】：象草(Pennisetum purpureum Schum)、杂交狼尾草(Pennisetum americanum×P.purpureum)作为优质牧草和能源植物原料,在畜牧业、生物质能源与材料以及造纸工业都有较为广泛的应用价值和潜力。但是,其在盐碱等边际性土地的规模化、产业化种植,却面临着生物质产量低,耐盐能力差的问题。植物内生菌是一种重要的根际微生物,能促进植物生长、提高宿主抗逆性,同时还能有效地改造盐碱地。我们研究所的前期工作已从象草根际成功筛选出能够促进杂交狼尾草生长的泛菌属(Pantoea sp.)PP04菌株,并对其进行了促生特性、植物内定殖能力等初步研究,发现其具有固氮、溶磷的能力和较高的ACC脱氨酶活性。但是,该内生菌在植物规模化种植中的应用途径、相关技术与机制仍未明确,针对这一问题,本研究试图明确其在不同盐胁迫条件下,对宿主植物种子萌发和幼苗生长的影响及其缓解盐胁迫的作用机制,为象草、杂交狼尾草内生菌生物肥料开发及应用奠定理论基础。具体结果如下:1.泛菌属PP04内生菌能够有效缓解中(200 mmol·L-1)、低(100 mmol·L-1)盐浓度胁迫对杂交狼尾草种子萌发的毒害作用,对种子的发芽率、发芽指数、胚芽长度都有显著的增益和改善作用。在低盐浓度胁迫下,施加内生菌(E+),种子发芽率、发芽指数和胚芽长度较E-(未施加内生菌处理)组分别高出16.25%、19.59%、20.98%,在中盐胁迫条件下,E+植物发芽率提高21.28%,发芽指数提高35.75%,胚芽长度是E-处理的3.36倍。然而,在高盐(300 mmol·L-1)胁迫条件下,内生菌缓解盐胁迫的毒害能力作用下降或不明显。2.泛菌属PP04显著降低盐胁迫对杂交狼尾草生物量的影响,增加其叶绿素含量和根系活力。尤其在100、200 mmol·L-1的NaCl浓度下时,内生菌促生长作用最明显,E+组株高较E-组增加29.24%、18.33%,鲜重增加59.44%、49.00%。3.在不同浓度盐胁迫下,泛菌属PP04能够通过诱导增加杂交狼尾草体内过氧化氢酶(CAT)、抗坏血酸酶(APX)、超氧化物歧化酶(SOD)和过氧化物酶(POD)活性。在100 mmol·L-1盐处理下,E+组的上述四种酶活性较E-组分别增加64.18%、73.14%、32.34%和65.40%,表明PP04通过调节植物体内的抗氧化酶活性,减少膜脂过氧化产物MDA的积累,从而缓解盐环境对杂交狼尾草造成的氧化胁迫,增强其耐盐能力。4.PP04可通过增加杂交狼尾草渗透调节物质的含量来提高植物对盐胁迫的耐受能力。特别是在中、高盐浓度下,E+处理显著提高脯氨酸、可溶性蛋白和可溶性糖的含量。在低、中盐浓度下,E+处理的杂交狼尾草地上部分P含量的积累增加,从一定程度上提高其耐盐能力。低浓度的NaCl使得植物体内K+/Na+与无盐胁迫相比降低了62.08%,但施加内生菌能够使杂交狼尾草的K+/Na+比未施加内生菌显著提高47.14%。本文初步明确了泛菌属PP04内生菌通过诱导杂交狼尾草体内的几种主要抗氧化保护酶的活性、增强其渗透调节能力及调节离子平衡等三种作用机制,显著缓解了盐胁迫条件对杂交狼尾草生长的毒害,进而促进和保证了杂交狼尾草种子正常萌发及幼苗生长。研究结果表明,该菌株是优良的杂交狼尾草植物的促生内生菌,但实际生产应用中还需考虑多方面的因素,进行实际的大田试验环节,以期实现内生菌的产业化,对于该菌株将来在各种生态环境中发挥长期稳定的作用具有十分重要的现实意义。
[Abstract]:As a raw material of high-quality forage and energy plant, the pennisetum purpureum Schum and the Pennisetum americanum (P. purpureum) have a wide application value and potential in the animal husbandry, the biomass energy source and the material and the paper industry. However, the large-scale and industrialized planting of marginal land, such as saline and alkali, faces the problems of low biomass yield and poor salt tolerance. The plant endophytic bacteria is an important rhizosphere microorganism, which can promote the growth of the plant, improve the stress resistance of the host, and can effectively transform the saline-alkali soil. The preliminary work of our institute has been successfully screened from the grass-roots level to promote the growth of the hybrid Pennisetum (Pantanea sp.). ) The P04 strain and its growth-promoting property and the ability to colonize the plant were studied, and it was found that it had the ability of nitrogen fixation, phosphorus-dissolving and high ACC deaminase activity. However, the application of the endophytic bacteria in the large-scale plant cultivation of the plant remains unclear. In response to this problem, the present study attempts to clarify the effect of the endophytic bacteria on the germination of the host plant seeds and the growth of the seedlings under different salt stress conditions and the mechanism of the action to alleviate the salt stress. In ord to lay a theoretical foundation for that development and application of the endophytic bacteria, such as grass and hybrid Pennisetum. The specific results are as follows:1. Pan-type PP04 endophytic bacteria can effectively relieve the toxic effects of the medium (200 mmol 路 L-1) and low (100 mmol 路 L-1) salt concentration on the germination of the hybrid Pennisetum. The germination rate, the germination index and the germ length of the seeds have significant gain and improved effect. Under the stress of low salt concentration, the germination percentage, the germination index and the germ length of E + were 16.25%, 19.59% and 20.98%, respectively. Under the condition of medium salt stress, the germination percentage of E + plants increased by 21.28%. The germination index was increased by 35.75%, and the length of the germ was 3.36 times that of E-treatment. However, under the condition of high salt (300 mmol 路 L-1) stress, the toxic ability of endophytic bacteria to relieve the salt stress is reduced or not obvious. The effect of salt stress on the biomass of the hybrid Pennisetum was significantly reduced by the pan-strain PP04, and the content of chlorophyll and the activity of the root system were increased. In the concentration of 100,200 mmol 路 L-1, the growth of endophytic fungi was the most obvious. The higher E-group of E + group increased 29.24%, 18.33% and the fresh weight was 59.44%, 49.00%. Under the stress of different concentration of salt, the P04 can increase the activity of catalase (CAT), ascorbic acid (APX), superoxide dismutase (SOD) and peroxidase (POD) by inducing the increase of the in-vivo catalase (CAT), ascorbic acid (APX), superoxide dismutase (SOD) and peroxidase (POD). Under the treatment of 100 mmol 路 L-1 salt, the above four enzyme activities of E + group increased by 64.18%, 73.14%, 32.34% and 65.40%, respectively, indicating that PP04 can reduce the accumulation of MDA in the membrane lipid peroxidation products by adjusting the antioxidant enzyme activity in the plant, And the resistance of the plant to salt stress can be improved by increasing the content of the osmotic adjusting substance of the hybrid Pennisetum. In particular, in that medium and high salt concentration, E + treatment significantly improve the content of proline, soluble protein and soluble sugar. Under the low and medium salt concentration, the accumulation of P content in the ground part of the hybrid of the E + was increased, and the salt tolerance was improved to a certain extent. The low concentration of NaCl reduced the K +/ Na + in the plant by 62.08%, but the application of endophytic bacteria could increase the K +/ Na + ratio of the hybrid Pennisetum to 47.14%. In this paper, the activity of the main anti-oxidation protective enzymes of the P04 endophytic bacteria of the genus P04 through induction, the osmotic adjustment ability and the regulation of the ion balance are enhanced, and the toxicity of the salt stress condition to the growth of the hybrid Pennisetum is obviously relieved. So as to promote and ensure the normal germination of the hybrid Pennisetum and the growth of the seedlings. The results of the study show that the strain is an excellent endophytic bacterium of the hybrid Pennisetum, but it is also necessary to take into account various factors in the practical production application, so as to realize the industrialization of endophytic bacteria. It is of great practical significance for the strain to play a long-term and stable role in various ecological environments in the future.
【学位授予单位】：江苏大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：S54

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