Abstract: [Objective] HX2 can biosynthesize indole-3-acetic acid (IAA) and pyrroloquinoline quinone (PQQ).This study aims to focus on mechanisms of pyrroloquinoline quinone and indole-3-acetic acid in plant growth ptomotion of Rahnella aquatilis HX2.[Method]In this study, plant growth, nutrition absorption and root morphology of maize were analyzed by using tube and greenhouse experiments with the treatments of PQQ, IAA, HX2 and its derivative strains.[Result]Compared to the control, PQQ, IAA, and HX2 could significantly promote maize growth, including plant biomass (shoot length, root length, fresh weight and dry weight), plant nutrient (total nitrogen, total phosphorus and total potassium), and in the three treatments, HX2 treatment showed more effects on the maize growth.MH15, which was disrupted by the pqq gene could not produce PQQ, the maize growth also could be promoted compared to control.However, the effect of MH15 was lower than that of HX2 and CMH15(pqq).In PQQ and IAA treatments, slender root length, middle root length, total root length and root surface area of maize were improved, and the root average diameter of maize was reduced compared to the control.In treatment of HX2, root surface area, total root length, thick root length, middle root length and slender root length of maize were improved and maize root system was elongated and coarsened compared to the control.[Conclusion]IAA and PQQ, as promoting factors in HX2, were involved in regulating action in enhancing plant biomass.Also it can improve nutrient intake and enhance root morphology of maize.

摘要： [目的]Rahnella aquatilis HX2菌株能合成吡咯喹啉醌(PQQ)和吲哚乙酸(IAA),探明PQQ与IAA在HX2菌株促生作用中的作用与机理.[方法]通过试管苗试验、温室砂培试验,分别以纯品PQQ、纯品IAA、HX2菌株及PQQ合成缺失突变体及互补菌株等处理接种玉米,对各处理的玉米生长量、营养以及根形态方面的影响进行检测和分析.[结果]与空白对照相比,PQQ、IAA纯品处理均能在促进玉米生长方面均有好的效果,HX2处理在玉米生物量(株高、鲜重和干重)、玉米营养(全N、全P、全K)摄入有显著提高,处理效果更好;PQQ合成缺失突变体MH15处理,虽对玉米鲜重、干重、全N、全P与对照相比有促进作用,但与HX2和互补菌株CMH15(pqq)处理玉米的促生效果相比较低.纯品PQQ、IAA处理主要提高了其细根长、中根长、总根长的长度和根表面积增加,但其根平均直径降低;而HX2菌株处理增加了其细根长、中根长、粗根长的长度,使玉米根系不仅伸长,且根系变粗.[结论]PQQ可作为直接促生因子和IAA,共同参与了HX2菌株对增加玉米生物量,提高玉米营养的摄入,促进其根形态等方面起到关键调控作用,明确了HX2菌株-PQQ-玉米、HX2菌株-IAA-玉米之间的相互作用.