Moradtalab Narges, Ahmed Aneesh, Geistlinger Joerg, Walker Frank, Höglinger Birgit, Ludewig Uwe, Neumann Günter
Institute of Crop Science (340h), University of Hohenheim, Stuttgart, Germany.
Institute of Bioanalytical Sciences, Anhalt University of Applied Sciences, Bernburg, Germany.
Front Plant Sci. 2020 Apr 24;11:396. doi: 10.3389/fpls.2020.00396. eCollection 2020.
Low soil temperature in spring is a major constraint for the cultivation of tropical crops in temperate climates. This study aims at the exploitation of synergistic interactions of micronutrients, consortia of plant growth-promoting microorganisms and N forms as cold-stress protectants.
Maize seedlings were exposed for two weeks to low root zone temperatures at 8-14°C under controlled conditions on a silty clay-loam soil (pH 6.9) collected from a maize field cultivation site. A pre-selection trial with fungal and bacterial PGPM strains revealed superior cold-protective performance for a microbial consortium of OMG16 and with Zn/Mn supplementation (CombiA), particularly in combination with N-ammonium as a starting point for the characterization of the underlying physiological and molecular mechanisms.
In nitrate-treated plants, the cold stress treatment increased oxidative leaf damage by 133% and reduced the shoot biomass by 25%, related with reduced acquisition of phosphate (P), zinc (Zn) and manganese (Mn). The supplying of N as ammonium improved the Zn and Mn nutritional status and increased the ABA shoot concentration by 33%, as well as moderately increased detoxification of reactive oxygen species (ROS). Moreover, use of N as ammonium also increased the root auxin (IAA) concentration (+76%), with increased expression of auxin-responsive genes, involved in IAA synthesis (), transport (), and perception (). Additional inoculation with the microbial consortium promoted root colonization with the inoculant strain OMG16 in combination with ammonium fertilization (+140%). An increased ABA/cytokinin ratio and increased concentrations of jasmonic (JA) and salicylic acids (SA) were related to a further increase in enzymatic and non-enzymatic ROS detoxification. Additional supplementation with Zn and Mn further increased shoot IAA, root length and total antioxidants, resulting in the highest shoot biomass production and the lowest leaf damage by oxidative chemical species.
Our results suggest the mitigation of cold stress and reduction of stress priming effects on maize plants due to improved ROS detoxification and induction of hormonal stress adaptations relying on the strategic combination of stress-protective nutrients with selected microbial inoculants.
春季土壤低温是温带气候下热带作物种植的主要限制因素。本研究旨在开发微量营养素、促进植物生长的微生物群落和氮形态之间的协同相互作用，作为冷胁迫保护剂。
在可控条件下，将玉米幼苗置于8-14°C的低根区温度环境中两周，土壤为从玉米田种植地采集的粉质粘壤土（pH 6.9）。一项针对真菌和细菌促植物生长微生物菌株的预选试验表明，OMG16微生物群落与锌/锰补充剂（组合A）具有卓越的冷保护性能，特别是与铵态氮结合，以此作为表征潜在生理和分子机制的起点。
在硝酸盐处理的植株中，冷胁迫处理使叶片氧化损伤增加了133%，地上部生物量减少了25%，这与磷（P）、锌（Zn）和锰（Mn）的吸收减少有关。以铵态氮形式供应氮改善了锌和锰的营养状况，使地上部脱落酸（ABA）浓度增加了33%，并适度增加了活性氧（ROS）的解毒作用。此外，使用铵态氮作为氮源还使根系生长素（IAA）浓度增加（+76%），生长素响应基因的表达增加，这些基因参与生长素的合成（）、运输（）和感知（）。额外接种微生物群落促进了接种菌株OMG16在根系的定殖，特别是与铵态氮肥结合时（+140%）。脱落酸/细胞分裂素比值增加以及茉莉酸（JA）和水杨酸（SA）浓度增加，与酶促和非酶促ROS解毒作用的进一步增强有关。额外补充锌和锰进一步增加了地上部生长素、根长和总抗氧化剂，从而使地上部生物量产量最高，氧化化学物质对叶片的损伤最小。
我们的结果表明，通过改善ROS解毒作用以及依靠应激保护营养素与选定的微生物接种剂的策略性组合诱导激素应激适应，可减轻玉米植株的冷胁迫并减少胁迫引发效应。
