Moradtalab Narges, Weinmann Markus, Walker Frank, Höglinger Birgit, Ludewig Uwe, Neumann Guenter
Institute of Crop Science (340h), University of Hohenheim, Stuttgart, Germany.
Institute of Phytomedicine (360), University of Hohenheim, Stuttgart, Germany.
Front Plant Sci. 2018 Apr 26;9:420. doi: 10.3389/fpls.2018.00420. eCollection 2018.
Low soil temperature in spring is a major constraint for the cultivation of tropical and subtropical crops in temperate climates, associated with inhibition of root growth and activity, affecting early growth and frequently plant performance and final yield. This study was initiated to investigate the physiological base of cold-protective effects induced by supplementation with silicon (Si), widely recommended as a stress-protective mineral nutrient. Maize was used as a cold-sensitive model plant, exposed to chilling stress and low root-zone temperature (RZT) during early growth in a lab to field approach. In a pot experiment, 2-weeks exposure of maize seedlings to low RZT of 12-14°C, induced leaf chlorosis and necrosis, inhibition of shoot and root growth and micronutrient limitation (particularly Zn and Mn). These phenotypes were mitigated by seed treatments with the respective micronutrients, but surprisingly, also by Si application. Both, silicon and micronutrient treatments were associated with increased activity of superoxide dismutase in shoot and roots (as a key enzyme for detoxification of reactive oxygen species, depending on Zn and Mn as cofactors), increased tissue concentrations of phenolics, proline, and antioxidants, but reduced levels of HO. These findings suggest that mitigation of oxidative stress is a major effect of Zn, Mn, and Si applied as cold stress protectants. In a soil-free culture system without external nutrient supply, Si significantly reduced large leaching losses of Zn and Mn from germinating seeds exposed to low-temperature stress. Silicon also increased the translocation of micronutrient seed reserves to the growing seedling, especially the Zn shoot translocation. In later stages of seedling development (10 days after sowing), cold stress reduced the root and shoot contents of important hormonal growth regulators (indole acetic acid, gibberellic acid, zeatin). Silicon restored the hormonal balances to a level comparable with non-stressed plants and stimulated the production of hormones involved in stress adaptation (abscisic, salicylic, and jasmonic acids). Beneficial effects of Si seed treatments on seedling establishment and the nutritional status of Zn and Mn were also measured for a field-grown silage maize, exposed to chilling stress by early sowing. This translated into increased final biomass yield.
春季土壤低温是温带气候下热带和亚热带作物种植的主要限制因素，它会抑制根系生长和活性，影响早期生长，并常常影响植株表现和最终产量。本研究旨在探究补充硅（Si）所诱导的抗寒效应的生理基础，硅被广泛推荐为一种应激保护矿物质营养元素。玉米被用作冷敏感模式植物，采用从实验室到田间的方法，在其早期生长阶段使其遭受低温胁迫和低根区温度（RZT）。在盆栽试验中，将玉米幼苗置于12 - 14°C的低根区温度下2周，会导致叶片黄化和坏死、地上部和根系生长受抑制以及微量营养素缺乏（特别是锌和锰）。这些表型通过用相应的微量营养素进行种子处理得到缓解，但令人惊讶的是，施用硅也能缓解。硅和微量营养素处理均与地上部和根系中超氧化物歧化酶活性增加（作为活性氧解毒的关键酶，依赖锌和锰作为辅因子）、组织中酚类、脯氨酸和抗氧化剂浓度增加以及过氧化氢水平降低有关。这些发现表明，减轻氧化应激是作为冷胁迫保护剂施用的锌、锰和硅的主要作用。在无外部养分供应的无土培养系统中，硅显著减少了遭受低温胁迫的发芽种子中锌和锰的大量淋失。硅还增加了微量营养素种子储备向生长中的幼苗的转运，尤其是锌向地上部的转运。在幼苗发育后期（播种后10天），冷胁迫降低了重要激素生长调节剂（吲哚乙酸、赤霉素、玉米素）的根和地上部含量。硅将激素平衡恢复到与未受胁迫植物相当的水平，并刺激了参与胁迫适应的激素（脱落酸、水杨酸和茉莉酸）的产生。对于通过早播遭受低温胁迫的田间种植青贮玉米，也测定了硅种子处理对幼苗建立以及锌和锰营养状况的有益影响。这转化为最终生物量产量的增加。
