硅提高盐胁迫下甘草药材产量和甘草酸含量的潜力及机制研究

Glycyrrhiza uralensis Fisch. is among the most important and widely used medicinal plants in traditional Chinese medicine, which is mainly distributed in desert and semi-desert area of northwest China. At present, the resource shortage has affected the sustainable development of traditional Chinese medicine industry and the ecological safety of northwest area in China. .Therefore, it has become a hot topic that how to stabilize and improve the yield and quality of G.uralensis cultivated in the saline soil in northwest China. However, recent studies showed that salinity stress increased the relative content of glycyrrhizic acid in root, but significantly inhibited plant growth and yield of G.uralensis, which result in the absolute content of glycyrrhizic acid in root was significantly reduced under salinity sterss condition. it is extremely important to find ways to improve salt tolerance of G.uralensis. To ensure traditonal Chinese medicine industry security and sustainable economy, it is extremely important to find ways to improve salt tolerance of G.uralensis. Silicon (Si) is the most abundant element in the earth's crust after oxygen. As an environment friendly element, Si is known to ameliorate the deleterious effects of salt on plant growth. The present study aims to improvement of G.uralensis production under different saline conditions using Si treatment. In this study, hydroponics simulation experiments were conducted to investigate the effect of Si on seed germination abilities, seedling growth and some metabolic activities including certain antioxidant enzymes to elucidate the role of Si in alleviating salt stress on G.uralensis plants at seed germination and seedling growth stages, further to optimize the level of Si for seed germination and seedling growth of G.uralensis under different saline environment. On this basis, a pot experiment was undertaken to analyse the effect of Si on growth and yield, physiological character, secondary metabolites, primary metabolites in cultivated G.uralensis under salt stress. The aim is to clarify the potential and mechanism of Si improvement growh, yield and glycyrrhizic acid accumulation of G.uralensis under salinity stress. This study should provide scientific basis for improving cultivation of G. uralensis by increasing its medicinal yield and quality under the saline soil in northwest China.

甘草为大宗传统中药材，年需求量居诸药之首，野生资源主要分布于我国宁夏、甘肃、内蒙等西部的荒漠半荒漠地区。目前其资源危机已威胁到中药产业和西北地区的生态安全，因此如何在西北大面积盐渍化土壤发展甘草种植、提高土地利用率已成为亟待解决的问题。本项目针对盐胁迫提高甘草酸含量的同时不能兼顾产量的问题，基于环境友好型元素硅有提高植物抗盐能力的特性，拟采用水培试验研究硅对盐胁迫下甘草种子萌发出苗、幼苗生长的促进效应及其生理生化机制；采用盆栽试验研究硅对盐胁迫下成药期甘草生长及产量、生理生化特性、主要次生代谢产物、初生代谢产物的影响，通过相关、通径等分析方法解析产量和甘草酸与其它各指标及硅浓度间的关系，揭示硅提高盐胁迫下甘草产量和甘草酸含量的潜力，阐明硅调控盐胁迫下甘草生长和甘草酸生物合成与积累的机制，确定不同程度盐胁迫下兼顾甘草产量和质量的需硅量，为甘草在西北大面积盐渍化土壤的高产优质栽培提供科学依据。

本项目采用沙培试验研究了外源硅对不同程度盐胁迫下甘草种子萌发出苗阶段和幼苗生长阶段的调控效应及其生理生化机制；采用土培盆栽试验研究了硅对不同程度盐胁迫下成药期甘草生长、产量和生理生化特性、活性成分等的影响效应，阐明硅提高盐胁迫下甘草药材产量和甘草酸含量的潜力及机制，为甘草在西北大面积盐渍化土壤的高产优质栽培提供科学依据。取得主要成果如下：.种子发芽和幼苗生长阶段： Si通过改变离子平衡、抗氧化系统和内源激素水平，进而促进盐胁迫下甘草种子萌发、幼苗生长及生物量积累，且这种作用程度因盐胁迫程度和Si浓度而异。.成药期土培盆栽阶段：（1）加Si处理明显促进甘草生长、增加其生物量。Si通过提高抗氧化系统的酶活性来减轻盐胁迫引起的氧化胁迫，调控K+、Na+和Si的吸收和分配来缓解盐胁迫引起的离子毒害，进而改善内源激素浓度及比例，最终缓解盐胁迫对甘草生长的抑制作用，提高其产量。（2）Si处理改变了NaCl胁迫下甘草主要物质组分含量的总和及比例，较高浓度Si提高了采样中期总糖所占比例，降低了粗纤维所占比例，为后期甘草酸等的合成提供了更多的起始物。（3）Si降低了不同程度NaCl胁迫下甘草酸合成中间产物角鲨烯和β-香树脂醇的含量。（4）Si提高了甘草药材活性成分积累量，但不同程度NaCl胁迫下Si提高各活性成分积累量的作用方式不同。具体表现为：在较低浓度NaCl胁迫下，Si主要通过增加活性成分相对含量来提高药材活性成分积累量；而在较高浓度NaCl胁迫下，Si主要通过同时增加生长量和活性成分相对含量来提高药材活性成分积累量。（5）Si提高不同程度盐胁迫下甘草酸的积累量，主要是通过促进根部生长、调整物质组分所占比例和提高次生代谢产物含量来实现的，其中前者主要通过调节抗氧化系统、离子平衡、植物内源激素等生理生化过程，进而缓解盐胁迫造成的伤害，维持其正常生长所致；后者主要通过调控物质组分含量及比例，进而促进总黄酮和总皂苷积累和促进甘草酸生物合成中间产物向甘草酸转化来实现。