旱盐逆境下硅提高甘草综合水分利用效率的生理生态机制

Glycyrrhiza uralensis Fisch. is among the most important and widely used medicinal plants in traditional Chinese medicine. At present, the G. uralensis of artificial cultivation is the main resource for market supply. Irrigation is main way for the normal growth of G. uralensis during the artificial planting. However, on the one hand, the shortage of water resource and soil salinization are particularly serious in main producing areas of G. uralensis; on the other hand, long-term irrigation will not only aggravate the shortage of water resources in G. uralensis artificial planting, but also to cause soil secondary salinization. At prsent, it has become a hot topic that how to improve the water use efficiency of G. uralensis under salt environment in the artificial planting. As an environment friendly element, Silicon (Si) has vital importance effect on plant water use efficiency and salt tolerance. The present project aims to improvement of G. uralensis water use efficiency under saline and drought conditions using Si treatment. In this project, a pot experiment was carried out to determine the effect of Si on growth, physiological biochemical character, water use efficiency and quality of G. uralensis under different degree drought and salt stress, and further to study the relationship between water use efficiency, quality and other index. Thus, the purpose was to confirming the regulation effects of Si on water use efficiency and quality of G. uralensis under different degree drought and salt stress, and futher to exploring the mechanism of silicon on water use efficiency and quality of G. uralensis under salt and drought environment. This study should provide research-based data for improving cultivation of G. uralensis by improving its water use efficiency and quality under salinization desert in northwest China, and further to play the role in healthcare, water conservation and ecological protection.

甘草为大宗传统中药材，年需求量居诸药之首。甘草主产区宁夏、甘肃、内蒙等地水资源短缺、土壤盐渍化严重，甘草种植的长期灌溉不仅会加剧这些地区水资源匮乏的困境，更容易引起土壤次生盐渍化；且其种植面积的不断扩大必然会出现与农作物争地的矛盾。本项目基于野生甘草抗旱耐盐的生理特性，利用环境友好型元素硅（Si）有提高植物抗旱性和耐盐性的特点，结合Si可提高盐胁迫下甘草幼苗水分利用效率（WUE）的预实验结果，采用盆栽试验研究盐生境中，Si对不同程度干旱胁迫下甘草生长、生理生态特性、药材品质及基于产量和品质的综合水分利用效率（CWUE）的影响，明确盐生境中Si对不同程度干旱胁迫下甘草CWUE的调控效应，通过相关分析和通径分析解析盐生境中甘草CWUE与其它各指标、干旱胁迫程度及Si浓度间的关系，揭示旱盐逆境中硅提高甘草CWUE的潜力及生理生态机制，为甘草在西北大面积盐渍化荒漠区的高效节水栽培提供科学依据。

本项目采用土培盆栽试验，以一年生甘草为材料，研究了Si对旱盐胁迫下甘草生长、药材产量和品质、生理生态特性和综合水分利用效率等的影响效应，阐明Si提高旱盐逆境下甘草综合水分利用的生理生态机制，为甘草在西北荒漠区的高效节水栽培提供科学依据。取得主要成果如下：.1. 生长、药材产量和品质：Si能促进旱盐胁迫下甘草生长，提高药材产量和品质，且这种促进效应因胁迫程度和生长进程而异。.2. 生理生态特性:（1）Si通过提高抗氧化酶活性和非酶抗氧化剂含量缓解了旱盐胁迫对甘草造成的膜脂过氧化损伤，但具体抗氧化酶种类和非酶抗氧化剂种类因胁迫程度和生长时期而异。（2）Si显著降低了旱盐胁迫下甘草根、茎、叶中Na+含量，进而提高了K+/Na+； Si在处理后期明显影响了有机渗透调节物脯氨酸、可溶性糖、可溶性蛋白质含量，这三者之间相辅相成，协调一致地发挥渗透调节作用。（3）Si通过提高甘草叶片碳代谢关键酶SS和SPS活性、氮代谢关键酶NR和GS活性，进而加强碳氮代谢、提高代谢产物碳和氮含量，且此效应以SD2最明显。（4）Si有效缓解了旱盐胁迫对甘草叶片结构造成的损伤，提高了叶绿素含量、RWC及光合参数（Pn、Tr、Gs和Ci），最终提高WUEP。（5）Si明显促进了旱盐胁迫下甘草根对Si的吸收和运转，显著提高了甘草叶片中Si含量。.3. 综合水分利用效率及其机制： Si提高旱盐逆境下甘草CWUE是通过提高WUEBY、WUEEY和WUEQ共同实现的，且这三种均受多因素控制的。首先Si在活化土壤营养的同时，促进甘草对Si 的吸收及运输缓解旱盐逆境对甘草叶片结构的损伤；进一步通过调控抗氧化系统缓解旱盐胁迫造成的氧化损伤，通过降低Na+、提高K+和Ca2+浓度来缓解旱盐胁迫造成的离子毒害，提高脯氨酸等有机渗透调节物质含量进而提渗透调节能力，进而调节碳氮代谢平衡，维持正常的生长，提高生物量和药材产量，最终提高WUEBY、WUEEY。与此同时，Si参与了甘草体内次生代谢产物再分配过程，进而影响甘草中有效成分含量，提高甘草药材中药效成分总量，最终提高WUEQ。