氮素营养对三七植株生长及其皂苷成分积累的调控机制研究

Panax notoginseng, which has more than 400 years cultivation history, is a characteristic biological resource of China, and its root is famous and valuable traditional Chinese medicine (TCM). There was a serious problems of excessive supply of nitrogen fertilizer in the production of P. notoginseng, and it has a strongly negative effect on the growth of P. notoginseng, such as reducing plant disease resistance, increasing diseasein field, decreasing the yield and quality of plant. It also impacted the safety of P. notoginseng product in clinical practice. So, it is very important to research the application of nitrogen in P. notoginseng. In this project, we adopt the technique of NIR, HPLC, microscopic identification and fingerprint to research the effect of different forms, level and application way of nitrogen on the growth and saponin accumulation of P. notoginseng by using pot experiment (sand culture and soil culture). The effect of nitrogen supply on the soil environment is also studied with the field experiment in order to find the law of regulation. And the tracer technique of 15N is used to study the law of N absorption, transport and distribution in P. notoginseng. We make further research on the photosynthetic efficiency, the carbon / nitrogen metabolism, hormone changes, mineral elements absorption and resistant physiological reaction of P. notoginseng with nitrogen supply. The correlation analysis is used to find the relationship between the physiological and biochemical index and saponins content. Based on the analysis, we verify the theory of adversity effect, indicate the regulation mechanisms of nitrogen supply on P. notoginseng from the physiological and biochemical responses, and give the scientific technique of nitrogen fertilization in production of P. notoginseng. All of these make further improvement on the quality and yield of P. notoginseng, and ensure the product of P. notoginseng to be safety, availability and stability.

三七为名贵中药材，也是我国独具特色的生物资源，具有重要的药用价值和经济价值。三七生产上普遍存在着滥施氮肥而导致植株抗病性降低、田间病害严重等问题，并造成三七产量和质量下降，严重影响临床用药安全，因此有必要对氮肥合理施用展开研究。本项目从植物和土壤两个层次，采用盆栽模拟试验（砂培、土培）和田间定位试验，利用IR、HPLC、显微鉴定和指纹图谱分析技术，系统研究不同氮素形态、用量和施用方式对三七生长发育、皂苷成分积累和三七立地土壤环境的影响及其调控，揭示相关调控作用规律；并采用15N示踪技术，分析三七对氮素营养的吸收、转运和分配规律；结合受控试验下植株光合效率、碳/氮代谢、激素变化、矿质元素吸收分配和植株抗逆性变化等生理生化反应，分析其同皂苷成分变化的关联性,验证中药材"逆境效应"理论，阐明调控的生理生化机制，确定生产上氮肥合理的施用技术，提高三七的品质与产量，保证三七产品安全、有效和稳定。

三七为名贵中药材，具有重要的药用价值和经济价值，市场上需求量不断扩大。开展规范化种植，是三七产业可持续发展的关键。种植生产上，施用氮肥是影响三七生长和药用成分皂苷合成代谢的重要因子。本项目以三七为研究对象，以不同形态氮素及其配比、氮肥用量和施用方式等作为试验因素，盆栽和大田试验结合，系统开展了氮营养对三七生长及皂苷成分积累调控的研究。结果表明：（1）三七为喜硝态氮植物，对硝态氮是主动吸收，施用硝态氮促进三七植株生长发育，提高产量和皂苷的累积量；而铵态氮对三七有着明显的铵胁迫毒害效应，三七对铵态氮是被动吸收，导致植株体内NH4+累积，抑制三七生长，降低三七产量和皂苷合成与累积。（2）生产上三七铵态氮胁迫途径和调控机理如下：三七种植立地环境为荫湿环境，大量施用铵态氮肥后，种植三七田间土壤不能及时硝化为硝酸盐（硝态氮），从而导致土壤酸化，表土大量的NH4+累积；三七根部对NH4+被动吸收，植株地上、地下累积大量的铵氮；累积的铵氮破坏了三七根尖生长点，导致根系活力降低和根部重要信号传导因子NO含量大幅下降，抗逆性指标（MDA、SOD、POD）上升，从而影响三七碳氮代谢；其中三七碳同化酶SS、SPS基因表达量大幅降低，植株可溶性糖、葡萄糖和蔗糖等碳代谢产物含量降低，而可溶性氨基酸和可溶性蛋白含量大幅上升，氮同化酶GS、GDH、NR活性降低。而且，被动吸收的NH4+不能及时转化，大量的氮积累在地下根部而不能转运到地上根部；植株积累的NH4+还拮抗了植株对K+、Ca2+和Mg2+的吸收累积，导致植株抗逆性下降；最终影响三七皂苷成分的合成和累积，导致三七中各单体皂苷和总皂苷含量的降低。（3）三七生产上氮肥的合理施用方式为：有机-无机氮各占50%配合施用，无机氮肥以硝酸钙等硝态氮肥为主（硝态氮比例不低于75%），氮肥合理施用量为150~300 kgN/公顷，氮肥70%做基肥施用，剩下30%一次性追施。施用氮肥时候，还应配合磷钾肥，特别是钾肥的配合施用。