干旱胁迫下草地早熟禾克隆分株间氮素生理整合及其机制

The clone plant of Kentucky bluegrass (Poa pratensis L.) is the most widely used cool-season turfgrass in Northern China. Both water and nitrogen content are two important factors adjusting the growth and ornamental quality. The current project continues to investigate the physiological adjustment mechanism of Kentucky bluegrass to nitrogen under drought stress and to reveal the pattern and mechanism of nitrogen transmission, transfer, distribution, and sharing between clonal ramets in population, by morphological, physiological, population ecological, and molecular biological theories and advanced technologies. The project is based on the characteristics and mechanisms of nitrogen metabolism of unique Kentucky bluegrass under water stress. The main study includes: investigation of clone ramet morphological plasiticity, growth, and nitrogen physiological integration, and its morphological mechanism under drought stress; study of direction, intensity, and transmission pattern of nitrogen integration between clone ramet under drought stress; study of adjustment mechanism of nitrogen physiological integration by enzyme system, osmoregulation substances, physiologically active substances and its genes expression; screening effective indexes of nitrogen integration of Kentucky bluegrass under drought stress.The results will be important to support the theory of plant nutrition metabolism and transportation, as well as to be significant in practice for turfgrass breeding.

克隆植物草地早熟禾（Poa pratensis L.）是我国北方应用最多的优良冷季型草坪草。水分和氮素是限制其生长和观赏质量的两个极其重要因素。本项目基于前期草地早熟禾单株水分胁迫下氮代谢及其机制研究基础上，采用形态学、生理学、种群生态学及分子生物学等多学科的理论和先进技术，拟创新性地探索草地早熟禾克隆分株群体水平上响应干旱胁迫的氮素生理整合特征，揭示氮素在群体水平上克隆分株间传输、转移、分配和共享的格局及其机制。主要研究内容有：干旱胁迫下草地早熟禾克隆分株形态可塑性、生长发育与氮素生理整合；草地早熟禾响应干旱克隆分株间氮素生理整合的方向、强度及传输格局；草地早熟禾克隆分株细胞中酶系统、渗透调节物质、生理活性物质及其基因调控氮素生理整合的机制。综合分析比较筛选出缺水条件下草地早熟禾克隆分株有效氮素生理整合特征指标。研究结果对丰富植物养分代谢与传输理论及培育草坪新品种具有重要理论和现实意义。

项目背景：从水氮两大限制草坪质量的环境因素着手，基于草地早熟禾由单株克隆的群体水平研究同源分株响应水分胁迫氮素生理整合特征和机制，弄清氮素在群体分株间传输、转移、分配和共享的格局，丰富和完善前期基于单个植株的水氮相关研究。采用形态学、生理学等技术揭示其内在机制。主要研究内容：干旱胁迫下草地早熟禾克隆分株形态可塑性、生长发育与氮素生理整合；草地早熟禾响应干旱克隆分株间氮素生理整合方向、强度及传输格局；草地早熟禾克隆分株细胞酶系统、渗透调节物质、生理活性物质及其基因调控氮生理整合机制。重要结果：干旱严重影响了同质和异质生境中草地早熟禾的农艺、结构和生理特性，而土壤氮素的适度供给可以减缓干旱的损伤，表现在提高了叶片含水量和水势，降低了组织碳氮比，提高了草坪草表观及生理特性，使组织结构完好。适宜水氮条件下，氮向基运输分配量多于向顶运输，且铵态氮对远端分株传输较多，硝态氮对近端分株传输较多；低氮水分下，铵态氮倾向于向顶运输到近端分株的叶片上，远端分株的叶片及根部分配的较少，同时干旱增强了铵态氮向基和向顶传输的能力，硝态氮向基分配的较多；高氮条件下，无论是根部还是叶部，中端分株的氮丰度最高。铵态氮处理的含水量及水势均高于硝态氮处理，且DR＞MR＞PR。不同水氮处理，硝酸还原酶、亚硝酸还原酶、谷氨氨酰胺合成酶、1,5-二磷酸核酮糖羧化酶活性均表现为硝态氮处理高于铵态氮处理，克隆分株间的渗透调节物质、抗氧化酶、氮代谢关键酶及生理活性物质在不同分株间存在生理整合。PpTIP1和PpGS1基因表达响应低氮和高氮及水分胁迫。铵态氮处理的基因表达量显著高于硝态氮处理的植株。PpTIP1基因在植株的根颈部位表达量高于叶片和根部，而PpGS1基因在根部的表达量高于根颈和叶片。通过研究可以有效筛选克隆分株间水氮代谢和整合的特征指标，对丰富植物养分代谢与传输理论及培育草坪新品种具有重要意义。