基于非标记化学成像的大气中铅颗粒物的茶树叶面吸收机理研究

Foliar uptake of airborne lead is an important way for transfer of exogenous lead from environment to plant. Plant cuticle acts as the first structural barrier between environment and leaves, its composition and structure are the important material basis of foliar lead uptake, so it is of profound significance to reveal the mechanism of cuticle in foliar uptake of lead. Focusing on the scientific topic of foliar uptake of lead, this project aims at construction of the interaction system of airborne lead particulates and foliar based on in situ chemical imaging technique taking tea as the research object. Firstly, in situ chemical imaging of cuticle composition and microstructure is developed based on confocal Raman microspectrometry. And the chemical nature, structure and arrangement of the cuticle components (cutin, waxes, phenolics and polysaccharides etc.) under lead stress will be detected in cross section and profile based in situ chemical imaging method. Then the composition and microstructure of cuticle will be combined with the speciation and temporal dynamic distribution of internalized lead, and a synchronous fusion analysis will be made to explore the effect mechanism of lead speciation, particle size, cuticle thickness, composition and structure of cuticle for the foliar lead uptake. At last, a interaction system will be established from leaf tissue, cellular and sub-cellular level to molecular level based on the in situ chemical imaging technique. So this project will illustrate the pathway and mechanism of foliar uptake of airborne lead particulates.

大气中铅颗粒物的植物叶面吸收是外源铅进入植物体的重要途径，而植物角质层作为叶面与环境交互的第一道结构性屏障，其成分和结构是叶面铅吸收的重要物质基础，揭示角质层在叶面铅吸收中的作用机制意义重大。本项目针对植物叶面铅吸收这个科学问题，以茶树为研究对象，构建基于原位化学成像技术的叶面-铅颗粒物交互作用体系研究。首先基于共聚焦显微拉曼光谱建立角质层成分和微结构的原位化学成像分析法，对铅胁迫下角质层组织横截面和剖面的结构和成分（角质、蜡质、酚类、多糖等）进行原位微区化学成像分析，然后把角质层的成分和结构信息与组织中铅的赋存形态及时空动态分布规律进行融合分析，探讨铅颗粒物粒径、化学形态和角质层厚度、成分和结构等对于叶面铅吸收的影响，实现从组织、细胞及亚细胞层面到分子层面的铅与叶面互作体系的原位分析，借助该方法阐述铅颗粒突破叶表面生物膜的机制，揭示大气中铅颗粒物的叶面吸收机制。

本项目聚焦气溶胶铅颗粒物胁迫下茶树的铅吸收、转移途径和茶叶的生理生化变化机制，以不同品种、铅颗粒物胁迫浓度下茶叶生理生化指标的变化为线索，揭示了气溶胶铅颗粒物胁迫下茶树叶面铅吸收的机制，并基于茶树的生理生化指标及其光谱响应特性构建了铅超标茶树的快速无损检测方法。主要结果如下：.（1）.研究了气溶胶铅颗粒物胁迫下茶树的铅吸收、转移途径以及茶叶组织细胞的微观形态变化，证明气溶胶铅颗粒物胁迫下存在铅的叶面吸收途径、叶面向茎转运的途径。发现了铅胁迫会对茶叶气孔产生损害，并证明气孔是空气中铅颗粒物进入植物体的一个通道。.（2）.比较了不同品种、胁迫浓度下茶叶生理生化指标的变化情况，对乌牛早和迎霜在不同浓度胁迫、不同时期茶叶内部的叶绿素a、叶绿素b、类胡萝卜素、抗坏血酸、谷胱甘肽和含水率含量进行测量，发现随着胁迫时间的增加，6种指标均表现出显著性差异。.（3）.建立生理生化指标的快速无损检测模型，采集不同品种、不同浓度胁迫下茶树叶片的可见近红外光谱，通过化学计量学方法，建立6种生理生化指标的原始和不同预处理数据的偏最小二乘回归、支持向量回归和主成分回归模型。.（4）.利用傅里叶变换红外光谱具有的“指纹峰”特点，对气溶胶铅颗粒物胁迫下茶叶叶片其他物质的变化情况进行半定量分析，证实铅胁迫会对多种物质产生影响。基于傅里叶变换红外宏观光谱分别建立了光合色素和抗氧化物的全波段PLS预测模型，绘制了果胶与纤维素在叶片切片上的分布图，实现了铅胁迫下叶片成分和结构在微观层面的原位化学成像。