芦荟叶表皮结构和组分对紫外线辐射胁迫的响应

Ozone depletion gives rise to the enhancement of ultraviolet B radiation in the earth's surface, has become an increasingly serious global environmental problems. The epidermal tissue of plant is the first barrier to prevent UV-B radiation injury . In the past few years, we have studied the structure and photophysical properties of aloe leaf epidermal cells and cuticle in natural growth environment. This project will continue to use aloe which resists UV-B radiation as experimental material, using the scanning electron microscope and transmission electron microscope to research the structure changes of leaf epidermal cells and cuticle under the stress of UV-B. Furthermore, useing the microscopic Raman spectroscopy, laser confocal microscope technology and high performance liquid chromatography technology to research leaf epidermal cells and horny layer ingredients on their dynamic changes of composition and distribution under UV-B stress ,such as lignin, anthraquinones, fatty acids, alkanes, fatty alcohol . Our goal is seeking the physiological and biochemical mechanism of leaf epidermis structure and component changes under UV-B stress . With the help of the optical and chemical bonding theory to research the relationship between aloe leaf epidermis structure along with components and the reflection, scattering, absorption as well as dissipation of UV-B radiation energy. Aimed at elucidating the mechanism that plant defenses ultraviolet radiation damage through their epidermal barrier.

臭氧层减薄导致地球表面紫外线B(UV-B)辐射增强，已成为日趋严重的全球性环境问题。植物表皮（含角质层）是防止UV-B辐射损伤的第一道屏障。在过去的几年里，我们研究了自然生境条件下芦荟叶表皮细胞和角质层的结构和光物理特性。本项目将继续以抗UV-B辐射的芦荟为实验材料，运用扫描和透射电子显微镜技术研究UV-B胁迫下芦荟叶表皮细胞和角质层结构的变化；运用显微拉曼光谱技术、激光共聚焦显微镜技术和高效液相色谱技术，研究UV-B胁迫下芦荟叶表皮细胞和角质层中木质素、蒽醌类物质、脂肪酸、烷烃、脂肪醇等组成成分和分布的变化动态。探寻UV-B胁迫下芦荟叶表皮结构和组分变化的生理生化机制。根据光学和化学键原理探讨芦荟叶表皮结构和组分与反射、散射、吸收耗散UV-B辐射能量的关系。旨在阐明植物通过表皮屏蔽方式防御紫外线辐射损伤的机制。

本项目综合运用结构植物学、光学和分析化学的方法，通过人工增强紫外线B辐射研究了芦荟叶表皮细胞结构和成分的变化与植物防御紫外线B辐射的相关性。研究结果发现植物表皮防御紫外线B辐射的策略主要有以下四种：1.反射:通过角质层和表皮细胞外侧壁反射掉部分紫外线B。2. 吸收: 通过角质层和表皮细胞减少紫外线B的透射率，角质层、表皮细胞中积累花青素等紫外线B吸收物质，过滤屏蔽掉部分紫外线B。3.转化：角质层和表皮细胞中产生蒽醌类物质，这类物质吸收紫外线B的能量，并发出蓝色或黄色荧光，将对植物有害的紫外线光转化为对植物无害的可见光。4.修复：植物受到紫外线B辐射损伤后通过增加抗氧化酶活性等，消除紫外线B辐射产生的氧自由基，修复受损结构。在植物表皮结构和成分的表现为增强紫外线B辐射角质层、表皮细胞外侧壁增厚、角质层表面纹路排列改变；角质层中吸收紫外线物质含量增加，表皮细胞中蒽醌类物质、花青素含量增加，这些变化增加了表皮对紫外线B的反射能力、过滤屏蔽能力和无害化转化能力。为进一步验证上述研究结论，本项目组扩展研究了景天三七、月季叶表皮细胞对紫外线B辐射的响应及其他物理射线对植物表皮的影响，证实了本研究结果。.本研究证明增强紫外线B辐射导致植物表皮角质层、细胞外侧壁增厚、角质层表面纹路排列改变、吸收紫外线物质含量增加，从而增加表皮对紫外线B的反射能力、过滤屏蔽能力和无害化转化能力。但外界紫外线B辐射信号诱导植物表皮产生一系列应激反应的信号传导途径尚不清楚，有待进一步研究。