UV-B absorbing compounds in present-day and fossil pollen, spores, cuticles, seed coats and wood: evaluation of a proxy for solar UV radiation
UV-B absorbing compounds in present-day and fossil pollen, spores, cuticles, seed coats and wood: evaluation of a proxy for solar UV radiation
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当今和化石花粉、孢子、角质层、种皮和木材中的 UV-B 吸收化合物：太阳紫外线辐射替代物的评估
DOI：
10.1039/b904515e
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发表时间：
2009
影响因子：
3.1
通讯作者：
R. Broekman
中科院分区：
文献类型：
--
作者：
J. Rozema;P. Blokker;M. M. Fuertes;R. Broekman
目前和化石花粉、孢子、角质层、种皮和木材中的 UV-B 吸收化合物 (UAC) 已被评估为过去紫外线的代表。该代理不仅可以提供南极臭氧空洞之前和期间（1974年至今）平流层臭氧和太阳紫外线变化的信息，还可以提供地球生命进化过程中平流层臭氧层和太阳表面紫外线的发展和变化信息。孢粉质和角质是高度抗性的生物聚合物，在地质记录中保存完好，并含有酚酸对香豆酸 (p CA) 和阿魏酸 (FA)。 p CA 和 FA 代表了基于植物的过去表面紫外线辐射的替代指标，因为它们是由太阳 UV-B 通过苯丙素途径 (PPP) 诱导的。花粉和孢子壁以及角质层中这些单体对 UV-B 的吸收可以防止对细胞代谢的损害。在温室实验中发现，暴露于增强 UV-B 的蚕豆花粉中 p CA 和 FA 增加。进一步的相关证据来自 1960 年至 2000 年孢子中的紫外线吸收化合物，比较了陆地植物（石松属物种）在臭氧消耗之前和期间暴露于太阳紫外线的情况，并比较了来自南极洲（严重臭氧消耗）、北极和其他臭氧消耗较少或可忽略不计的纬度的植物。木材衍生的化合物愈创木基 (G)、紫丁香基 (S) 和对羟基苯基 (P) 通过 PPP 生产。木质素中 P、G 和 S 的比例在不同植物类群（例如双子叶植物/单子叶植物、裸子植物/被子植物）之间有所不同。据推测，这种木质素成分以及木质素衍生的生理和物理特性（例如树木年轮木材密度）有潜力作为古紫外线气候的代表。然而，缺乏通过将树木暴露于增强的紫外线来进行验证。 p CA 和 FA 也构成角质聚合物的一部分，并存在于现存和化石银杏叶角质层中，如热辅助水解和甲基化 (THM)-热解-GC-MS 所示。潜在地，基于 UAC UV 代理重建臭氧柱厚度和 UV-B 的时间尺度可能是十年、百年、千年，甚至可能是数十年。为了进一步开发基于 UAC 和 p CA 和 FA 的 UV 代理，有必要基于户外植物紫外线辐射操作实验以及对储存的植物（植物标本）或相同或相关植物物种的化石材料的比较分析，获得 UV 剂量响应（孢子花粉和角质中 UAC、p CA 和 FA 的含量）关系进行验证。
UV-B absorbing compounds (UACs) in present-day and fossil pollen, spores, cuticles, seed coats and wood have been evaluated as a proxy for past UV. This proxy may not only provide information on variation of stratospheric ozone and solar UV in the period preceding and during the Antarctic ozone hole (1974–present day), but also on the development and variation of the stratospheric ozone layer and solar surface UV during the evolution of life on Earth. Sporopollenin and cutin are highly resistant biopolymers, preserving well in the geological record and contain the phenolic acids p -coumaric ( p CA) and ferulic acid (FA). p CA and FA represent a good perspective for a plant-based proxy for past surface UV radiation since they are induced by solar UV-B via the phenylpropanoid pathway (PPP). UV-B absorption by these monomers in the wall of pollen and spores and in cuticles may prevent damage to the cellular metabolism. Increased p CAand FA in pollen of Vicia faba exposed to enhanced UV-B was found in greenhouse experiments. Further correlative evidence comes from UV-absorbing compounds in spores from 1960–2000 comparing exposure of land plants ( Lycopodium species) to solar UV before and during ozone depletion and comparing plants from Antarctica (severe ozone depletion), Arctic, and other latitudes with less or negligible ozone depletion. Wood-derived compounds guaiacyl (G), syringyl (S), and p -hydroxyphenyl (P) are produced via the PPP. The proportions of P, G, and S in the lignin differ between various plant groups ( e.g. dicotyledons/monocotyledons, gymnosperms/ angiosperms). It is hypothesized that this lignin composition and derived physiological and physical properties of lignin (such as tree-ring wood density) has potential as a proxy for palaeo-UV climate. However validation by exposure of trees to enhanced UV is lacking. p CAand FA also form part of cutin polymers and are found in extant and fossil Ginkgo leaf cuticles as shown by thermally-assisted hydrolysis and methylation (THM)-pyrolysis-GC-MS. Potentially, the time scale for reconstruction of ozone column thickness and UV-B based on the UAC UV proxy may be decadal, centennial, millennial and possibly billenial. For further development of the UACs and p CA and FA-based UV proxy, it is necessary to obtain the UV dose–response (content of UACs, p CA and FA in sporopollenin and cutin) relationships for validation, based on outdoor UV radiation manipulations experiments with plants, and comparative analysis of stored plants (herbaria) or fossil material of the same or related plant species.