Section Crop and Horticultural Sciences, Institute of Crop Sciences and Resource Conservation, University of Bonn, Bonn, Germany.
J Agric Food Chem. 2010 Jun 23;58(12):7361-7. doi: 10.1021/jf9046072.
Solar radiation is a key environmental signal in regulation of plant secondary metabolism. Since metabolic responses to light and ultraviolet (UV) radiation exposure are known to depend on the ratio of spectral ranges (e.g., UV-B/PAR), we examined effects of different UV-B radiation (280-315 nm) and photosynthetically active radiation (PAR, 400-700 nm) levels and ratios on yield and pattern of monoterpenoid essential oil of peppermint. Experiments were performed in exposure chambers, technically equipped for realistic simulation of natural climate and radiation. The experimental design comprised four irradiation regimes created by the combination of two PAR levels including or excluding UV-B radiation. During flowering, the highest essential oil yield was achieved at high PAR (1150 micromol m(-2) s(-1)) and approximate ambient UV-B radiation (0.6 W m(-2)). Regarding the monoterpene pattern, low PAR (550 micromol m(-2) s(-1)) and the absence of UV-B radiation led to reduced menthol and increased menthone contents and thereby to a substantial decrease in oil quality. Essential oil yield could not be correlated with density or diameter of peltate glandular trichomes, the epidermal structures specialized on biosynthesis, and the accumulation of monoterpenes. The present results lead to the conclusion that production of high quality oils (fulfilling the requirements of the Pharmacopoeia Europaea) requires high levels of natural sunlight. In protected cultivation, the use of UV-B transmitting covering materials is therefore highly recommended.
太阳辐射是调节植物次生代谢的关键环境信号。已知植物对光照和紫外线（UV）辐射的代谢反应取决于光谱范围（如 UV-B/PAR）的比值，因此我们研究了不同 UV-B 辐射（280-315nm）和光合有效辐射（PAR，400-700nm）水平和比值对薄荷单萜精油产量和组成的影响。实验在暴露室中进行，这些暴露室技术上装备齐全，可实现对自然气候和辐射的真实模拟。实验设计包括四种辐照处理，由两种 PAR 水平（包括或不包括 UV-B 辐射）的组合形成。在开花期，在高 PAR（1150μmol m(-2) s(-1))和近似环境 UV-B 辐射（0.6W m(-2))下，精油产量最高。就单萜组成而言，低 PAR（550μmol m(-2) s(-1))和没有 UV-B 辐射导致薄荷脑含量降低，而薄荷酮含量增加，从而使油质量显著下降。精油产量与具缘腺毛状表皮结构的密度或直径（表皮结构专门用于生物合成）以及单萜的积累没有相关性。本研究结果表明，生产高质量的油（符合欧洲药典的要求）需要高水平的自然阳光。因此，在保护栽培中，强烈推荐使用能透过 UV-B 的覆盖材料。
