Goodwin S. Mark, Kolosova Natalia, Kish Christine M., Wood Karl V., Dudareva Natalia, Jenks Matthew A.
Department of Horticulture and Landscape Architecture, Purdue University, West Lafayette, IN 47907, USA Department of Chemistry, Purdue University, West Lafayette, IN 47907, USA.
Physiol Plant. 2003 Mar;117(3):435-443. doi: 10.1034/j.1399-3054.2003.00047.x.
Floral volatiles, which are small and generally water-insoluble, must move from their intracellular sites of synthesis through the outermost cuticle membrane before release from the flower surface. To determine whether petal cuticle might influence volatile emissions, we performed the first analysis of petal cuticle development and its association with the emission of flower volatiles using Antirrhinum majus L. (snapdragon) as a model system. Petal cuticular wax amount and composition, cuticle thickness and ultrastructure, and the amounts of internal and emitted methylbenzoate (the major snapdragon floral scent compound) were examined during 12 days, from flower opening to senescence. Normal (n-) alkanes were found to be the major wax class of snapdragon petals (29.0% to 34.3%) throughout the 12 days examined. Besides n-alkanes, snapdragon petals possessed significant amounts of methyl branched alkanes (23.6-27.8%) and hydroxy esters (12.0-14.0%). Hydroxy esters have not been previously reported in plants. Changes in amount of methylbenzoate inside the petals followed closely with levels of methylbenzoate emission, suggesting that snapdragon petal cuticle may provide little diffusive resistance to volatile emissions. Moreover, clear associations did not exist between methylbenzoate emission and the cuticle properties examined during development. Nevertheless, the unique wax composition of snapdragon petal cuticles shows similarities with those of other highly permeable cuticles, suggesting an adaptation that could permit rapid volatile emission by scented flowers.
花香挥发物分子较小，且通常不溶于水，它们必须从细胞内的合成位点穿过最外层的角质膜，才能从花朵表面释放出来。为了确定花瓣角质层是否会影响挥发物的释放，我们以金鱼草为模型系统，首次对花瓣角质层的发育及其与花香挥发物释放的关系进行了分析。在从花朵开放到衰老的12天时间里，我们检测了花瓣角质层蜡质的含量和成分、角质层厚度和超微结构，以及内部和释放的苯甲酸甲酯（金鱼草主要的花香化合物）的含量。在整个12天的检测过程中，正构烷烃被发现是金鱼草花瓣中主要的蜡质类别（占29.0%至34.3%）。除了正构烷烃外，金鱼草花瓣还含有大量的甲基支链烷烃（占23.6 - 27.8%）和羟基酯（占12.0 - 14.0%）。羟基酯此前尚未在植物中被报道过。花瓣内部苯甲酸甲酯含量的变化与苯甲酸甲酯释放水平密切相关，这表明金鱼草花瓣角质层可能对挥发物释放几乎没有扩散阻力。此外，在发育过程中检测的角质层特性与苯甲酸甲酯释放之间不存在明显的关联。然而，金鱼草花瓣角质层独特的蜡质成分与其他高渗透性角质层的蜡质成分相似，这表明存在一种适应性，可能使有香味的花朵能够快速释放挥发物。
