Floral scent variation in plants : pollinator attraction strategy dependent of display size

为了研究昼夜授粉对金色百合雌雄生殖成功的贡献，我们进行了昼夜授粉排斥试验，并对花香进行了分析。我们发现，无论是白天授粉还是夜间授粉都能导致金边莲花的雌性生殖成功：只允许白天授粉的花、只允许夜间授粉的花和对照花之间的种子/胚珠比没有显著差异。然而，植物需要白天和夜间的传粉者来获得雄性生殖成功：白天和夜间处理的花中残留的花粉粒数量都显著高于对照花。金银花挥发物总量呈时间序列节律变化，即夜间显著高于白天，并随着花龄的增加而逐渐减少。夜间，花的挥发物总量在开花后的第二天达到高峰，随后随着花龄的增加逐渐下降。在白天，花的挥发物总量一直很低。所有时间序列的花香成分主要是异戊二烯类化合物，常用作夜间天蛾的引诱剂，而脂肪酸类化合物较少，常吸引昼夜传粉者。花香成分也表现出时间序列的变化，但Sorensen的相似性指数表明，夜间气味可能比白天气味保持更恒定的成分随花龄变化。因此，这种夜间偏向的花香释放可能通过吸引夜间传粉者来实现雄性生殖成功，其视觉线索可能通过吸引昼夜传粉者来实现雄性生殖成功。这可能表明，这一物种的花香在雄性繁殖成功中发挥了作用，视觉线索也是如此。

To examine the contribution of diurnal and nocturnal pollination to male and female reproductive success in Lilium auratum, we conducted diurnal and nocturnal pollinator exclusion experiments and also analyzed floral scent. We found that either diurnal or nocturnal pollinators result in female reproductive success in L.auratum : there was no significant difference in the seed : ovule ratios among the flowers in which only diurnal pollination was allowed, those in which only nocturnal pollination was allowed, and the control flowers. However, plants required both diurnal and nocturnal pollinators for male reproductive success : the numbers of pollen grains remaining in both diurnal- and nocturnal-treated flowers were significantly greater than those in the control flowers. The total amount of floral volatiles of L.auratum showed a time-series rhythmic pattern, namely, they were significantly higher at night than during the day and gradually decreased with flower age. At night, the total amount of floral volatiles peaked on the second day from anthesis and subsequently gradually decreased with flower age. During daytime, the total amount of floral volatiles was constantly low. The composition of floral scent of all time-series examined was mostly isoprenoids, which often served as an attractant of the nocturnal hawkmoth, and there were less fatty acid-derivatives, which often attract diurnal pollinators. The floral scent composition also showed time-series changes, but Sorensen's similarity indices indicated that nocturnal scent might maintain a more constant composition with flower age than diurnal scent. Thus, such nocturnally biased floral scent emission of L.auratum might exist to fulfill male reproductive success by attracting nocturnal pollinators, and its visual cues might serve to fulfill male reproductive success by attracting diurnal pollinators. This may suggest that floral scent of this species plays a role in male reproductive success, as do visual cues.