Day-night fluctuations in floral scent and their effects on reproductive success in Lilium auratum

We examined the contribution of diurnal and nocturnal pollination to male and female reproductive success in Lilium auratum. Plants were bagged for either 12 h during the day or at night to allow either only nocturnal or only diurnal visitors to forage throughout the flowering period. We found that there was no significant difference in the seed:ovule ratio among diurnally pollinated, nocturnally pollinated, or control flowers. However, in terms of male reproductive success, it was more advantageous for the plants to be pollinated both diurnally and nocturnally: the numbers of pollen grains remaining in diurnally pollinated or nocturnally pollinated flowers were significantly greater than those in control flowers. The total amount of floral volatiles of L. auratum was significantly higher at night than during the day. The constituents of floral scent of all time series examined were mostly monoterpenoids, many of which serve as attractants for nocturnal hawkmoths. Such nocturnally biased floral scent emission of L. auratum might achieve male reproductive success by attracting nocturnal visitors, which may suggest that the relative contribution of floral scent in this species is biased towards male reproductive success.