| Volatile odours from flowers play an important role in plant-pollinator interaction.Some plant flowers use certain volatiles as reward signals to attract specific pollinators for their pollination.By apperceiving these chemical signals in advance,pollinators can quickly locate the flowers which offering food rewards,thus improving their collection efficiency.The honeybee(Apis mellifera)is an important pollinator.Is there a similar chemical communication mechanism between honeybees and phanerogams?In this thesis,the odours of 12 nectar plant species and 3 wind-pollinated species flowers were collected by Needle trap device and injected into gas chromatographymass spectrometry(GC-MS)for chemical structure anaylsis.A total of more than 110 floral scents were identified,and nonanal was the only common floral component among 12 nectar plants,which was not detected in wind-pollinated flowers.In addition,the ratio of nonanal in flower volatiles of mainstream nectar source plants was higher than that of nectar source plants that were less visited by honeybees.The electrophysiological responses of honeybee antennae to five main volatile substances(nonanal,benzaldehyde,phenylacetaldehyde,benzaldehyde diethyl acetal and linalool)in flowers of nectar plants were measured by EAG.The results showed that the electrophysiological response values of honeybee antennae to the five volatiles reached the highest level at 2 μL/m L.While testing the electrophysiological responses to the five volatiles by a same antenna,the nonanal showed the highest response values and was significantly higher than that of the other four volatiles.The content of nonanal in the flowers during different flowering states was quantitatively analyzed by Needle trap and GC-MS systems.The results showed that the release of nonanal in the blooming flowers of Ligustrum compactum was significantly higher than that in the buds and faded ones.In addition,it was found the release of nonanal content in flowers blooming at 9:00 and 15:00 was higher than that at 6:00,12:00 and 18:00,and the release of nonanal at 15:00 was significantly higher than that at 18:00 in the measurement of nonanal release from tallow flowers at five times of the day(6:00,9:00,12:00,15:00 and 18:00).This is consistent with the nactersecreting habits of Sapium sebiferum flowers in a day.The flowers of Sapium sebiferum,Ligustrum grandifolium and Castanea henryi were wrapped by nylon net for 2 hours,and the flowers without net were used as the control group.The retention of nectar and the volatilization of nonanal in the flowers of Sapium sebiferum,Ligustrum grandifolium and Castanea henryi were increased after the flowers were covered with nylon net for 2 hours to prevent pollinators from visiting them.The attraction effects of the above five main flower volatile odours on honeybees were tested by behavioral experiments.Results showed that the number of bee visits on mimic flowers with nonanal was significantly higher than that of other four compounds.In addition,nonanal was also detected in the honey of the experimental colonies.In conclusion,nonanal was the only common volatile in the flowers of nectar source plants,and it was positively correlated with the flowering states and nectar yield of flowers.EAG response and behavioral test also confirmed that nonanal had the strongest attraction to honeybees.Therefore,nonanal may play an important role in the chemical communication between honeybees and plant flowers. |
