Abstract:

【Objective】The relationship between odorous substances in flowers and the visiting behavior of insects has attracted increasing attention from biologists. However, previous studies on specific plants and pollinators are scare. The present study investigated the species differences and dynamic changes in the volatile organic components of male and female flowers of Ilex rotunda during flowering, and recorded the species and behaviors of pollinators. The study aimed to elucidate the characteristics of the pollinating system, explore the potential effects of volatile compounds on the behaviors of pollinating insects, and provide a reference for improving the pollination and fruiting of I. rotunda.【Method】The changes in the volatile components during the four flowering stages, the big bud stage, first blooming stage, full blooming stage, and final flowering stage, were determined by head space solid phase microextraction (HS-SPME) and gas chromatography-mass spectrometry (GC-MS). The species, visiting behavior, and visiting frequency of the pollinators were recorded by observation.【Result】The results demonstrated that the flowering of I. rotunda began in late April and ended in early May in Nanjing, with a flowering period of nearly half a month. A total of 30 volatile substances were detected from the flowers, of which 19 and 21 were detected from female and male flowers, respectively. There was a moderate difference in the overall number of male and female plants. The results revealed that the levels of β-caryophyllene and other major components increased initially, reached a peak at the full-opening stage, and decreased thereafter. The proportion of the main components generally decreased at the final flowering stage. However, there was an increase in the proportion of alcohols and alkanes during final flowering, which was accompanied by the production of several new compounds. The sole insect pollinator of I. rotunda is Apis cerana. There was a considerable overlap between male and female plants during the peak visiting period. The findings revealed that A. cerana preferred visiting male flowers, and that there was a positive correlation between the changes in the visiting frequency pattern and β-caryophyllene content.【Conclusion】The results indicated that β-caryophyllene could be used as an information substance to attract A. cerana for pollinating I. rotunda. Additionally, male and female I. rotunda plants can be planted in a centralized and reasonable manner according to the “centralized” flower visiting behavior of A. cerana. The success rate of I. rotunda pollination can be effectively improved by complying with the consistent flowering period, the concentrated flowering period, and planting large numbers of male plants.

Key words: Ilex rotunda, Apis cerana, volatile organic compounds, pollinating insect, gas chromatography-mass spectrometry(GC-MS)