Essential oil yield and composition of three Helichrysum species occurring in the Eastern Cape Province of South Africa

A.M. Ras
2013 South African Journal of Botany  
Floral nectar is a complex mixture of primary and secondary compounds. While most of the research has focused on the role of primary compounds for the interaction with pollinators, the role of secondary compounds is much less understood. Volatile organic compounds (VOCs) have only recently been investigated as part of the complex mixture of the chemicals found in nectar. They might play a role as pollinator attractants or as a repellent for herbivores. In addition VOCs in nectar may reduce
more » ... tar may reduce fermentation of sugars in nectar by microorganisms. However, there might be a trade-off between these different functions. The floral and nectar VOCs of nine bee selected flower species were investigated using GC-MS. The response of honeybees (Apis mellifera L.) to four different concentrations (0.01%; 0.1%; 0.5%; 1%) of linalool, phenylethanol, and hexanoic acid were tested in choice tests against an unscented sugar solution (40% sucrose). Rejection of linalool began at 1%. Phenylethanol was rejected at a concentration of 1%. Hexanoic acid was a strong repellent even at low concentrations of 0.01%. Antimicrobial activity was found for all three VOCs over a period of six days. Different concentrations of VOCs (0.01%; 0.10%; 1%) did not have an effect on antimicrobial activity. The data indicates that some VOCs like hexanoic acid in nectar can have a strong repellent effect on honeybees while others like linalool are tolerated even at relatively high concentrations such as 1%. The findings indicate that nectar scent does have an effect on the behaviour of honeybees. The data also suggests that potential trade-offs between the antimicrobial activity of VOCs and repelling pollinators may be compound specific.
doi:10.1016/j.sajb.2013.02.157 fatcat:ziv7ucnnp5g5taulwjyydyawsy