Floral nectar, which is mainly composed of sugar, plays a major role in attracting pollinators. However, many studies show that most of the nectar also contains antiherbivore secondary compounds, such as phenolics, which could keep away some flower visitors.
Although the non-sugar components, such as phenolics in pollen and nectar, are believed to mediate a plant's interaction with flower visitors, little experimental work has been reported. The compounds have been assumed to act primarily as deterrents.
Teaming up with colleagues from the Smithsonian Tropical Research Institute in US, researchers from the CAS Xishuangbanna Botanical Garden discovered the synergism between nectar phenolics and sugar may provide a mechanism for plants to encourage pollinating bees and reduce energy investment in nectar, operating as exaptations by co-opting defense mechanisms against herbivores. The work was reported in a recent issue of
Functional Ecology.
In the experiments, the researchers tested the interplay between nectar sugar concentrations and phenolic compounds, using feeding assays with a tropical Asian honey bee in its native habitat. Their findings suggest that sugar and secondary components in nectar interact, and a non-linear response by foragers to nectar constituents can either augment or diminish pollinator attraction to nectar containing secondary compounds, while reducing plant expenditure in attracting and maintaining the service of pollinators.
