by Pattrick et al.
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| Refractometers for sugar measurements |
Floral nectar mediates the interactions between plants and pollinators. It is the main reason many pollinators visit flowers. Nectar composition is dominated by sugars – most commonly sucrose, fructose and glucose – which make nectar a carbohydrate-rich energy source for floral visitors. The sugar concentration of nectar is therefore a key metric which defines how energy rich a particular nectar is. There are multiple methods of describing the concentrations and relative proportions of the constituent sugars in nectar. A potential source of confusion in pollination biology research is that several of these methods are commonly expressed as percentages, ratios or proportions and so can give the appearance of describing the same parameter when they are actually completely different measures. Furthermore, without prior knowledge that these different approaches exist, it is easy to confuse the different methods. Here we aim to bring clarity to this topic, consolidating previous work to describe the most commonly used methods for reporting sugar concentrations and how they differ. We offer suggestions for reporting these values to improve clarity and provide equations for converting between methods. We also present worked examples on how to calculate the energetic content of sugars in nectar and discuss how the relative energetic content of nectar varies depending on the respective proportions of the constituent sugars. We hope that this manuscript serves as a useful resource for pollination biologists.
