Analysis of nectar from low‐volume flowers: A comparison of collection methods for free amino acids

Abstract

Floral nectar is a reward offered by flowering plants to visiting pollinators. Nectar chemistry is important for understanding plant nutrient allocation and plant–pollinator interactions. However, many plant species are difficult to sample as their flowers are small and produce low amounts of nectar.We compared the effects of different methods of nectar collection on the amino acid composition of flowers with low volumes of nectar. We used five methods to collect nectar from 60 (5 × 12) Calluna vulgaris flowers: microcapillary tubes, a low‐volume flower rinse (the micro‐rinse method, using 2 μl water), filter paper, a high‐volume flower rinse (2 ml water) and a flower wash (2 ml water). We analysed the samples for free amino acids using quantitative UHPLC methods .We found that the micro‐rinse method (rinsing the nectary with enough water to only cover the nectary) recovered amino acid proportions similar to raw nectar extracted using microcapillary tubes. The filter paper, 2 ml rinse and 2 ml wash methods measured significantly higher values of free amino acids and also altered the profile of amino acids. We discuss our concerns about the increased contamination risk of the filter paper and high‐volume rinse and wash samples from dried nectar across the floral tissue (nectar unavailable to floral visitors), pollen, vascular fluid and cellular fluid.Our study will enable researchers to make informed decisions about nectar collection methods depending on their intended chemical analysis. These methods of sampling will enable researchers to examine a larger array of plant species' flowers to include those with low volumes of nectar.

Anti-aphrodisiac pheromone, a renewable signal in adult butterflies

“…Later studies showed that all amino acids found in proteins, as well as non-protein amino acids, have been identified in various plant nectars 35–38 . In general Phe, serving as a precursor for anti-aphrodisiac production in P. napi males , is present at various ratios in nectar of a broad range of flowering plants 31,35,36,39,40 . In our study, the newly developed method was carried out to document its presence, rather than quantify Phe in the nectar of B. orientalis flowers.…”

Network modelling, citizen science and targeted interventions to predict, monitor and reverse bee decline

“…Nectar also varies in both amino acid content and sugar concentration. Nectar sugar concentration can range from 7% to 70% w/w (7 to 70 g per 100 g of nectar; Power, Stabler, Borland, Barnes, & Wright, ). Pollen quality and diversity has been shown to have direct impacts on honeybee health (see references in Goulson et al, ), growth, development, immuno‐competence, longevity, body size, ovary development and larval growth (Vanderplanck et al, ).…”

“…Nectar nutritional quality can be estimated as sugar concentration plus amino acid content (e.g. Corbet, ), and nectar and pollen amino acid content can be quantified using gas chromatography–mass spectrometry (GC‐MS) or liquid chromatography techniques (Power et al, ). Using these empirical data on plant resource reward quantity and quality for pollinators, and pollination service rewards for plants, it would be possible to develop empirically based edge weights and symmetry estimates for plant–pollinator networks.…”

A simple and effective ground‐based tool for sampling tree flowers at height for subsequent nectar extraction

“…There are several nectar sampling methods used to accurately measure the content of nectar within flowers (Morrant, Schumann, & Petit, 2009; Power, Stabler, Borland, Barnes, & Wright, 2018). As their effectiveness may depend on various factors such as floral morphology, nectar type and the sampling system (Bolten & Feinsinger, 1978; Kearns & Inouye, 1993), the selection of the proper technique can be challenging (Lloyd, Ayre, & Whelan, 2002).…”