# Volatile Profile of 16 Unifloral Pollen Taxa Collected by Honey Bees (Apis mellifera L.)

## TL;DR

This study analyzed the volatile compounds in 16 types of unifloral bee pollen to understand how their aroma influences honey bee behavior and preferences.

## Contribution

The study provides the first comparative analysis of volatile profiles in 16 unifloral pollen taxa and links specific compounds to bee visitation rates.

## Key findings

- Pollen from Erica manipuliflora, Papaver rhoeas, and Sisymbrium irio had the highest number of volatile organic compounds.
- Isothiocyanate compounds in Brassicaceae pollen may correlate with higher bee visitation rates.
- 4-methyl-5-nonanone was uniquely found in E. manipuliflora pollen, suggesting a role in bee attraction.

## Abstract

The aroma of a flower is composed of a mixture of numerous volatile compounds. Various floral organs contribute to this aroma, including the anthers and the pollen they produce. Although it is often assumed that pollen scent influences honey bee preferences, research on insect attraction to bee pollen aromas is limited and has not extensively focused on unifloral pollen species. In this study, the volatile profiles of 16 unifloral bee pollen taxa with significant importance to beekeeping were analyzed, re-vealing differences in their volatile compound profiles. Certain volatile compounds, such as isothiocyanate compounds found in the pollen of the Brassicaceae family, may be associated with higher bee visitation rates. This suggests a potential explanation for honey bees’ behavior during pollen collection and their preference for specific pollen types.

Bee pollen’s aroma combined with other floral components serve various purposes, including attracting pollinators and signaling the availability of food sources. The present study aimed to comparatively analyze the volatile profiles of unifloral pollen taxa. Bee pollen loads were collected using pollen traps and sorted based on their botanical origin, determined by color and pollen grain morphology. The separated pollen samples were analyzed using a Purge & Trap/GC-MS system, identifying the volatile profiles of pollen from 16 plant species. The analysis revealed distinguished differences in the total volatile organic compounds (VOCs) among the various pollen species. Notably, the pollen from Erica manipuliflora, Papaver rhoeas, and Sisymbrium irio contained the highest number of VOCs, with 54, 51, and 42 substances detected, respectively. Certain volatile compounds appeared to correlate with increased bee visitation. For instance, 4-methyl-5-nonanone was uniquely found in E. manipuliflora pollen, while isothiocyanate compounds were exclusively present in species of the Brassicaceae family. Therefore, given the significant impact of VOCs on honey bees’ preferences, it is essential to consider not only the nutritional value of bee pollen when evaluating its beekeeping value, but also its aroma profile.