Pollen and nectar (Fig. 32) are produced by flowers as rewards for pollinators in exchange for pollination. Pollen is essential in the reproduction of plants while nectar, a sugary solution, secreted by glands called nectaries, is a product that is not part of the sexual system of plants (Dafni, 1992), but attracts pollinators to ensure the spread of the pollen. Both pollen and nectar are collected for various reasons in honey bee research, particularly in studies addressing foraging biology, pollination research and exposure risks to environmental pollutes (Sammataro and Avitabile, 2011; see also the BEEBOOK paper on toxicology, Medrzycki et al., 2013).
Studies have shown a change in both appearance and nutritional composition of pollen during collection and storage by honey bees (Fig. 33) (Human and Nicolson, 2006). Through the addition of nectar and glandular secretions (Winston, 1987; Roulston and Cane, 2000) and certain bacterial ﬂora associated with stored pollen the digestibility and nutritional value of the beebread/ stored pollen is increased (Herbert and Shimanuki, 1978). The sampling and collection methods depend upon the intended use of the floral source and the specific endpoints of measurements. However, it is important to know that quality of pollen decreases over time and should be stored appropriately and preferably be used within a year of sampling (Pernal and Currie, 2000). Here we describe methods to collect pollen (from the flowers, from the bees and stored in their combs) as well as various methods to collect nectar.
Fig. 32. Aloe greatheadii var davyana flower showing pollen on anthers
and a droplet of nectar. Photo: V Dietemann.
Fig. 33. Scanning electron microscopy pictures of Aloe greatheadii var. davyana pollen showing physical differences occurring in pollen grains after addition of nectar and glandular secretions; (A) Fresh pollen, (B) Bee collected pollen and (C) Stored pollen. Photos: H Human.