Chemical composition of the 'low quality' pollen of sunflower (Helianthus annuus, Asteraceae)

The nutritional needs of bees are receiving renewed attention in the context of declining bee populations and changes in land use that threaten floral resources. We present a comprehensive analysis of the nutritional composition of sunflower (Helianthus annuus L.) pollen, comparing hand-collected, bee-collected and stored pollen. As found in previous studies, the protein content of sunflower pollen was relatively low compared to other important bee forage plants. In the cultivars tested, two essential amino acids, methionine and tryptophan, are likely to be below the minimum requirements for honeybees. Fatty acid composition showed lauric acid to be most abundant, followed by palmitic and alpha-linolenic acids. While sunflower offers abundant and accessible pollen, its quality may hinder bee development when it is an exclusive pollen source, and the cultivars of such mass-flowering crops may vary in value for pollinators.