Chemical composition of pollen from kiwifruit vines

The chemical composition of kiwifruit (Actinidia deliciosa var. deliciosa) pollen was examined using hand-collected samples from nine staminate clones-'Matua', 'M51-M58', and one pistillate cultivar ('Hayward'). Measurements included: ash, minerals, ether-extractable lipid, total dietary fibre, extractable carbohydrates, protein amino acids, and free amino acids. There were no major compositional differences amongst the staminate clones. The ash, lipid, and fibre content of the sterile pistillate pollen, on the other hand, was greater, and the protein content lower, than that of the male clones. Nitrogen (N) (67.6), potassium (10.6), and phosphorus (10.0 g/kg dry weight (DW)) were the elements present in greatest concentration in staminate pollen, and N (24.3) and calcium (12.0 g/kg DW) in pistillate pollen. Zinc and iron were the principal trace elements in both instances. Fructose accounted for as much as 76% of the extractable carbohydrate, followed by glucose and minor amounts of sucrose. The predominant amino acids in acid hydrolysates of staminate clones were glutamate (12.6), aspartate (12.2), lysine (72), and arginine (7.1 g amino acid per 100g of protein). By contrast, asparagine was the major free amino acid. Comparison of the distribution of amino acids between free and proteinaceous forms indicated that aspartate-asparagine and proline were preferentially concentrated in the free fraction, but that most of the essential amino acids required for the nutrition of the honeybee (threonine, methionine, isoleucine, leucine, phenylalanine, lysine, and histidine) were present as protein. With regard to the dietary adequacy of kiwifruit pollen protein for honeybees, staminate pollen represents a rich source of crude protein (37.2%) and contains adequate amounts of all the essential amino acids required, with the exception of isoleucine.