Macronutrient chemistry of pollen

Concentrations of total and water‐extractable macronutrients varied with pollen species and genus. Total nitrogen and organic carbon levels were found to be greater in Ambrosia than Pinus. The same trends were not observed for total sulfur or phosphorus. About 60% of the sulfur in Pinus pollen was water‐extractable, while the proportion in Ambrosia was only 5%. Trends for nitrate were similar, but the portion that was water‐extractable was lower by an • order of magnitude. Nitrate levels were highest in Wisconsin pollen, indicating that levels of this nutrient may be related to region of origin. The proportion of phosphate to total phosphorus, approximately 60%, was fairly similar for all species of pollen. Potassium concentrations were consistently lower in the commercially available pollen, which may indicate that the levels of this nutrient are sensitive to sample handling and storage procedures. Water‐extractable nutrients probably represent a nutrient reserve that is used during pollen tube formation and to stimulate development of seeds.