Understand a pollen analysis report

The pollen (from the Greek “pales” = “flour” or “dust”) is the set of tiny grains produced by the flowers of angiosperms (or the male pine-cones of gymnosperms), which are the male reproductive elements or microgametophyte.
The pollen grains are typically rounded, though the pine are winged, and they are very small, only a few microns. The tiniest pollen grain known is from the Myosotis with about 6 microns (0.006 mm) in diameter. The shape and ornamentation of pollen grains are typical of each family or of the same kind of plants. Pollen contains a large proportion of proteins (16-40%) containing all known amino acids, as well as numerous vitamins, particularly vitamins C and PP (vitamin B3 or Niacin).

Eucalyptus spp. and Castanea spp. pollen

The existing pollen in honey has a great impact on the honey floral variety, and consequently may be requested a pollen analysis in order to ensure the provenance and to be provided a quantitative measure of floral origin.
The pollen analysis are based on grain counting and frequency determination. To provide suitable statistical precision, relative percent abundances are based on a total count of at least 500 pollen grains, and standard deviation limits calculated.

An analysis of pollen is not difficult to interpret, and it’s almost self-explanatory (see an example), however there are some concepts that should be taken in consideration.

The following terms are used for frequency classes:

  • Predominant pollen (more than 45% of the pollen grains counted);
  • Secondary pollen (16-45%);
  • Important minor pollen (3-15%);
  • Minor pollen (less than 3%).

The pollen grains of some flowers are over-represented, i.e. the percentage of pollen in honey is greater than the percentage of the corresponding nectar in the honey. With some other pollens the situation is reversed; they are under-represented.

In Pollen analysis, over-represented pollen is excluded from the counting and not to be considered. The most extreme case of over-representation of pollen known is Myosotis spp. (forget-me-not). The pollen of Castanea sativa is also likely to be over-represented, and only honeys containing 90% or more of pollen from Castanea sativa can be regarded as Castanea honey.

The most important pollens known to be under-represented are listed below. If the frequency of any of these pollens is as high as the percentage quoted, the honey is mainly from that source.

  • Citrus 10-20%
  • Lavandula angustifolia X Lavandula latifolia (lavandin) 10-20%
  • Rosmarinus 10-20%
  • Salvia (European) 10-20%
  • Robinia 20-30%
  • Tilia 20-30%
  • Medicago 20-30%

To finish and for those interested in observing pollen, with a optical microscope, under x200, you will be able to just make out the ‘sculpting’ on the surfaces of pollen grains, and you may even be able to see that they have different shapes. You really need a microscope with a magnification of x400 or better, and the patience to piece together different views. Pollen grains are too small to see with the eye, or even with a hand lens, but they are too large for you to focus on the whole grain at one time under high power.
If you want to take a photo, you need to manipulate the images with a neat bit of software like ImageJ from the National Institutes of Health in the USA. This is simple to use, but not entirely intuitive, so I advise you to read the documentation.

I want to thank Dr. Miguel Maia from Apismaia, for giving me permission to use, as an example, one of his pollen analysis.