Localization of allergenic molecules in pollen grains

The wall of the mature pollen grain contains several layers, of which the outermost, the exine, is formed by the mother plant. Numerous proteins are incorporated in the exine. During the normal germination process on the stigma, these proteins interact with the stigmatic proteins. The interaction results into either enhancement or cessation of the pollen tube growth. It has been shown that most of these proteins diffuse into surrounding solutions already in a few seconds. They also cause allergic reactions in man. The diffusion of proteins and their allergic properties are not dependent on the germination of the pollen grains, and probably not either on their viability. The pollen grains of conifers are very weak allergens; their structure and function are different from those of the remaining flowering plants.