EXINE RECEPTORS

Structures that receive sporopollenin are similar in the pollen grains of a wide variety of angiosperms and in the conifer Pinus. These stru ctures are rod-shaped, with a central core that accepts stains strongl y and an outer binder zone that only weakly accepts stains. These spor opollenin-accumulating rods are substructures of the exine units we ca ll ''tufts''. In many taxa tuft substructures are covered by receptor- independent (extra-tuft) accumulated sporopollenin and surfaces are sm ooth. We show an example (Quercus coccifera) of the acetolysis resista nce of extra-tuft accumulated sporopollenin followed by its removal th rough oxidation which reveals the tufts.