Receptor‐Independent Sporopollenin

Pollen of some species of the genus Quercus shows rod‐shaped substructures in fresh or acetolysed exines, while in other species rod substructure is mostly masked by sporopollenin. Oxidation with potassium permanganate removes exine substance (sporopollenin) from between the rod substructures. We propose that the rods include receptors for sporopollenin. The sporopollenin between rods we refer to as ‘ receptor‐independent sporopollenin ’. Pollen of Typha , when mature, has tectal surfaces with concave tops and sides, whereas during development the tectal surfaces are smoothly rounded. After acetolysis treatment followed by potassium permanganate the tectum surfaces again appear rounded. When these exines are subsequently eroded by a fast atom source, rod‐shaped substructures are seen to protrude from the tectum. These structures are equivalent in size and shape to the rods of the exine of Quercus . Sporopollenin that accumulates over and masks rod substrucutre is less resistant to our degradative methods than the sporopollenin in rod structures of exines. We suggest that the exine material we call “receptor‐independent sporopollenin” be given a simple positive name, such as masking‐sporopollenin or abbreviated to masking‐spn .