Scanning electron microscopic obser vations of pollen grains and stigma in the self-incompatible heteromorphic species Primula malacoides Franch. and Forsythia x intermedia Zab., and genetics of sporopollenin deposition

Summary

Scanning electron microscopic observations revealed differences in surface morphology and size of stigmatic papillae and pollen grains in the two forms of flower of the dimorphic species Primula malacoides and Forsythia x intermedia. In P. malacoides pin papillae are longer and have more inflated globose tips than those of the thrum form which have oval tips, and the larger thrum pollen grain has a rougher form of exine sculturing than pin pollen grain. The correspondence of exine pattern dimorphism with the dimorphism of floral form associated with the sporophytically controlled incompatibility system, indicates that the control of sporopollenin deposition is also sporophytically determined.

Scanning electron microscope observations have also been made of pollen grain-stigma interactions in compatible and incompatible pollinations.

Recent literature on the control of sporopollenin deposition is briefly discussed. It is concluded that the extent of deposition of the sporopollenin is controlled by the meiocytes but the actual template determination is controlled by the tapetal material, and much, if not all, of the sporopollenin itself may be synthesized in, and derived from, the tapetum.