Release of proteins from the pollen wall of Linum grandiflorum

Summary The emission of proteins from the pollen wall of Linum grandiflorum stained with Coomassie blue was followed directly in moistened grains as well as in pollen prints. Within the first minute of the grain being moistened exine-borne proteins emerged from both inter-apertural and apertural sites; subsequently, proteins of a different nature were discharged from the apertures only. In a fraction of the grains the release of intine proteins was not preceded by that of exine proteins. Pin and thrum pollen did not differ in terms of mode or site of this protein emission. The presence and emergence of exine proteins from the apertures is explained by the process of infolding of the colpal wall at desiccation and its expansion at rehydration, which causes an initial trapping and subsequent re-exposure of surface materials. This explanation may also account for the occurrence of poral sporophytic proteins in the pollens of many dictoyledons.