Wall projections in the vegetative cell of Parietaria officinalis L. pollen

Ultrastructural aspects of pore development in Parietaria officinalis L. pollen are described. The main feature is the presence of intine wall projections formed in correspondence to the pores during the late microspore stage and persisting in the shedding pollen. This structure coexists with the tubules occurring in the pore and first appearing as evaginations of the plasma membrane. The morphological evidence and other features such as the occurrence of mitochondria next or in contact with wall projections lead us to compare the pollen vegetative cell to a transfer-cell. The possible functions of these transfer-cell type structures are discussed. © 1980 Springer-Verlag.