A radial system of microtubules extending between the nuclear envelope and the plasma membrane during early male haplophase in flowering plants.

The angiosperm male meiocyte is unusual among plant cells in that during early development ordered cellulosic microfibrils are not deposited at the protoplast surface. Instead, a complex series of events takes place which leads to the formation of the pollen wall 'primexine'. The use of immuno-cytochemistry, electron microscopy and experiments with an inhibitor have revealed this cell to contain no cortical microtubules, and its cytoskeleton to be radially organised with microtubules extending from the nucleus to the plasma membrane. It is proposed that these microtubules, perhaps organised from the nuclear envelope, play a part in orientation of the nucleus and in the transport of materials to the cell surface.