Amoeboid Tapetum - Tapetum

It is also known as invasive or periplus modial tapetum. This type of tapetum is more prevalent in the monocotyledons (Arum) than in the dicotyledons (Helianthus). In the amoeboid tapetum, there is a break-down of the inner tangential cell wall followed by the enlargement and movement of protoplasts into the anther sac, where they fuse and form periplus modium. The formation of periplus modium occurs at different developmental stages ranging from meiotic prophase to tetrad stage of pollen development, in different species.

In the anther sac, such fused protoplasts or the periplus modia closely surround the developing microspores and play an important role in pollen development. At the tetrad stage the tapetal cytoplasm produces the enzyme callase which breaks down the callose wall around the microspore tetrads, releasing the microspores into the periplus modium. Towards the end of pollen development, the periplus modium degenerates, dries up and becomes coated on the surface of the pollen wall as pollen kitt material.