Tapetum (botany)

Schematic of anther (1: Filament 2: Theca 3: Connective 4: Pollen sac or Microsporangium)
Section of anther, showing dehiscence and release of pollen (1: Vascular bundle 2: Epidermis 3: Fibrous layer 4: Tapetum 5: Pollen)

The tapetum is a specialised layer of nutritive cells found within the anther of flowering plants, located between the sporogenous tissue and the anther wall. Tapetum is important for the nutrition and development of pollen grains and a source of precursors for the pollen coat.[1] The cells are usually bigger and normally have more than one nucleus per cell. As the sporogenous cells undergo mitosis, the nuclei of tapetal cells also divide. Sometimes, this mitosis is abnormal, which is why many cells of mature tapetum become multinucleated. Polyploidy and polyteny can also be seen sometimes. The tapetum's unusually large nuclear constitution helps it provide nutrients and regulatory molecules to the forming pollen grains. The following processes are responsible for this:

  • Endomitosis
  • Normal mitosis not followed by cytokinesis
  • Formation of restitution nuclei
  • Endoreduplication

Tapetum helps in pollen wall formation, transportation of nutrients to the inner side of the anther, and synthesis of callase enzyme to separate microspore tetrads.