What is tapetum? Mention it's significance

The tapetum is a specialised layer of nutritive cells found within the anther, of flowering plants, where it is located between the sporangenous tissue and the anther wall. ... The unusually large nuclear constitution of the tapetum helps it in providing nutrients and regulatory molecules to the forming pollen grains. Usually the cells are larger and have more than one nucleus per cell. The nuclei of tapetal cells also split as the sporogenous cells undergo mitosis. Sometimes, this mitosis is not normal due to which many cells of mature tapetum become multinucleate. Tapetum nourishes the developing pollen grains. The layer of the anther wall that helps in anther dehiscence is endothecium. The cells of endothecium develop fibrous thickenings at maturity which radiate from the inner tangential walls. ... These thickenings are hygroscopic and thus, help in anther dehiscence.