Explain the role of tapetum in the formation of pollen-grain wall .

Explanation

Tapetum is the innermost wall of the microsporangium . The tapetal cells may be uni bi -or multinucleate and possess dense cytoplasm. The various roles played by tapetum are
(i) Secretion of hormones and various enzymes .
(ii) Transportation of nutrients to the developing pollen grains .
(iii) Production of ubisch bodies coated with sporopollenin cause exine thickening.
(iv) Secretion of pollenkit (oily substance ) outside mature pollen .
Secretion of proteins for pollen to be compatible during fertilization .