In angiosperm all the four microspores of tetrad are covered by a layer which is formed by:

Step-by-step solution

Callose wall surrounds the sporocytes during the meiotic stage. It provides an isolation barrier sealing off one meiotic cell (megaspore mother cell) from another. Related Theory Tetrad is a group of four haploid and immature pollen grains in tetrahedral fashion produced by meiotic microsporogenesis. The tetrads are of five types namely tetrahedral (most common), isobilateral, T shaped, decussate and linera. In dicots, the most common type of pollen tetrad is tetrahedral.