In angiosperm all the four microspores of tetrad are covered by a...

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.