How tapetal cells could become bi-nucleate?

Tapetal cells:

These are very large cells with many nuclei which are special as they are nutritive.
Tapetal cells become bi-nucleate:

1. These cells are used in the development and growth of pollen grains.
2. Once mitosis occurs, the nucleus divides but cytokinesis does not take place.
3. Hence, they end up being bi-nucleate, polynucleate, etc.