How tapetal cells could become bi-nucleate?

Tapetal cells are very large cells with more than one nucleus. They assist with pollen grain growth and development. Tapetal cells undergo endomitosis where the nucleus in the nuclear membrane splits, but cytokinesis does not happen. They become bi / multi nucleate because of this. 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. It is also possible to see polyploidy and polyteny at times.