What would be the ploidy of the cells of tetrad?
I know of no such thing as a “cell of Tetrad.” Some cells can be tetraploid, if that’s what you mean. Many of the cardiac muscle cells and bladder lining cells have 2 nuclei, which would make the cell tetraploid (4n) with 46 chromosomes per nucleus. Tetraploidy is relatively common in plants, however; many of our well known food crops are plants that arose spontaneously by an ancestor becoming tetraploid or polyploid. Watermelon is one example. The word tetrad, in biology, means the way homologous chromosomes pair up in prophase I of meiosis.