Punnet square can be described as a diagram which is used to check the probability of offsprings produced by crossing over of parents.
If a homozygous white plant is crossed with a heterozygous white plant, then none of the F1 offsprings will not have purple flowers. Considering white-flowered plant to be dominant for the trait.
If a heterozygous white plant is crossed with a heterozygous white plant, then about 25% of the F1 plants will have purple flowers. Considering white trait to be dominant.
