Biology 11th Edition by Cecie Starr ,Ralph Taggart

Exercise 21

In sweet pea plants, an allele for purple flowers ( P ) is dominant to an allele for red flowers ( p ). An allele for long pollen grains ( L ) is dominant to an allele for round pollen grains (l). Bateson and Punnett crossed a plant having purple flowers/long pollen grains with one having white flowers/round pollen grains. All F 1 offspring had purple flowers and long pollen grains. In the F 2 generation, the researchers observed the following phenotypes:
296 purple flowers/long pollen grains
19 purple flowers/round pollen grains
27 red flowers/long pollen grains
85 red flowers/round pollen grains
What is the best explanation for these results