Final answer:
The probability of purple offspring in pea plants from a cross between a white and a purple plant depends on the genotype of the purple parent. It can be either 100% if the purple parent is homozygous dominant (AA) or 50% if the purple parent is heterozygous (Aa).
Step-by-step explanation:
In pea plants, the purple flower color (A) is dominant to the white flower color (a). If a white flowered plant (aa) is fertilized by a purple flowered plant, we must consider the genotype of the purple plant. Since the question does not specify the genotype of the purple parent, we will assume it can either be AA (homozygous dominant) or Aa (heterozygous).
If the purple parent is AA, all offspring will be Aa and display purple flowers, resulting in a 100% probability of purple offspring. However, if the purple parent is Aa, the cross would be aa x Aa. Using a Punnett square, we can determine that this cross would yield two types of genotypes: Aa (purple) and aa (white), each with a 50% probability. Therefore, in this case, the probability of purple offspring is 50%.
Without additional information on the genotype of the purple parent, we cannot provide a single probability answer. Therefore, the overall probability of purple offspring can be either 100% if the purple parent is homozygous dominant (AA) or 50% if the purple parent is heterozygous (Aa).