The correct conclusion based on the information provided is:
If a plant has white flowers, then its genotype must be pp.
In pea plants, only plants with the genotype "pp" (homozygous recessive) will have white flowers, since the allele for purple flowers (P) is dominant over the allele for white flowers (p). Therefore, if a plant has white flowers, it cannot have any dominant alleles (P) and its genotype must be "pp."