Final answer:
In the case of a plant with alleles for red and white flowers, a heterozygous plant would exhibit a pink phenotype due to incomplete dominance, resulting in a blend of the two colors.
Step-by-step explanation:
If there are alleles for both red and white plants, a heterozygous plant's phenotype would be pink. This is due to the expression of both alleles where neither the red nor the white allele is completely dominant over the other. This type of inheritance pattern indicates a blend of the two parental phenotypes, rather than a complete dominance of one over the other. The red and white alleles show incomplete dominance, which results in a phenotypic ratio of 1:2:1 for red:pink:white in the F₂ generation after self-crossing the F₁ heterozygotes.