Final answer:
The most likely genotypes of the two parent pea plants producing 25% short and 75% tall pea plant offspring are both heterozygous (Tt). This would give rise to a 3:1 tall-to-short phenotypic ratio, consistent with Mendelian inheritance patterns.
Step-by-step explanation:
The phenotypes of pea plants with respect to height are determined by a simple dominant-recessive inheritance pattern of alleles. The genotypes that give rise to tall plants are either homozygous dominant (TT) or heterozygous (Tt), both resulting in the tall phenotype because the dominant allele (T) for tallness masks the recessive allele (t). A plant will only be short if it possesses a homozygous recessive genotype (tt).
In the case where offspring show a 3:1 ratio of tall to short pea plants, the most likely genotypes of the two parent pea plants are heterozygous (Tt) for each. This stems from the fact that two heterozygous parents can produce offspring with the following genotypes through random segregation: TT, Tt (which will appear tall), and tt (which will appear short). Using a Punnett square, the predicted genotypic ratio from this cross would be 1:2:1, with the corresponding phenotypic ratio being 3:1, favoring the tall trait.