Final Answer:
The expected phenotype ratio of the F₁ generation is 1:2:1 for green seeds with tall stems, yellow seeds with tall stems, and green seeds with tall stems, respectively.
Step-by-step explanation:
When crossing two parental plants that are homozygous for one trait and heterozygous for another, it involves a dihybrid cross. In this case, the parental plants are denoted as GGTT (green seeds with tall stems) crossed with GgTt (heterozygous for yellow seeds and tall stems).
The gametes produced by the first plant are GT, and by the second plant, GT, gT, Gt, and gt. The combinations of these gametes result in the following genotype combinations in the F₁ generation: GGTT, GgTt, GGTt, and GgTT.
The phenotypes associated with these genotypes are green seeds with tall stems, yellow seeds with tall stems, and green seeds with tall stems. The ratio of these phenotypes is 1:2:1, representing the expected phenotypic ratio of the F₁ generation. This ratio is a result of the independent assortment of alleles for seed color and stem length during gamete formation.
Each trait segregates independently, and the combination of alleles in the F₁ generation follows Mendel's laws of inheritance, leading to the observed phenotypic ratio. In summary, the 1:2:1 phenotypic ratio in the F₁ generation reflects the combination of different alleles for seed color and stem length inherited from the parental plants.