Final answer:
In the second generation, we would expect the phenotypic ratio of short pea plants to be 3:1. If the second generation contains 400 plants, 100 of them would be short pea plants.
Step-by-step explanation:
In the second generation, assuming Mendelian inheritance, we would expect the phenotypic ratio of short pea plants to be 3:1. This means that for every 4 plants, 1 would be short. If the second generation contains 400 plants, we can calculate the number of short pea plants as follows:
Number of short pea plants = (1/4) * 400 = 100