Why did short pea plants reappear in Gregor Mendel’s second generation of offspring?

Short pea plants reappeared in the second generation (F₂) of Gregor Mendel’s experiments because the trait for shortness is recessive, meaning it can be masked by the dominant trait for tallness in the first generation (F₁) hybrids.12

Although the F₁ hybrids appeared tall, they carried both the dominant and recessive genes for height. According to Mendel’s law of segregation, these alleles separate during the formation of sex cells. When the F₁ plants were self-pollinated, the random union of these gametes allowed the recessive genes to pair up again in some offspring, resulting in the reappearance of the short phenotype in approximately 1/4 of the F₂ generation. This demonstrated that the recessive traits were not consumed or lost in the first generation but were instead preserved as distinct, uncontaminated units of heredity.13