Answer:
They were recessive traits
Explanation:
In Mendel's experiment, all the plants produced in first generation were tall despite one parent being dwarf. The dwarf trait was hidden in the first generation and in the second generation it was observed again.
The allele responsible for dwarf height was a recessive allele. A recessive allele only expresses itself when it is present in two copies. Since here it was paired with a tall height dominant allele, it was not expressed and the entire progeny was tall in f1 generation,
TT X tt = Tt : Recessive allele is still present in f1 generation but the trait is hidden by dominant allele
When these Tt plants were self crossed to get f2 generation,
Tt X Tt = TT, Tt, Tt, tt : One fourth of the progeny had tt combination so the recessive allele could finally be expressed and these plants were dwarf.
