I had some issues while studying Mendel’s rules of inheritance.
How did Mendel, while running his test crosses, know if the plants in his F0 generation were TT (homozygous tall) or Tt (heterozygous tall)?
There seems no way to differentiate between them, and I do not know of any sophisticated tools which may do so, but surely they were not available to him?
There may be some flaws in my logic, as I am a beginner, but I am not able to find any sources which tackle this problem. I am familiar with the basics of inheritance.