Final answer:
True-breeding plants refer to plants that always produce the same traits over successive generations. Mendel verified true-breeding pea plants for certain traits before conducting his experiments.
Step-by-step explanation:
The term "True-breeding" refers to plants that always produce the same traits over successive generations. Mendel verified true-breeding pea plants for certain traits before undertaking his experiments. These true-breeding plants, also known as purebreds, only produce offspring that look like the parent plant, ensuring consistent traits for his experiments.