Final answer:
A Ttyy plant can make two types of gametes, Ty and ty, due to being heterozygous for height and homozygous recessive for the other trait.
Step-by-step explanation:
If a parent plant has the genotype Ttyy, it can produce two different types of gametes when it comes to the tall (T) or short (t) trait, T and t, because it is heterozygous (Tt) for height. However, since it is homozygous recessive (yy) for the other trait, it can only produce one type of gamete with the y allele for that trait. Combining these, the parent can produce two types of gametes: Ty and ty. This follows from Mendel's law of segregation which states that allele pairs separate or segregate during gamete formation and randomly unite at fertilization.